大黄鱼盐干加工过程中含氮物变化特点的一些考察

鱼类盐干加工是我国广大渔区重要加工保藏方式之一。研究它加工过程中鱼体蛋白质和各种含氮物有关生物化学变化特点,用来考查加工制品的品质和食用价值以及工艺方面问题是具有重要意义。我们在进行舟山地区大黄鱼盐干品防止腐败变质和减少用盐量的研究中,对大黄鱼无头鮝在加工过程中含氮物的变化特点进行了研究。测定了在腌干加工过程中盐渍平衡、盐渍保藏、漂淡三个阶段总氮量、蛋白氮、非蛋白氮、氨基氮、挥发性盐基氮。考察了在腌制过程中苯甲酸和醋酸作为防腐剂和减少用盐量时对含氮物变化的影响。现将初步研究结果报告如下。

STUDIES ON THE CHANGES OF SOME NITROGENEOUS COMPOUNDS OF LARGE YELLOW CROAKER(PSEUDOSCIAENA CROCEA)DURING SALTING AND DRYING PROCESSES

A number of Large Yellow Croakers (Pseudosciaena crocea) of the Chu Shandistrict were cured under local processing conditions in summer, 1964. Two dif-ferent concentrations of NaCl were employed for comparison of final results.One was 29% of NaCl alone and the other, 24% NaCl plus 0.1% benzoic acidand 0. 1% acetic acid as preservatives. The curing process was technically divided into three periods: (1) saltingperiod of about 8 days, at the end of which NaCl concentration both in thebrine and in the fish bodly nearly reached an equilibrium. (2) keeping periodof almost two months, during which time the cured fish were kept in the ori-ginal brine pending further treatment. and (3) de-salting period, lasting only20-30 minutes, when the NaCl content of the cured fish was lowered throughdialysis. At the different intervals of each period the fish samples as well as thebrine were drawn for chemical analysis of their nitrogeneons components, namelytotal N, protein N, non-protein N, amino N and volatile base N. Analytical results showed that nutrients lost both in periods 1 and 3 of theprocesses were mainly soluble nitrogeneous material. However, in period 2 thedegradation of the fish protein was mainly due to the active enzymes or micro-organisms that may be present in the brine. Addition of preservatives (benzoic and acetic acids) apparently inhibited orreduced putrefaction. Hence, it helped to preserve both the nutritive and flavor-ing qualities of the cured fish. Three suggestions are made for the improvement in the technology of fishcuring in Chu Shan Area: (1) The salting period should be ended as soon as the NaCl and mixture content of the fish body reaches an equalibrium, in order toavoid degradatory changes of the nitrogeneous substances of the fish. (2) Addsome preservative to inhibit hydrolytic actions of micro-organisms, in case thesalting period must be prolonged. (3) The reduction of the amount of NaCl inthe curing process should be given serious consideration, becanse high concen-tration of NaCl eventually leads to the loss of soluble nitrogeneous materialfrom the fish and thus lowers the nutritional and eating qualities of the finalproduct. Addition of preservatives can safely reduce the use of NaCl in thesalting process.