Fillets of lean (cod) and fatty fish (herring and mackerel) were stored in a hypobaric chamber at -1.1, -0.55, and 0°C under a pressure of 10 mm Hg. The atmosphere was changed twice hourly, and had a relative humidity greater than 95%. The growth of bacteria in the filets was slowed, and a qualitative shift in the microflora occurred, compared with fillets held at 0°C on ice. The rate of development of rancidity in the fatty fillets was also decreased. Because of these changes, a lo-15% extension in keeping times of hypobarically stored fillets was obServed at 0°C. The storage life of fillets at low pressure was further extended by the decrease of storage temperature and by treating the fillets with Na, H EDTA. EDTA did not increase the storage life of the fatty fillets.
The apparently good shelf stability of salt minced fish produced by the quick salting technique is due to the very low halophiiic bacteria content. The nature of the quick salting method and the quality of the curing salt used are responsible for this condition. With no loss in palatability the salted minced fish was rendered stable at 35°C either by reducing water activity to 0.7 or by adding 0.3% sorbic acid into the minced flesh with the curing salt. A sorbic acid residue in the desalted product of 0.1% was less than the limit allowed in some food products.
The recovery of bacterial extracellular alkaline and neutral proteinases was investigated using mineral hydrocolloid bentonite in combination with the organic flocculant Hernostan B for the removal of solid compounds and cells from fermentation broth. The flocculation was effective in the pH range of 7.0 -8.5at concentrations of bentonite of 2.0-5.0 g . dm-3 and Hernostan B of 1.0-5.0 g . d~n -~. The results show that, by means of this technique, it is possible to achieve a yield of proteinases above 90% on a laboratory, and up to 85% on a pilot plant scale.
SUMMARYRecovery of a bacterial alkaline proteinase after treatment of the fermentation broth with 16 different flocculating additives has been investigated. The polyelectrolyte Sedipur TF 5 was the most effective at 150 ppm and pH 7.0-9.0, giving a 74% yield of enzyme activity.
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