Jianyou Zhang

Deodorisation of fish oil by nanofiltration membrane process: focus on volatile flavour compounds and fatty acids composition

This study focuses on the investigations for the deodorisation of tuna oil and squid oil through n-hexane extraction and nanofiltration membrane process with a molecular weight cut-off of 360 Da. The change of the odour and the fatty acids composition were analysed. Volatile components analysed by monolithic material sorptive extraction (MMSE) combined with gas chromatography–mass spectrometry (GC-MS) suggested that nanofiltration membrane process could remove the majority of the volatile components, and the removal rate was approximate to 80%. The odour activity values (OAVs) of the volatile components in tuna oil and squid oil were significantly reduced from 125.23 to 17.47 and 129.76 to 10.06 (P < 0.05), respectively. On the other hand, the contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were increased as expected. These results indicated that the organic solvent nanofiltration technique had obvious effects on deodorisation of fish oil, and it would be a promising deodorisation method in fish oil refining industry.

Extraction of oil from high-moisture tuna liver by subcritical dimethyl ether: feasibility and optimization by the response surface method

The purpose of this paper is to explore the possibilities of subcritical dimethyl ether extraction (SDME) of oil from tuna liver with high-moisture content. The results showed that the oil and water were successfully co-extracted from the liver, and could be easily separated by centrifugation. In addition, the response surface method was employed to optimize the process parameters of SDME, including temperature/pressure, time and stirring speed. It was predicted that a temperature/pressure of 42/0.80 °C/MPa, time of 50 min and stirring speed of 925 rpm were the optimum within the experimental ranges, with an oil yield of 17.46 ± 0.23%. Furthermore, supercritical carbon dioxide extraction (SC-CO2) was studied comparatively. Only minor differences were observed between the oils extracted by SDME and SC-CO2, which indicated the high-quality of the SDME-oil. With no freeze-drying procedure and the relatively low pressure used in SDME, SDME could be a promising technique for extraction of marine fish liver oil.

Using Pretreatment of Carbon Monoxide Combined with Chlorine Dioxide and Lactic Acid to Maintain Quality of Vacuum-Packaged Fresh Beef

Due to microbial growth, beef easily gets corrupt in retail conditions, and the color and quality of the meat will be deteriorated. Therefore, hurdle technology, namely, pretreatment of carbon monoxide (CO), chlorine dioxide, and lactic acid, is used for vacuum-packaged beef to decontaminate beef and increase its quality stability. Beef was pretreated with 100% CO (C1), 100% CO and 50 mg/L chlorine dioxide (C2), and 100% CO and 50 mg/L chlorine dioxide and 30 g/L lactic acid (C3). The untreated samples were used as control (CK). During storage, the color parameters of C1, C2, and C3 were significantly higher than that of CK, indicating CO pretreatment is a good way to maintain color appearance of beef, and chlorine dioxide and lactic acid did not affect the color-protecting role of CO on beef. C3 showed the strongest antimicrobial activity with the lowest total viable counts, followed by C2, C1, and CK. Samples in C3 also showed the lowest total volatile basic nitrogen, pH, thiobarbituric acid reactive substance, and metmyoglobin during the mid-late storage. Moreover, C3 can keep beef with higher unsaturated fatty acids. In conclusion, CO pretreatment combined with chlorine dioxide and lactic acid displayed efficient antimicrobial and color-stability activity for vacuum-packaged beef. It would be a potential way to use pretreatment of CO combined with chlorine dioxide and lactic acid to maintain the quality of vacuum-packaged beef.

Decrease of Lipid Oxidation for Dried Shrimp (Acetes chinensis) Preservation Using Alkaline Lipase Hydrolysis Technology

ABSTRACT In this study, the degreasing technology using alkaline lipase hydrolysis for Chinese dried shrimp (Acetes chinensis) was investigated, with the purpose of decreasing lipid oxidation during dried shrimp preservation. The salt, moisture, and lipid contents of the shrimp were 6.01, 32.51, and 2.95%, respectively. The optimum enzymatic hydrolysis condition for effective decrease of shrimp lipid was obtained: lipase concentration 40 U/mL, pH 10, soaking time 60 min, soaking temperature 30°C, and shrimp/liquid ratio 1:20 (w:v). Under this optimum condition, the residual lipid of the shrimp was reduced to 2.28%, and the degreasing rate reached 49%. During 30-day preservation, the thiobarbituric acid-reactive substances (TBARS) value (0.185 mg/kg of dried shrimp and 0.131 mg/kg of degreased dried shrimp at Day 30) of degreased shrimp was lower than the shrimp without degreasing, indicating alkaline lipase hydrolysis could effectively prevent lipid oxidation and inhibit oxidative rancidity during dried shrimp preservation.