Abstract
Gelatin hydrolysates from autolysed non-swollen and swollen unicorn leatherjacket skin prepared using partially purified glycyl endopeptidase (GE) from papaya latex were examined for their antioxidative activities. Autolysed swollen skin was more hydrolysed by GE as indicated by higher α-amino group content, compared with autolysed non-swollen skin. ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP) of hydrolysates were increased with increasing levels of GE used. Antioxidative gelatin hydrolysate from autolysed skin, both non-swollen and swollen skins, using 8 % GE termed ‘NS-8GE’ and ‘SS-8GE’ exhibited different modes of action. When both hydrolysates were tested in lecithin liposome system, the efficiency in retardation of lipid oxidation was in a dose-dependent manner. Antioxidative activity of hydrolysates at 5.0 g/L was comparable to that of 0.1 g/L Trolox, in which the oxidation was almost completely inhibited. NS-8GE and SS-8GE also showed their antioxidative activities in gastrointestinal tract model system (GIMs). ABTS radical scavenging activity of both hydrolysates increased, but FRAP decreased in a duodenal condition. Based on size exclusion chromatography, major antioxidative peptides in NS-8GE and SS-8GE had molecular weight of 1,170 and 750 Da, respectively. Therefore, GE could enhance antioxidative activity of autolysed skin. Additionally, swelling process directly determined the modes of actions of resulting gelatin hydrolysates. NS-8GE had high ABTS radical scavenging activity, whereas SS-8GE showed high FRAP.
Highlights
Lipid oxidation has been known as a serious cause of food deterioration as well as various human diseases, such as cardiovascular diseases and cancers (Lobo et al 2010)
This result was in accordance with Karnjanapratum and Benjakul (2014a) who reported that the increase in enzyme/substrate (0.5, 1.0 and 2.0 %) resulted in the increase in degree of hydrolysis of gelatin hydrolysate from unicorn leatherjacket skin prepared using papain
Autolysis of gelatin in unicorn leatherjacket skin at 55 °C caused by indigenous protease (Kaewruang et al 2013) yielded available peptides for further hydrolysis by glycyl endopeptidase (GE)
Summary
Lipid oxidation has been known as a serious cause of food deterioration as well as various human diseases, such as cardiovascular diseases and cancers (Lobo et al 2010). Enzymatic hydrolysis has been intensively employed to produce antioxidative gelatin hydrolysates (Gomez-Guillen et al 2011). The high cost of production is mainly associated with enzyme, energy consumed and production process. Autolysis mediated by indigenous protease was used as the aid for production of gelatin hydrolysates with antioxidative activity from unicorn leatherjacket skin that could reduce the amount of commercial proteases and energy used (Karnjanapratum and Benjakul 2014a). The selection of proper enzyme to substrate was crucial for production of antioxidative gelatin hydrolysate from Alaska pollack skin (Kim et al 2001). Kittiphattanabawon et al (2012) found that glycyl endopeptidase, the major cysteine protease in papaya latex, showed the effectiveness in cleaving peptide bonds with Gly at P1 of fish gelatin from blacktip shark skin, yielding antioxidative gelatin hydrolysate with high degree of hydrolysis. The active fraction of glycyl endopeptidase from papaya latex was prepared using aqueous two-phase system to remove offensive odour compounds (Karnjanapratum and Benjakul 2014b)
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