28 



THE SALTING OF FISH. 



chlorine into the fish was chosen as a criterion. The writer realized, 

 however, that this alone was hardly a satisfactory criterion. Even 

 if the salt penetrates fish with equal rapidity, it is no proof that the 

 fish are keeping equally well. Different moisture contents would 

 cause unequal keeping qualities; also, some impurities in the salt 

 might have a greater preservative action than sodium chloride. 



4 



6 



10 



Fig. 4. — Curves show retardation of penetration of salt due tc 10 per cent of sodium 

 sulphate impurity (section one-half to 1 cm. deptli). Figures at loft indicate per cent 

 of chlorine in dry fish ; at bottom, time in days. 



It was considered essential to have some means of measuring the 

 amount and rate of decomposition of protein in order to judge as to 

 how much decomposition took place while any given lot of fish was 

 being salted. If the amount of decomposition at the end of the salt- 

 ing process were known, the real value of any salting method as a 

 means of preserving fish would be known. 



When proteins decompose, they break up, first, into simpler pro- 

 teins, then into polypeptids, and then into amino acids. It is ver^'^ 

 difficult to measure accurately the amounts of simpler proteins and 

 polypeptids in fish. However, the total amino-acid content of fish 

 and brine is easily determined. 



