A Review on Solar Drying of Fish

Abstract

Oman is one of the larger fish producers in the region. Due to high perishable rate of fish products, many preservation techniques were used such as smoking, drying, chilling, brining and freezing. Solar drying is the most popular technique due to its simplicity and low cost compared to other techniques. Objective. This study aims to review the different types of solar drying techniques and highlight the quality measures of solar dried fish. Review findings. Solar drying techniques can be divided into three types; open-sun drying, direct and indirect solar drying. The open-sun drying is the most adoptable method because it is the cheapest preservation technique. However, this technique has several drawbacks such as the uncertainty of weather, large implementation area, time-consuming, poor drying rate, high labour costs, attacking by insects, microorganism and birds, and mixing with dust and foreign materials. Solar dryers, on the other hand, overcome most of the drawbacks associated with open-sun drying. They have shorter drying time and higher drying rate, and at the same time they enhance the physical properties of dried fish. For better understanding of the drying processes many regression models were used and the exponential model was found to be the best fitted model describing the drying behaviour. The fish have very good nutritional value due to higher amount of proteins, lipids and ash contents with comparison to fresh fish. For higher shelf life fish has to meet certain characteristics with respect to pH, water activity, microbial load, total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N) and enzymatic autolysis. For a very good quality, the pH must be ranging from 6.0-6.9 and the water activity must be lower than 0.7. The TVB-N and TMA-N are indicators of spoilage and their upper acceptable limits are 10-15 mg/100g and 35-40 mg/100g, respectively. Total plate count (TPC) and total fungal count (TFC) are two attributes used to assess the microbiological quality of fish products. The autolysis changes in the fish lead to spoilage as a result of the production of biogenic amines and microbial growth. Conclusions. Studying the health aspect of dried fish is very important for the human body to obtain a greater proportion of proteins and important substances away from the harmful chemicals that may appear in traditional draying technique.