RESEARCHES ON THE EVOLUTION OF CONCENTRATED FRUIT JUICES QUALITY AT STORAGE

Abstract

The purpose of the study was to compare some concentration methods of clear fruit juices without added chemicals, foaming agents, clarification. For this study we chose three apples varieties (Idared, Golden Delicious and Red Delicious) and they were processed into clear juice using a robot type fruit squeezer. Apple juices were concentrated in a Rotavapor type concentrator at 40°C temperature and 175 mbar pressure from almost 12% dry matter to almost 25%. The samples were examined over a period of 30 days shelf life at refrigeration temperature. The physical and chemical determinations were: acidity, pH and dry matter variation. We also made for juice the following microbiological determinations: total number of yeasts and moulds, mesophilic aerobic bacteria and osmofile yeasts. The three types of apple juice concentrates have shown stability all over the storage period at refrigeration temperatures (6-8°C), their aspect being determined by the acidity variation of the products. We also noticed that the dry matter variations in the three types of concentrated juices are constant during the storage period. The difference between the values of the dry matter is made by the apple varieties, as follows: for Golden Delicious is higher (26.3%) than the one for Idared which is the lowest (25%). After the microbiological analyses have been made we reached the conclusion that the concentrated apple juice of Idared variety has the greater loading number of microorganisms ( mesophilic aerobic bacteria - 13 x10⁶).