SOME QUALITY INDICATORS OF VEGETABLE OILS UNDER DIFFERENT STORAGE CONDITIONS
The aim of our work was to study the quality of vegetable oils - unrefined sunflower oil (grade I) and soy hydrated oil (grade I). One of the stages of the study was to determine the quality of vegetable oils - peroxide value (characterizes the amount of primary oxidation products of fats - peroxide compounds) and acid number (characterizes the total content of free fatty acids) in the samples of vegetable oils. The acid number was determined by titration (neutralization) of free fatty acids with alkali in the presence of an indicator (phenolphthalein). The peroxide number was determined by titration of the isolated iodine with a solution of sodium thiosulfate. Each study was reproduced 5 times. First of all, the quality indicators of oils (acid number and peroxide number) were determined in samples of fresh oils. Subsequently, the oil was kept for 3 months (in compliance with the recommended requirements for storage of oils and without compliance with the requirements for storage of oils) and re-determined these indicators.
The quality of the investigated vegetable oils was determined by the indicators of acid number and peroxide number in accordance with the established requirements of the State Standards of Ukraine (DSTU EN ISO 660: 2009; DSTU 4570: 2006).
The results of our research show that the level of acid number and peroxide level in samples of fresh oils meet the requirements of the State Standards of Ukraine (DSTU EN ISO 660: 2009; DSTU 4570: 2006) for this type of oil, which confirms the quality of oils and compliance with production , processing and transportation. It is shown that in the samples of aged oils (3 months, subject to storage requirements) the level of acid number and the level of peroxide number increases within normal limits. However, in the samples of aged oils (3 months, without compliance with storage requirements) there is a significant increase in the level of acid number and peroxide number, which does not meet the requirements of State Standards of Ukraine.
As a result of research it is shown that the quality of vegetable oils depends on compliance with the recommended norms and conditions in the process of production, processing, transportation and storage. It is proved that under the conditions of violation of the recommended norms of storage in samples of high-quality vegetable oils the level of quality indicators of vegetable oils - acid number and peroxide number significantly increases.
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