冻藏期间罗非鱼腥味变化及形成机理

对鱼肉品质变化指标和鱼腥味变化的测定分析,探究了冻藏期间罗非鱼腥味的主要形成机理。实验结果显示:共轭二烯(CD)值随着储藏时间的延长而不断增加,说明脂肪氧化发生于整个冻藏期间;挥发性盐基氮(TVBN)在贮藏9d后迅速上升,表明在鱼肉中已开始出现明显的微生物腐败;表征脂肪氧化程度的硫代巴比妥酸值(TBARS)值在12d的冻藏期中不断上升,并且在9d后急剧上升。对冻藏期间罗非鱼肉腥味进行感官评价,在新鲜鱼肉中青草味占主体,其强度随着贮藏时间延长而降低,然而鱼腥味、哈喇味、腐败味随之加剧,6d后样品中鱼腥味和哈喇味强度增加,9d后鱼肉中开始出现腐臭味。将品质变化指标与鱼腥味感官评价结果进行相关性分析发现,罗非鱼肉中鱼腥味等异味的产生主要是由于贮藏过程中鱼肉发生脂肪氧化,在后期也伴随着明显的微生物腐败。     

基于漂洗工艺的冷冻鱼糜冻藏过程中品质的变化规律

以西伯利亚鲟鱼肉为原料,通过漂洗制备冷冻鱼糜,研究冻藏期间蛋白质、脂肪和质构的变化规律。试验结果表明,冻藏过程中冷冻鱼糜肌原纤维蛋白质发生氧化,空间结构发生变化,使内部疏水基团暴露,肌原纤维蛋白活性降低,而漂洗可延长肌原纤维蛋白质的冷冻变性时间。冻藏过程中鲟鱼鱼糜的脂肪也不断氧化,而漂洗工艺可延缓脂肪酸的氧化。结合硫代巴比妥酸反应物值(TBARS)和气相分析结果,二十二碳六烯酸(DHA)和二十碳五烯酸(EPA)在冻藏中期开始迅速氧化。质构分析表明,漂洗工艺可抑制冻藏过程中冷冻鱼糜蛋白结构的劣化。     

不同速冻处理方式对大口黑鲈鱼肉冻藏期间品质变化影响

为比较液氮速冻、冷冻液浸渍速冻和平板速冻3 种速冻方式对大口黑鲈鱼肉冻藏期间品质变化的影响,将鲜活样品宰杀切块后冻藏,期间分别测定总挥发性盐基氮（total volatile base nitrogen,TVB-N）含量、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARs）值、pH值、剪切力、色差、解冻损失率和加压失水率等指标,综合分析冻藏期间鱼肉的品质变化。结果表明,冻藏0～12 周期间液氮速冻组鲈鱼块TVB-N含量显著低于平板速冻组与冷冻液速冻组（P＜0.05）,冻藏24 周时平板速冻组鲈鱼块TVB-N含量最低。冻藏期间TVB-N含量、TBARs值与解冻损失率呈上升趋势,加压失水率、剪切力均呈下降趋势,pH值呈先下降后上升趋势。冻藏结束时,平板速冻组鲈鱼块亮度值最低,液氮速冻组鲈鱼块红度值最大,冷冻液速冻组鲈鱼块黄度值最大。相关性分析结果表明,鱼肉脂肪氧化程度与持水性、新鲜度、色泽均呈极显著相关性（P＜0.01）。综上所述,液氮速冻可在一定程度上延缓鲈鱼肉冻藏品质的劣变,且较适用于短期贮藏。     

冻藏对淡水鱼肉品质及氯霉素残留的影响

选择鲢鱼、鲤鱼和鲶鱼肉为研究对象,对冻藏期间三种淡水鱼中品质及氯霉素残留消长变化进行了测定。结果显示:加入标准氯霉素后,随着冻藏时间的延长,三种淡水鱼肉的蛋白含量呈下降趋势,水分和灰分含量差异显著,脂肪变化无规律;三种鱼肉的L*值先升后降, 6周后,鲢鱼和鲤鱼呈上升趋势,而鲶鱼先升后降;冻藏期间,鲶鱼的a*值和b*值相比鲤鱼和鲢鱼差异显著;鱼肉的p H随着冻藏时间先下降后趋于平缓;鲢鱼和鲶鱼的硫代巴比妥酸值(TBARS)一直处于平缓,而鲤鱼6周后, TBARS值急剧增加;在冻藏初期,细菌总数有所下降,随冻藏时间的延长,三种鱼的细菌总数不同程度的提高;冻藏可以降解三种淡水鱼中的氯霉素残留量。结论:鲶鱼可以贮藏4周,鲢鱼和鲤鱼鱼肉可以贮藏6周。     

不同冻藏温度对金枪鱼肉肉色变化的影响

以黄鳍金枪鱼背部肌肉为研究对象,测定不同的冻藏温度(-18℃,-25,-55℃)对肌肉颜色(a*值)、高铁肌红蛋白的含量、脂肪氧化的影响。结果表明:随着冻藏时间的延长,a*值呈下降趋势;高铁肌红蛋白含量增加、脂肪氧化值增加;在不同的冻藏温度下,肌肉a*值变化显著(p<0.05);冻藏温度越低,a*值,脂肪氧化值变化越小,肌红蛋白氧化成高铁肌红蛋白的量越少。     

冻藏肉及其制品中蛋白氧化的研究进展

冻藏是肉及其制品最重要的贮藏方式,可有效抑制微生物生长繁殖及酶促反应,从而延长其货架期。然而,肉及其制品在长期冻藏过程中不可避免地发生品质下降。除冰晶、嗜冷微生物、干耗、脂肪氧化等因素外,蛋白氧化在品质劣化中所发挥的作用受到关注。本文综述肉及其制品中蛋白氧化的发生机制、氧化结果以及检测方法;冻藏过程中影响蛋白氧化的因素,包括冻藏温度、冻藏时间、原料性状、冻前处理、温度波动及反复冻融;由冻藏引发的蛋白氧化对肉及其制品食用品质的影响,包括持水性、质构、风味、色泽与营养。蛋白氧化为研究肉及其制品冻藏过程中品质变化机理提供了一个新的研究角度。     

冻藏条件对带鱼鱼肉及其鱼糜凝胶特性的影响

为研究不同冻藏条件对带鱼鱼肉及其鱼糜凝胶特性影响,将新鲜带鱼分别置于-7、-13、-18和-23℃下冻藏15～120 d,期间测定带鱼鱼肉理化特性(羰基、巯基、Ca²⁺-ATPase活性、TBARS),随后将鱼肉制成鱼糜凝胶后测定凝胶特性(色泽、凝胶强度、持水力),并结合扫描电镜观察微观结构。结果表明,随着冻藏时间的延长,鱼肉羰基含量和TBARS值逐渐升高,巯基含量和Ca²⁺-ATPase活性下降。冻藏温度越低,鱼肉的各项指标变化程度越小。除-7℃冻藏60 d后的样品TBARS值大于0.58 mg MDA/kg外,其余样品均未发生腐败。随冻藏时间的延长,带鱼鱼糜凝胶色泽逐渐劣变,持水力逐渐降低,冻藏温度越低色泽和持水力的变化越小。带鱼鱼肉在四个温度下冻藏120 d制成的鱼糜凝胶,其凝胶强度分别下降了72.33%、54.13%、39.17%和29.31%。通过SEM观察发现更低的冻藏温度能够使鱼糜凝胶保持良好的三维网状结构,抑制带鱼凝胶的劣变。综上,随冻藏时间的延长,带鱼鱼肉及其鱼糜凝胶特性逐渐劣变,随着冻藏温度由-7℃降低到-23℃,劣变过程...     

蓝鳍金枪鱼脂肪氧化和鱼肉色泽的变化研究

结合脂肪氧化和鱼肉色泽指标,观察蓝鳍金枪鱼赤身肉、中腹肉和大腹肉在低温冻藏条件(-18℃)下的变化情况,并对各指标进行相关性分析。结果显示:随着冻藏时间的延长,3个部位肌肉的TBA值和metMb%(高铁肌红蛋白含量)增加;a*值、总色素含量和感官评定值都呈下降趋势;大腹肉变色最快,中腹肉次之,赤身肉最不明显;metMb%与a*值呈极显著负相关(R=-0.943,P0.01),与TBA值呈极显著正相关(R=0.914,P0.01)。分析认为蓝鳍金枪鱼各部位肌肉虽都有褐变的趋势,但速率不同,脂肪含量越高的部位褐变越快;若要保证金枪鱼鱼肉的色泽,必须采取措施防止脂肪氧化和高铁肌红蛋白的产生。     

谷氨酰胺转氨酶对鱼肉保水性的影响

以罗非鱼肉为原料,研究了谷氨酰胺转氨酶对鱼肉保水性的影响。结果表明,谷氨酰胺转氨酶具有明显的保水作用,鱼肉浸泡增重率随谷氨酰胺转氨酶浓度的增加而增加,解冻损失率随之减小。经不同浓度谷氨酰胺转氨酶处理的鱼肉浸泡增重率达6.5%以上,大于对照组2%复合磷酸盐的5.35%,谷氨酰胺转氨酶浓度为0.6%时,浸泡增重率和冻藏1d时解冻损失率分别为8.04%和3.4%,保水效果较优;考察了谷氨酰胺转氨酶处理的鱼肉冻藏40d期间的蒸煮损失率和持水力的变化,冻藏40d的鱼肉蒸煮损失、水分含量和持水力值均小于冻藏1、10、20d的,说明鱼肉冻藏40d内的鱼肉品质仍较好。谷氨酰胺转氨酶保水效果显著,其浓度在0.6%时能有效保持鱼肉的持水性能,赋予鱼肉很好的品质。     

冷冻贮藏引起的鱼肉蛋白变性及物理化学特性的变化

冷冻贮藏是鱼类重要的贮藏方法,但不适当的冻藏和缓化会引起鱼肉肌原纤维蛋白的变性,造成鱼肉质量降低。鱼肉蛋白质变性主要和蛋白质的结构变化有关,包括空间结构的变化、溶解性的变化、Ca2+-ATPase活性变化、巯基和二硫键含量变化、表面疏水性变化及海水鱼中甲醛含量的变化,而结构的变化进一步影响蛋白质的功能特性。本文主要论述鱼肉蛋白质的冷冻变性机理,并对鱼肉蛋白质在冷冻贮藏期间引起的蛋白质物理化学特性的变化进行论述。     

Enrichment of Chicken Nuggets with Microencapsulated Omega-3 Fish Oil: Effect of Frozen Storage Time on Oxidative Stability and Sensory Quality

This work studies for the first time the elaboration of frozen chicken nuggets enriched with microcapsules of omega-3 fatty acids using fish oil. Three types of chicken nuggets were prepared: control (C), enriched in bulk fish oil (BFO), and with added microencapsulated fish oil (MFO). Effect of length of frozen storage after pre-frying and before domestic frying was studied. The pre-fried nuggets were stored during 24 h at refrigeration temperature (0–2 °C) (T0) or during 1 month (T1M) or 3 months (T3M) in a domestic freezer at ?18 °C before frying. Length of frozen storage after pre-frying and before domestic frying promoted lipid and protein oxidative reactions in omega-3-enriched nuggets. Microencapsulation showed a protective effect against lipid and protein oxidation, especially during the first month of storage. In MFO, sensory traits were not affected by enrichment. In BFO-T0, a higher juiciness and saltiness and a less intense meat flavor in comparison with C-T0 and MFO-T0 was found. Time of frozen storage did not influence the sensory quality of chicken nuggets enriched with omega-3. Microencapsulation seems to be a promising method for enrichment of pre-fried frozen meat products with fish oil, improving the oxidative shelf life and preserving the sensory quality characteristics of the enriched products.     

FROZEN STORAGE STUDIES OF VALUE-ADDED MINCE-BASED PRODUCTS FROM TILAPIA (OREOCHROMIS MOSSAMBICUS, PETERS 1852)

Tilapia ( Oreochromis mossambicus ) is a relatively abundant, low-value fish that has wide distribution in India because of its adaptability to different environments. However, the fish has limited scope for consumption in the fresh form. This study is an attempt to explore the possibilities of better utilization of this species by development of mince-based value-added products and the evaluation of shelf life during frozen storage. Mince from tilapia was used for the preparation of value-added products viz., chilly fish, fish cutlets and fish balls. The biochemical and sensory parameters of these products were analyzed to study the quality changes and shelf life of these products in frozen storage at − 20C. Fish cutlets and fish balls remained acceptable up to 18 weeks of storage after which loss in flavor and texture was noticed. Chilly fish remained acceptable for 21 weeks in frozen condition.

PRACTICAL APPLICATIONS

The study aims in value addition of tilapia ( Oreochromis mossambicus ), a low-value fish, which at present has only limited scope for consumption in fresh form. Earlier studies showed that the mince yield of this species is 32–36%. The quality of tilapia mince is comparable to that from other marine and freshwater species of commercial importance. Utilization of the mince for the production of cutlets, fish balls and chilly fish are simple and a cost-effective means of converting tilapia to value-added convenience products. Shelf life studies indicate that in frozen storage, the products can retain the sensory qualities for 18–21 weeks. Commercialization of these products can contribute to diversification in the fish processing industry through better utilization of a relatively underutilized species.     

Effects of chitosan coating on quality and shelf life of silver carp during frozen storage

The effects of chitosan coating on quality and shelf life of silver carp during frozen storage were investigated. Fish samples were treated with aqueous solution of 2% chitosan, and then stored at −3 °C for 30 days. The control and the treated fish samples were analyzed periodically for microbiological (total viable count), chemical (pH, TBA, TVB-N, K-value), and sensory characteristics. The results indicated that the effect of chitosan coating on fish samples was to retain their good quality characteristics and extend the shelf life during frozen storage, which was supported by the results of microbiological, chemical, and sensory evaluation analyses.     

Effect of plant extracts on lipid oxidation during frozen storage of minced fish muscle

The aim of the study is to determine the effect of pomegranate seed extract (PSE) and grape seed extract (GSE) addition to chub mackerel minced muscle on lipid oxidation during frozen storage. Each extract was added to minced fish muscle at 2% concentration and then stored at ?18 °C for 3 months. The effect of plant dietary fibres to control lipid oxidation was compared with untreated samples (control). Formation of lipid hydroperoxides and thiobarbituric acid‐reactive substances (TBARS) was significantly inhibited by PSE and GSE addition when compared with control. Both extracts significantly retarded lipid oxidation according to the results of TBARS. A significant reduction of L* (lightness), a* (redness) and b* (yellowness) values was detected during frozen storage. GSE added samples had the highest redness and the lowest lightness and yellowness. However, samples with PSE showed the lowest redness and highest yellowness and h° (hue angle) values. The results from this study suggest GSE is a very effective inhibitor of primary and secondary oxidation products in minced fish muscle and have a potential as a natural antioxidant to control lipid oxidation during frozen storage of fatty fish.     

Effect of brine pre-treatment on lipid stability of frozen horse mackerel (<Emphasis Type="Italic">Trachurus trachurus</Emphasis>)

The rancidity development during the frozen storage (-20 °C) of an under-utilised medium-fat fish species (horse mackerel; Trachurus trachurus) was investigated. Special attention was given to a pre-freezing treatment consisting of an immersion in NaCl solution (5%, 10%, and 20%) and its effect on lipid damage during the fish frozen storage. Lipid hydrolysis (free fatty acid content) and oxidation (conjugated dienes formation; peroxide value, PV; thiobarbituric acid index, TBA-i; fluorescence formation, FR) were studied up to 270 days of frozen storage. Oxidative rancidity measured by the PV, TBA-i, and FR showed an increase with the frozen storage time and also as a result of an increasing salt content in fish muscle. A high peroxide formation was observed at day 210 of frozen storage, especially in the case of 20% NaCl treated samples. Lipid hydrolysis also increased with the frozen storage time; at the end of the experiment (270 days), a decreasing effect of muscle salt content on lipid hydrolysis was observed. Employment of appropriate antioxidant additions is recommended if salting pre-treatment is to be needed to avoid a large lipid oxidation development and ensure a longer shelf-life time.     

Lipid Hydrolysis and Oxidation Related to Astaxanthin Content in Light and Dark Muscle of Frozen Stored Rainbow Trout (Oncorbynchus mykiss)

Astaxanthin decreased significantly during frozen storage in both light and dark muscle of farmed rainbow trout (Oncorhynchus mykiss). Astaxanthin sunolementation did not affect lipid hydrolysis and oxidation during frozen storage of fish muscle. Deposition of astaxanthin was higher in dark muscle than in light muscle. Astaxanthin decreased in both supplemented and nonsupplemented fish. The sum of trans-astaxanthin and its cis-isomers decreased during frozen storage, indicating mechanisms other than trans-cis isomerization were causes. α-Tocopherol decreased to the same extent in both light and dark muscle for both diets.     

Evaluation of the effectiveness of a new active packaging film containing natural antioxidants (from barley husks) that retard lipid damage in frozen Atlantic salmon (Salmo salar L.)

Salmon is a perishable fish that contains high level of PUFAs (polyunsaturated fatty acids), which have many positive effects on human health, but which are extremely susceptible to oxidation. The development of new food packaging films by incorporation of antioxidants is expected to improve the shelf life of food and thus increase consumer safety and health. Determination of peroxide value (PV), conjugated dienes (CD), conjugated triene hydroperoxides (TH), free fatty acids (FFA), totox value (TV), thiobarbituric acid index (TBARS) and p-anisidine value (AV) by established methods proved suitable for studying lipid hydrolysis and primary and secondary lipid oxidation in samples of salmon during frozen storage. The results obtained confirm the efficacy of natural antioxidants derived from barley husks (NABH) in slowing down lipid hydrolysis and increasing the oxidative stability of salmon flesh. This study demonstrates the potential usefulness of natural antioxidants extracted from barley husks in the development of active packaging films for food preservation.     

去头/内脏处理对秋刀鱼冷藏特性的影响

为了探究去头/内脏处理对秋刀鱼冷藏货架期和腐败特征的影响,分析了不同形态秋刀鱼在4 ℃贮藏过程中感官评分、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、硫代巴比妥酸反应物（thiobarbituric acid-reactive substance,TBARS）值、微生物指标（细菌总数）以及气味组成的变化规律。结果显示,随着贮藏时间的延长,2 组秋刀鱼样品的感官评分都呈下降趋势,去头/内脏处理组的下降趋势更为明显;处理组的TVB-N值在第8天时接近30 mg/100 g,而对照组在第12天时才达到该界限值,略滞后于感官评分指示的货架期终点;去头/内脏处理加速了鱼肉脂质的氧化速度,但2 组样品在货架期终点时TBARS均未超过5 mg/kg的限值;处理组的细菌总数初始值显著高于对照组（P＜0.05）,在第8天时超过7.0（lg（CFU/g））,对照组样品在贮藏第10天时接近该界限值。完整态秋刀鱼4 ℃贮藏的货架期为10～12 d,去头/内脏处理组的货架期约为8 d。货架期终点时2 组样品对应的电子鼻气味组成有显著性差异,表明腐败进程明显不同。     

Influence of feeding state and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus)

Lipid deterioration of mackerel caught in Icelandic waters was studied, as affected by different frozen storage temperatures (?18 °C vs. ?25 °C) and seasonal variation (August vs. September). The lipid stability was investigated by analyses of hydroperoxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acids, as well as changes in fatty acid composition. Results showed significant lipid deterioration with extended storage time, where the lower storage temperature showed significantly more protective effects. Furthermore, a higher lipid oxidation level was recorded for fish caught in September than in August, although lipid hydrolysis occurred to be greater for fish in August than in September. Moreover, results indicated a rather stable level of omega‐3 fatty acid during the whole frozen storage period. The analysis indicated that both lipid oxidation and hydrolysis were affected by the frozen storage temperature and the stability differed with regard to season of catch.     

Effects of plant extracts on lipid oxidation in fish croquette during frozen storage

The aim of this study was to investigate the effects of tomato and garlic extracts on lipid oxidation in fish croquette during frozen storage. The fish for croquette was purchased from the main fish market in Antalya, Turkey. Commercial tomato and garlic extracts were added into the croquette formulation. Lipid quality of frozen croquettes was analyzed at monthly intervals. There was no difference in free fatty acids and UV absorbance values of treatment groups. Treatment of tomato and garlic extracts kept oxidation at low levels. The results for thiobarbutiric acid, para-anisidine, and conjugated-diene values showed that tomato extract was the most effective in delaying lipid oxidation than garlic extract.