Effect of Freeze Drying On Qualities of Fresh Cow Milk and Soy Cheeses

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, 3x103cfu/g bacteria and 2.54 x 106cfu/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, 2.76x103cfu/g bacteria and 2.60 x 106cfu/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 3x103cfu/g to 2.72 x 103cfu/g, 2.54 x 106cfu/g to 2.35 x 106cfu/g, and 2.76 x 103cfu/g to 2.54 x 103cfu/g, 2.60 x 106cfu/g to 2.38 x 106cfu/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.

Istražen je uticaj sušenja primenom procesa liofilizacije, na kvalitet svežeg sira od kravljeg i mleka od soje, sa ciljem da se očuvaju osobine sira u stabilnijem obliku. Uzorci kravljeg i sojinog sira pripremljeni su u svežem stanju sa dimenzijama 2 x 3 cm i debljine od 0,2 cm. Kravlji i sojin sir su podeljeni u 6 porcija težine po 100 g. Početne osobine uzoraka sireva određene su korišćenjem dela od 100 g za svaki uzorak od 500 g koji su sušeni postupkom smrzavanja. Hranjivi, mikrobiološki i senzorni kvaliteti zamrznutih sireva određivani su standardnim metodama. Rezultati su pokazali da sveže pripremljeni sir od kravljeg mleka sadrži : 54,02% vlage, 20,34% proteina, 6,40% pepela, 18,11% masti i 4,25% ugljenih hidrata, 3,52 mg / 100 g natrijuma, 7,02 mg /100 g kalijuma, 5,22 mg /100 g magnezijuma, 6,32 mg/100 g gvožđa, 11.12mg/100g kalcijuma, 3x103cfu/g bacterija and 2.54 x 106cfu/g gljivica. Sveže pripremljeni sojin sir sadrži: 50.89% vlage, 22.05% proteina, 6.31% pepela, 19.02% masti i 4.06% ugljenih hidrata, 3,52mg / 100g natrijum, 7.04mg /100g kalijuma, 5.14mg/100g magnezijuma, 6.20mg / 100g gvožđa, 10.76mg /100g kalcijuma, 2.76x103cfu/g bacterija and 2.60 x 106cfu/g gljivica. Sadržaj vlage i masti u smrznutom osušenom kravljem i sojinom mleku značajno se smanjio (P <0,05) sa 54,02% na 4,28%, 18,11% na 4,05% i 50,89% na 4,19%, 19,02% na 4,30%. Sušenjem primenom procesa liofilizacije značajno je smanjen sadržaj bakterija i gljivica u svežim sirevima; smanjen je sa vrednosti 3x103cfu/g na vrednost 2.72 x 103cfu/g, 2.54 x 106cfu/g, na vrednosti 2.35 x 106cfu/g, na vrednost 2.76 x 103cfu/g , na vrednost 2.54 x 103cfu/g, 2.60 x 106cfu/g, na vrednost 2.38 x 106 cfu/g za kravlje mleko i sojin mlečni sir, retrospektivno. Sadržaj ugljenih hidrata, proteina, pepela, kalcijuma, natrijuma, magnezijuma, zatim ukus, izgleda, aroma i prihvatljivost sireva od kravljeg mleka značajno se povećava (P <0,05) kada se primeni postupak sušenja sa smrzavanjem. Smanjenje količine vlage, broja masti i mikroba u sirevima povećava stabilnost i rok trajanja sira, ako se on pravilno pakuje.