Uticaj procesa liofilizacije na kvalitet svežeg sira od kravljeg i mleka soje

Abstract

The effect of freeze drying on the qualities of fresh cow milk and soy milk cheeses was investigated, with a view to preserve and present them in a more stable and portable form. The cow milk cheese and soy milk cheese used were freshly prepared with dimension of 2 x 3 cm and 0.2 cm thickness. The cow milk and soy cheese were divided into 6 portions of 100 g each. The initial properties of the cheeses samples been determined using a portion of 100 g each, the remaining 500 g were freeze dried. The nutritional, microbial and sensory qualities of the freeze dried cheeses were determined using standard methods. Results showed that freshly prepared cow milk cheese contains 54.02% moisture, 20.34% protein, 6.40% ash, 18.11% fat and 4.25% carbohydrate, 3.52mg/100g sodium, 7.02mg/100g potassium, 5.22mg/100g magnesium, 6.32mg/100g iron, 11.12mg/100g calcium, 3x103 cfu/g bacteria and 2.54 x 106 cfu/g fungi whereas freshly prepared soy cheese contains 50.89% moisture, 22.05% protein, 6.31% Ash, 19.02% fat and 4.06% carbohydrate, 3.52mg/100g sodium, 7.04mg/100g potassium, 5.14mg/100g magnesium, 6.20mg/100g iron, 10.76mg/100g calcium, 2.76x103 cfu/g bacteria and 2.60 x 106 cfu/g fungi. The moisture and fat contents of the freeze dried cow milk and soybean milk decreased significantly (P < 0.05) from 54.02% to 4.28%, 18.11% to 4.05% and 50.89% to 4.19%, 19.02% to 4.30% respectively. Freeze drying significantly decreased the bacteria and fungi contents of fresh cheeses; it decreased from 3x103 cfu/g to 2.72 x 103 cfu/g, 2.54 x 106 cfu/g to 2.35 x 106 cfu/g, and 2.76 x 103 cfu/g to 2.54 x 103 cfu/g, 2.60 x 106 cfu/g to 2.38 x 106 cfu/g for cow milk and soy milk cheese respectively. The carbohydrate, protein, ash content, calcium, sodium, magnesium, taste, appearance, flavour, acceptability of the cow milk cheeses increased significantly (P < 0.05) when freeze dried. Decreases in moisture content, fat and microbial counts of cheeses would enhance its stability and shelf life if properly packaged.