Shuxian Hao

The effects of different extraction methods on composition and storage stability of sturgeon oil.

The objective of this study was to assess the effect of different extraction methods on oil yield, colour attributes, oxidative stability, fatty acids composition and production of volatile compounds in sturgeon oil during storage. The supercritical fluid extraction (SFE) method with carbon dioxide resulted in higher oil yields, better colour attributes, and higher oxidative stability compared to other traditional extraction methods such as enzymatic extraction, amino, and wet reduction. After storage at 4 °C for 33 days, the aldehyde content in oil extracted by the enzymatic extraction and wet reduction methods was twice as high as that obtained by the other methods. There was a significant reduction in the content of total acids in oils extracted by the enzymatic extraction and wet reduction methods (p<0.05), whereas amine compounds were mainly detected in oil extracted by the amino method. The oil extracted by SFE exhibited higher UFA and lower SFA. Significant diffidence among PUFA with C above 20 was observed in oil extracted with SFE.

Effect of Ultrastructure on Changes of Textural Characteristics between Crisp Grass Carp (Ctenopharyngodon Idellus C.Et V) and Grass Carp (Ctenopharyngodon Idellus) Inducing Heating Treatment

The research studies the ultrastructure effect on texture of crisp grass carp (CGC) and grass carp (GC) fillets inducing heating for 15, 25, and 40 min with boiling water. After heating, the hardness, fracturability, springiness, chewiness, resilience, and cohesiveness of CGC were higher than that of raw CGC, whereas the all textural characteristics of heating GC were lower obviously than that of raw GC. The hardness, fracturability, springiness, chewiness, resilience, and cohesiveness of CGC for heating 15 min were higher by 6.3%, 9.0%, 27.0%, 71.8%, 9.4%, and 23.9%, respectively, than that of raw CGC (RCGC). The hardness increasing of CGC flesh with the extension of heating time related closely to more coagulating connective tissue in interstitial spaces, especially relating to smaller muscle fiber diameter and denser muscle fiber density. The more and larger spaces between fiber and fiber with the extension of heating time results in the decrease of cohesiveness and resilience of CGC flesh. For chewiness, the stronger chewiness of cooked CGC associated with more detachment of myofiber-myocommata and fiber-fiber. Overall, the results show that the changes of texture characteristics of CGC fillet with extension of heating time correlates positively with the ultrastructure.

Changes in apoptosis factors and activation of caspase-3 in tilapia muscle during storage

ABSTRACT The activation of the apoptosis pathway in tilapia muscle during postmortem storage was studied. Changes in caspase-3 activity, ATP content, cytochrome c levels, and ratio of Bcl-2/Bax levels of tilapia muscle were observed during postmortem storage at 20°C. Caspase-3 activity was found to be significantly increased at first, followed by a decrease (P < 0.05); the highest caspase-3 activity was observed at 1 h. The ATP content decreased significantly (P < 0.05), and almost exhausted after 10 h storage. The cytochrome c level in the cytosol showed a significant increase after 5 h of storage (P < 0.05), while the mitochondrial cytochrome c levels showed a decrease. The Bcl-2/Bax ratio was stable from 0–5 h, followed by a rapid decreased at 10–20 h and a significant increased after 20 h (P < 0.05), suggesting that the apoptosis process occurred until 20 h of postmortem storage. Thus, we concluded that the availability of ATP and the increase in cytosolic cytochrome c levels are essential for the activation of caspase-3, and that the former partly limits caspase-3 activity.