Bacterial Spoilage Profiles to Identify Irradiated Fish

Effects of low dose γ-irradiation of fish product on spoilage potentials of bacteria (Aeromonas hydrophila, Salmonella typhimurium, Bacillus megaterium, and Pseudomonas marinoglutinosa) and mixed flora were examined for ability to proliferate in radurized fish and produce volatile acids (TVA) and bases (TVBN). Bacteria proliferated well in unirradiated and irradiated fish, but formation of VA and VB were lower in irradiated than unirradiated counterparts. This was found in Bombay duck, Indian mackerel, white pomfret, seer and shrimp gammairradiated at 0 to 5 kGy under ice. TV A and TVBN produced by the organisms or mixed flora from fish were only 30–50% those of controls. A method for identifying radiation-processed fish could evolve based on lower susceptibility of irradiated fish to bacterial spoilage.     

A Simple Method for Evaluating Textural Changes of Frozen Fish Minces

A simple and objective method for the evaluation of fracture force of frozen fish minces is presented. Fracture force determinations during frozen storage of red hake (Urophycis chuss) minces indicated a relative coefficient of variation of 4.7% and a significant correlation between fracture force data of frozen samples and force of compression data of thawed samples. No significant changes of fracture force of frozen samples have been observed between 2 and 45 days of storage, but fracture force increased five times between 45 and 90 days of frozen storage.     

Flavor Profiles of 17 Species of North Atlantic Fish

A modified traditional Flavor Profile? method was used by a trained panel to develop sensory profiles of the cooked muscle of 17 species of North Atlantic fish. Species were characterized for aroma and flavor total intensity, amplitude, order and intensity of character notes, and aftertaste. This information provides a data base for grouping species according to similarities in their characteristics. Flavor data were analyzed by cluster procedures and revealed four distinct groupings characterized by: (1) less than moderate total flavor intensity with a shellfish note; (2) less than moderate total flavor intensity with an earthy note; (3) a moderate flavor intensity with fish oil, gamey and sour notes; (4) high total flavor intensity with fish oil, sour, and stronger gamey notes.     

Qualitative and Quantitative Textural Assessment of Cooked Ground Beef Patties

Cohesiveness of extruded, sliced hamburger patties from two manufacturers was studied in relation to cooking performance. Tensile determinations of ultimate strength and toughness were related to cohesiveness as measured with an Instron Universal Testing Machine. Light and environmental scanning electron microscopy was used to relate physical and macroscopic observations. Very cohesive samples had values of ultimate strength 7>1.45N and toughness >3.70 × 10^?4J, and noncohesive samples had values of ultimate strength <0.90N and toughness <1.50 × 10^?4J. Tensile results allowed discrimination between levels of cohesiveness among ground beef patties and could serve as a monitoring device to ensure consistency and indicate failure of the product at the serving outlet.     

Implication of Muscle Alkaline Proteinase in the Textural Degradation of Fish Meat Gel

Unlike the actomyosin paste, white croaker meat paste showed poor elastic gel when heated around 60°C. The hydrolysis of muscle protein by muscle proteinase was observed in the poor gel. There are at least four kinds of proteinases in white croaker muscle: cathepsin D, neutral proteinase, calpain and alkaline proteinase. Among them only alkaline proteinase could act at pH of meat paste and around 60°C. Above facts confirmed the previous work that the heat-stable alkaline proteinase is probably implicated in the textural degradation of fish meat gel around 60°C.     

增城丝苗米米饭理化性质与质构特性的相关性分析

选用7份增城丝苗米的原料大米,研究米饭的质构特性,并分析其与大米的热特性、糊化特性和理化指标之间的相关性。结果表明,增城丝苗米原料大米的硬度、粘性的差别较大,而凝聚性、胶粘性、咀嚼性和回复性均较接近。大米直链淀粉含量与米饭质构特性呈显著相关,米饭硬度、粘性与大米淀粉的糊化起始温度呈正相关,与热焓值呈负相关。米饭的硬度、粘性、凝聚性、胶粘性、咀嚼性和回复性与大米淀粉糊化的最终粘度、崩解值呈负相关,与消减值呈正相关,粘性与回生值呈负相关。因此,开发大米配方时, 将直链淀粉含量检测与大米的糊化特性、米饭硬度和粘性测试分析相结合,对于提高大米配方的品质稳定具有重要意义。     

Covalent Cross-linking Effects on Thermo-Rheological Profiles of Fish Protein Gels

The extent of covalent cross-linking in surimi sols by transglutaminase was modified by addition of either EDTA (inhibition by calcium sequestering), variation of preincubation time at 25°C to allow action of endogenous transglutaminase, or by addition of a microbial transglutaminase. Gels were cooked following preincubation to fix the effects of the cross-linking reaction. Torsion, dynamic (small strain) test and stress relaxation measurements were made on the gels over a range of temperatures. Gels preincubated with EDTA had similar rheological response to temperature as gels cooked without preincubation. The stress relaxation and thermo-rheological profiles of gels with increased covalent cross-linking (induced by added or endogenous transglutaminase) were increasingly rubber elastic in their behavior.     

Discriminative Characterization of Different Texture Profiles of Various Cooked Fish Muscles

Textural differences in cooked fish muscle tissues, according to species, were demonstrated quantitatively by acquiring fresh tissue samples of five species, cooking them under specific conditions, measuring the common physical properties of each (drip, residual weight, fumness, cohesiveness, penetration, fiber volume, fiber diameter, and fiber length) and scoring them in a range of −1.2 to −1.8 for skipjack to 1.0 to 2.0 for channel rock fish using discriminant analysis.     

Chemically Induced Covalent Crosslinks Affect Thermo-Rheological Profiles of Fish Protein Gels

Effects of inducing covalent crosslinks in surimi gels by adding potassium bromate or 1-ethyl-3(3-dimethylamino propyl) carbodiimide (EDC) were investigated. Potassium bromate induces disulfide crosslinking of proteins and EDC induces crosslinking between amino and carboxyl groups. Thermorheological properties compared to a control (no additive) were determined by torsion, dynamic (small strain) and stress relaxation testing. Profiles of gels with increased covalent cross-linking induced by potassium bromate or EDC showed increased rubber-elastic behavior. At the levels used, potassium bromate effected greater change in thermo-rheological response than EDC. These results confirmed that as covalent crosslinks increased, surimi gels become more rubber elastic in thermo-rheological responses.     

Initial Fish State and Mixing Time Effects on Textural Characteristics of a Restructured Catfish Product

A restructured catfish product similar to a corn dog was developed using tumbled catfish from low cost fillets. The product when made from fresh fillets, was more tender but had tougher skin than when made from frozen fillets. Mixing more than 5 min resulted in a more rubbery and tougher product as demonstrated by higher Instron peak load and longer relaxation time.     

鱼骨粉添加量对鮰鱼鱼肉火腿肠色度、质构及感官特性的影响

研究添加鱼骨粉对鮰鱼鱼肉火腿肠品质的影响。采用梯度添加鱼骨粉的方法制作鱼肉火腿肠,并对其色度和质构进行测定,同时进行感官评定。结果表明：鱼骨粉添加量为2%时,白度值下降显著(P＜0.05) ;鱼肉火腿肠的硬度、咀嚼性随着鱼骨粉添加量的增多而增大,弹性变小;当添加量为2.5%时,鱼肉火腿肠的硬度、咀嚼度和弹性变化趋势极显著(P＜0.01),但黏聚性变化不明显;随着鱼骨粉添加量的增加,鱼肉火腿肠切面较粗糙,咀嚼时颗粒感较强,当鱼骨粉添加量为3%时鱼肉火腿肠总体可接受度较差。综合考虑,鱼骨粉添加量为1.5%时,鱼肉火腿肠色度和质构较好,感官总体可接受度高。     

Assessment of the Textural Quality of Meat Patties: Correlation of Instrumental and Sensory Attributes

Compression, shear, tensile and punch tests were used to assess the mechanical strength of a ground meat product and discriminate between effects of various treatments on this type of product. These measurements, together with chemical and moisture retention measurements, were related to sensory attributes of the cooked products. Most of the sensory textural attributes were satisfactorily (i.e., about 80% of the variance) explained or described by a combination of Warner-Bratzler shear parameters and certain compression measurements. Principal co-ordinate analysis showed that tensile measurements related better to sensory greasiness and juiciness than to mechanical strength. Methods for measuring juiciness were not adequate and indicated the need for further investigation.     

鱼露中乳酸菌及其主要产品指标关系研究

分析来自湛江和汕头市场5种鱼露中的乳酸菌种类,以及一些微生物含量和化学指标,探讨乳酸菌与产品指标的相关性.结果显示:5种鱼露含有13种不同的乳酸菌,其中乳杆菌11种,乳球菌2种;主要产品指标分析表明5种鱼露样品的微生物指标和化学指标均符合鱼露标准;乳酸菌和耐盐茵含量大小顺序比较接近;乳酸菌含量较高的样品亚硝酸盐和挥发性盐基氮含量较低.乳酸茵发酵过程产生多种酶系,可降低亚硝酸盐含量,而且乳酸菌可以抑制腐败茵的生长,从而降低产品中挥发性盐基氮含量.     

Effect of Soy Flour, Soy Protein Concentrate and Sodium Alginate on the Textural Attributes of Minced Fish Patties

A mixture response statistical design was used to investigate the textural attributes of minced fish patties. Patties formulated with pollock were significantly firmer than those made from turbot and pollock blends or from turbot alone. Breakpoint values and firmness scores were negatively correlated with flavor and acceptability scores indicating that as patty firmness increased general acceptability declined. Higher acceptability for softer patties formulated with more turbot were attributable to the higher fat content. Increasing the soy protein levels and decreasing alginate content increased patty firmness regardless of fish composition. The patty formulation with maximum predicted acceptability was 78% turbot, 11% soy flour, and 11% soy protein concentrate.     

5种淡水鱼肉的质构特性及与营养成分的相关性分析

为了分析鱼体体质量和季节对鱼肌肉组织特性的影响,以及质构特性与基本营养成分的关系,以湖北最常见的5种淡水鱼(草鱼、鲫鱼、鲢鱼、鲤鱼、武昌鱼)为对象,对其基本营养成分和质构进行测定和分析。结果表明：5种淡水鱼肌肉硬度大小为：草鱼＞鲤鱼＞鲫鱼＞武昌鱼＞鲢鱼,随季节不同肌肉硬度值有所增减。随着鱼体的生长,体质量的增加,肌肉硬度、弹性、胶着度和咀嚼度均有增加,与水分含量呈负相关,与脂肪含量呈正相关。春季鱼的肌肉质构指标值大于夏季和冬季。对7个质构指标进行了主成分分析,提取出3个主成分,累计方差贡献率为94.62%,其中硬度和弹性是影响鱼肉质构特性的主要因素。     

Vane Rheometry for Textural Characterization of Cheddar Cheeses: Correlation with Other Instrumental and Sensory Measurements

The relationship between instrumental (vane method, texture profile analysis (TPA), uniaxial compression) and sensory texture measurements of Cheddar cheeses was investigated. A Haake VT 550 viscotester equipped with a four-bladed vane rotor was used for the vane test. Instrumental TPA was performed with a TA.XT2 Texture Analyser, and compression variables were calculated from TPA data. Vane parameters were significantly correlated with respective variables of compression and TPA (r=0.56-0.91), and sensory tests (r=0.54-0.88). Multivariate analysis indicated that seven sensory attributes of ten commercial Cheddar cheeses were satisfactorily predicted (calibration regression coefficient,R_cal >0.62) by variables of the vane, uniaxial compression and TPA tests. In particular, cheese firmness and cohesiveness evaluated by sensory panel were well described by vane stress and apparent strain. The results validate the vane method as an alternative to the existing cheese testing methods for rapid evaluation of cheese texture.     

5 种脱色剂对粗鱼油挥发性风味物质及脂肪酸组成的影响

为探究凹凸棒土、硅藻土、活性炭、沸石及活性白土5?种脱色剂对粗鱼油挥发性风味物质及脂肪酸组成的影响,采用气相色谱仪和顶空固相微萃取-气相色谱-质谱联用仪,对脱色鱼油的挥发性风味物质及脂肪酸的相对含量进行测定分析,并结合感觉阈值确定该鱼油主体风味成分。结果表明,赋予鱼油腥味、脂肪香味、蜡香等主要风味的壬醛、己醛、2-壬酮,其相对含量经脱色后有明显降低,风味改善效果显著。脱色后,鱼油的饱和脂肪酸相对含量呈下降趋势,而不饱和脂肪酸的相对含量则有增加趋势;酸价与过氧化值变化差异较大,而碘值及皂化值则无明显变化。凹凸棒土和活性白土脱色效果最佳,但脱腥效果较硅藻土、活性炭和沸石差。本研究结果对改善鱼油脱色工艺及脱色剂选择和不良风味等方面有一定理论指导意义。