Improved qualities of salt-reduced tilapia surimi by adding konjac glucomannan: Insight into the edible traits, gel properties and anti-freezing ability

Abstract

This study aimed to investigate the potential of different levels (0.05%, 0.1%, 0.15%, 0.2%, and 0.25%, w/w) of konjac glucomannan (KGM) supplement in improving the gel quality and anti-freezing ability of salt-reduced tilapia surimi (1.25% NaCl, w/w). Directly reducing the salt addition level generated adverse effects on the water retention of gel, network structure, and texture compared to those of surimi added with normal salt level (2.5% NaCl). A proper KGM supplement (0.15%, w/w) effectively improved the low-salt surimi gel strength and whiteness, accompanied by less liquid loss. The microstructure results intuitively illustrated that excess addition of KGM was prone to absorbing sufficient water in the composite gel and hinder protein-protein cross-linking, rendering the continuous network looser. In terms of frozen storage, the salt-reduced surimi supplied with KGM shortened the time spent in forming the maximum ice crystals. The mechanical damage induced by ice crystals and the subsequent thawing loss of frozen surimi were thus alleviated. Supplement of KGM added to low-slat frozen surimi could enhance freezing-thawing stability by the modification of ice crystals, limited water migration, and inhibition of network destruction. The TBA and rheology results further indicated that KGM displayed anti-oxidation ability, and enhanced the salt-reduced surimi stability during frozen storage. Hence, an appropriate KGM supplement could be a feasible strategy to minimize the gel deterioration and improve the anti-freezing ability of low-salt surimi gel.