Description of Challenge
Fish salting to preserve it for a long time. In some countries this is part of culture and is eaten in Easter in the feasts.Fish preservation using salt
Solution
Salted fish, such as kippered herring, is fish preserved or cured with salt. Drying and salting, either with dry salt or brine, was the only widely available method of preserving fish until the 19th century. Salting is the preservation of food with dry edible salt. It is related to pickling (preparing food with brine, i.e. salty water), and is one of the oldest methods of preserving food. Salt inhibits the growth of microorganisms by drawing water out of microbial cells through osmosis. Concentrations of salt up to 20% are required to kill most species of unwanted bacteria.
Smoking, often used in the process of curing meat, adds chemicals to the surface of meat that reduce the concentration of salt required. Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt.
Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated.The water activity in a fish is defined as the ratio of the water vapour pressure in the flesh of the fish to the vapour pressure of pure water at the same temperature and pressure. It ranges between 0 and 1, and is a parameter that measures how available the water is in the flesh of the fish.
Available water is necessary for the microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water or remove it by reducing the aw. Traditionally, techniques such as drying, salting and smoking have been used, many for thousands of years. In more recent times, freeze-drying, water binding humectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used.
