Influences of salt and koji contents on chemical properties of fish sauce from tilapia frames

Abstract

Influences of salt (5%–20% w/w of digested material) and soybean koji (3%–10% w/w of digested material) on chemical properties of fish sauce from tilapia frame after 4 months’ fermentation using response surface methodology was studied. Results found that the salt content showed quadratic effect on ammonia nitrogen and amino nitrogen while linear effect on formaldehyde nitrogen and NaCl contents of samples were observed (P < 0.05). Estimation response surfaces revealed that the formaldehyde nitrogen, ammonia nitrogen and amino nitrogen contents decreased while NaCl content increased as salt content increased. For the effect of koji, the significant effect of koji content on non-enzymatic browning value of fish sauce samples in linear manner was observed (P < 0.05). The non-enzymatic browning value of sample increased as koji content increased. The both of salt and koji contents showed the linear effect on total acidity value while two-factor interaction terms on total nitrogen of sample was found (P < 0.05). For the consumer acceptability testing, an acceptance score of the incubated fish sauce sample with a values of 6.50–7.43 (like slightly to like moderately) was obtained. The results showed that it is possible to make a good quality fish sauce from tilapia frame by-product.