Effects of pH values on the properties of buffalo and cow butter-based low-fat spreads

A.M. Abdeldaiema,b,*, Q. Jina, R. Liua and X. Wanga,*

aState Key Laboratory of Food Science and Technology, Synergetic Innovation Center of Food Safety and Nutrition, School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu China

bDepartment of Dairy Science, Faculty of Agriculture, Suez Canal University, Ismailia, 41522, Egypt

*Corresponding authors: ahmed52_2007@yahoo.com; wxg1002@qq.com

 

SUMMARY

The objective of this study was to characterize the effects of pH values (5, 5.5, 6, 6.5 and 7) on the properties of buffalo and cow butter-based low-fat spreads. Sensory evaluation of the samples decreased with an increase in pH values and during the storage periods. In addition, phase separation occurred with pH 6, 6.5 and 7. The differences in peroxide values and oil stability index among the samples compared to the control samples were slight, while peroxide values and oil stability index decreased during the storage periods. Changes in fatty acid composition among the pH treatments and during the storage periods were detected. Differences in solid fat contents among pH treatments separately and during the storage periods were negligible. A decline in the hardness and viscosity of the samples were accompanied by an increase in pH values, and the treatments had increased effects during the storage periods. Generally, an increase of pH values did not affect the melting profiles of the spreads. Additionally, changes between the melting profiles of buffalo and cow butter-based low-fat spreads were detected.

 

RESUMEN

Efecto del pH en las propiedades de mantequillas para untar baja en grasa de búfalos y vacas. El objetivo fue determinar los efectos del pH (5, 5.5, 6, 6.5 y 7) en las propiedades de mantequillas para untar bajas en grasa de búfalos y vacas. La puntuación sensorial de las muestras disminuyó con el aumento del pH y durante los períodos de almacenamiento, además, la separación de fases se produjo con pH de 6, 6,5 y 7. Se observaron diferencias en los valores de peróxido e índice de estabilidad de la grasa de las muestras en comparación con las muestras control, mientras que los valores de peróxido incrementaron, el índice de estabilidad de la grasa disminuyó durante los períodos de almacenamiento. Se observan cambios en la composición de ácidos grasos entre los tratamientos de pH y durante los períodos de almacenamiento. Las diferencias en el contenido de grasa sólida entre los tratamientos de pH por separado y durante los períodos de almacenamiento fueron no significativas. La disminución en la dureza y la viscosidad de las muestras fueron proporcionales al incremento del pH, y los tratamientos aumentan los efectos durante los períodos de almacenamiento. En general, un aumento de los valores de pH no afectó a los perfiles de fusión de los untables. Además, se observaron cambios entre los perfiles de fusión de los untables bajos en grasa a base de mantequilla búfalos y vacas.

 

Submitted: 7 January 2014; Accepted: 5 May 2014

Citation/Cómo citar este artículo: Abdeldaiem AM, Jin Q, Liu R,Wang X. 2014. Effects of pH values on the properties of buffalo and cow butter-based low-fat spreads. Grasas Aceites 65 (3): e038. doi: http://dx.doi.org/10.3989/gya.0105141.

KEYWORDS: Buffalo butter; Cow butter; Fatty acids composition; Low fat spreads; Melting behavior; Sensory evaluation; Viscosity

PALABRAS CLAVE: Comportamiento de fusión; Composición en ácidos grasos; Evaluación sensorial; Mantequilla de búfalo; Mantequilla de vaca; Untable bajo en grasa; Viscosidad

Copyright: © 2014 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial (by-nc) Spain 3.0 Licence.


 

CONTENT

1. INTRODUCTIONTOP

In recent years scientists all over the world have come up with general nutritional recommendations which aim at reducing calories and tending towards healthier habits have resulted in the production of different types of low fat butter spreads with a fat content of 40%. This has increased market interest and drawn extensive attention for food technologists. The fat phase in low fat butter spread makes an important contribution to its physical properties, rheological measurements and chemical reactions as well as organoleptic properties. The overall goals are to inhibit water droplet aggregation and to make the product’s process and shelf life stable, and to provide emulsions that break down easily and give good flavor release in the mouth (Mageean and Jones 1989).

The factors that have influenced low fat spreads can be generalized as follows: fat phase, stabilizers, emulsifiers, homogenization and aqueous phase. Such large reductions in fat content alter the nature of the emulsion structure and it is difficult to maintain the continuous fat nature of such products. In order to overcome this problem, stabilizers have to be added to immobilize the aqueous phase by increasing its viscosity. The most widely used aqueous phase stabilizers in low-fat spreads are milk proteins, alginates, starch derivatives and gelatin. In particular, gelatin is used in many formulations to provide the aqueous phase with a consistency and melting behavior close to those of the fat phase (Janssens and Muyldermans 1994).

Four types of such agents have been identified (Moran 1991). These are viscous (high levels of milk protein or high-molecular-weight polysaccharides), gelling (hydrocolloid agents used to gel the aqueous phase), phase-separating (with thermo-dynamically incompatible hydrocolloids) and synergistic (exploiting known synergistic interactions between hydrocolloids).

An appreciable portion of the population in both developing and developed countries, particularly young children adolescents, the elderly, and women of child-bearing age can suffer from nutrient deficiencies at borderline or pathological levels (Richardson 1990).

In the last three decades, due to economic and health factors, low fat spreads have been produced with reduced fat contents while attempting to retain the texture and flavor of butter. An increase in the water phase associated with the fat phase reduction in spreads significantly changes the rheological properties and sensory evaluation of W/O spread above a certain water level. This introduces specific problems in low-fat spreads such as the occurrence of loose moisture upon spreading. The properties required for W/O spreads include having a relatively firm consistency and a plastic rheology so that the product does not become much thinner during spreading (Bot and Vervoort 2006).

The main objective of the present study was to investigate the effects of the pH values on the sensory and morphological evaluations, peroxide values (PV), oil stability index (OSI), fatty acid composition (FAC), solid fat content (SFC), rheological and melting properties of buffalo butter-based low-fat spreads (B-LFS) & cow butter-based low-fat spreads (C-LFS).

2. MATERIALS AND METHODSTOP

2.1. MaterialsTOP

Buffalo butter (Table 1) was obtained from the Department of Dairy Science, Faculty of Agriculture, Suez Canal University (Ismailia, Egypt). Cow butter (Table 1), skim milk powder and sodium chloride (table salt) were purchased from a local market in Wuxi (Jiangsu, China). Halal gelatin (80-280 BLOOM) was purchased from Gelatin & Protein Co., Ltd (Hangzhou, China). DIMODAN®HP-C distilled monogelyceride was obtained from Danisco Co. (Shanghai, China). Citric acid anhydrous, sodium bicarbonate and k-sorbate were purchased from Shanghai Honghao Chemical Co., Ltd (Shanghai, China). All other reagents and solvents were of analytical or chromatographic grade to suit analytical requirements.

Table 1. Buffalo and cow butter specifications
Characteristics Buffalo butter Cow butter
Fat (%) 83.48 82.68
Solid not fat (%) 2.91 1.75
Moisture (%) 13.61 15.57
Peroxide value 0.145 0.135

2.2. Preparation of buffalo and cow butter oilTOP

Butter oil preparation was performed according to Fatouh et al. (2003) with some modifications. Both buffalo and cow butter were melted separately at 50 °C instead of 60 °C, and the top oil layer was decanted and filtered through glass wool. The oil was then re-filtered under vacuum to obtain clear buffalo and cow butter oil.

2.3. Preparation of B-LFS and C-LFS with pH valuesTOP

The procedure for the pH treatments (B-LFS and C-LFS) was carried out according to Madsen (2000) with some modifications. The treatments consisted of the following (percentage, w/w): Buffalo and cow butter oil 40%, DIMODAN®HP-C distilled monogelyceride 0.5%, halal gelatin 2%, skim milk powder 1%, sodium chloride 1%, k-sorbate 0.1% and distilled water (to 100%). The sample preparation steps were as follows:

1.  Water phase. The ingredients: Halal gelatin, skim milk powder, NaCl and k-sorbate were blended together with distilled water at 70 °C for 10 min using a JJ-1B Electric Blender (Changzhou Runhua Electric Appliance Co., Ltd, China).
2.  The temperature of the water phase was then reduced to 40 °C and the pH was adjusted to 5, 5.5, 6, 6.5 and 7 [with citric acid 20% (w/w) and sodium bicarbonate 20% (w/w)] while blending.
3.  Fat phase. A portion of the melted buffalo and cow butter oil (~5×the weight of the emulsifier) was removed and heated to 70 °C with blending until the emulsifier dissolved, which was then added back to the melted butter oil at 40 °C.
4.  The water phase was then slowly added to the fat phase while mixing using a homogenizer (IKA®T18 Basic ULTRA-TURRAX®, Germany) for 5 min at speed No. 2.
5.  The mixture was then pasteurized at 75 °C for 10 min in a water bath while blending.
6.  The mixture was homogenized once using a laboratory Homogenizer (Model: GYB, Donghua High Pressure Homogenizer Factory, Shanghai, China) at a pressure of 17 MPa at 60 °C.
7.  The treated samples were kept in sterilized plastic cups (30 g) at room temperature for 15 hours (h) and then moved to the refrigerator (4 °C).

2.4. Sensory evaluationsTOP

Sensory evaluations of the samples (B-LFS ad C-LFS) were carried out according to Patange et al. (2013) using a panel of 12 judges selected from Egypt, Sudan and Yemen. Both B-LFS and C-LFS samples were approximately 30 g and were presented to the panelists at refrigeration temperature (4 °C). The color and appearance, spreadability, body and texture, flavor and overall acceptability, of the products were rated on a 9-point scale ranging from 1 (disliked extremely) to 9 (liked extremely). Spreadability was assessed by the panelists using a slice of bread onto which the sample was spread at 4 °C.

2.5. Morphology evaluationTOP

Morphology evaluations of the pH treatments were recorded with a digital camera (Sony Camera T500, Japan).

2.6. Peroxide valueTOP

The PV was modified from International Dairy Federation (IDF) Standard 74:1974 (Alexa et al. 2010). The samples of pH treatments (B-LFS and C-LFS) (40 g each) were placed into 50 mL conical centrifuge tubes and placed in a 50 °C water bath for 20 min, followed by centrifugation (RJ-TDL-50A, Low-speed desktop centrifuge, China) for 20 min at 5000 rpm. The top fat layers were decanted into a beaker and then dried over excess anhydrous sodium sulfate to remove residual water. The fat was separated from the anhydrous sodium sulfate by vacuum filtration through a Whatman No. 4 filter paper to obtain a clear fat. A 0.1 mL of melted fat was dissolved with 10 mL of a chloroform/methanol (70:30) mixture, followed by the addition of ammonium thiocyanate (0.05 mL) and ferrous chloride (0.05 mL), respectively. Using glass stoppers, the tubes were inverted and placed in a dark cupboard for 10 min. At the same time, a blank test with only reagents and no sample was carried out. The absorbance of the samples was read at 505 nm on a Spectrophotometer (Alpha-1500, China). After calibration, the blank value was subtracted from the sample values (1) and the PVs were calculated. All of the experiments were carried out in triplicate and the mean results are reported.

where, OD is the optical density.

2.7. Oil stability indexTOP

The oxidation induction time (OIT) of the extracted fat (see PV) was determined by the AOCS method Cd 12b-92 (Firestone 2004) with the Rancimat 743 apparatus (Metrohm AG, Herison, Switzerland). Samples of pH treatments (B-LFS and C-LFS) were prepared in triplicate by weighing 3 g of extracted fat into the reaction vessels. Distilled water (50 mL) was added to the measuring vessels, which were maintained at room temperature. Electrodes were attached for measuring changes in conductivity. The samples were heated at 120 °C under a purified air flow rate of 20 L·h−1. The induction time is defined as the time necessary to reach the inflection point of the conductivity curve.

2.8. Fatty acids compositionTOP

The preparation of the methyl esters of the fatty acids was determined according to GB/T 17376 (2008). Briefly, 60 mg of extracted fat were weighed (see PV) into a 10 mL screw-capped test tube. Then, 5 mL of n-hexane to dissolve the sample, and 250 μL of 2 M potassium hydroxide in MeOH were added to the test tube. The mixtures were vigorously shaken for 2 min, and then 1 g NaHSO4 was added into the tube and the mixtures were vigorously shaken for 2 min. After vortexing, 2 mL from the separated upper layer was added into the screw-capped test tube, and then centrifuged at high speed (TGL-16B, Shanghai Anting scientific factory, China) for 10 min at 10,000 rpm. One μL of purified hexane extract was injected into a GC-14B gas chromatograph (GC) equipped with a fused-silica capillary column (CP-Sil88, 100 m×0.25 mm×0.2 mm) and a flame ionization detector (Shimadzu, Tokyo, Japan). Both, injector and detector temperatures were set at 250 °C. The column oven temperature was as follows: 45 °C for 4 min, raised at 13 °C·min−1 to 175 °C, held for 27 min, raised at 4 °C·min−1to 215 °C, held for 20 min. Nitrogen was the carrier gas. The identification of the peaks was achieved by comparing the retention times with authentic standards analyzed under the same conditions. Results were expressed as w/w (%) total fatty acid.

2.9. Solid fat contentTOP

The SFC was performed according to the AOCS Official Method Cd 16b-93 (Firestone 2004). The SFC of the samples was determined on a PC120 pulsed nuclear magnetic resonance (pNMR) spectrometer (Bluker, Karlsrube, Germany). A 2.5 mL melted fat (see PV) added by the micropipette into glass tubes of pNMR. The samples were tempered by heating in a water bath at 100 °C for 15 min−1, then at 60 °C for 15 min−1 followed by 60 min at 0 °C, and finally 30 min at each chosen measuring temperature. The determination of SFC was performed in the temperature range of 0–40 °C at 5 °C intervals. All of experiments were carried out in triplicate and the mean results are reported.

2.10. Rheological measurementsTOP

2.10.1. HardnessTOP

The pH treatments (B-LFS and C-LFS) in plastic cups (diameter×height =4×2.5 cm) were kept in the refrigerator at 4 °C before the determination of the texture evaluation. The hardness was defined as the necessary force to reach the maximum penetration using a probe. The samples were removed from the refrigerator, and quickly placed on the platform of a TA-XT 2i texture analyzer (Stable Micro System, Ltd, UK). A puncture test was performed immediately using a probe (P/5–0.50 cm-diameter cylindrical probe) at pretest speed 1 mm·s−1, test speed 1 mm·s−1, posttest speed 1 mm·s−1 and a data acquisition rate of 200 points·s−1. The test was stopped when a penetration of 12 mm had been reached. All measurements were repeated at least 3 times in each test series.

2.10.2. Apparent viscosityTOP

Both B-LFS and C-LFS with pH values were removed from the refrigerator (4 °C), and kept at room temperature for 1 h, then the apparent viscosity of the samples was measured at 25 °C with the 5 cm parallel-plate geometry of the Physica MCR 301 Rheometer (Anton Paar, Austria). The shear rates were from 0 to 200·s−1, whereas the apparent viscosity was determined at a shear rate of 100·s−1.

2.11. Melting behaviorTOP

Differential scanning calorimetry (DSC Q2000 V24.9 Build 121, TA Instruments, New Castle, DE, USA) was used to determine the melting behavior of the samples. The system was purged with nitrogen gas at 20 mL·min−1 during the analysis, and liquid nitrogen was used as a refrigerant to cool the system. Calibration was performed with indium, eicosane, and dodecane standards. An empty aluminum pan was used as a reference. The samples (5–8 mg) were hermetically sealed in an aluminum pan, heated to 80 °C and held for 5 min to completely destroy the previous crystal structure. The samples were then cooled to −40 °C and maintained for 5 min. Following this step, the melting profiles were obtained by heating the samples to 80 °C at a rate of 10 °C·min−1. DSC melting curves were recorded from −40 °C to 80 °C. Data analysis was carried out with the software provided with the DSC.

2.12. Statistical analysisTOP

B-LFS and C-LFS with different pH values were analyzed separately, and values from the different tests were expressed as the mean ± standard deviation. One–way analysis of variance using SPSS 16 for windows (SPSS Inc., Chicago, USA) was performed on all experimental data sets. The Duncan analysis was applied to evaluate the significance of differences between means at P<0.05.

3. RESULTS AND DISCUSSIONTOP

3.1. Effects of pH values on the sensory and morphological evaluations of B-LFS and C-LFSTOP

Results from the sensory evaluation tests (color and appearance, body and texture, spreadability, flavor and overall acceptability) for the pH treatments (B-LFS and C-LFS) are presented in Table 2 (a and b). The yellow color of the pH treatments (C-LFS) reflected the coloring agent (β-carotene) in the fat phase of C-LFS. In general, the differences in sensory evaluation tests between B-LFS and C-LFS with pH 5 were negligible, while with pH 6, 6.5 and 7, the differences were clear when compared to the control samples. In addition, the scores of all the treatments with pH 6, 6.5 and 7 were decreased in the following order: pH 6>6.5>7. On the other hand, all sensory evaluation values were decreased during the storage periods (3 to 90 days).

The sensory evaluation of color and appearance was in correlation with the morphology evaluation of pH treatments, especially with increasing pH values (Fig. 1). In addition, no separated phase was observed for pH 5 of B-LFS and C-LFS compared to the control samples. In contrast, the treatments with pH 6, 6.5 and 7 had a separated phase (Fig. 1) compared to the control samples, and the phase separation was increased in the following order: pH 7>pH 6.5>pH 6. Furthermore, the phase separation occurred due to the fact that the attraction potential (attractive van der Waals forces) was greater than the repulsion potential, and vice versa with both pH 5 and 5.5. Also, the pH was far from the isoelectric point of the protein molecules when compared to the control samples (Cheng et al. 2008). No darkness was observed in the color or appearance of the samples during the storage periods, while both darkness and mould growth were observed at 80 days with the samples of pH 7. This observation is quite different when compared to Kristensen et al. (2000), who observed a darker and more yellow color during storage.

Table 2a. Effect of different pH values on the sensory evaluation of B-LFS
Storage (days) Sensory evaluation scoresa
B-LFS
pH 5.00 pH 5.50 (control) pH 6.00 pH 6.50 pH 7.00
Color & appearance 3 8.77±0.09aA 8.47±0.11aB 7.98±0.09aC 7.44±0.10aD 6.43±0.07aE
15 8.64±0.09abA 8.42±0.08aA 7.94±0.11aB 7.41±0.25abC 6.41±0.12abD
30 8.58±0.12abcA 8.36±0.09abB 7.87±0.11abC 7.37±0.05abD 6.38±0.10abE
45 8.55±0.07bcA 8.33±0.14abB 7.82±0.11abC 7.17±0.11bcD 6.27±0.08abcE
60 8.41±0.14cdA 8.33±0.09abA 7.81±0.12abB 7.10±0.10cdC 6.25±0.15bcD
75 8.32±0.13deA 8.21±0.09bcA 7.79±0.13abB 6.90±0.18deC 6.17±0.04cD
90 8.19±0.13eA 8.13±0.07cA 7.70±0.13bB 6.81±0.11eC 6.13±0.05cD
Body & texture 3 8.61±0.09aA 8.49±0.07aA 8.17±0.20aB 7.17±0.13aC 6.41±0.06aD
15 8.60±0.10aA 8.41±0.11abAB 8.14±0.02aB 7.10±0.06abC 6.37±0.31abD
30 8.56±0.10abA 8.42±0.10abA 8.05±0.20abB 6.95±0.13abcC 6.31±0.10abcD
45 8.43±0.06bcA 8.33±0.08abcA 7.94±0.33abB 6.87±0.11bcC 6.15±0.13abcdD
60 8.36±0.13cA 8.24±0.12bcdAB 7.90±0.15abB 6.81±0.32cC 6.11±0.23bcdD
75 8.36±0.09cA 8.16±0.11cdB 7.84±0.10abC 6.80±0.12cD 6.04±0.11cdE
90 8.17±0.09dA 8.08±0.12dA 7.76±0.31bB 6.76±0.11cC 6.00±0.10dD
Spreadability 3 8.45±0.09aB 8.67±0.08aA 8.10±0.11aC 7.12±0.05aD 6.58±0.14aE
15 8.41±0.22abA 8.56±0.10abA 8.00±0.11abB 7.06±0.09abC 6.52±0.13aD
30 8.35±0.08abcA 8.55±0.09abA 7.94±0.10abcB 6.92±0.09bcC 6.51±0.21aD
45 8.32±0.12abcA 8.41±0.29abcA 7.89±0.12abcB 6.87±0.09cdC 6.47±0.12aD
60 8.33±0.13abcA 8.38±0.08bcdA 7.82±0.30bcB 6.73±0.11deC 6.40±0.14abD
75 8.18±0.20bcA 8.25±0.14cdA 7.78±0.11bcB 6.68±0.08eC 6.35±0.11abD
90 8.11±0.07cA 8.11±0.22dA 7.69±0.06cB 6.61±0.12eC 6.18±0.12bD
Flavor 3 8.66±0.08aA 8.53±0.11aA 8.00±0.19aB 7.47±0.12aC 7.54±0.07aC
15 8.62±0.12abA 8.51±0.10abA 7.94±0.10abB 7.41±0.10abC 7.50±0.29abC
30 8.56±0.09abcA 8.44±0.10abA 7.88±0.13abB 7.35±0.08abC 7.44±0.09abC
45 8.51±0.07abcA 8.36±0.11abA 7.87±0.12abB 7.28±0.14bcC 7.37±0.10abcC
60 8.47±0.15bcA 8.33±0.10bcA 7.79±0.13abB 7.25±0.09bcdC 7.31±0.27abcC
75 8.39±0.10cdA 8.15±0.13cdB 7.70±0.10abC 7.13±0.09cdD 7.25±0.07bcD
90 8.21±0.11dA 8.13±0.11dA 7.69±0.32bB 7.07±0.11dC 7.14±0.07cC
Over-all Acceptability 3 8.62±0.08aA 8.55±0.11aA 7.85±0.12aB 7.23±0.09aC 6.44±0.14bD
15 8.53±0.10abA 8.48±0.08abA 7.81±0.10aB 7.23±0.13aC 6.37±0.14aD
30 8.51±0.10abA 8.45±0.07abA 7.75±0.10abB 7.18±0.09aC 6.26±0.09abD
45 8.47±0.11abcA 8.36±0.32abcA 7.68±0.11abB 7.11±0.11abC 6.17±0.11bcD
60 8.38±0.15bcdA 8.31±0.08abcA 7.66±0.30abB 6.97±0.10bcC 6.16±0.14bcD
75 8.27±0.21cdA 8.22±0.13bcA 7.52±0.11bB 6.83±0.08cdC 6.11±0.08bcD
90 8.18±0.11dA 8.14±0.09cA 7.51±0.09bB 6.78±0.10dC 6.04±0.07cD
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=12.
Table 2b. Effect of different pH values on the sensory evaluation of C-LFS
Storage (days) Sensory evaluation scoresa
C-LFS
pH 5.00 pH 5.50 (control) pH 6.00 pH 6.50 pH 7.00
Color & appearance 3 8.66±0.07aA 8.48±0.05abB 8.00±0.11aC 7.33±0.10aD 6.58±0.06aE
15 8.54±0.17abA 8.52±0.10aA 7.97±0.09abB 7.33±0.07aC 6.54±0.07aD
30 8.55±0.07abA 8.44±0.09abA 7.93±0.11abB 7.26±0.14aC 6.47±0.27abD
45 8.43±0.11bcA 8.40±0.07abcA 7.96±0.17abB 7.17±0.14aC 6.41±0.14abD
60 8.39±0.19bcA 8.33±0.15bcA 7.86±0.28abB 7.10±0.20abC 6.36±0.16abD
75 8.22±0.11cdA 8.24±0.05cdA 7.83±0.07abB 7.12±0.06abC 6.45±0.05abD
90 8.13±0.14dA 8.14±0.14dA 7.72±0.07bB 6.89±0.17bC 6.21±0.17bD
Body & texture 3 8.47±0.05aA 8.37±0.09aA 8.10±0.05aB 7.14±0.09aC 6.23±0.07aD
15 8.51±0.05aA 8.33±0.08aA 8.05±0.14abB 7.05±0.03abcC 6.17±0.14aD
30 8.46±0.11aA 8.35±0.06aA 7.96±0.11abcB 7.07±0.19abC 6.11±0.13abD
45 8.41±0.17aA 8.23±0.08abA 7.91±0.31abcB 6.92±0.06bcdC 6.14±0.08abD
60 8.43±0.10aA 8.18±0.04bB 7.89±0.14abcC 6.88±0.11cdD 6.06±0.12abcE
75 8.36±0.07aA 8.16±0.13bB 7.81±0.09bcC 6.83±0.06dD 5.96±0.15bcE
90 8.17±0.13bA 8.13±0.08bA 7.70±0.07cB 6.79±0.08dC 5.90±0.05cD
Spreadability 3 8.38±0.11aA 8.41±0.11aA 7.92±0.14aB 6.96±0.06aC 6.64±0.07aD
15 8.33±0.13abA 8.28±0.06abA 7.88±0.07abB 6.91±0.17abC 6.55±0.05abD
30 8.36±0.12aA 8.27±0.08abA 7.85±0.11abB 6.85±0.12abC 6.48±0.13abD
45 8.31±0.07abA 8.15±0.18bA 7.76±0.17abB 6.81±0.31abC 6.42±0.18bD
60 8.25±0.18abA 8.12±0.09bA 7.71±0.11bB 6.83±0.14abC 6.35±0.08bcD
75 8.19±0.13abA 8.13±0.09bA 7.73±0.08bB 6.74±0.06abC 6.37±0.15bcD
90 8.14±0.11bA 8.11±0.09bA 7.69±0.12bB 6.68±0.11bC 6.20±0.15cD
Flavor 3 8.39±0.11aA 8.30±0.04aA 7.80±0.05aB 7.38±0.12aC 7.32±0.09abC
15 8.38±0.04aA 8.31±0.05aA 7.85±0.16aB 7.28±0.32abC 7.35±0.09abC
30 8.33±0.04abA 8.28±0.06abA 7.73±0.11abB 7.22±0.07abC 7.36±0.09aC
45 8.31±0.08abA 8.22±0.07abcA 7.69±0.06abB 7.16±0.16abC 7.21±0.11bcC
60 8.27±0.06abA 8.14±0.04bcA 7.66±0.11abB 7.13±0.19abC 7.11±0.06cdC
75 8.21±0.09bcA 8.11±0.15cA 7.55±0.25bB 7.13±0.15abC 7.03±0.07deC
90 8.11±0.05cA 8.10±0.09cA 7.50±0.09bB 7.04±0.13bC 6.95±0.08eC
Over-all acceptability 3 8.43±0.09aA 8.38±0.09aA 7.70±0.15abB 7.10±0.08aC 6.36±0.07aD
15 8.39±0.05abA 8.23±0.07abB 7.75±0.05aC 7.11±0.06aD 6.25±0.09abE
30 8.27±0.14abcA 8.22±0.10abA 7.67±0.11abcB 6.95±0.14abcC 6.22±0.12abcD
45 8.23±0.16abcA 8.18±0.18abA 7.61±0.06abcB 7.03±0.15abC 6.17±0.26abcD
60 8.21±0.13abcA 8.16±0.10abA 7.62±0.11abcB 6.88±0.07bcC 6.19±0.07abcD
75 8.19±0.13bcA 8.12±0.19bA 7.55±0.08bcB 6.83±0.14bcC 6.11±0.06bcD
90 8.10±0.15cA 8.10±0.11bA 7.52±0.06cB 6.79±0.17cC 6.00±0.18cD
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=12.

Figure 1. Effects of different pH values on the morphological evaluation of B-LFS and C-LFS.
A1) B-LFS with pH 5; A2) B-LFS with pH 5.5 (control); A3) B-LFS with pH 6; A4) B-LFS with pH 6.5; A5) B-LFS with pH 7. B1) C-LFS with pH 5; B2) C-LFS with pH 5.5 (control); B3) C-LFS with pH 6; B4) C-LFS with pH 6.5; B5) C-LFS with pH 7.

 

The decline in body and texture scores of pH treatments (B-LFS and C-LFS) during the storage periods is presumably due to the proteolytic action for microorganisms in the non-fat portion of the table spread (Patange et al. 2013).

With regards to spreadability, we found changes in the sensory evaluation of spreadability in our treatments during storage attributed to the changes in the overall consistency of the product due to protein degradation and/or decreased water holding by the non-fat fraction resulting in an increased softening of the spread particularly towards the end of the storage period (Patange et al. 2013). The flavor scores of all samples had decreased effects during the storage periods, which can be explained by a loss in freshness (Patange et al. 2013). Furthermore, no rancid flavor in the samples was observed, due to the storing of samples at 4 °C, the addition of k-sorbate and the pasteurization, which led to the inhibition of lipase.

The fresh samples were highly acceptable in overall acceptability. In addition, the scores of samples decreased during the storage periods due to the decline in flavor of the spread as well as to softening of the product (Patange et al. 2013).

It could be noted that the pH treatments (B-LFS and C-LFS) of all the parameters were accepted by the panelists. Furthermore, the highest scores in the sensory evaluations of color and appearance, body and texture, spreadability, flavor and overall acceptability related to B-LFS as follows: 8.77 (pH 5), 8.61 (pH 5), 8.67 (pH 5.5), 8.66 (pH 5) and 8.62 (pH 5) respectively at 3 days, while the lowest scores at 90 days were 6.13 (pH 7 with B-LFS), 5.90 (pH 7 with C-LFS), 6.18 (pH 7 with B-LFS), 6.95 (pH 7 with C-LFS) and 6 (pH 7 with C-LFS), respectively.

3.2. Effects of pH values on the PV of B-LFS and C-LFSTOP

The effects of pH values on the oxidative stability of the pH treatments as measured by the PV test are presented in Table 3. The rate of increasing PVs in each B-LFS and C-LFS with pH values was higher from 3–30 days, but after 30 to 90 days of storage, the rate became lower. The differences among all the pH treatments compared to the control samples were slight. Moreover, the PVs of the pH treatments (B-LFS) were greater than C-LFS, due to the fact that the fat phase in the cow butter for the C-LFS samples contained a color agent (β-carotene), and β-carotene has been reported to be an antioxidant (Mallia 2008). In addition, Britton (1995) reported that β-carotene has been shown to protect lipids from free radical autoxidation by reacting with peroxyl radicals, thereby inhibiting propagation and promoting termination of the oxidation chain reaction. Furthermore, the PVs of all pH treatments increased noticeably (P<0.05) during the storage periods. On the other hand, the pH treatments were in accepted in an industrial setting, because the highest PV was 0.486 (pH 7 with B-LFS at 30 days); however, the samples are considered rancid and unacceptable when the PVs are over 5, while the ideal PV should be below 1–1.5 (Stathopoulos et al. 2009).

It is remarkable that, the oxidation was promoted in our treatments due to the incorporation of air and the commencement of oxidation during the preparation of the butter oil (Alexa et al. 2010). Furthermore, the heat treatments caused the oxidation of samples (Mallia 2008). Interestingly, the viscosity of each B-LFS and C-LFS with pH values increased during the storage periods; however, the viscosity was not able to delay the process of oxidation during the storage periods (Basaran et al. 1999).

Table 3. Effect of different pH values on peroxide values (meq O2 ·kg−1 of fat) of B-LFS and C-LFS
Storage (days) pH 5 pH 5.5 (control) pH 6 pH 6.5 pH 7
B-LFS
3 0.259±0.026cA 0.239±0.024cA 0.246±0.014cA 0.229±0.014dA 0.236±0.013dA
30 0.356±0.024bB 0.383±0.021bAB 0.392±0.017bAB 0.388±0.024cAB 0.414±0.017cA
60 0.390±0.013abC 0.414±0.013abB 0.408±0.015bBC 0.422±0.013bB 0.455±0.009bA
90 0.416±0.017aC 0.443±0.024aBC 0.455±0.026aAB 0.454±0.012aAB 0.486±0.012aA
C-LFS
3 0.195±0.026cA 0.170±0.011cA 0.186±0.024cA 0.198±0.020cA 0.204±0.013dA
30 0.330±0.015bA 0.340±0.012bA 0.319±0.014bA 0.327±0.023bA 0.333±0.026cA
60 0.364±0.011abAB 0.392±0.017aA 0.345±0.014bB 0.355±0.026bB 0.367±0.019bAB
90 0.394±0.027aA 0.417±0.019aA 0.409±0.021aA 0.414±0.027aA 0.427±0.009aA
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.

3.3. Effects of pH values on the OSI of B-LFS and C-LFSTOP

The effects of pH values on the OSI values of the samples are given in Table 4. As indicated, no significant differences (P<0.05) were observed in the OIT between each B-LFS and C-LFS samples and the control samples, while the OIT significantly decreased (P<0.05) during the storage periods. However, our results were in agreement with those observed for the OSI of NaCl and CaCl2 treatments, which are still under study in our lab. Likewise, Krause et al. (2008) noticed that the OSI values for stick cow butter decreased during the storage periods under refrigeration conditions. The correlation between the OSI values and the PVs (Table 3) were reversible. In addition, all OSI values in the pH treatments (B-LFS) were lower than C-LFS (see PV). Furthermore, β-carotene led to a prolonging of the OIT for C-LFS samples as compared to B-LFS.

Table 4. Effect of different pH values on OSI values (h) of B-LFS and C-LFS
Storage periods (days) pH 5 pH 5.5 (control) pH 6 pH 6.5 pH 7
B-LFS
3 4.33±0.09aA 4.27±0.17aA 4.39±0.12aA 4.20±0.16aA 4.24±0.12aA
30 4.21±0.12aAB 4.14±0.08abAB 4.30±0.16aA 4.10±0.10aAB 4.02±0.17abB
60 3.94±0.06bB 3.96±0.16bcAB 4.14±0.10abA 3.99±0.09abAB 3.95±0.09bB
90 3.89±0.08bA 3.86±0.18cA 3.94±0.15bA 3.87±0.09bA 3.90±0.07bA
C-LFS
3 5.33±0.09aA 5.24±0.17aA 5.36±0.15aA 5.47±0.06aA 5.33±0.16aA
30 5.14±0.18abA 5.12±0.13aA 5.23±0.07abA 5.22±0.16bA 5.15±0.09abA
60 4.94±0.13bcA 4.85±0.10bA 5.04±0.11bA 4.95±0.10cA 4.94±0.16bA
90 4.76±0.07cA 4.63±0.05bA 4.75±0.12cA 4.78±0.15cA 4.66±0.14cA
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.

3.4. Effects of pH values on the FAC of B-LFS and C-LFSTOP

The effects of the pH values on the FAC of each B-LFS and C-LFS are shown in Table 5 (a and b). Obviously, the differences among pH treatments (B-LFS) were significant compared to the control samples, while saturated fatty acids (SFA) (at 3 and 90 days), C14 (at 90 days), C15 (at 3 days), C15:1 (at 90 days), C16:1 (at 90 days), C18:2C (at 3 days), and the total FA (at 3 and 90 days) were not significant. Likewise, the differences among pH treatments (C-LFS) were significant compared to the control samples, while the SFA (at 90 days), C14 (at 90 days), C15 (at 3 days), C17 (at 3 days), C18:2T (at 3 days) and total FA (at 3 and 90 days) were not significant. Furthermore, there were changes in the proportions of fatty acids within pH treatments (B-LFS and C-LFS) during the storage periods, presumably due to the degradation of fat under pasteurization and oxidation (Samet-Bali et al. 2009).

With regard to the differences among pH treatments (B-LFS and C-LFS together), we found the percentages of SFA and trans FA (TFA) to be lower and monounsaturated fatty acids (MUFA) to be higher for all the pH treatments in B-LFS than in C-LFS. In addition, the percentages of polyunsaturated fatty acids (PUFA) were close to each other in the B-LFS and C-LFS samples although our results were in contrast with those observed by Varricchio et al. (2007), because they found that buffalo milk fat contained higher amounts of SFA and lower amounts of unsaturated fatty acids than cow milk fat. However, results of the previous authors were from other breeds which are different from the breed of Egyptian buffalo animals. Furthermore, Samet-Bali et al. (2009) reported that the FAC depends on several factors such as animal species, nutrition, climate and environmental conditions. However, our results were in agreement with those observed by Haggag et al. (1987), who reported that unsaturated fatty acids for Egyptian buffalo milks were higher than Egyptian cow milks.

The proportions of C4, C15, C16, C17, C14:1, C15:1, C16:1, C17 and C18:2T with pH treatments (B-LFS) were higher than the C-LFS samples, while C6, C8, C10, C11, C12, C13, C14 and C18:1T with C-LFS were higher than the B-LFS samples. More over, Patel et al. (2002) found that an averages of C4, C16, C17 and C18 in buffalo milk fat was higher than cow milk fat, while C6, C8, C10, C10:1, C12, C14, C14:1 and C18:1 in cow milk fat was higher than buffalo milk fat.

It is clear that the changes in FAC during the storage periods of the samples were slight; although our results were in agreement with those found by Mallia (2008), who mentioned that the differences in FAC before and after 8 weeks of storage were negligible in each unsaturated fatty acids/conjugated linoleic acid enriched and conventional butter. On the other hand, the differences observed during the storage periods of the samples, are presumably attributed to degradation of nonenzymatic, pasteurization and microbiological aspects.

Table 5a. Effect of different pH values on FAC of B-LFS
Storage (days) FAC (%)a
B-LFS
pH 5 pH 5.5 (control) pH 6 pH 6.5 pH 7
SFA 3 68.20±1.95aA 67.79±2.11aA 65.73±2.41aA 66.19±1.24aA 67.26±1.41aA
90 67.16±2.09aA 64.94±1.71aA 66.91±2.83aA 65.67±1.82aA 67.51±1.09aA
C4 3 3.48±0.11aB 2.89±0.08aC 2.76±0.12bC 2.15±0.13aD 3.85±0.16bA
90 3.67±0.14aB 2.32±0.17bC 4.29±0.15aA 2.40±0.12aC 4.48±0.13aA
C6 3 1.56±0.12aA 0.51±0.15bC 0.87±0.14bB 0.63±0.05bBC 1.46±0.20aA
90 1.34±0.17aB 1.00±0.20aC 1.87±0.17aA 0.88±0.02aC 1.63±0.16aA
C8 3 1.05±0.02aA 0.60±0.04aB 0.59±0.26aB 0.60±0.02aB 1.00±0.03aA
90 0.53±0.04bAB 0.45±0.06bB 0.81±0.31aA 0.53±0.05aAB 0.72±0.20aAB
C10 3 1.75±0.05aAB 1.79±0.20aAB 1.44±0.19aB 1.70±0.21aB 2.08±0.27aA
90 1.24±0.05bBC 1.26±0.07bBC 1.55±0.23aAB 0.97±0.20bC 1.84±0.22aA
C11 3 0.08±0.02aBC 0.14±0.05aAB 0.11±0.04aABC 0.05±0.01aC 0.15±0.04aA
90 0.07±0.01aB 0.26±0.07aA 0.10±0.06aB 0.09±0.03aB 0.11±0.02aB
C12 3 2.74±0.05aA 2.68±0.19aAB 1.89±0.18aC 2.05±0.08aC 2.42±0.26aB
90 1.53±0.05bB 2.51±0.26aA 1.69±0.22aB 1.38±0.19bB 1.50±0.21bB
C13 3 0.17±0.03bA 0.20±0.05aA 0.24±0.04aA 0.21±0.05aA 0.20±0.04aA
90 0.32±0.04aA 0.11±0.03aC 0.22±0.06aB 0.14±0.03aC 0.29±0.05aAB
C14 3 10.56±0.59aA 10.55±0.57aA 10.11±0.53aAB 10.15±0.50aAB 9.26±0.50aB
90 9.88±0.60aA 10.11±0.56aA 9.98±0.49aA 9.89±0.61aA 9.72±0.60aA
C15 3 1.61±0.03bA 1.69±0.16aA 1.65±0.15aA 1.69±0.17aA 1.73±0.21aA
90 2.00±0.12aA 1.61±0.06aB 1.76±0.18aAB 1.63±0.15aB 1.55±0.17aB
C16 3 35.45±0.80aAB 35.70±0.83aA 34.44±0.77aAB 35.40±0.74aAB 34.15±0.70aB
90 35.92±0.85aA 34.88±0.72aAB 34.56±0.60aB 36.10±0.75aA 35.40±0.77aAB
C17 3 0.90±0.03aAB 0.92±0.03aAB 0.97±0.09aA 0.89±0.09aAB 0.81±0.03aB
90 0.95±0.02aA 0.81±0.04bB 0.71±0.04bC 0.77±0.04aBC 0.72±0.03bC
C18 3 8.85±0.44aB 10.11±0.38aA 10.65±0.47aA 10.66±0.37aA 10.15±0.42aA
90 9.71±0.48aB 9.64±0.45aB 9.37±0.43bB 10.88±0.38aA 9.54±0.50aB
US MUFA 3 27.09±0.69aB 27.67±0.78aB 29.17±0.76aA 27.79±0.49aB 27.97±0.79aAB
90 26.79±0.74aB 28.75±0.44aA 27.94±0.42aAB 29.14±1.02aA 28.24±1.25aAB
C14:1 3 1.65±0.05aB 1.77±0.17aAB 1.95±0.16aA 1.75±0.18aAB 1.58±0.01aB
90 1.14±0.04bB 1.53±0.23aA 1.63±0.19aA 1.53±0.17aA 1.46±0.18aA
C15:1 3 0.33±0.05aB 0.26±0.12aB 0.43±0.11aAB 0.40±0.02aAB 0.58±0.16aA
90 0.37±0.03aA 0.44±0.05aA 0.35±0.14aA 0.41±0.11aA 0.42±0.13aA
C16:1 3 3.66±0.04aA 3.65±0.17aA 3.57±0.16aA 3.67±0.18aA 3.28±0.06aB
90 3.13±0.20bA 3.16±0.07bA 3.10±0.20bA 3.20±0.17bA 3.04±0.19aA
C17:1 3 0.14±0.02bD 0.24±0.05bB 0.38±0.03aA 0.22±0.04bBC 0.16±0.04bCD
90 0.42±0.03aB 0.60±0.06aA 0.40±0.06aB 0.47±0.03aB 0.47±0.04aB
C18:1 3 21.30±0.80aB 21.76±0.67aAB 22.84±0.62aA 21.76±0.47bAB 22.38±0.62aAB
90 21.72±0.85aB 23.03±0.72aA 22.45±0.63aAB 23.53±0.56aA 22.85±0.73aAB
PUFA 3 1.75±0.19aAB 1.84±0.09bAB 1.48±0.14aB 2.08±0.54aA 1.98±0.25aAB
90 1.93±0.04aAB 2.32±0.13aA 2.30±0.58aAB 2.18±0.10aAB 1.80±0.22aB
C18:2C 3 1.20±0.05aA 1.21±0.04bA 1.15±0.32aA 1.39±0.37aA 1.22±0.03bA
90 1.27±0.01aB 1.53±0.05aAB 1.63±0.40aA 1.45±0.06aAB 1.39±0.04aAB
C18:3n3 3 0.55±0.14aAB 0.63±0.05bAB 0.47±0.04aB 0.69±0.17aAB 0.76±0.22aA
90 0.66±0.05aAB 0.79±0.08aA 0.68±0.19aA 0.73±0.16aA 0.41±0.18aB
Trans FA 3 2.43±0.03aB 2.39±0.15aB 2.37±0.08aB 2.67±0.12aA 2.76±0.11aA
90 2.48±0.11aAB 2.38±0.34aAB 2.34±0.13aB 2.66±0.06aA 2.41±0.27aAB
C18:1T 3 1.87±0.03aC 1.78±0.10aC 1.92±0.21aBC 2.16±0.06aA 2.10±0.05aAB
90 1.91±0.05aAB 1.72±0.30aB 1.77±0.26aAB 2.14±0.06aA 1.72±0.25aB
C18:2T 3 0.56±0.05aABC 0.61±0.05aAB 0.45±0.14aC 0.51±0.06aBC 0.66±0.06aA
90 0.58±0.12aABC 0.66±0.04aAB 0.47±0.14aC 0.52±0.03aBC 0.70±0.03aA
Total FA 3 99.47±2.80aA 99.69±2.65aA 98.74±3.02aA 98.73±2.15aA 99.97±1.84aA
90 98.37±2.81aA 98.39±2.35aA 99.38±2.54aA 99.64±2.80aA 99.96±2.29aA
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column with the same fatty acids. amean±S.D; n=3.
Table 5b. Effect of different pH values on FAC of C-LFS
Storage (days) FAC (%)a
C-LFS
pH 5 pH 5.5 (control) pH 6 pH 6.5 pH 7
SFA 3 75.14±1.67aA 69.32±1.83aB 70.75±1.54aB 68.77±2.06aB 72.01±2.41aAB
90 74.29±2.38aA 70.64±2.54aA 71.00±2.28aA 72.28±1.44aA 70.97±3.55aA
C4 3 3.38±0.18aA 1.50±0.21bC 2.46±0.26bB 2.49±0.18bB 3.45±0.25aA
90 3.68±0.11aB 2.04±0.06aD 3.24±0.17aC 4.25±0.10aA 3.51±0.19aB
C6 3 2.37±0.21bAB 0.91±0.02bC 2.22±0.05bB 1.01±0.04bC 2.65±0.30aA
90 3.27±0.13aA 1.38±0.25aD 2.73±0.23aB 2.86±0.13aB 2.38±0.19aC
C8 3 1.76±0.07aB 0.80±0.07aD 1.51±0.07aC 0.69±0.09bD 2.27±0.11aA
90 1.53±0.16aC 0.69±0.10aD 1.52±0.05aC 1.73±0.08aB 1.98±0.12bA
C10 3 3.07±0.08bB 2.75±0.17aBC 3.72±0.07aA 2.47±0.44bC 4.07±0.42aA
90 3.52±0.17aB 2.52±0.34aC 3.72±0.04aAB 4.14±0.37aA 3.75±0.13aAB
C11 3 0.46±0.06aA 0.28±0.06aB 0.41±0.10aA 0.28±0.03bB 0.42±0.06aA
90 0.48±0.04aA 0.26±0.05aC 0.39±0.06aB 0.41±0.05aAB 0.40±0.01aB
C12 3 6.21±0.27aA 4.58±0.25aC 4.70±0.08aBC 4.61±0.17aC 5.09±0.40aB
90 5.31±0.08bA 3.82±0.33bD 4.22±0.11bC 4.69±0.14aB 4.17±0.22bCD
C13 3 0.36±0.01aA 0.24±0.04aB 0.24±0.10aB 0.23±0.04bB 0.30±0.06bAB
90 0.37±0.04aBC 0.22±0.05aC 0.38±0.15aB 0.59±0.08aA 0.70±0.06aA
C14 3 13.00±0.74aA 12.12±0.68aAB 11.95±0.62aAB 11.89±0.67aAB 11.47±0.69aB
90 12.36±0.73aA 11.83±0.68aA 11.75±0.68aA 11.56±0.65aA 12.04±0.73aA
C15 3 1.29±0.23aA 1.42±0.21aA 1.36±0.13aA 1.29±0.19aA 1.28±0.32aA
90 0.90±0.08bB 1.74±0.27aA 0.83±0.10bB 0.94±0.16aB 1.10±0.26aB
C16 3 33.34±1.03aA 33.27±0.89aA 30.50±0.80aBC 31.84±0.86aAB 30.07±0.91aC
90 32.93±1.02aB 34.73±0.95aA 32.17±0.95aB 32.04±0.89aB 32.05±1.05aB
C17 3 0.83±0.05aA 0.81±0.06aA 0.85±0.08aA 0.79±0.30aA 0.89±0.10aA
90 0.73±0.04bA 0.69±0.42aA 0.22±0.05bB 0.13±0.03bB 0.23±0.03bB
C18 3 9.07±0.58aC 10.65±0.52aAB 10.83±0.50aAB 11.28±0.46aA 10.03±0.55aB
90 9.21±0.52aB 10.72±0.55aA 9.83±0.51aAB 8.94±0.51bB 9.76±0.54aB
US MUFA 3 19.11±0.67aC 23.69±1.14aA 22.99±0.93aAB 24.16±1.04aA 21.94±0.54aB
90 18.73±1.10aB 22.23±0.51aA 21.06±1.04aA 21.77±1.21aA 21.25±1.29aA
C14:1 3 1.03±0.05aB 1.50±0.18aA 1.37±0.34aA 1.42±0.09aA 1.31±0.08aAB
90 0.95±0.15aBC 0.45±0.06bD 1.09±0.05aB 0.91±0.08bC 1.32±0.12aA
C15:1 3 0.33±0.03aA 0.32±0.05aAB 0.23±0.04aB 0.34±0.09aA 0.23±0.04bB
90 0.32±0.10aB 0.25±0.03aB 0.26±0.04aB 0.37±0.07aB 0.60±0.09aA
C16:1 3 1.68±0.25aB 2.63±0.06aA 2.49±0.35aA 2.64±0.26aA 2.62±0.36aA
90 1.47±0.15aB 2.17±0.30aA 1.63±0.13bB 1.45±0.21bB 2.10±0.34aA
C17:1 3 0.13±0.04aB 0.14±0.06bB 0.13±0.01bB 0.18±0.03aB 0.38±0.05aA
90 0.16±0.01aB 0.27±0.04aA 0.27±0.02aA 0.19±0.01aB 0.26±0.04bA
C18:1 3 15.94±1.03aC 19.11±0.89aA 18.78±0.82aAB 19.58±0.77aA 17.40±0.89aBC
90 15.84±0.92aC 19.08±0.86aA 17.82±0.80aAB 18.85±0.85aA 16.97±0.95aBC
PUFA 3 1.92±0.07aAB 2.15±0.39aAB 1.64±0.27aB 2.31±0.43aA 2.00±0.37aAB
90 2.02±0.11aAB 2.19±0.14aA 1.86±0.31aB 2.18±0.07aA 1.78±0.08aB
C18:2C 3 1.17±0.05aBC 1.70±0.29aA 0.97±0.09aC 1.66±0.54aAB 1.36±0.17aABC
90 1.26±0.03aB 1.36±0.09aAB 1.04±0.19aC 1.50±0.09aA 1.23±0.14aBC
C18:3n3 3 0.75±0.06aA 0.45±0.09bB 0.67±0.19aAB 0.65±0.12aAB 0.64±0.20aAB
90 0.76±0.14aA 0.83±0.05aA 0.82±0.12aA 0.69±0.03aAB 0.55±0.06aB
Trans FA 3 3.15±0.38aB 4.05±0.37aA 3.77±0.41aA 3.85±0.20aA 3.51±0.19aAB
90 3.74±0.15aB 4.59±0.65aA 4.06±0.10aAB 3.56±0.06aB 3.65±0.18aB
C18:1T 3 2.59±0.33aB 3.67±0.33aA 3.46±0.45aA 3.43±0.10aA 3.19±0.49aAB
90 3.18±0.20aB 4.16±0.40aA 3.81±0.05aA 3.24±0.09aB 3.16±0.14aB
C18:2T 3 0.56±0.05aA 0.37±0.04aA 0.31±0.04aA 0.42±0.10aA 0.32±0.30aA
90 0.56±0.05aA 0.43±0.25aABC 0.25±0.05aC 0.31±0.03aBC 0.48±0.04aAB
Total FA 3 99.32±1.91aA 99.21±2.98aA 99.16±2.64aA 99.09±3.71aA 99.45±2.40aA
90 98.78±3.52aA 99.64±3.56aA 97.98±3.73aA 99.80±2.64aA 97.65±5.03aA
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column with the same fatty acids. amean±S.D; n=3.

3.5. Effects of pH values on the SFC values of B-LFS and C-LFSTOP

The effects of the pH values on the pH treatments are shown in Table 6 (a and b). The SFC was defined at a number of temperatures, typically from 0 to 40 °C, covering the range of practical uses. The pH treatments (B-LFS and C-LFS) exhibited a gradual decreasing in the SFC with an increase in the temperature from 0 °C to completely melting. In addition, the differences in SFC among the pH treatments and during the storage periods were negligible.

The SFC of the pH treatments (C-LFS) was higher than B-LFS from 0 to 15 °C, while both C-LFS and B-LFS were completely melting at 30 and 35 °C, respectively. Our results resembled those observed for the SFC of CaCl2 and the NaCl treatments (data not shown). Furthermore, there are correlations between the SFC of the pH treatments (from 30 to 35 °C) and the melting behavior, with regard to the high melting zones (Fig. 2).

Figure 2. Effect of different pH values on the melting behavior of B-LFS and C-LFS at 3 days (solid lines) and after 90 days (dashed lines). The letters indicate the main endothermic peaks.

 
Table 6a. Effect of different pH values on SFC of B-LFS
Temperature (°C) Storage (days) SFC (%)a
B-LFS
pH 5.00 pH 5.50 (control) pH 6.00 pH 6.50 pH 7.00
0 3 58.67±1.00bC 58.97±0.60cBC 59.50±1.22aABC 60.97±0.78bA 60.27±0.34bAB
30 60.37±0.52aA 61.17±0.42bA 60.77±0.78aA 60.77±0.96bA 60.13±0.38bA
60 58.80±0.82bC 63.43±0.78aA 60.03±0.76aBC 60.10±0.40bB 60.77±0.62abB
90 57.83±0.50bD 59.10±0.38cC 60.80±0.76aB 62.60±0.68aA 61.63±0.86aAB
5 3 58.00±0.74bcB 58.27±0.78bB 57.80±0.34bB 60.47±0.64bA 59.40±0.30bA
30 60.03±0.60aAB 60.57±0.36aA 59.53±0.72aBC 59.83±0.42bABC 59.40±0.64bC
60 58.90±0.42abB 61.47±0.60aA 58.90±0.80abB 59.70±0.32bB 59.47±0.54bB
90 57.27±0.88cC 58.07±0.76bC 59.77±0.36aB 62.07±1.00aA 61.20±0.74aA
10 3 51.43±0.74abC 52.07±0.80bBC 51.70±0.38bC 54.23±0.78bA 53.13±1.02abAB
30 52.67±0.74aA 53.17±0.88abA 52.50±1.06abA 53.23±0.48bcA 52.57±0.62bA
60 51.93±0.98abC 54.43±0.62aA 52.90±0.88abBC 52.40±0.46cBC 53.33±0.44abAB
90 50.60±0.80bD 52.23±0.62bC 53.93±0.70aB 55.83±0.28aA 54.47±0.98aB
15 3 40.17±0.92aB 40.97±0.36bAB 40.20±0.72abB 42.03±1.02abA 40.90±0.84bAB
30 40.33±0.76aA 40.47±0.38bcA 40.00±0.60bA 40.90±0.70bA 40.27±0.62bA
60 39.90±0.74aB 42.00±0.32aA 41.03±0.40abA 40.93±0.58bAB 41.17±0.86abA
90 39.97±0.38aD 40.13±0.60cC 41.37±0.74aB 43.33±0.84aA 42.43±0.40aAB
20 3 22.87±0.55aCD 23.67±0.37aBC 22.33±0.72bD 25.17±0.62bA 24.57±0.26abAB
30 23.17±0.65aA 23.87±0.50aA 23.40±0.71bA 23.93±0.42cA 23.37±0.35cA
60 23.83±0.54aB 24.30±0.35aAB 24.77±0.71aAB 25.23±0.52bA 24.37±0.43bAB
90 23.61±0.56aC 23.83±0.40aC 25.35±0.58aB 26.48±0.44aA 25.04±0.27aB
25 3 14.13±0.45aB 14.17±0.38aB 13.17±0.63cC 15.37±0.35aA 14.50±0.28aB
30 14.07±0.59aAB 14.17±0.43aAB 13.47±0.50bcB 14.37±0.56bA 13.53±0.34bAB
60 14.23±0.58aC 14.47±0.47aBC 15.43±0.54aA 15.37±0.52aAB 14.50±0.45aBC
90 13.90±0.54aC 14.00±0.46aC 14.50±0.71abBC 15.97±0.40aA 15.07±0.30aAB
30 3 6.77±0.55aC 7.20±0.34aBC 7.30±0.58bcBC 8.23±0.35abA 7.90±0.22aAB
30 7.23±0.35aAB 7.27±0.34aAB 6.67±0.31cB 7.40±0.44cA 6.67±0.19bB
60 7.43±0.26aB 7.77±0.29aB 8.47±0.44aA 8.57±0.36aA 7.63±0.26aB
90 7.07±0.35aB 7.67±0.34aAB 7.53±0.33bAB 7.63±0.49bcAB 8.03±0.39aA
35 3 1.53±0.33aA 1.57±0.29aA 1.50±0.38aA 2.00±0.27aA 1.73±0.37aA
30 1.30±0.34aAB 1.20±0.29abAB 1.47±0.10abA 1.13±0.27bAB 0.93±0.24bB
60 1.43±0.33aB 1.67±0.34aAB 1.87±0.29aAB 2.23±0.33aA 1.63±0.32aB
90 1.43±0.20aB 0.93±0.17bC 1.00±0.13bC 2.30±0.21aA 1.63±0.24aB
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.
Table 6b. Effect of different pH values on SFC of C-LFS
Temperature (°C) Storage (days) SFC (%)a
C-LFS
pH 5.00 pH 5.50 (control) pH 6.00 pH 6.50 pH 7.00
0 3 67.63±0.60bAB 66.80±0.82bBC 65.70±0.52bC 68.47±0.98aA 67.83±0.80bcAB
30 64.90±0.80cB 66.30±0.34bAB 66.37±1.08abA 67.03±0.86bA 66.67±0.68cA
60 68.33±0.62abBC 70.00±0.92aA 67.37±0.56aC 69.33±0.32aAB 69.33±0.94aAB
90 69.07±0.84aA 68.87±0.58aA 67.57±0.72aB 69.23±0.38aA 68.97±0.70abA
5 3 63.67±0.90bBC 63.30±0.72bBC 62.67±0.84cC 65.27±0.62bcA 64.47±0.46bcAB
30 62.20±0.72bC 63.67±0.54bAB 63.23±0.66bcBC 64.57±0.78cA 63.77±0.64cAB
60 65.40±0.70aAB 66.43±0.44aA 64.40±0.74abB 66.43±0.36abA 65.57±0.84abA
90 66.30±0.88aAB 66.17±0.46aAB 64.93±0.78aB 66.77±0.64aA 66.03±0.98aAB
10 3 57.37±1.04bB 56.57±0.38bB 56.67±0.66bcB 58.83±0.60bA 57.67±0.60bcAB
30 55.53±1.26cC 57.10±0.66bABC 56.23±0.98cBC 58.43±0.40bA 57.53±0.80cAB
60 58.60±0.80abBC 59.93±0.76aAB 57.97±0.66abC 60.23±0.82aA 59.03±0.62abABC
90 59.50±0.66aAB 59.63±0.54aAB 58.37±0.38aB 60.30±0.86aA 59.33±1.00aAB
15 3 42.77±0.82bB 43.20±0.80bcB 43.00±0.64aB 44.63±0.56abA 43.03±0.90abB
30 41.07±0.58cC 42.53±0.70cB 40.80±0.22bC 43.83±0.38bA 42.73±0.72bB
60 43.93±0.56abB 44.30±0.76abAB 42.43±0.46aC 45.23±0.86aA 43.87±0.70abB
90 44.47±0.66aA 45.10±0.38aA 42.80±0.58aB 45.57±0.94aA 44.47±0.88aA
20 3 24.33±0.50aB 24.37±0.42abB 23.20±0.57aC 25.40±0.66abA 24.20±0.53aB
30 22.53±0.44bC 23.63±0.62bB 22.90±0.39aBC 24.77±0.47bA 23.33±0.62aBC
60 24.27±0.52aB 24.23±0.50abB 23.40±0.44aB 25.57±0.49abA 24.13±0.54aB
90 25.14±0.48aB 25.11±0.49aB 23.67±0.43aC 26.21±0.56aA 24.27±0.45aBC
25 3 14.47±0.41aBC 15.17±0.40aAB 14.37±0.40aC 15.40±0.42aA 14.43±0.52abBC
30 13.50±0.46bC 14.47±0.40aAB 14.17±0.41aBC 15.30±0.51aA 13.53±0.56bC
60 14.53±0.55aBC 15.10±0.40aAB 13.83±0.40aC 15.73±0.53aA 14.30±0.47abBC
90 14.47±0.58aB 14.43±0.47aB 13.93±0.47aB 16.07±0.43aA 14.50±0.50aB
30 3 6.33±0.39aA 6.57±0.44abA 6.30±0.33aA 7.03±0.50aA 6.50±0.39aA
30 6.17±0.48aAB 6.10±0.29bAB 5.77±0.54aB 6.80±0.41aA 5.97±0.32aB
60 6.23±0.42aB 6.40±0.22abB 6.03±0.51aB 7.27±0.34aA 6.23±0.43aB
90 6.63±0.51aA 6.67±0.20aA 5.87±0.49aB 7.00±0.41aA 6.47±0.36aAB
35 3
30
60
90
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.

It is worth noting that the SFC of our treatments was not increased during the storage periods. In contrast, Laia et al. (2000) found that the SFC values of table margarine showed an increasing trend during storage. The differences in our study could be explained by the experimental samples of previous authors were stored and measured at 20 and 30 °C without the tempering by heating at 100 °C·15 min−1, and then 60 °C·15 min−1 before measuring by pNMR. Fatouh et al. (2003) determined the SFC of buffalo butter oil as a follows: 41.7, 34.6, 28.0, 18.6, 11.9, 9.6, 3.3 and 1.4 g·100g−1 at 0, 5, 10, 15, 20, 25, 30 and 35 °C; however, the differences between our results and those observed by previous authors may be due to seasonal variation, geographical location, the ratio of solid to liquid fat present, and the shape and size of the fat crystals.

The highest and lowest decreasing trends in the SFC values of each B-LFS and C-LFS with pH values were at 15–20 °C and 0–5 °C respectively; however, our results were in agreement with those observed by Nahid (2007). Furthermore, the decreasing rates in the SFC values of the pH treatments (C–LFS) at (0–5 °C), (10–15 °C), (20–25 °C) and (25–30 °C) were higher than in the B-LFS.

3.6. Rheological propertiesTOP

3.6.1. Effects of pH values on the hardness of B-LFS and C-LFSTOP

The effects of pH values on the hardness of the pH treatments are shown in Table 7. The texture evaluation showed that the differences in the hardness of each B-LFS and C-LFS with pH 5 compared to the control samples were slight, while the differences between other pH treatments compared to the control samples were noticeably decreasing (P<0.05); the decline in hardness was in the following order: pH 6>6.5>7. Furthermore, all the pH treatments had an increasing effects (P<0.05) during the storage periods, due to the slow post-crystallization processes and development of bonds within the fat crystal network that took place during storage, which resulted in an increase in the solidness of samples at 4 °C (Alexa et al. 2010). Kolanowski et al. (2004) noticed a slight increasing trend in the hardness of the control sample and fish oil-enriched spreadable fat during storage, which is explained by the changes in the β-structure of fat crystals during storage. Furthermore, Glibowski et al. (2011) found that a slight increasing in the hardness during the storage of O/W emulsions with inulin. Although the hardness in all the pH treatments during storage was increased, it was shown that the hardness was decreased with an increase in pH from 5 to 7. This can be explained by the fact that the stability of B-LFS and C-LFS began to decrease at pH 6 to pH 7 (Fig. 1).

From 0 to 15 °C, the SFC of pH treatments (C-LFS) was higher than B-LFS [Table 6 (a and b)], whereas the C-LFS samples were softer than B-LFS from 30 to 35 °C, thus the SFC values at the 30–35 °C range affected the hardness of pH treatments more than in range of 0–15 °C. Therefore, the hardness of the pH treatments (B-LFS) were slightly higher than C-LFS. However, we also noticed that the pH treatments (B-LFS) began to crystallize at a higher temperature than C-LFS (data not shown). Therefore, it is clear that both the solidifying point and the crystallization are responsible for the hardness test results. The range of the solidifying point for buffalo milk fat (16.0–28.0 °C) was higher than for cow milk fat (15.0–23.5 °C) (Patel et al. 2002), thus the fat phase affected the texture evaluation of B-LFS and C-LFS.

Table 7. Effect of different pH values on the hardness (g)a of B-LFS and C-LFS
Storage periods (days) pH 5 pH 5.5 (control) pH 6 pH 6.5 pH 7
B-LFS
3 54.96±0.61dA 53.07±0.84dB 37.21±0.35dC 37.85±0.38cC 35.48±0.26dD
30 58.42±0.61cA 55.33±0.85cB 38.89±0.34cC 38.24±0.30cCD 37.36±0.29cD
60 61.43±0.71bA 62.21±1.00bA 41.06±0.80bB 39.16±0.28bC 39.00±0.36bC
90 66.70±0.61aA 64.96±0.93aB 43.02±0.38aC 40.85±0.48aD 39.65±0.26aE
C-LFS
3 51.17±0.59dA 51.70±0.61bA 38.07±1.03bB 36.77±0.96cB 34.69±0.57cC
30 54.26±0.65cA 52.25±0.51bB 38.08±0.57bC 37.38±0.72bcC 36.23±0.43bD
60 58.66±0.71bB 62.04±0.55aA 39.13±0.71abC 38.54±0.71bC 37.97±0.58aC
90 64.22±0.51aA 62.87±0.47aB 40.56±0.73aC 40.11±0.77aC 38.05±0.47aD
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.

3.6.2. Effects of pH values on the viscosity of B-LFS and C-LFSTOP

Table 8 shows the effects of pH values on the viscosity of B-LFS and C-LFS. The differences in viscosity of the treatments (B-LFS and C-LFS) with pH 5 were negligible; while with pH 6, 6.5 and 7 they were noticeably decreased (P<0.05) as compared to the control samples. The trends of pH from 7 to 5 were accompanied by a reduction in the negative charge on the protein, which results in a large increase in the viscosity of B-LFS and C-LFS due to partial aggregation (Keogh 2006). Furthermore, phase separation occurred with pH 6, 6.5 and 7 in both B-LFS and C-LFS, and the phase separation was increased with an increase in the pH from 6 to 7, therefore the phase separation affected the viscosity values. Moreover, the differences in all pH treatments during the storage periods were increased significantly (P<0.05) due to the post-crystallization processes (Alexa et al., 2010), and to the changes in the β-structure of fat crystals during the storage periods (Kolanowski et al., 2004). However, Glibowski et al. (2011) found that the viscosity of O/W emulsions with inulin increased during storage due to the conformational changes in the inulin chains.

The SFC values at 25 °C in each B-LFS and C-LFS with pH values were similar, while both C-LFS and B-LFS samples were completely melted at 30 and 35 °C respectively [Table 6 (a and b)]; therefore the pH treatments (B-LFS) were greater than C-LFS in total high melting species, which was in correlation with the hardness and viscosity results (Aguedo et al. 2008), and the viscosity values of the pH treatments (B-LFS) were slightly higher than C-LFS. However, our results have shown that the samples, which had the same SFC values, various crystal types and/or network structures that are formed upon crystallization of hard fats can result in variability in hardness and therefore the viscosity (Braipson-Danthine and Deroanne, 2004). The viscosity was highly correlated with the hardness of samples (Glibowski et al., 2008); however, there are studies that reported an increase in viscosity during storage, for instance Glibowski et al. (2011).

Table 8. Effect of different pH values on the apparent viscosity [ηapp (Pa s) at 100 γs−1]a of B-LFS and C-LFS
Storage periods (days) pH 5 pH 5.5(control) pH 6 pH 6.5 pH 7
B-LFS
3 0.34±0.04cA 0.36±0.06cA 0.21±0.03bB 0.18±0.03bB 0.14±0.03cB
30 0.41±0.05bcA 0.43±0.07bcA 0.23±0.03bB 0.20±0.05bB 0.19±0.04bcB
60 0.49±0.06abA 0.50±0.04abA 0.28±0.06bB 0.30±0.07aB 0.25±0.03bB
90 0.59±0.07aA 0.58±0.06aA 0.37±0.04aB 0.37±0.04aB 0.33±0.05aB
C-LFS
3 0.27±0.04cA 0.26±0.02cA 0.20±0.01bB 0.16±0.04cB 0.16±0.05bB
30 0.39±0.06Ba 0.39±0.07bA 0.26±0.06abB 0.22±0.06bcB 0.18±0.05bB
60 0.47±0.07abA 0.46±0.04abA 0.28±0.04abB 0.27±0.03abB 0.25±0.05abB
90 0.52±0.02aA 0.52±0.03aA 0.34±0.06aB 0.32±0.06aB 0.30±0.08aB
Capital letters mean average values with different letters are statistically significant (p<0.05) within each row. Small letters mean average values with different letters are statistically significant (p<0.05) within each column. amean±S.D; n=3.

3.7. Effects of pH values on the melting behavior of B-LFS and C-LFSTOP

The melting thermogram of the samples before and after 90 days from the storage periods are presented in Fig. 2. The differences in temperatures of the endothermic zones of each B-LFS and C-LFS were negligible with an increase in pH from 5 to 7, while the endothermic zones of F were only detected with pH 6.5 (C-LFS at 3 days) but disappeared after 90 days of storage.

The differences in the temperatures of the deepest peaks (A and G) for pH treatments (B-LFS and C-LFS separately and together) were slight with an increase pH values and during the storage periods. In addition, we noticed that the intermediate zones of C (at 3 days) were shifted to the endothermic zones of B and D after 90 days from the beginning of storage. Furthermore, the endothermic zones of K were detected with pH 5.5, 6 and 7 with C-LFS at 90 days from the beginning of storage. With regard to the intermediate zones of C and H (at 3 days) we found that the temperatures were with in C and H and together were close to each other. Moreover, the differences in the temperature ranges of high melting zones (E and L separately) among the pH treatments and during the storage periods were slight; however, the temperature ranges for the endothermic zones of E (B-LFS samples) were greater than L (C-LFS samples). This mean a slight increase in total high melting species (Aguedo et al. 2008), which was in total agreement with the hardness and viscosity. The temperature ranges of the high melting zones in our experiments resembled those observed for the melting behavior of the CaCl2 and NaCl treatments (data not shown).

4. CONCLUSIONSTOP

The sensory evaluation scores showed that B-LFS and C-LFS with pH values were accepted by panelists. The pH values did not have any influence on protecting of samples against oxidation. No significant differences were observed in the OIT between the pH treatments (B-LFS and C-LFS separately) and the control samples, while the OIT significantly decreased (P<0.05) during the storage periods. An increase in the pH values were accompanied by changes in the FAC of the pH treatments. In addition, the pH values did not affect the SFC among B-LFS and C-LFS separately or during the storage periods. An increase in the pH values led to a decrease in both the hardness and viscosity, and in turn had an increased effect during the storage periods. The changes in the melting profile between pH treatments (B-LFS and C-LFS separately) and during the storage periods were slight; however, there were differences in the melting behavior between B-LFS and C-LFS together.

ACKNOWLEDGMENTTOP

This work was supported by the National Key Technology Research and Development Program in the 12th Five-year Plan of China (Contract No. 2012BAD36B06). 2011BAD02B03/04. Also, the authors wish to express their thanks to the China Scholarship Council (CSC), which financially supported our research.

 

REFERENCESTOP


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