INFLUENCE OF STORAGE PERIOD ON THE CONSUMER PROPERTIES OF DAIRY BEVERAGES

Abstract

Sour milk products, or they can also be called fermented products, occupy a special and very important place in the human diet among the huge range of dairy products. Fermented milk products have dietary and medicinal properties, high biological and nutritional value. The technological conditions of production, the type of fermented milk products, terms and conditions of their storage have a significant influence on the quality of finished fermented products. Thus, the purpose of this work was to study the consumer properties of industrially produced fermented milk drinks depending on their type and shelf life. Dairy raw materials, from which fermented milk products were made, were also studied, compliance with norms and standards regarding the quality of dairy raw materials was investigated. The material for the study was kefir of different fat content (1% and 3.2%) and ryazhenka with a fat content of 2.5% produced by JSC «Zhytomyr Maslozavod». Also, the material for our research was raw milk, which was sent for processing to JSC «Zhytomyr Maslozavod». According to the results of research on the raw milk, it was found that it meets all the standards and requirements for raw milk and corresponds to the grade of extra and first class. About 14% of milk received for processing with titrated (total) acidity below 16 0T. In the vast majority of milk (85%), the index of titrated (total) acidity was 16-18 0T. And only 1% of raw milk had an acidity higher than 18 oT. Since we needed samples of different ages of their storage, all fermented milk drinks were purchased at retail outlets in the city of Zhytomyr and, at the time of research, corresponded to a 3-day period from the time of their production. The analytical part of the experiment included the study of organoleptic and physico-chemical properties of fermented milk drinks on the 3rd, 7th and 14th day of their storage. It was established that according to organoleptic and physicochemical indicators, all fermented milk drinks on the third day of storage met the requirements of the relevant national standards and differed among themselves in terms of indicators, depending on their type and fat content. Kefir with a high fat content (3.2%) and ryazhanka with a fat content of 2.5% showed the highest organoleptic value, which includes indicators such as color, taste, smell, consistency and appearance. Kefir with a low fat content (1%) was organoleptically evaluated worse. It had the thinnest consistency and the sharpest and most sour taste. After 14 days of storage in refrigerated conditions (temperature 5oC), the color, taste and smell of all fermented milk drinks deteriorated somewhat, especially in kefirs with a lower fat content in the composition. In kefir with a fat content of 1%, a more liquid consistency was observed with slight gas formation in the form of individual points. Kefir with a fat content of 3.2% and ryazhenka with a fat content of 2.5% received the highest sensory evaluation result at the end of the shelf life.