EFFECTS OF HEAT-TREATMENT AND POSTTREATMENT HOLDING TIME ON RENNET CLOTTING OF MILK
EFFECTS OF HEAT-TREATMENT AND POSTTREATMENT HOLDING TIME ON RENNET CLOTTING OF MILK
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DOI：
10.3168/jds.s0022-0302(85)80854-7
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发表时间：
1985-01-01
影响因子：
3.5
通讯作者：
BROWN, RJ
中科院分区：
文献类型：
--
作者：
USTUNOL, Z;BROWN, RJ
生全脂牛奶的样品分别在25度、50度和75度下加热。温度为0、30、60、120和240分钟。加热后，每个样品被细分成保持在0度的部分。C加热0、30、60和120分钟。在第二个实验中，牛奶样品分别在25度和50度的温度下加热。C的间隔和以前一样，但在75度。C分别为5、10、15和20分钟。在所有3种温度下加热的样品保持在0度。热处理后，在室温下放置30分钟。加热后，测量每个样品的pH值，并通过formaggraph仪器测定恒定凝乳酶浓度下牛奶的凝乳酶凝血特性。0度冷藏。温度升高2小时对牛奶的pH值或凝血酶凝血特性没有显著影响。从25度增加到50度。C和长时间加热降低pH值和凝血时间。牛奶加热时间对凝乳凝固率和切割时间有影响。当牛奶在75度加热时。C、凝血时间、凝乳固形率、凝乳切割时间明显缩短。牛奶在75度加热。C治疗30分钟或更长时间未发生凝血。
Samples of raw whole milk were heated at 25, 50 and 75.degree. C for 0, 30, 60, 120 and 240 min. After heating, each sample was subdivided into portions that were maintained at 0.degree. C for 0, 30, 60 and 120 min. In a 2nd experiment samples of milk were heated at 25 and 50.degree. C for the same intervals as before but at 75.degree. C for only 5, 10, 15 and 20 min. Samples heated at all 3 temperatures were kept at 0.degree. C for 30 min after heat treatments. Following heating, pH of each sample was measured, and rennet clotting properties of milk at a constant rennet concentration were determined by the Formagraph instrument. Cold storage at 0.degree. C for up to 2 h did not have a significant effect on pH or on rennet clotting properties of milk. Increase from 25 to 50.degree. C and prolonged heating reduced pH and clotting time. Curd firming rate and cutting time were affected by the time milk was heated. When milk was heated at 75.degree. C, clotting time, curd firming rate, and cutting time of curd were reduced markedly. Milk heated at 75.degree. C for 30 min or longer did not clot.