Enhanced Thermal Stability of Potato Starch by Compounding with Collagen Peptide and Cross-linking with Transglutaminase

Abstract

Starch is applied to many processed foods to build or modify their physical properties, because it exhibits characteristic thermal behavior as represented by gelatinization. A number of studies have thus been carried out to investigate the effects of many coexisting substances on such gelatinization and swelling behavior, and to control the texture of processed foods with the chemically and physicallymodified starches. Heating at a high temperature such as that involved a retort treatment still results in extensive swelling and subsequent collapse of the swollen starch granules, thus developing a sticky and pasty texture that is often disliked in starchy foods. However, it has not been possible to inhibit such degradation by conventional means. We have paid particular attention to controlling the gelatinization behavior by adding charged amino acids and charged amino acid-rich peptides, 1 8) and by conjugating or compounding non-starchy substances by simultaneous modification with a heatmoisture treatment and the Maillard reaction.9 12) These studies have clarified that charged amino acids would be valuable for providing an improved paste with a higher gelatinization temperature and depressed swelling. It has also become apparent that conjugating or compounding non-starchy substances, in particular, conjugating with a fatty acylated saccharide through lysine, 12) could substantially contribute to endowing its pasting properties with a high gelatinization temperature, low solubility, swelling and digestibility, high thermal resistance, and easy vaporization. However, controlling only by adding amino acids and peptides would be insufficient, because changes in environmental conditions during practical food processing would have varied effects and result in unstable control of starch. The fatty acylated saccharide-conjugated starch through compounding with lysine resulted in unfavorable browning due to heating at a high temperature. It has recently been demonstrated that oleylating with lipase could provide a conjugated starch without involving browning and with such improved pasting properties as markedly low swelling and viscosity. 13) However, high heat resistance could not be achieved because of complete dissolution by retorting at 120 C for 20 min. A further high heat resistance thus needs to be achieved by other suitable and unconventional means. Cross-linking between starch chains by phosphorylation could be an effective solution. However, no such crosslinking method has been adopted for food use, because chemical modification involving phosphorylation is generally disliked. Instead of direct cross-linking in this way, enzymatic cross-linking between the peptide moieties of peptide-compounded starch without resulting browning, this being called indirect cross-linking, may thus be more appropriate to provide a starch material with high thermal resistance for food use. A low-molecular-weight collagen J. Appl. Glycosci., 61, 109 112 (2014)