| China is known as’the kingdom of bamboo’. It is rich in not only the area of bamboo forest, but also the bamboo culture with long history. There are a wide range of edible and medicinal products from bamboo that have been used for a long history. Bamboo extract is a series of plant metabolites, produced from different parts of bamboo via modern technology, including flavone of bamboo leaves, antioxidant of bamboo leaves, triterpenoid of bamboo shavings, sterol of bamboo shoot, peptide of bamboo shoot, bamboo polysaccharide, etc.Antioxidant of bamboo leaves (AOB), is produced from the phenol composition of Phyllostachys Sieb. Et Zucc., in which the flavone of bamboo leaves is the main ingredient, and also approved as food antioxidants in Chinese national standards (GB-2760). AOB, with the flavonoids and phenol acids as main compounds, could not only inhibit oil oxidation, but also mitigate the formation of endogenous chemical pollutants (acrylamide) in the heating food producing.Green bamboo extract (GBE), extracted from different parts of bamboo by patent technology, including the phenol acids of bamboo leaves, polysaccharide of bamboo shavings and peptide of bamboo shoot. It is a kind of excellent biological antioxidants, lipid metabolism regulator and immune function reinforcing agent, rich in plant secondary metabolites, which mainly included flavones, phenolic acid, polysaccharide, terpene lactones, anthraquinone, amino acids, polypeptides, mineral element and so on. GBE has the huge potential of research and application as feed additive.The key research contents:1) AOB was used in cookie (a kind of crisp biscuit with high level of oil, sugar, protein) processing as a food antioxidant and acrylamide inhibitor;2) GBE was used in cultured large yellow croaker as a feed additive to improve the edible quality and safety. The main research results were summarized as follows:1) Determination of total flavonoid content is the key point of bamboo extract quality control. Researchers found that bamboo extract contains a considerable amount of poly-hydroxyl phenolic acid, which also could chelate with aluminium ion, affecting the chromogenic reaction results; In addition, bamboo extract contains no rutin, but isoorientin as its characteristic flavonoid. These two reasons made the Al (NO3)3-NaNO2colorimetric method using rutin as standard not suitable for the total flavonoids determination of bamboo extract. This research established the ultraviolet spectrophotometric method with isoorientin as the standard in detection of total flavonoids of bamboo extract for the first time. After polyamide purification, bamboo extract could be directly detected at340nm with isoorientin as the standard, befitting the rapid detection in the bamboo extract production. This method was more suitable for the total flavonoids determination of bamboo extract and subsequent products than the Al (NO3)3-NaNO2colorimetric method, for its high reliability, accuracy and sensitivity.2) We optimized the microwave extraction technology of total flavonoids in bamboo leaves by orthogonal experiment. The influence of four factors on total flavonoids yield was sequenced by range analysis as follows:ethanol concentration> microwave power> liquid-solid ratio> microwave irradiation time. In the variance analysis, the ethanol concentration, microwave power and liquid-solid ratio affected the flavonoid yield very significantly (p<0.0\), while microwave irradiation time performed significantly (p<0.05). In the condition of ethanol concentration (12.5%), solid-liquid ratio (1:12), microwave irradiation time (4.5min) and microwave power (900W), the flavonoid yield could reach83.23%. Compared to the traditional heat reflux extraction, microwave technology could be more effective in the flavonoid extraction of bamboo leaves, with lower consumption of organic solvent, less heating time. This technology was an environmentally friendly and low-energy consumesd method, which would be more suitable for the large-scale production of bamboo leaves extract.3) Antioxidant of bamboo leaves (AOB), a legal food additive, used in cookies processing, could reduce the acrylamide level effectively. Tested in the antioxidant evaluation in-vitro system, antioxidant activity of AOB was found positively correlated with the content of flavonoid. The AOB prepared by solution adsorption method performed better than the AOB purificated by macro porous resin in acrylamide inhibition, although the latter had higher flavonoid content and stronger antioxidant activity. According to the composition analysis, the acrylamide inhibition ability of food additive couldn’t be supposed to relate with flavonoid content and the antioxidant activity, which maybe actually relate with the other substances (such as phenolic acid, etc.) in the antioxidant. The antioxidant activity of cookie system decreased, along with the acrylamide inhibition by exogenous AOB. It indicated that AOB could influence the Millard reaction processing at a certain degree, leading to the reduction of melanoidins, which contributed obviously to the antioxidant activity. In comparison of five antioxidants in the inhibition of acrylamide formation and sensory evaluation, AOB (0.2g/kg) and VE (0.1g/kg) mitigated the formation of acrylamide by63.9%and71.2%, respectively, with the achievement of the balance between acrylamide reduction and sensory acceptance. This work showed the potential effectiveness of AOB in practical food system for decreasing acrylamide formation.4) Green bamboo extract (GBE) was used in the cultivation of large yellow croaker, to activate its lipid metabolism, strengthen the body immunity and anti-stress ability, improve the quality and ameliorate the edible safety. The large yellow croaker fed by the new environmental feed added with0.3%green bamboo extract (0#feed), was compared with the control group and the wild ones. The results indicated that there is significant decrease in the fat content in the liver, abdominal muscle and back muscle of test group, after6-month feeding. The fatty liver disease symptom was improved obviously, along with the reduction of liver-body ratio. Moreover, the polyunsaturated fatty acids (particularly linoleic acid and linolenic acid) level in the fish meat increased, which was very important to the nutrition value and fish immunity. Sensory evaluation, including the flavor, meat quality and taste, showed that the similarity between0#group and wild ones was close to80%, with an obvious sensory improvement compared to control group. Transmission electron microscope results showed that the fish muscle from test group, whose muscle texture was closer to the wild group, was rich in collagen and mitochondria, but low in fat. In addition, large yellow croakers fed by GBE had built up greater immunity, and stronger disease resistance. In the measurement by a gas chromatograph coupled to a high resolution mass spectrometer, persistent organic pollutants level (including polychlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls, and polybrominated diphenyl ethers) in fish from GBE group was lower than in wild group, which could be considered as a key factor to the edible safety.5) Based on the previous experiments, GBE was optimized by adjusting the ratio of bamboo leaves extract, bamboo shavings extract and bamboo shoots extract as three formulas(1#,2#,3#), which was then added in the feed by0.3%, compared with control group,0.1%astaxanthin positive control group and0#group in the sea-cages breeding of large yellow croaker. The results showed that1#and2#formulas performed better in reducing muscle fat and liver fat content than0#, close to and even better than the effect of astaxanthin. In measurement of adiponectin level, fish from1#and2#group activated in lipid metabolism, for the higher level of adiponectin, which indicated that the way of promoting lipid metabolism by these formulas was via regulating lipid metabolism related hormone. Feed added by GBE could effectively regulated the CAT and SOD activity, which could be considered as an important factor to enhance the body against free radicals, especially the degradation products of polyunsaturated fatty acid peroxidation (MDA, etc.), avoiding the liver damage. It was possible that the composition of flavour amino acids was the major cause of sensory improvement of GBE groups, according to the results of sensory evaluation and amino acid determination. Comprehensively, the feed added with0.3%GBE2#could increase the level of total amino acids, essential amino acids, flavour amino acids, polyunsaturated fatty acid (especially DHA and EPA) and UFA/SFA index, etc. similar to the effect of0.1%astaxanthin. It showed that GBE could be used as a natural feed additive in high-end aquatic breeding. |
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