Chaohua Zhang

Response surface methodology for autolysis parameters optimization of shrimp head and amino acids released during autolysis

Protein hydrolysates were prepared from the head waste of Penaens vannamei, a China seawater major shrimp by autolysis method. Autolysis conditions (viz., temperature, pH and substrate concentration) for preparing protein hydrolysates from the head waste proteins were optimized by response surface methodology (RSM) using a central composite design. Model equation was proposed with regard to the effect of temperature, pH and substrate concentration. Substrate concentration at 23% (w/v), pH at 7.85 and temperature at 50°C were found to be the optimal conditions to obtain a higher degree of hydrolysis close to 45%. The autolysis reaction was nearly finished in the initial 3h. The amino acid compositions of the autolysis hydrolysates prepared using the optimized conditions in different time revealed that the hydrolysates can be used as a functional food ingredient or flavor enhancer. Endogenous enzymes in the shrimp heads had a strong autolysis capacity (AC) for releasing threonine, serine, valine, isoleucine, tyrosine, histidine and tryptophan. Endogenous enzymes had a relatively lower AC for releasing cystine and glycine.

Structure and characteristics of acid and pepsin-solubilized collagens from the skin of cobia (Rachycentron canadum)

Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were extracted from the skin of cobia (Rachycentron canadum). The yields of ASC and PSC were 35.5% and 12.3%, respectively. Based on the protein patterns and carboxymethyl-cellulose chromatography, ASC and PSC were composed of α1α2α3 heterotrimers and were characterised as type I collagen with no disulfide bond. Their amounts of imino acids were 203 and 191 residues per 1000 residues, respectively. LC-MS/MS analysis demonstrated the high sequences similarities of ASC and PSC. Fourier transform infrared spectroscopy spectra showed that the amide I, II and III peaks of PSC were obtained at a lower wave number compared with ASC. The thermal denaturation temperatures of ASC and PSC, as measured by viscometry, were 34.62 and 33.97°C, respectively. The transition temperatures (T(max)) were 38.17 and 36.03°C, respectively, as determined by differential scanning calorimetry (DSC). Both collagens were soluble at acidic pH and below 2% (w/v) NaCl concentration.

Physical and chemical analysis of Passiflora seeds and seed oil from China.

The physical and chemical properties of seeds and seed oil from ‘Tainung No. 1’ passion fruit in China have been analyzed in order to evaluate their nutritional value. Proximate analysis shows that the seeds have a high amount of protein (10.8±0.60%) and are rich in oil (23.40±2.50%). The seeds are found to be a good source of minerals. They contain considerable amounts of sodium (2.980±0.002 mg/g), magnesium (1.540±0.001 mg/g), potassium (0.850±0.001 mg/g), and calcium (0.540±0.002 mg/g). The passion fruit seeds contain the 17 amino acids that are found naturally in plant protein (tryptophan is not analyzed). The essential amino acids account for 34% of the 17 amino acids. The amino acid score of passion fruit seeds protein is 74 and the first limiting amino acid is methionine and cystine. The oil extracted by solvent and supercritical dioxide carbon is liquid at room temperature and the color is golden–orange. The specific gravity of the oil is about 0.917. Comparing the chemical properties of the oil extracted by solvent with that by supercritical dioxide carbon, the latter may be suitable as edible oil directly, while the former will be edible after it must be refined to improve on clarity. Fatty acid composition of the seed oil indicates that the oil contains two essential fatty acids (linoleic acid and linolenic acid), but the content of linoleic acid (72.69±0.32%) is by far greater than that of linolenic acid (0.26±0.00%). The present analytical results show the passion fruit seed to be a potentially valuable non-conventional source for high-quality oil.

Optimization of peptic hydrolysis parameters for the production of angiotensin I-converting enzyme inhibitory hydrolysate from Acetes chinensis through Plackett–Burman and response surface methodological approaches

BACKGROUND Angiotensin I-converting enzyme (ACE) plays an important physiological role in regulating blood pressure. The elevation of blood pressure could be suppressed by inhibiting ACE. ACE inhibitory peptides derived from food proteins could exert antihypertensive effects without side effects. Acetes chinensis is a marine shrimp suitable for the production of ACE inhibitory peptides. The principal objective of this study was to screen for the significant variables, and further to optimize the levels of the selected variables, for the enzymatic production of ACE inhibitory peptides from Acetes chinensis. RESULTS Plackett-Burman design and response surface methodology were employed to optimize the peptic hydrolysis parameters of Acetes chinensis to obtain a hydrolysate with potent ACE inhibitory activity. The peptic hydrolysis variables were subject to a Plackett-Burman design for screening the main factors. The selected significant parameters such as pH, hydrolysis temperature and enzyme/substrate (E/S) ratio were further optimized using a central composite design. The optimized conditions were: pH 2.5, hydrolysis temperature 45 °C, E/S ratio 17 800 U kg(-1) shrimp and substrate concentration 200 g L(-1). The results showed that 3-5 h hydrolysis could result in a hydrolysate with ACE inhibition IC(50) of 1.17 mg mL(-1) and a high DH of 25-27%. CONCLUSION Plackett-Burman design and RSM performed well in the optimization of peptic hydrolysis parameters of Acetes chinensis to produce hydrolysate with ACE inhibitory activity. A hydrolysate with potent ACE inhibitory activity and high degree of hydrolysis was obtained, so that the yield of ACE inhibitory peptides in it was high.

Optimization of microbial inactivation of shrimp by dense phase carbon dioxide

Microbial inactivation of Litopenaeus vannamei by dense phase carbon dioxide (DPCD) treatment was investigated and neural network was used to optimize the process parameters of microbial inactivation. The results showed that DPCD treatment had a remarkable bactericidal effect on microorganism of shrimp. A 3×5×2 three-layer neural network model was established. According to the neural network model, the inactivation effect was enhanced with pressure, temperature and exposure time increasing and temperature was the most important factor affecting microbial inactivation of shrimp. Cooked appearance of shrimp by DPCD treatment was observed and seemed to be more positively acceptable by Chinese diet custom. Therefore, color change of shrimp by DPCD treatment could have a positive effect on quality attributes. Moderate temperature 55 °C with 15 MPa for 26 min treatment time achieved a 3.5-log reduction of total aerobic plate counts (TPC). The parameters combination might be appropriate for shrimp process by DPCD.

Ultraviolet irradiation and gradient temperature assisted autolysis for protein recovery from shrimp head waste

A novel autolysis method using ultraviolet (UV) irradiation and gradient temperature was investigated to efficiently recover proteins from the head of the shrimp Penaeus vannamei. The proteolytic activity of shrimp head subjected to 30W UV irradiation for 20 min was increased by 62%, compared with that of untreated samples. After irradiation, the enzymes remained active across a wide range of temperatures (45-60°C) and pH (7-10). An orthogonal design was used to optimize autolysis condition. After 5h autolysis, protein recovery from the UV-heat treated samples was up to 92.1%. These results indicate the potential of using UV irradiation in combination with gradient temperatures to improve recovery of proteins from shrimp head waste.

Effects of intragastric administration of five oyster components on endurance exercise performance in mice.

Abstract Context: Oysters [Crassostrea plicatula Gmelin (Ostreidae)] are widely used for food in coastal areas. It is reported to have several qualities such as improving sexual and immune function. They has been approved by Chinese Ministry of Health as a functional food. Objective: The effects of five types of oyster components (oyster meat, oyster glycogen, oyster protein, cooked liquid components, and water-insoluble components) on the swimming endurance of mice were investigated. Materials and methods: First, the amino acid composition and sugar content of the five oyster components were analyzed by a physicochemical test. In the in vivo test, the control group was administered distilled water, and the five intervention groups were treated with various samples for 15 consecutive days [0.8 mg protein/(g BW·d) or 0.2 mg glycogen/(g BW·d)]. The swimming time was recorded through the exhaustive swimming test. The levels of serum lactic acid, blood urea nitrogen (BUN), liver glycogen, and gastrocnemius muscle glycogen were determined. Results: Oyster protein had a minimum F-value (the mole ratio of branched-chain amino acids to aromatic amino acids) (2.68), contained 1.85 mmol/mL taurine and no sugar. The components (except for oyster protein) significantly improved endurance capacity of mice and increased the liver and muscle glycogen contents (p < 0.05), and reduced the lactic acid and BUN levels (p < 0.05). Oyster protein had little effect. Discussion and conclusion: The effects of oyster components on the swimming endurance of mice may be attributed to the high ratio of the branched-chain amino acid composition, bioactivity of taurine, and glycogen.

Identification of Sensory Quality of Rapid Fermented Fish Using Electronic Nose

In order to shorten the production cycle of traditional fermented fish, cured fish was fermented by Lactobacillus plantarum and Staphylococcus xylosus. Considering sensory quality of products affected the acceptance of consumer, electronic nose (E-nose) and sensory evaluation by human taste panel were used to analysis fish flavor. The results of principal component analysis (PCA) indicated the flavor quality of rapid fermented fish was close to the traditional fermented fish, even though cured fish had more response value of sensor. When traditional fermented fish was acted as standard, rapid fermented fish located nearer accepted range than cured fish by analysis of Statistical Quality Control (SQC). The result was explained by sensory evaluation of human taste panel: only cured fish had strong fishy smell, peculiar flavor of salted fish, and little aroma; traditional fermented fish had thick aroma and a little bad smell for oil oxidation; rapid fermented fish had obvious aroma. The result indicated that rapid fermentation for production of traditional fish was possible. The differences of flavor among three groups of fish were distinguished by E-nose, same as sensory evaluation. So E-nose acted as a new method could be successfully used in aroma identification of foods.

Biochemical, Nutritional, and Sensory Quality of the Low Salt Fermented Shrimp Paste

ABSTRACT Changes in the biochemical, nutritional, and sensory properties of the low salt fermented shrimp paste during fermentation were studied. The total volatile base nitrogen (TVB-N) content and total viable counts significantly increased. The pH value significantly decreased, while thiobarbituric acid (TBA) content significantly increased over 14 days. The lightness (L*) value significantly decreased during the initial 7 days of fermentation and significantly increased thereafter. The redness (a*) and yellowness (b*) values and astaxanthin content of the low salt fermented shrimp paste gradually increased during the 30 days of fermentation. C16:0, C18:0, C18:1n9t, C20:1n7c, C20:5n3, and C22:6n3 were the predominant fatty acids, while aspartate, glutamate, alanine, leucine, lysine, arginine, and proline were the predominant amino acids in the shrimp paste. N-containing compounds, such as pyrazine, comprised the majority of the volatile compounds. The results obtained from quantitative descriptive analysis showed that low salt fermentation can improve the flavor of the shrimp paste and is, therefore, a promising method to industrially prepare the shrimp paste.

Extraction, purification, and structure characterization of polysaccharides from Crassostrea rivularis

Abstract Crude polysaccharide was prepared from Crassostrea rivularis by 30% (w/v) potassium hydroxide solution at 90°C for 120 min. Three fractions (OG1, OG2, and OG3) were purified by DEAE‐52 cellulose and Sepharose 2B gel column chromatography. The chemical structures were determined using gas chromatography (GC), high‐performance gel permeation chromatography (HPGPC), Fourier‐transform infrared (FT‐IR) spectroscopy, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The results indicated that OG1 was composed of rhamnose and little mannose (8.71%), the ratio of Rha: Gal: Xyl: Fuc in OG3 were 14:5.5:3:1. And their average molecular weights (Mw) were about 1.66 × 106 and 2.33 × 106 Da, respectively. OG2 was composed only of glucose (98.23%), which means it was glycogen. OG2 was consisted mainly of →4)‐ α‐D‐Glc‐(1→, with the branch chain every 6.5 glucose residues on average, which is →4,6)‐α‐D‐Glc‐(1→ and trace amount of α‐D‐Glc‐(1→ branched units. The Mw was 2.27 × 106 Da. It provides the bases for the bioactivity research.