微凍是將水產品保藏在-3℃左右介質中的一種輕度冷凍的保鮮方法。
(一)冰鹽混合微凍 bingyanhunhewushiyizhongyouxiaodeqihanji。dangyanchanzaisuibingli,yanjiuhuizaibingzhongrongjieerfashengxirezuoyong,shibingdewendujiangdi。bingyanhunhezaiyiqi,zaitongyishijianneihuifashengliangzhongzuoyong:一種是冰的融化熱;另一種是鹽的融解吸收融解熱。因此,在短時間能吸收大量的熱,從而使冰鹽混合物溫度迅速下降,它比單純冰的溫度要低得多。
冰鹽混合物的溫度高低,是依據冰中摻入鹽的百分數而決定的,如用鹽量為冰的 29%時,最低溫度可達-21℃。因此,利用冰鹽混合物,可以進行魚貝類的冷卻和凍結。要使魚貝類達到微凍溫度-3℃,一般可在冰中摻人占其重量3%的食鹽。冰鹽混合要均勻,才能達到最好的冷卻凍結效果。
由you於yu冰bing融rong化hua快kuai,冷leng卻que溫wen度du也ye低di,冰bing融rong化hua後hou,冰bing水shui吸xi熱re溫wen度du回hui升sheng,魚yu貝bei類lei溫wen度du的de回hui升sheng也ye快kuai。因yin此ci,在zai冰bing鹽yan微wei凍dong過guo程cheng中zhong需xu要yao逐zhu日ri補bu充chong適shi當dang的de冰bing和he鹽yan,以yi期qi保bao溫wen。
(二)低溫鹽水微凍 由於鹽水傳熱係數大,因此將漁獲物浸在-1~-5℃低溫鹽水中進行冷卻與凍結,其速度很快。
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