Characteristics and nutritional value of biscuits fortified with debittered salmon (Salmo salar) frame hydrolysate

Effect of debittered salmon frame hydrolysate (DSFH) at various levels (0, 5, 10, 15, 20 and 25 g/100 g) on physicochemical, textural, sensory and nutritional properties of biscuits was investigated. The highest thickness was obtained for the sample with 25 g/100 g DSFH (P < 0.05). There was no difference in diameter among all the biscuit samples (P > 0.05). The samples added with DSFH had lower weight, water activity and moisture content than the control (CONT, without DSFH) (P < 0.05). DSFH at 15 g/100 g showed no detrimental effect on sensory properties of resulting biscuits (DSFH-15). The DSFH-15 biscuit showed reduction in cutting force and fracturability. Scanning electron microscopic and cross-sectional images showed that DSFH-15 biscuit had more porous structure, compared to the CONT. The biscuits fortified with 15 g/100 g DSFH had higher protein but had lower energy value, fat and carbohydrate content than the CONT.     

Feasibility of fishmeal replacement by shrimp head silage protein hydrolysate in Nile tilapia (Oreochromis niloticus L) diets

This study provides information on the use of shrimp head silage protein hydrolysate (SPH) as an alternative protein source for tilapia feeding. Six diets (28% protein, 12% lipid) were prepared where fishmeal protein was replaced at levels of 0 (control), 10, 15, 20, 25 and 30% with the hydrolysate. The diets were supplied to Nile tilapia fry (338 mg initial weight) stocked in plastic recirculating 20 l tanks (10 animals per tank), with three replicates per treatment. After an 8 week experimental period, fish fed the diets containing 10 and 15% SPH showed significantly better performance in terms of final body weight, weight gain (%), mean daily weight gain (mg day^?1), specific growth ratio and feed conversion ratio than those fed the control diet (fishmeal as protein source) and higher‐SPH diets. It is concluded that shrimp head hydrolysate is a promising alternative protein source for tilapia feeding, improving growth ratio at dietary inclusion levels as high as 15%. In addition, the diets with added shrimp silage protein were well accepted by the fish, which avidly consumed the feed during the experiment. © 2002 Society of Chemical Industry     

冰乙酸和胃蛋白酶依次提取新鲜林蛙皮胶原蛋白

采用冰乙酸和胃蛋白酶依次对新鲜林蛙皮胶原蛋白进行提取.在冰乙酸提取过程中,首先通过控制单一因素变量对料液比、pH值、冰乙酸浓度、酸解时间和温度等5个因素对新鲜林蛙皮胶原蛋白提取率的影响进行研究,并采用正交实验考察林蛙皮胶原蛋白酸解提取的最佳工艺;其次,在冰乙酸提取的最优条件下,利用胃蛋白酶将酸解后的残余物进行再次酶解提取.实验结果表明,最佳酸解的工艺条件是:料液比为1∶30,pH为7.5,酸解时间为48 h,酸解温度为4℃,冰乙酸浓度为0.5 mol/L.在此工艺条件下,胶原蛋白的提取率为11.85％,胃蛋白酶对蛙皮残渣的提取率为5.25％,所得胶原蛋白的纯度为64.70％.     

壳聚糖固定胃蛋白酶的研究

以壳聚糖为载体、戊二醛为交联剂将胃蛋白酶固定化．戊二醛质量分数为5％，载体处理温度为30℃，胃蛋白酶与壳聚糖用量比为O．Ol，pH=4．O，固定12h以上，酶活性回收率达65％～70％。固定化酶最适温度为70℃，比游离酶提高了20℃；固定化酶最适pH值为3．O，而游离酶为2．O；固定化酶的表观米氏常数Km=3．32g／L，而游离酶Km=1．5lg／L。固定化酶重复使用3次时的酶活性回收率分别为73．9％，58．4％。42．6％。2个多月重复使用，活力未见明显下降。     

Process optimisation and physicochemical characterisation of enzymatic hydrolysates of proteins from co‐products of Atlantic Salmon (Salmo salar) and Yellowtail Kingfish (Seriola lalandi)

The aim of this study was to develop an enzymatic hydrolysis process of protein co‐products for two major commercial fish species in Australia: Atlantic salmon (AS) and Yellowtail kingfish (YTK). The outcomes are to produce high protein recovery of fish protein hydrolysates within controlled molecular weight ranges that display enhanced physicochemical properties of oil binding and emulsification. Three enzymes (Flavourzyme, Neutrase and Alcalase) were applied to processing co‐products. Protein recovery and physicochemical properties were evaluated with increasing hydrolysis time from 30 min to 180 min and ratio of enzyme to substrate (E/S) from 0.5% to 3.0%. In order to achieve a product with optimum emulsifying capacity (50 ± 0.6 m² g^?1), an E/S ratio of 0.6–1.3% Flavourzyme was applied for 30–111 min with a protein recovery of 55%; in order to achieve a product with optimum oil‐binding capacity (8.3 ± 0.3 g oil g hydrolysates^?1), an E/S ratio of 2.3–3.0% Flavourzyme was applied for 25–64 min with a protein recovery of 70%. YTK protein hydrolysates were further membrane‐fractionated into five fractions (>100 kDa, 50–100 kDa, 30–50 kDa, 10–30 kDa and <10 kDa), and of these, the 10–30 kDa exhibited the best properties of oil binding (19 ± 0.3 g oil g hydrolysates^?1) and emulsification (57 ± 0.7 m² g^?1). These results demonstrate the importance of enzymatic hydrolysis of seafood co‐products into high‐value ingredients for food products and processing.     

Angiotensin I‐converting enzyme inhibitory activity of protein hydrolysates prepared from three freshwater carps (Catla catla,Labeo rohita and Cirrhinus mrigala) using Flavorzyme

Fish protein hydrolysates from three freshwater carps, Catla catla, Labeo rohita and Cirrhinus mrigala with different degree of hydrolysis (DH) (5%, 10%, 15% and 20%), were prepared using Flavorzyme enzyme and designated as HCF, HRF and HMF, respectively. The angiotensin I‐converting enzyme (ACE) inhibitory activity of hydrolysates was found to vary from 43 ± 2% to 71 ± 3%. Based on ACE inhibitory activity, HRF with DH‐15% was taken up for further study. The mode of ACE activity inhibition by HRF‐DH 15% was mixed type as revealed by Lineweaver–Burk plot. Sequential digestion of HRF‐DH 15% using pepsin and pancreatin decreased the ACE inhibitory activity from 76% to 63%. Partial purification of HRF‐DH 15% by size exclusion chromatography gave three different fractions designated as F‐1, F‐2 and F‐3 with the molecular mass in the range of 6456–407 Da. Fraction 2 had significantly higher ACE inhibitory activity than the other fractions.     

Rheological properties and gel strength of Phaseolus lunatus protein/carboxymethylated flamboyant gum systems

The rheological behaviour and gel strength of hydrocolloid mixture systems (HMSs) of carboxymethylated flamboyant gum (CFG) with protein hydrolysates (PHs) of Phaseolus lunatus were examined to evaluate the influence of the protein/polysaccharide ratio (2:1 and 3:1), pH (3 and 9) and concentration of solids, according to a 2³ factorial design. The protein concentrate of P. lunatus was hydrolysed with pepsin–pancreatin enzymes. The flow curve results were fitted to the Ostwald–de Waele model. The flow behaviour index (0.66–0.78) for all conditions studied was indicative of the shear‐thinning behaviour. For the HMS, the consistency index (k) values ranged from 0.4 Pa sⁿ to 1.2 Pa sⁿ. The analyses of variance showed that the ratio of PH/CFG and pH were the main variables that had significant effect on k values (P < 0.05). Only PH system presented a weak gel‐like viscoelastic behaviour. Both functional properties were affected by the protein degree of hydrolysis (DH).     

Effects of pepsin hydrolysis on the soy β‐conglycinin aggregates formed by heat treatment at different pH

The effects of pepsin hydrolysis on the β‐conglycinin aggregates formed by heat treatment at different pH were investigated. Results showed that fibrils were still observed, whereas the random aggregates were easily to be digested in the simulated gastric fluid. Electrophoresis and molecular weight analysis indicated that large aggregates still existed after pepsin treatment for fibrils. Hydrolysis resulted in changes in the apparent viscosity (ηapp) of 6% fibril solutions. The ηapp at the shear rate range (0–30 s^?1) increased in the order of fibrils < fibrils with pepsin for 60 min < fibrils with pepsin for 30 min. Smaller peptide/fibril fragments were generated, and additional aggregates were reformed during the hydrolysis process, as evidenced by thioflavin T and atomic force microscopy images. The native β‐conglycinin hydrolysates comprised a mixture of polypeptides enriched in about 47 kDa. These findings would provide valuable information about effects of enzymatic hydrolysis on plant oligometric globulin aggregates.     

Hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (αs1-, β- and k-casein) after enzymatic hydrolysis with pepsin and enzymatic extract from Pleurotus eryngii

The aim of this study was to estimate the hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (α_s1-, β- and k-casein) after in vitro digestion with two different enzymatic systems: pepsin from porcine gastric mucosa (EP) and a crude enzymatic extract from the edible mushroom Pleurotus eryngii. The used enzymes showed a different mode of casein catalysis with a consequent production of peptides of different antioxidant activity. The CN haplotype significantly influenced peptides production; in fact, the amino acid substitutions caused by genetic polymorphisms at the α_s1-, β- and k-CN loci influenced the sites of enzymatic cleavage and therefore the produced peptides. The above is evidenced by the different antioxidant activity found in the hydrolysates depending on the used enzymatic system, the CN haplotype, and the CN haplotype × enzymatic treatment interaction. The findings of this study are a perspective for the production of specific foods that exert a biological effect in addition to the nutritional one.