Chau-Jen Chow

Characteristic and antioxidant activity of retorted gelatin hydrolysates from cobia (Rachycentron canadum) skin

Alkali-pretreated cobia (Rachycentron canadum) skin was extracted in a retort (121°C) for 30min to obtain a retorted skin gelatin hydrolysate (RSGH). The molecular mass distributions and antioxidant activities of cobia RSGH and enzyme-treated RSGHs (ET-RSGHs) derived from bromelain, papain, pancreatin, and trypsin digestion were then characterized. The molecular mass distribution of the RSGH ranged mainly between 20,000 and 700Da and those of ET-RSGHs ranged between 6500 and 700Da. The DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging effects (%) of 10mg/ml of RSGH and 10mg/ml of the four ET-RSGHs were 55% and 51-61%, respectively. The lipid peroxidation inhibition (%) of RSGH and ET-RSGHs (10mg/ml) were 58% and 60-71% on the fifth day in a linoleic acid model system, respectively. The 3Kd-ET-RSGHs, obtained by using a series of centrifugal ultrafiltration filters (molecular weight cut-offs of 10, 5, and 3kDa done sequentially with decreasing pore size), exhibited dramatically improved antioxidant activity, with most of the molecular mass ranging below 700Da. Compared to 10mg/ml of the RSGH, 10mg/ml of 3Kd-ET-RSGHs exhibited 45-65% more scavenging of DPPH radical and 24-38% more inhibition of lipid peroxidation. The peptides with molecular masses below 700Da in the ET-RSGHs or 3Kd-ET-RSGHs significantly affect the antioxidant properties. These peptides are composed of a small number of amino acids or free amino acids and have the potential to be added as antioxidants in foods.

Composition, characteristics, and in-vitro physiological effects of the water-soluble polysaccharides from Cassia seed

The popular beverage ingredients Cassia obtusifolia and Cassia tora were found to have considerable amounts of water-soluble polysaccharides (WSPs) (58.5 and 55.9/100g of dried extract). The composition, characteristics, and in-vitro physiological effects of these polysaccharides and their possible health benefits were investigated. The major polysaccharide components in the WSP of C. obtusifolia were possibly pectic polysaccharides and hemicellulose, while C. tora WSP was mainly composed of arabinoglucan and pectic polysaccharides. These WSPs had inhibitory effects on the activities of α-amylase and pancreatic lipase, while they rendered an increase in protease activity. These WSPs also had the ability to bind bile acids and reduce the amount of cholesterol available for absorption. This suggested that these WSPs had potential application as herbal ingredients in beverages. Further investigations on their in-vivo hypocholesterolaemic effects and intestinal functions using animal-feeding experiments are under way.

Textural and histological changes of different squid mantle muscle during frozen storage

Mantles from three species of squids, Loligo edulis, Sepia pharaonis, and Illex argentinus, were frozen and stored at −20 °C for 0, 0.5, 1, 2, and 4 months, and their textural properties were investigated. The toughness of all squid mantles increased during frozen storage, and there was a significant difference between prefrozen and postfrozen storage. There was no significant difference in drip amount and SDS gel electrophoresis patterns after 4 months of frozen storage. Histology observation of mantle showed that the muscle fibers were injured and aggregated while the frozen time increased. These changes in tissue structure during frozen storage might cause the toughening of mantle. Keywords: Squid; frozen storage; freezing drip; electrophoresis; histological properties

Effects of acid and alkaline pretreatment on the discoloration rates of dark muscle and myoglobin extract of skinned tilapia fillet during iced storage

Discoloration profiles of dark muscle of skinned tilapia fillets were examined during iced storage after pretreatment with lactic acid (LA) or sodium carbonate (SC). During the subsequent storage, the a* values decreased gradually, and changed more rapidly when the pH was lower than 6.3. The fillet pretreated with 10% (v/v) LA exhibited the highest metmyoglobin formation ratio (MetMb%), followed by the fillet pretreated with 5% (v/v) LA, the control fillet, and the fillet pretreated with 10% (w/v) SC. The sample pretreated with 10% LA showed a marked decrease in the a* value. Discoloration of the control was not observed until the ninth day of iced storage, and no discoloration was observed up to the 11th day for the fillet pretreated with 10% SC. These fillet discoloration profiles were subsequently verified using the myoglobin (Mb) fraction prepared from the dark muscle. MetMb% of the Mb fraction gradually increased during storage, and this increase accelerated at pH values of <6.3. Discoloration of the Mb fraction also showed a similar tendency, and no significant discoloration was observed at pH values of >6.5. These results suggest that pH greatly affects the discoloration rate of the dark muscle of skinned fillet, and the critical pH for the accelerated autooxidation of tilapia Mb is in the range 6.3–6.5.

Water-insoluble fiber-rich fraction from pineapple peel improves intestinal function in hamsters: evidence from cecal and fecal indicators

Pineapple peel, a byproduct of agricultural processing, contains high levels of water-insoluble fiber-rich fraction (WIFF) (~42%, wt/wt). Our previous work has demonstrated that cellulose, hemicellulose (xylan and xyloglucan), and pectic substances are the major polysaccharides of pineapple-peel WIFF. Based on its chemical composition and unique characteristics, we hypothesized that daily consumption of WIFF would improve intestinal function in hamsters. Male Golden Syrian hamsters were fed a diet supplemented with either 5% cellulose or various amounts of WIFF (2.5%, 5%, or 10%). Activities of fecal bacterial enzymes, short-chain fatty acid concentrations, and microbial number in the cecal content, and also biochemical indicators in the cecal and feces of hamsters, were evaluated in all groups. The supplementation of WIFF in a diet at a level of 2.5% significantly (P < .05) decreased the daily fecal ammonia output; shortened the gastrointestinal transit time; reduced the activities of β-D-glucosidase, β-D-glucuronidase, mucinase, and urease in feces; and also enhanced the total amounts of short-chain fatty acid in the cecal content and the growth of gut microflora such as Lactobacillus spp and Bifidobacterium spp. These results indicate that WIFF could improve cecal ecosystem function of hamsters by reducing the toxic compounds excreted by intestinal microflora. Therefore, pineapple-peel WIFF could be a promising candidate for a functional ingredient beneficial to human intestinal function and health.

Structural and autooxidation profiles of myoglobins from three species and one hybrid of tilapia (Cichlidae, Perciformes)

cDNAs encoding myoglobin were cloned from the slow skeletal muscles of three representative species of tilapia, namely, Nile tilapia Oreochromis niloticus, blue tilapia O. aureus, Mozambique tilapia O. mossambicus and one hybrid O. niloticus female symbol x O. aureus male symbol, and the primary structures were deduced. All cDNAs contained an open reading frame of 444 base pairs, encoding 147 amino acids. The amino acid sequences of Mb were completely conserved among these species, though species variations in the nucleotide sequences were recognized both in coding and non-coding regions. The amino acid sequence identity was around 70-80% compared to other teleostean Mbs. In comparison of each alpha-helical segment (A through H) and the intersegment regions to the counterparts of tuna myoglobin, the alpha-helical segments C and F as well as the intersegment regions F-G and G-H were identical. The identities of alpha-helical segments B and H and the intersegment region F-G were relatively low. Differences were also recognized in the hydropathy plot and the tertiary structures obtained by homology modeling. The autooxidation rates at 25 degrees C of myoglobin fraction from the slow skeletal muscle were essentially the same among the above tilapia species, as expected from the conserved amino acid sequences.

Angiotensin I-converting enzyme inhibitory and hypocholesterolemic activities: Effects of protein hydrolysates prepared from Achatina fulica snail foot muscle

ABSTRACT The angiotensin I-converting enzyme (ACE) inhibitory activity and hypocholesterolemic effect of Achatina fulica snail foot muscle protein hydrolysates (SFMPH) and its hydrolysates were studied. The SFMPHs were prepared at a temperature of 121°C for 60 min. To obtain the enzymatic hydrolysates, the SFMPHs were further hydrolysed with three proteases (papain, trypsin, or alcalase). Among all the hydrolysates, alcalase hydrolysate showed the highest degree of hydrolysis and was dominated by a small molecular size fraction (189–686 Da). The SFMPH treated by alcalase was effective in disintegrating intact cholesterol micelles. Furthermore, alcalase hydrolysate with a hydrolysis time of 60 min showed a strong ACE inhibitory activity in vitro with an IC50 of 0.024 mg/mL. Therefore, alcalase hydrolysate may be a promising ingredient for the use in functional foods.