| Bamboo extract is a series of plant metabolites produced from different parts of bamboo via modern technology. Green bamboo extract (GBE) is an excellent biological antioxidant, lipid metabolism regulator and immune function reinforcing agent. Its main components include flavones, phenolic acids, polysaccharides, triterpenes, lactones, anthraquinone, amino acids, polypeptides, and mineral elements, etc. GBE has large potential for research and application as feed additive. Antioxidant of bamboo leaves (AOB-w) with flavonoids and phenol acids as its main compounds is a natural food additive. AOB is characterized as anti-free radical, anti-oxidation, anti-bacterial and antimicrobial, etc.This research focused on two major aspects:1) GBE was used on cultured large yellow croaker as a feed additive to improve its quality and2) AOB was used on refrigerated large yellow croaker as a biological preservative. Results were as follows:1. Biological indicators of the large yellow croaker fed by the new environmental feed with0.3%green bamboo extract and those of the control group fed by frozen wild fish were compared. Results showed that there were significant decreases in the fat content in the liver, abdominal muscle and back muscle in the GBE group (p<0.05). Symptoms of fatty liver disease were alleviated. In the same group, levels of polyunsaturated fatty acids (particularly linoleic acid and linolenic acid), essential amino acids and flavor amino acids in the fish meat were improved. Compared to control group, levels of calcium, iron, potassium and zinc were also higher by relatively large margins (calcium content was about300%that in the control group). Back muscle transmission electron microscope results showed that fish muscle in the GBE group was rich in collagen and mitochondria but low in fat. Sensory evaluations on the flavor, meat quality and taste showed that the GBE group had an apparent advantage over the control group. The results indicated that GBE used in the cultivation of large yellow croaker could help stimulate lipid metabolism, prevent fatty liver and improve its eating quality.2. To prolong the shelf life of refrigerated large yellow croaker water solutions of AOB concentrated at0.1%and0.2%were applied to samples from the control group before refrigerated at (4±1)℃.0.2%of Tea Polyphenols (TP) and saline were used as positive control and blank control, respectively. During the refrigeration the thiobarbituric acid (TBA) value, pH, texture, the volatile basic nitrogen (TVB-N) value and the K value were determined every two days to evaluate the effects of AOB as a biological preservative. Results showed that both AOB and TP could effectively extend the shelf life of refrigerated large yellow croaker but AOB showed higher efficacy with the same concentration. The best performance of AOB was observed with concentration of0.1%. It was proved that AOB was a potential biological preservative for seafood. In addition, comparisons of the thiobarbituric acid (TBA) value, pH, the volatile basic nitrogen (TVB-N) value and the K value of the fish samples from the GBE group and the control group during refrigeration revealed that corruption speed and degree of metamorphism of the GBE group were significantly lower than those of the control group.3. Different freezing and processing methods of frozen large yellow croaker were studied. Fish samples were frozen in liquid nitrogen and-80℃for10min. Slow freezing was used as blank control. The samples were frozen at (-20±0.5)℃for15months. During the period pH、the K value and the thevolatile basic nitrogen (TVB-N) value were determined every three months to assess the changes in biochemical characteristics of large yellow croaker. Results showed that, although the quick-freeze processes failed to prevent the dropping of salt-soluble protein content and pH value, compared to the blank control, quick-freeze processes to some extent lowered the speed of corruption and protein denaturation and improved the quality of fish. In addition, the degree of metamorphism in the GBE group was significantly lower than in the control group when both frozen at (-80±0.5)℃.To summarize, GBE as a feed additive could help improve the quality of and preserve cultured large yellow croaker. AOB has the potential as a biological preservative for seafood. |
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