Flavour changes due to effect of different packaging materials on storing of cottonseed oil, hydrogenated oil and margarine

Aceite de semilla de algodón decolorado, aceite de palma parcialmente hidrogenado y margarina fueron envasados en latas metálicas y botellas de plástico blancas y almacenados durante siete meses a temperatura ambiente en estantes. Se relacionó la evaluación de la estabilidad de los aceites con la deterioración del flavor. La deterioración del flavor producida en aceite de semilla de algodón decolorado, aceite de palma parcialmente hidrogenado y margarina fue observada debido al aumento en la cantidad de aldehidos y cotonas que juegan un importante papel en la deterioración de los aceites. A partir de los resultados obtenidos se encontró que las latas metálicas ofrecieron una adecuada y mejor protección frente a la deterioración que los envases de plásticos para aceite de semilla de algodón y aceite de palma parcialmente hidrogenado. Por otra parte, los recipientes de plástico fueron mejores para el almacenamiento de margarina y esto es debido a la presencia de agua y sales en ella en una proporción del 16% y 2% respectivamente.


INTRODUCTION
Exposure to diffuse daylight or artificial light is well known to cause a marked acceleration in the deterioration of unsaturated oil.This deterioration is probably sensitized by chromophoric impurities of oils, especially residual natural dyes and pigments, which absorbed strongly in visible or near ultraviolet light (1 -3) and cause significant deterioration of oil quality in the presence of air (4)(5)(6)(7)(8)(9).
Volatile oxidation products responsible for flavour alteration were studied by many authors (10)(11)(12)(13) who found that fatty substances underwent autoxidation to produce small quantities of low molecular weight aldehydes, ketones and acids which have very objective odour and taste.This piece of work was done to study the effect of packing materials on storing of lipids.

MATERIALS AND METHODS
Bleached cottonseed oil, partially hydrogenated palm oil and margarine were stored in metal cans and white plastic bottles with air in the headspace and served at room temperature during the whole periodo of investigation.
Suitable amount of aroma -concentration was prepared according to the method proposed by Sattar Co-workers (14).
The method of preparation of aroma concentrated was carried out by heating the samples on silicon oil (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) http://grasasyaceites.revistas.csic.esbath at 190° C but for margarine at 135° C in 500 ml round bottom flask under reduced pressure (about 30 mm Hg) for two hours.The aroma was collected in traps cooled to -20° C using crushed ice-salt acetone mixture.The collected distillated was thrice extracted with peroxide-free ether/and the combined extracts were dried over anhydrous sodium sulphate.The extract was filtered and ether was then removed by distillation at 40° 0 to obtain the aroma concentrate.
Flavour of cottonseed oil, partially hydrogenated palm oil and margarine was detected at zero time (control), four and seven months storing by using gas liquid chromatography, the analysis was run using varian 3700 gas chromatograph, equipped with flame ionization detector under the following conditions: -Column package 10% diethylene glycol succinate (DEGS) on chromosorb W (80-100 mesh). -

RESULTS AND DISCUSSION
Volatile components of control sample (zero time storing), were found to be composed of butanoic acid, 2-hexanol, methyl valerate, hexanoic acid, methyl hexanoate, heptanal and 3-ethyl hexanone (Table I).These volatile components constituted more than 79% of the total volatile components of bleached cottonseed oil at zero time storing.
In metal can backage 2-hexanol increased after four and seven months, on the other side butanoic acid, methyl valerate, hexanoic acid, methyl hexanoate and heptanal completely disappeared after storing for four months for metal can and plastic containers propanal, pentanal, 2-hexanol, 2-4, nonadienal and undecanol formed about 66.0% and 58.0% after storage for four months in metal can and plastic container respectively, while they composed 65.6% and 55.0% after storage for seven months in both packages, respectively.
The deterioration of flavour developed from hydrogenated oil is reported in (Table II).A remarkable oxidation was observed due to increase amount of hexanal.Ketones played an important role in the flavour of partially hydrogenated palm oil.Alcohols and ester were also identified in the aroma of partially hydrogenated palm oil.
The changes in the flavour developed from margarine stored in metal can and white plastic package for four and seven months compared with control sample were reported in (Table III).
A remarkable oxidation was observed due to increase of aldehydes and some ketones.Short chain fatty acids were probably produced by chain breaking through autoxidation and they play a major role in the odour of margarine.Alcohols generally played a minor role in the aroma of margarine.-Propanal increased in both metal cans and white plastic package after 7^^ month storage, while hexanal increase in both 4*^ and 7*^ months storage in two kinds of package in cottonseed oil.
-Decanoic acid was highly increased in margarine in both 4th and 7^^ months storage and in the two kinds of packaging materials.
-Nonenal and 2,4-nonadienal were highly increased in partially hydrogenated palm oil in both kings of package.
Generally from all these results it could be traced that propanal might arise from 1 -decomposition of the hydroperoxide of linolenate, 2-stepwise oxidation of nnonanal through the G2.4 alkanals to propanal (10) and 3-oxidation of n-propanol with alcohol dehydrogenase.
Alcohols may be derived from unsaturated acids by the formation and reduction of the corresponding aldehydes (17).2,4-nonadienal could be postulated as being formed from linoleic acid as proposed by Hoffmann (18).These results are in agreement with the peroxide value of bleaching cottonseed oil, partially hydrogenated palm pol and margarine (Table IV).

Figure 1 -
Figure 1-4 show the characteristic volatile components of cottonseed oil, partially hydrogenated palm oil and margarine during storing period.From these figures we can trace:-Propanal increased in both metal cans and white plastic package after 7^^ month storage, while hexanal increase in both 4*^ and 7*^ months storage in two kinds of package in cottonseed oil.-Decanoicacid was highly increased in margarine in both 4th and 7^^ months storage and in the two kinds of packaging materials.-Nonenaland 2,4-nonadienal were highly increased in partially hydrogenated palm oil in both kings of package.

Table III (
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