This study was conducted to investigate the effects of processing aids and techniques such as talcum powder (2% w/w), calcium carbonate (2% w/w), warm water dipping (45 °C), combined treatment (warm water dipping+2% calcium carbonate) and control (without adding processing aid) on extractability and quality of ‘Tarom 7’ olive oil as randomized complete block design with three replicates. The results showed that there were no significant differences in the carotenoid content, K232, fatty acid profile or the Cox’s value in the oil obtained from untreated and treated fruits with processing aids. The highest chlorophyll content (0.84 mg/kg), total phenolic content (236.94 mg/kg), paste extractability (8.5%) and the lowest peroxide values (0.32 meqO2/kg), K270 (0.38) were obtained from the oil extracted with 2% talc powder. According to the results, it can be suggested that the 2% talc powder treatment could have a positive effect on olive oil quality and paste extractability.
Este estudio se llevó a cabo para investigar los efectos de los coadyuvantes del procesamiento y técnicas, como talco (2 % p/p), carbonato de calcio (2 % p/p), inmersión en agua tibia (45 °C), tratamiento combinado (inmersión en agua tibia + carbonato de calcio al 2%) y control (sin adición de coadyuvante) sobre la extractabilidad y calidad del aceite de oliva ‘Tarom 7’ en un diseño de bloques completos al azar con tres repeticiones. Los resultados mostraron que no hubo diferencias significativas en el contenido de carotenoides, K232, perfil de ácidos grasos y el valor de Cox del aceite obtenido de frutos no tratados y tratados con coadyuvantes de procesamiento. El mayor contenido de clorofila (0,84 mg/kg), contenido de fenoles totales (236,94 mg/kg), extractabilidad de la pasta (8,5%) y los valores más bajos de peróxidos (0,32 meqO2/kg) y K270 (0,38) se obtuvieron para el aceite extraído con 2 % de talco. De acuerdo con los resultados, se puede sugerir que el tratamiento con talco al 2% podría tener un efecto positivo sobre la calidad del aceite de oliva y la extractabilidad de la pasta.
Olive trees,
Reviews have shown that only 70-80 % of the oil located in the vacuoles of pulp cells can be extracted during the oil extraction process (
It has been reported that most olive oil-producing countries (such as Spain and Italy) have utilized processing aids (co-adjuvant agents and techniques) to improve oil extraction efficiency (up to 10 to 30%) and to reduce the loss in oil in pomace (
However, no report indicating the negative impacts of processing aids on organoleptic and chemical characteristics of oil upon adding the processing aids has been published (
One of the major problems in olive production areas in the Southwest of Iran is the high temperature during the accumulation of oil in the fruit, which causes the amount of oil produced, in particular, ‘Tarom 7’ cultivar of olive, to be reduced. Considering that there is no study on the effect of the processing aids on increasing oil extractability and improving the chemical properties of oil of ‘Tarom 7’ olive cultivar, in Iran, the present study aimed to investigate the effects of processing aids on the oil extractability and quality of olive cv. Tarom 7.
This study was conducted on 15-year-old olive trees of cv. ‘Tarom 7’ grown with 5×6 m between and within rows in the olive orchard collection at Shahid Chamran University of Ahvaz, located in the western area of Karun River in Ahvaz city, Iran (31°20´ N, 48°41´ E, 22 m above sea level).
From each tree, 3 kg of healthy fruits were harvested by handpicking in early November, 2016. Fruits of 15 trees were picked according to the maturity index of 4.2 (
30 kg of healthy olive fruits were harvested and divided into 5 groups of 6 kg (three repetitions of 2 kg each). Each group was considered as a treatment. For the extraction of olive oil, an Abencor system (Commercial Abengoa S.A., Sevilla) was used. First, the olive fruits were crushed with a hammer mill, and the paste was malaxed for 30 minutes in the thermoheater at 25 ºC. Then the paste was centrifuged at 5000 rpm for 30 minutes. Finally, the oil samples were separated and stored at 4 ºC in the dark.
Talc powder (2% w/w) and calcium carbonate (2% w/w) were added to the paste at the beginning of the malaxation stage. For each replicate, 1.96 kg paste was taken from olive fruits crushed with a hammer mill then 40 g talc powder or calcium carbonate were added at the beginning of the malaxation stage.
Healthy olive fruits were immersed in a thermostatic water bath at 45 ° C for 5 min prior to the beginning of the oil extraction process.
First, fruits were treated with warm water dipping (45 ° C for 5 min) before oil extraction, and then, 1.96 kg paste was taken from olive fruits crushed for each replicate and 40 g calcium carbonate were added to the paste at the beginning of malaxation. Olive oil extracted without any treatments was considered as control.
Free acidity (% oleic acid per 100 g oil) was determined as described by the European Community Reg. 2568/91 (
Where N is normality; Mwt is the molecular weight of oleic acid (282); and M is molarity.
The chlorophyll and carotenoid contents in the oil were determined using a spectrophotometer (UNICO UV-2100, manufactured in USA) as described by
Where A is the absorption number and d is cell thickness.
To evaluate the specific extinction coefficient (K232 and K270), 250 mg of oil were diluted with 25 mL of cyclohexane (of spectrophotometry grade) and then homogenized with a vortex for 30 seconds. The absorption of the solution was then determined at wavelengths of 232 nm and 270 nm by a spectrophotometer (UNICO UV-2100, manufactured in the USA) according to the European Commission Regulation EEC/2565/91 (
Peroxide value (milliequivalents of active oxygen per kilogram of oil) was determined according to
Briefly, 30 mL of acetic acid-chloroform solution (3:2 v/v) were added to 5 g of oil. Then, 0.5 mL of saturated potassium iodide solution (KI) was added to the solution and the mixture was left for 1 minute. Subsequently, 30 mL of distilled water were added immediately.
The solution was titrated with 0.1 N sodium thiosulfate until the yellow iodine color almost disappeared. Next, a few drops of starch were added to the solution before being titrated with a 0.02 N thiosulfate solution. Finally, the corresponding peroxide value was obtained from
Where B is the volume of titrant (mL of blank), S is the volume of titrant, mL of sample, N is the normality of the sodium thiosulfate solution.
The total phenolic content in the oil was obtained according to
Where V is the volume of the solution, W is the weight of the oil sample.
The Fatty acid composition was determined according to European Official Methods of Analysis (
The cox value or oxidation index was obtained based on the content in 18-carbon fatty acids, according to the following
Where C18:1, C18:2, and C18:3 are the oleic acid, linoleic acid, and linolenic acid contents, respectively (
These experiments were conducted with a completely randomized design in three replicates. The data were subjected to analysis of variance (ANOVA) using SAS Ver. 9.1 Software. Mean comparison of data was performed using Duncan’s multiple range test at 5% significance level.
As shown in
Oil quality indices | Processing aids treatments | ||||
---|---|---|---|---|---|
Control | Warm water dipping (45 °C) | Calcium carbonate (2 % w/w) | Talc powder (2% w/w) | Warm water dipping (45 °C)+ Calcium carbonate (2% w/w) | |
Chlorophyll (mg/kg) | 0.41±0.19c | 0.70±0.09b | 0.83±0.09a | 0.84±0.11a | 0.57±0.06c |
Carotenoid (mg/kg) | 0.25±0.07a | 0.22±0.12a | 0. 31±0.10a | 0.32±0.11a | 0.32±0.18a |
Free acidity (% oleic acid) | 0.35±0.01a | 0.32±0.01b | 0.26±0.01c | 0.31±0.01b | 0.25±0.01c |
K270 | 0.37±0.06b | 0.33±0.07b | 0.44±0.02a | 0.38±0.05b | 0.45±0.03a |
K232 | 2.79±0.06a | 2.79±0.07a | 2.74±0.05a | 2.73±0.08a | 2.79±0.08a |
Peroxide value (meq O2/kg oil) | 0.40±0.01a | 0.37±0.01b | 0.29±0.01d | 0.32±0.01c | 0.32±0.01c |
Total phenol content (mg/kg) | 174.44±2.03d | 181.38±12.51c | 222.77±3.08b | 236.94±4.21a | 193.86±12.38c |
Values (Mean± Standard Deviation) in the same row with different superscripts are significantly different (p < 0.05) using Duncan’s multiple range test.
Number of replicates = 3
No statistically significant difference in the K232 extinction coefficient was found between the oil extracted from untreated (control) and treated fruits with processing aids and techniques (
Furthermore, the results showed that the processing aids and techniques had a statistically significant effect on the K270 extinction coefficient. The lowest value for the K270 extinction coefficient (0.33) was observed in the oil extracted with warm water dipping, which did not show a significant statistical difference between the oils extracted with either 2% talc powder (0.38) or the control treatment (0.37). The highest value for the K270 extinction coefficient (0.45) was related to the combined treatment (warm water dipping+2% carbonate calcium), which indicated no significant difference with the 2% calcium carbonate treatment (0.41) (
Values (Mean±Standard Deviation) with different letters are significantly different (p < 0.05) using Duncan’s multiple range test. Number of replicates = 3
Moreover, the value for the K270 extinction coefficient in the oils treated with 2% calcium carbonate was approximately 18.91% higher than that of the control treatment. The increased rate of the K270 extinction coefficient in fruits treated with warm water dipping+2% carbonate calcium was 21.62% compared to the untreated fruits (
A significant difference was observed in free acidity between treated fruits treated with processing aids and untreated fruits. The highest and lowest values for free acidity were obtained for the control (0.35%) and combined treatment (warm water dipping+2% carbonate calcium) (0.25%), respectively (
Moreover, the results showed that free acidity was the same in warm water dipping treated and untreated fruits. Also, there was no significant difference in the free acidity in the oil obtained from talc powder and combined treatments (
Based on the results, the acidities of the extracted oils with warm water dipping, 2% calcium carbonate, combined treatment (warm water dipping+2% carbonate calcium), and 2% talc powder were 8.57, 25.71, 25.71, and 11.42% higher than that of the extracted oil under control treatment, respectively (
The data showed that the processing aid treatments had a significant effect on total phenol content. The highest total phenol content (236.94 mg/kg of oil) was related to the oil extracted with 2% talc treatment; while the oil extracted with the combined treatment (warm water dipping+2% carbonate calcium) showed the lowest total phenol content (174.44 mg/kg of oil). Compared to the control treatment, the 2% talc and 2% calcium carbonate treatments exhibited 22.24 and 14.93% higher total phenolic contents, respectively; while the oil extracted with warm water dipping or under the combined treatment (warm water dipping + 2% carbonate calcium) showed lower values for total phenolic content by 6.42 and 10%, respectively.
As shown in
The results indicated that the oils extracted from fruits which were treated and untreated with processing aids showed the same values for palmitoleic acid (C16:1), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), linolenic acid (C18:3), oleic acid/linoleic acid ratio (C18:1/C18:2), monounsaturated fatty acids-to-polyunsaturated fatty acids ratio (MUFA/PUFA), unsaturated fatty acids-to-saturated fatty acids ratio (UFA/SFA), and the Cox value; whereas the value for palmitic acid (C16:0) was different between the oils extracted with processing aids and that of the control treatment (
Fatty acid composition (%) | Processing aids treatments | ||||
---|---|---|---|---|---|
Control | Warm water dipping (45 °C) | Calcium carbonate (2% w/w) | Talc powder (2% w/w) | Warm water dipping (45 °C)+ Calcium carbonate (2% w/w) | |
Palmitic acid (C16:0) | 16.26±0.12a | 16.03±0.11b | 16.30±0.19a | 16.08±0.15b | 16.09±0.08b |
Palmitoleic acid C16:1) | 1.67±0.31a | 1.58±0.23a | 1.59±0.21a | 1.58±0.19a | 1.59±0.23a |
Stearic acid (C18:0) | 2.2±0.35a | 2.22±0.20a | 2.18±0.18a | 2.15±0.15a | 2.19±0.31a |
Oleic acid (C18:1) | 54.3±0.71a | 54.07±1.37a | 53.59±0.98a | 54.53±1.01a | 53.95±0.96a |
Linoleic acid (C18:2) | 12.95±0.61a | 12.87±0.40a | 13.15±0.71a | 13.26±0.81a | 13.16±0.92a |
Linolenic acid (C18:3) | 1.72±0.31a | 1.73±0.22a | 1.68±0.09a | 1.71±0.12a | 1.70±0.26a |
SFAc | 18.46±0.35a | 18.25±0.42a | 18.48±0.32a | 18.23±0.52a | 18.28±0.62a |
MUFAd | 54.97±1.31a | 55.65±1.02a | 55.18±1.32a | 56.11±1.41a | 55.54±0.01a |
PUFAe | 14.67±0.91a | 14.60±0.52a | 15.18±0.62a | 14.97±0.71a | 14.86±0.01a |
MUFA/PUFAf | 3.81±0.40a | 3.82±0.22a | 3.72±0.33a | 3.74±0.62a | 3.73±0.01a |
UFA/SFA | 3.82±0.62a | 3.84±0.42a | 3.78±0.34a | 3.91±0.22a | 3.85±0.01a |
Oleic/Linoleic | 4.19±0.31a | 4.21±0.28a | 4.07±0.21a | 4.11±0.31a | 4.11±0.01a |
a-b Values (Mean± Standard Deviation) in the same row with different superscripts are significantly different (p < 0.05) using Duncan’s multiple range test.
c: Saturated fatty acids. d: Monounsaturated fatty acids. e: Polyunsaturated fatty acids. f: Monounsaturated fatty acids / Polyunsaturated fatty acids. Number of replicates = 3
Number of replicates = 3
The highest and lowest contents in palmitic acid (16.30 and 16.03%, respectively) were related to 2% calcium carbonate and warm water dipping treatments, respectively.
The impact of the use of processing aids and technique treatments on paste extractability is shown in
Chlorophyll and carotenoid are the main pigments in olive oil. These pigments play an important role in oxidative activity (
According to published reports, the extinction coefficient provides a measurement of secondary oxidation processes in the oil that lead to the formation of conjugated dienes (K232), aldehydes, and ketones (K270) (
Previous studies have shown that oil acidity is a result of the formation of free fatty acids upon the activity of a particular type of enzyme to decompose triglycerides (
However, these findings were not in agreement with the results of
The results of the present experiment showed that the processing aids affected the release of phenolic compounds and their transmission into the oil phase. Contrary to the pigments which develop in particular parts of the fruit, phenolic compounds are found in most parts of fruit in various forms, i.e. water-soluble or fat-soluble. The processing aids significantly affected the solubility and release of these compounds. Among other treatments, the 2% talc powder imposed the largest impacts on the solubility and release of these compounds.
Although the results of this study were inconsistent with previous reviews about exposing olive fruits of ‘carrascina’, ‘Galega’, ‘Cobrançosa’ and ‘Vulgar’cultivras to warm water and talc (
According to existing reports, peroxide value represents the primary oxidation of the oil and serves as an important factor in determining the quality of olive oil, indicating whether the oil is healthy or rather spoiled. When olive oil or olive fruit is exposed to free air where it comes in contact with oxygen in the presence of adverse temperature conditions, primary oxidation of the oil or fruit begins; this process then contributes to increased peroxide content in the oil and the formation of free radicals in the oil (
The difference in the results could possibly be due to the type of cultivar, concentration, and type of processing aids.
The results of this study indicated that the profile of fatty acids and Cox value were not affected by processing aids. these findings were similar to the results of
According to the results, adding processing aids increased paste extractability. While paste extraction rate was lower in untreated fruits with processing aids. In fact, the highest paste extractability was related to the 2% talc powder treatment. The results of this research were in agreement with the reports published by
In this experiment, the processing aids and techniques used could facilitate the process of oil extraction and enhance the efficiency of the process compared to the control by contributing to the coalescence of fine and coarse oil droplets and altering the cell wall and membrane to release larger amounts of oil content from the cells and other fruit components. According to the results, the value of oil extracted with 2% talc powder was greater than the other treatments. Furthermore, the values for chlorophyll content and total phenol content in oils extracted with 2% talc powder were higher than the control and other treatments. The amount of acidity and peroxide value were significantly reduced in oils obtained by adding 2% talc powder compared to the control treatment. Therefore, the best processing aid used in this study was the 2% talc powder treatment, which was able to improve oil extraction yield and oil quality parameters.
This study was supported by research deputy of Shahid Chamran University of Ahvaz, Iran. We thank the anonymous reviewer for his/her most helpful comments.