QUALITY OF FROZEN/THAWED SPRAT (SPRATTUS SPRATTUS SPRATTUS) STORED IN CLING FILM AND ALUMINUM FOIL AT 4C1

Frozen sprats (Sprattus sprattus sprattus) were thawed and separated into three lots: two lots were wrapped and kept chilled in a refrigerator at 4C, one wrapped in aluminum foil (AF), the other in cling film (CF) and a third lot left unpackaged and held in melting ice. Biochemical tests, performed at intervals over a 16‐day period, showed better quality and an extension of shelf‐life for sprats stored unpackaged in ice compared with those held at 4C packed in AF or CF. The levels of trimethylamine oxide‐nitrogen (TMAO‐N) decreased throughout storage and significant differences (P<0.05) were observed between the lot in ice and the lots stored in AF or CF (P<0.05). However, significant differences (P<0.05) were not observed between AF and CF lots during the experiment. Increases in total volatile base nitrogen (TVB‐N) and trimethylamine‐nitrogen (TMA‐N) were significantly retarded, as were reductions in sensory quality, in the ice‐stored fish compared with packaged, refrigerated fish.     

TRANSGLUTAMINASE IN DAIRY PRODUCTS: CHEMISTRY, PHYSICS, APPLICATIONS

Literature on the effects of microbial transglutaminase on various dairy‐based systems is discussed. Beginning with a short synopsis on the development of microbial transglutaminase as a functional tool for modifying foods, the principles of reactions catalyzed by transglutaminase and their structural implications, as well as the mechanisms of formation and cleavage of isopeptide bonds are reviewed. After summarizing the present knowledge on the specificity of microbial transglutaminase towards milk proteins, including reactions determined by individual lysine and glutamine residues, emphasis is placed on the effects of enzymatic cross‐linking on physicochemical properties in foods and, particularly, dairy‐based systems. Discussed are implications of cross‐linking on acidified milk gels including yogurt and effects on single milk protein fractions, with respect to several physicochemical properties including rheology and mechanical properties of these systems, but also syneresis, and emulsification behaviour.     

Biochemical and Physicochemical Properties of Actomyosin from Pre- and Post-spawned Hake (Merluccius hubbsi) Stored on Ice

Biochemical and physicochemical properties of natural actomyosin (NAM) from pre- and post-spawned hake stored on ice were studied. At the beginning of storage both reduced viscosity and ATPases activities of NAM from post-spawned hake were about 3 times higher than those of the pre-spawned ones, except for the Mg²⁺-(Ca²⁺)-ATPase. Higher loss of functional components during pre-spawned hake NAM purification was found compared to NAM from post-spawned fish. Reduced viscosity and Mg²⁺-(EGTA)-ATPase activity of NAM from both pre- and post-spawned hake decreased following ice storage. SDS-PAGE patterns of NAM from pre-spawned hake showed an absence of the myosin heavy chain and the presence of a 160 kDa component at zero time of storage. No proteolysis occurred in ice-stored fish caught in both gonadal stages.     

Amino Acid Profiles of Fermenting Wheat Sour Doughs

The free amino acid patterns of unfermented and fermented wheat sour doughs started with Lactobacillus plantarum were related by factor analysis to dough yield, ash content of flour, fermentation temperature and presence/absence of yeast, from data corresponding to a central composite design of samples. Individual levels of hydrophobic, acid and basic amino acids as well as total amino acid content positively correlated with extraction rate of flours. The presence of yeast promoted metabolism of histidine, aspartic acid and asparagine, particularly in samples made with whole and wholemeal flours. Proliferation of predominant amino acids by enzymatic release was more notable at higher fermentation temperatures and wholemeal samples. Sour doughs with maximum levels of hydrophobic and basic amino acids were started with no yeast bacterial cultures, made with whole and wholemeal flours and fermented at 35°C.     

USE OF SEMITRAINED PANEL MEMBERS IN THE SENSORY EVALUATION OF HAKE (MERLUCCIUS MERLUCCIUS, L) ANALYZED STATISTICALLY

Abstract The main objective of this study was to evaluate the responses of semitrained sensory assessors to parameters traditionally used in the sensory analysis of hake and to compare their performance with that of trained inspectors. Appropriate statistical methods were used to validate this objective.
The study was carried out with whole gutted hake stored for 7 and 12 days in a controlled atmosphere consisting of 60%/15%/25% (CO₂/O₂/N₂), followed by conventional storage in ice. The hake stored under the CA conditions were preserved better than the control hake at 7 days and at 12 days the difference was even more in favor of the CA storage. Ten parameters evaluated in the sensory tests could be reduced to five with no loss in essential information. The evaluations of the semitrained assessors largely correlated with those of trained inspectors. A model using five parameters and semitrained assessors could be routinely used to evaluate the quality of cooked hake previously stored in ice.     

Oxidative stress indicators in human and bottlenose dolphin leukocytes in response to a pro-inflammatory challenge

Marine mammals undergo cycles of tissue ischemia and reperfusion during the dive response. Reperfusion injury can result in oxidative tissue damage and the activation of a pro-inflammatory immune response. The risk of oxidative damage is reduced by antioxidants. Our hypothesis is that the reported higher antioxidant defenses within marine mammal tissues provide additional protection in situations that produce oxidative stress, like inflammation, in comparison to terrestrial mammal tissues. Leukocytes were isolated from the whole blood of Pacific bottlenose dolphins (Tursiops truncatus gilli) and humans (Homo sapiens) and were exposed to lipopolysaccharides (LPS, 10 µg/mL) in vitro to simulate a pro-inflammatory challenge. Oxidative stress indicators, including superoxide radical (O₂^•−) production, activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST), as well as oxidative protein damage, were quantified by spectrophotometry. Following 48 h under experimental conditions, bottlenose dolphin leukocytes produced 1.9 times more O₂^•− but displayed 2.0 times lower protein carbonyl concentrations compared to human leukocytes. Following 48 h under experimental conditions, bottlenose dolphin leukocytes displayed 7.9, 2.0, 11.1, and 3.3 times more activities of CAT, GPx, GR, and GST, respectively, compared to human leukocytes. These results suggest that, under cell culture conditions, the antioxidant defenses in bottlenose dolphin leukocytes provide additional protection against pro-inflammatory challenges in comparison to human leukocytes, likely as an adaptive advantage.     

Quantifying the structural integrity of nanorod arrays

Arrays of aligned nanorods oriented perpendicular to a support, which are accessible by top‐down lithography or by means of shape‐defining hard templates, have received increasing interest as sensor components, components for nanophotonics and nanoelectronics, substrates for tissue engineering, surfaces having specific adhesive or antiadhesive properties and as surfaces with customized wettability. Agglomeration of the nanorods deteriorates the performance of components based on nanorod arrays. A comprehensive body of literature deals with mechanical failure mechanisms of nanorods and design criteria for mechanically stable nanorod arrays. However, the structural integrity of nanorod arrays is commonly evaluated only visually and qualitatively. We use real‐space analysis of microscopic images to quantify the fraction of condensed nanorods in nanorod arrays. We suggest the number of array elements apparent in the micrographs divided by the number of array elements a defect‐free array would contain in the same area, referred to as integrity fraction, as a measure of structural array integrity. Reproducible procedures to determine the imaged number of array elements are introduced. Thus, quantitative comparisons of different nanorod arrays, or of one nanorod array at different stages of its use, are possible. Structural integrities of identical nanorod arrays differing only in the length of the nanorods are exemplarily analysed.     

INFLUENCE OF TEMPERATURE ON SHELF LIFE OF BUTTERHEAD LETTUCE LEAVES UNDER PASSIVE MODIFIED ATMOSPHERE PACKAGING

The aim of the present work was to study the influence of temperature on sensory and microbiological qualities, and on shelf life of butterhead lettuce leaves in passive modified atmosphere packages. Butterhead lettuce was washed and placed under ambient air in 30  ×  40 cm polypropylene bags, and stored at 5, 10 and 15C. A first-order equation was obtained for the development of the evaluated appearance sensory attributes as a function of storage time. For all the evaluated storage temperatures, microbiological shelf lives (14, 17 and 42 days at 5, 10 and 15C) were higher than estimated sensory shelf lives (8, 14 and 26 days at 5, 10 and 15C), showing that shelf life of lettuce in passive modified atmosphere packages was limited by sensory properties and not by microbial growth.

PRACTICAL APPLICATIONS

Sensory shelf life of lettuce in passive modified atmosphere packages was estimated using consumer data, which are an improvement of a more arbitrary criteria presented in most studies. Moreover, if failure criteria used in other studies were applied, consumer rejection at the end of shelf life would be higher, suggesting that more conservative criteria are necessary to assure the product's quality at the end of its shelf life.     

火灾探测过程模拟研究

将火灾模型和烟气传感器结合起来模拟传感器对不同火灾情况的反应。将NIST的FDS模型和Duisburg-Essen大学通讯系统学院开发的烟气传感器模型结合了起来。某火灾烟气流动的模拟结果作为适合烟气传感器模型的输入数据。为了模拟烟气传感器，选择了几个必要的参数来描述烟气、传感器和房间的情况。烟气粒径的大小分布是描述烟气的一个重要参数。对影响粒径大小分布的烟气颗粒的凝结做了适当处理。联合模型的模拟结果与开敞式火灾和阴燃火灾的测量值做了比较。模拟了一个散射光感器和一个电离室。测量和模拟结果显示，传感器模拟的重质取决于所燃烧的燃料。