Peptidomic Analysis of a Disintegrated Surimi Gel from Deep-Sea Bonefish Pterothrissus gissu.

Surimi gel is a commonly found gelled product in Japan. Disintegration of the surimi gel is mainly caused by proteolytic degradation of the myosin heavy chain (MHC) under an inappropriate heating process. Many studies have reported the decrease in MHC in the disintegrated surimi gel but the mechanistic details of this degradation remain unclear. This study employed peptidomic analysis of disintegrated surimi gels from deep-sea bonefish Pterothrissus gissu to reveal the MHC cleavage causing gel disintegration. More peptides derived from an MHC rod were found in the disintegrated P. gissu surimi gels than in the integrated gel. Most MHC peptides were derived from the Src homology 3 domain or near the skip residues. The results of the terminome analysis suggest that the catalytic type of the proteases is responsible for light meromyosin cleavage activated at ∼35 °C. These results showed the temperature-dependent cleavage of the MHC rod, causing disintegration of the P. gissu surimi gel.

The effects of endogenous proteases within abdominal muscle parts on the rheological properties of thermally induced gels from white croaker (Pennahia argentata).

Three types of material meats were prepared from a so-called normal muscle part of white croaker (Pennahia argentata) containing 0, 4.2 and 8.4% of an abdominal muscle part. Thermally induced gels were then prepared from these materials by pre-heating at 65 °C for 30 or 60 min and subsequent heating at 85 °C for 20 min. The breaking strength and breaking strain rate of thermally induced gels decreased with increasing contamination levels of the abdominal muscle part, in which degradation of myosin heavy chains was observed. The proteolytic activity in the abdominal muscle part homogenate was highest at 62.5 °C. These results suggest that the abdominal muscle part contains proteases that induce the modori phenomenon. Technical experts assume that a contaminated abdominal muscle part leads to quality deterioration in surimi production industries. Our findings will aid the production of high-quality surimi-based products.

Deterioration of white croaker (Pennahia argentata) meat thermally-induced gel products caused by proteolytic enzymes in the contaminated intestine and kidney.

Thermally-induced gels were made from white croaker (Pennahia argentata) meat in the presence of its organ extracts by pre-heating at 40 and 65°C for 20 min and subsequent heating at 85°C for 20 min. The breaking strength of the gels decreased with increasing concentrations of the intestinal extracts accompanying decomposition of myosin heavy chains. However, no significant changes in the gel strength occurred when the kidney extract was added. The proteolytic activity in the intestinal extracts examined in the meat homogenate had a maximum at 60°C and pH 8.90. These results suggest that the intestinal rather than kidney proteolytic activities are responsible for gel softening known as a modori phenomenon. Thus, the removal of intestinal tracts is essential to maintain a high quality of surimi-based products.

The pepsin digestibility of thermal gel products made from white croaker (Pennahia argentata) muscle in associating with myosin polymerization levels.

Thermal gels were made from white croaker (Pennahia argentata) surimi at various polymerization levels of myosin heavy chains induced by suwari treatment at 38 °C for various time periods and subsequently heated at 85 °C for 20 min. Myosin heavy chain polymerization levels were also achieved in the presence of microbial transglutaminase (MTG) added at various concentrations in the surimi. The breaking strength and breaking strain rate were markedly increased during suwari treatment up to 60 min in accordance with the increased levels of myosin heavy chain polymerization. MTG enhanced myosin heavy chain polymerization during suwari treatment for 15 and 30 min, resulting in the increase of breaking strength. The solubilization in 8 M urea and pepsin digestibility of these gels as well as angiotensin I-converting enzyme (ACE) inhibitory activity of their pepsin digests were decreased with the increased levels of myosin heavy chain polymerization. These results suggest that myosin heavy chain polymerization affects not only rheological properties of thermal gels but also their functional properties for human health.