【作者】 应巧玲；

【导师】 励建荣； 蒋跃明；

【作者基本信息】 浙江工商大学 ， 食品科学与工程， 2011， 硕士

【摘要】 海鳗因其肉质细嫩,味道鲜美,营养丰富,其各种制品广受人们的青睐。海鳗产业不仅在我国渔业经济中占重要地位,而且已成为一些地方经济的支柱产业。然而由于海鳗肌肉中脂肪含量较高,极易产生氧化酸败的问题,不仅会使产品产生油哈败味,还会使产品发生褪色、褐变、维生素破坏,降低产品品质和营养价值,甚至产生有害物质引起食物中毒,氧化安全性差,导致其加工难度增大,达不到制成品应有的货架期要求。倘若能有效控制海鳗脂肪氧化酸败,则不仅能保护其食用品质,更能使其加工难度降低,节省大量的能耗和成本,使企业增效。基于上述原因,本文以海鳗为研究对象,从脱脂和添加抗氧化剂两方面开展研究：(1)选用碱性脂肪酶进行海鳗脱脂,通过响应面设计优化酶法脱脂工艺,并考察了酶法脱脂对海鳗氧化酸败的抑制作用,以及对海鳗脂肪酸组分的影响；(2)选用茶多酚(TP)、蜂胶、迷迭香提取物、葡萄籽提取物、甘草提取物、Vc、生姜提取物、大蒜提取物8种天然抗氧化剂,通过体外自由基清除能力的比较以及在海鳗体系中单一抗氧化效果的比较,筛选出4种天然抗氧化剂(TP、蜂胶、迷迭香提取物和葡萄籽提取物),进一步研究其协同作用,并利用混料设计中的单纯形质心设计法进行复合抗氧化剂的配方优化；最后综合研究了脱脂与复合天然抗氧化剂的结合在海鳗体系中的抗氧化效果以及对货架期的影响。主要结论如下：通过响应面设计确定了海鳗酶法脱脂的最优条件,即：酶用量38U/mL,最适pH9.7,浸泡时间61 min,鱼液比1：4(W/V),最适温度30℃。脱脂对海鳗抗氧化酸败有较明显的作用,有效地控制了脂肪氧化异味的产生。经过酶法脱脂后,多不饱和脂肪酸相对含量有所增加,特别是二十碳五烯酸(EPA)从6.257%增加到11.222%,说明酶法脱脂对EPA有一定的保留作用,即EPA等不饱和脂肪酸在脱脂过程中破坏较少或不会被破坏。经各种天然抗氧化剂对DPPH自由基、超氧阴离子自由基和羟自由基清除能力的比较,初步筛选出TP、迷迭香提取物、蜂胶、葡萄籽提取物、Vc和甘草提取物6种。然后在海鳗体系中进行进一步筛选,结果表明：TP、迷迭香提取物、蜂胶和葡萄籽提取物的抗氧化活性都较好,浓度在0.03%时就能明显降低海鳗片的TBA值,且在0.05%以内,对海鳗片的质构、色泽和感官影响可忽略。4种天然抗氧化剂两两协同作用研究表明：在试验浓度范围内,除了TP和迷迭香提取物之间协同作用不明显,其他几种抗氧化剂之间均表现出明显的协同增效作用。基于成本与海鳗片品质的问题,本试验选用TP、蜂胶和葡萄籽提取物进行复合。应用混料设计中的单纯形质心法,确定了复合天然抗氧化剂的优化配比,即：TP浓度为0.0144%,蜂胶浓度为0.0061%,葡萄籽提取物浓度为0.0096%。脱脂与复合天然抗氧化剂的结合应用研究表明：从抗氧化效果来讲, (脱脂+抗氧化剂)处理组的效果最明显,在第16天时TBA值为0.094mg/kg,抗氧化剂处理组在第16天时TBA值为0.247mg/kg,脱脂组在第12天时TBA值超过1mg/kg,而空白组在第8天时TBA值就超过1mg/kg。说明脱脂与复合天然抗氧化剂的结合能更好地抑制海鳗的氧化酸败,能进一步增强抗氧化效果；从货架期方面考虑,该复合天然抗氧化剂对海鳗片能起到一定的保鲜防腐作用,经复合抗氧化剂处理后,菌落总数、TVB-N值和pH值相对较低,而脱脂对海鳗片的货架期没有显著影响,起不到延长货架期的效果,脱脂与复合天然抗氧化剂的结合对货架期的延长也没有协同作用。更多还原

【Abstract】 Eel products are favored by consumers at home and abroad by the flesh of eel is tender, delicious, and nutrient. The eel industry occupies an important position in our country fishery economy, and has become one of the pillar industries in some local economy. However, due to the high fat content, eel products were oxidated easily. The oxidative rancidity problems occurred easily and made the quality of eel products decrease.For example, the tapinoma-odour is produced, fading and browning is happened, and the vitamins are damaged, even some harmful substances are forming. All these changes make the processing of eel difficult and the shelf life of eel products short. If the oxidative rancidity problem of eel products can be controlled effectively, the good quality of eel products will be kept, and a lot of energy and cost will be saved.Based on those above reasons, Pike eel process was studied in two ways (defatting and addition of antioxidant) in this paper:(1) The defatting test of Pike eel fillet by alkaline lipase was studied. The optimum conditions were selected by response surface methodology (RSM). Meanwhile, the difference of anti-oxidative effects between defatted and nondefatted pike eel fillet was comparied, and the effect of defatting on Pike eel’s fatty acid composition was determined. (2) Eight kinds of natural antioxidants (TP, propolis, rosemary extract, grape seed extract, licorice extract, Vc, ginger extract and garlic extract) were choosed. These antioxidants were sifted by the free radical-scavenging activity and the antioxidant activity in the eel, four kinds of natural antioxidants (TP, propolis, rosemary extract and grape seed extract) which had higher antioxidant activity were determined. Then synergistic effect based on these four kinds of natural antioxidants was studied. The composite antioxidants’formulation was optimized by the simplex centroid mixture design. At last, the combined action of defatting and complex natural antioxidants was studied. The results were shown as follows:The optimum conditions of enzymatic dafatting selected by response surface methodology were:alkaline lipase concentration:38 U/mL; pH: 9.7; marinating time:61 min; fish/liquid ratio:1/4(W/V); temperature: 30℃. The results showed that defatting have certain antioxidation. Fatty acid analysis showed that the polyunsaturated fatty acids’relative content were increased after defatting, especially the relative content of eicosapentaenoic acid (EPA) was increased to double almost. It indicated that the alkaline lipase could retain more EPA. Namely, the unsaturated fatty acid, such as EPA, was less destroyed, even without destruction in defatted process.Six natural antioxidants (TP, rosemary extract, grape seed extract, propolis, Vc and licorice extract) were preliminary screened through comparison of DPPH·, O2 and the hydroxyl radical scavenging capacity. Then, further experiments show that:TP, rosemary extract, propolis and grape seed extract have higher antioxidant activity in the eel system.The synergistic effects based on four natural antioxidants in the eel system were studied. The results showed that the strong synergistic effect was existed between each other in the test range, except TP and rosemary extract, the synergistic effect between them was not obvious. Based on the cost and quality problem, TP, propolis and grape seed extract were selected to composite, the optimal proportion determined by the simplex centroid mixture design was:TP concentration:0.0144%, propolis concentration:0.0061%, grape seed extract concentration:0.0096%.On the antioxidative effect, combination of defatting and complex natural antioxidants could decrease fat oxidation of eel products preferably. Combination could enhance the antioxidant activity. On the Shelf-life, the complex natural antioxidants had antiseptic effect, could extend the shelf-life of eel products, whereas defatting had no effect on the shelf-life of eel products, combination of defatting and complex natural antioxidants didn’t show obvious enhancement effect.更多还原