Abstract
The raw milk produced in Korea was heated at $70^{\circ}C$, $75^{\circ}C$, $80^{\circ}C$, $85^{\circ}C$, $90^{\circ}C$, $95^{\circ}C$ and $100^{\circ}C/15sec.$. The changes in chemical composition and microbiological aspects of the milk were summarized as following results: 1. In high temperature pasteurized milks as the heat treatment increased, pH value decreased but protein, fat, lactose and ash did not show significant changes in their contents while casein nitrogen and non-protein nitrogen increased but non-casein nitrogen and filterable nitrogen decreased in their contents. 2. Calcium content of raw milk decreased from 119.79mg/100g to 111.86mg/100g at $75^{\circ}C$ and to 106.24mg/100g at $100^{\circ}C$. Vitamin C decreased from $1.37mg/100m{\ell}$ of raw milk to $1.15mg/100m{\ell}$ at $75^{\circ}C$ and $0.94mg/100m{\ell}$ at $100^{\circ}C$. Artificial digestibility increased as the heat treatment got higher. 3. Viable bacteria counts decreased from $9.0{\times}10^3/m{\ell}$ at $75^{\circ}C$ to $3.4{\times}10^2/m{\ell}$ at $100^{\circ}C$. Coliforms were not found at $70^{\circ}C$ and thermoduric bacteria, thermophiles, psychrotrophic bacteria, mould and yeast decreased rapidly as the heat treatment increased. 4. The results of Keeping quality test for high temperature pasteurized milk showed that the' milks preserved at $25^{\circ}C$ and $37^{\circ}C$ were clotted just after 1 day but the milk preserved at $4^{\circ}C$ showed good shelf life which did not have any deterioration in titratable acidity, microorganisms and com positions.
국산우유(國産牛乳)를 원료(原料)로 한 적정(適正) 살균조건(殺菌條件)을 검토(儉討)하기 위하여 원유(原乳)를 $70^{\circ}C$, $75^{\circ}C$, $80^{\circ}C$, $85^{\circ}C$, $95^{\circ}C$ 및 $100^{\circ}C$의 각온도(各溫度)에서 15초간(秒間) 가열살균(加熱殺菌)하고 처리유(處理乳)의 화학적(化學的) 조성(組成) 및 미생물학적(微生物學的) 성상(性狀)의 변화상태(變化狀態)를 시험(試驗)한 결과(結果)는 다음과 같다. 1. 고온처리유(高溫處理乳)는 가열온도(加熱溫度)의 상승(上昇)에 따라 pH가 저하(低下)하였고 단백질(蛋白質), 지방(脂肪), 유당(乳糖) 및 회분등(灰分等)은 변화(變化)가 거의 없었으며 Casein 태질소(態窒素)와 비단백태질소함량(非蛋白態窒素含量)은 증가(增加)하고 비(非)Casein 태질소(態窒素) 및 여과성질소함량(濾過性窒素含量)은 감소(減少)하였다. 2. Calcium함량(含量)은 원유(原乳)의 119.78mg/100g로부터 $75^{\circ}C$ 가열(加熱)에서는 111.86mg/100g, $100^{\circ}C$ 가열(加熱)에서는 106.24mg/100g로 감소(減少)하였으며 Vitamin C에 있어서는 원유(原乳)의 $1.37mg/m{\ell}$로부터 $75^{\circ}C$ 가열(加熱)에서는 $1.15mg/100m{\ell}$, $100^{\circ}C$ 가열(加熱)에서는 $0.94mg/100m{\ell}$로 감소(減少)하였고 인공소화율(人工消化率)에 있어서는 가열온도(加熱溫度)의 상승(上昇)에 따라 증가(增加)하였다. 3. 생균수(生菌數)는 $75^{\circ}C$ 가열(加熱)에서 $9.0{\times}10^3/m{\ell}$로, $100^{\circ}C$ 가열(加熱)에서는 $3.4{\times}10^2/m{\ell}$로 감소(減少)하였고 대장균(大腸菌)은 $70^{\circ}C$ 가열(加熱)에서 검출(檢出)되지 않았으며 내열성균(耐熱性菌), 호열성균(好熱性菌), 호냉성균(好冷性菌) 및 곰팡이, 효모수도 가열온도(加熱溫度)의 상승(上昇)에 따라 크게 감소(減少)하였다. 4. 고온살균처리유(高溫殺菌處理乳)의 보존시험(保存試驗) 결과(結果) $25^{\circ}C$ 및 $37^{\circ}C$에 있어서는 l일후(日後)에 응고(凝固)하였고 $4^{\circ}C$ 보존(保存)에 있어서는 10일(日)까지 산도(酸度), 일반조성분(一般組成分), 미생물수등(微生物數等)이 변화(變化)가 거의 없어 우수한 보존성(保存性)을 나타내었다.