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.     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.     

MASS TRANSFER IN PACIFIC HAKE (Merluccius australis) PACKED IN REFRIGERATED MODIFIED ATMOSPHERE

The objective of this research was to develop, and experimentally validate a fully mathematical model, to predict mass transfer phenomena in Pacific Hake (Merluccius australis) packed in refrigerated modified atmosphere. A mathematical model to predict mass transfer of CO₂, O₂, N₂ and water vapor was developed and validated. The diffusion model was developed utilizing Fick's second law, considering fish fillet as an infinite slab and applied to Pacific Hake (lean fish species) under refrigeration conditions. CO₂ diffusivity of Pacific Hake was determined by an inverse procedure at OC and resulted in a value of 5.19 × 10^?10 [m²/s] that is in accordance with values reported in the literature. However, postmortem variations of pH could affect solubility and diffusivity of CO₂ in fish muscle.     

ABSENCE OF PROTEOLYSIS IN PURIFIED MYOFIBRILS OF POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI) DURING IN VITRO STORAGE AT 37C

The biochemical behavior of myofibrils from postspawned hake during in vitro storage at 37C was investigated. SDS‐PAGE, densitometric analysis of the band areas corresponding to the major myofibrillar proteins, and TCA soluble peptides determination showed no evidence of proteolysis in myofibrils after 44 h of incubation either in presence or in absence of a cocktail of protease inhibitors (1 mMPMSF+1mMiodoacetic acid + 1mM of EDTA). The absence of proteolysis in stored postspawned hake myofibrils contrasts with the autolysis in those from prespawned fish previously reported, indicating an influence of the reproductive cycle on the proteolytic activity closely associated to myofibrils.     

AUTOLYSIS OF PROTEINS FROM PRESPAWNED HAKE (MERLUCCIUS HUBBSI MARINI) DURING IN VITRO STORAGE OF MYOFIBRILS AT 20 AND 37C

The in vitro autolysis of hake myofibrillar proteins was investigated. No evidence of proteolysis was observed in myofibrils after 44 h of incubation either in presence or in absence of protease inhibitors at 20C. A 180‐kDa component present at zero time in the SDS‐PAGE gels of myofibrils from prespawning hake was degraded after 44 h of incubation at 37C. Degradation of the 180‐kDa component was accompanied by an increase in low molecular weight and TCA soluble peptides. These changes were not observed in myofibrils incubated in the presence of protease inhibitors (1 mM PMSF+ 1 mM iodoacetic acid + 1 mM of EDTA). Both PMSF and EDTA used alone partially inhibited the degradation of myofibrillar proteins. This inhibition was lower than that produced in the presence of both inhibitors, Azocaseinolytic activity was almost exclusively associated with the 180 kDa‐component eluted from SDS‐PAGE gels. These results suggest that both metallo and serine proteinases could be involved in the autolysis of myofibrils at 37C.     

MATHEMATICAL MODEL TO PREDICT YIELD LOSS OF MEDIUM AND LARGE TIGER SHRIMP (PENAEUS MONODON) DURING COOKING

Cooking causes moisture loss and reduces the yield of shrimp. This can be affected by its size, cooking temperature and time. A finite difference mathematical model to predict temperature distribution during heating/cooling of shrimp was modified to enable prediction of yield loss. The relationship between cooking temperature, time and yield loss was determined by isothermal experiments. For medium and large Tiger shrimp (Penaeus monodon), data were fitted into the following form: % Yield Loss = a + b*T + c *T²+ d*t²+ e*t + f*T*t where T is temperature and t is time. These equations were used in the model. Each volume element in the model was allowed to have its own yield loss; and overall yield loss was found by calculating mass average values. Experiments were conducted to cook Tiger shrimp under regular conditions and determine its yield loss, and the predictions of the model were compared with experimental data. Close agreement was obtained. This model can be used to predict yield losses during cooking of shrimp.     

EFFECTS OF NITRITE AND SULFANILAMIDE ON THE 2-THIOBARBITURIC ACID (TBA) VALUES IN AQUEOUS MODEL AND CURED MEAT SYSTEMS

The absorbance of the 2-thiobarbituric acid-malonaldehyde (TBA-MA) complex at 532 nm for aqueous model systems and cured meats were measured. Addition of sulfanilamide played a beneficial role in evaluating the oxidative state of cured meats, prepared with the addition of ≧ 100 ppm NaNO₂, in that it prevented the underestimation of the TBA values. However, in the absence of nitrite, sulfanilamide may interact with malonaldehyde to produce a 1-amino-3-iminopropene derivative. Fluorescence spectroscopic studies showed an excitation maximum at 395 nm and an emission maximum at 460 nm for the adduct of malonaldehyde and sulfanilamide. Therefore, the TBA test for the evaluation of the oxidative state of cured meats may only be used when the content of nitrite in the cure or final product is known.     

EFFECT of WATER ACTIVITY ON VITAMIN A DEGRADATION IN WHEAT FLOUR (ATTA)

ABSTRACT. The effect of water activity (a_w) on the stability of vitamin A palmitate adsorbed onto wheat flour, starch, gluten, enzyme inactivated wheat flour and micro-crystalline cellulose was investigated. In wheat flour the rate of vitamin A degradation was lowest at 0.0 a_w. In gluten, starch and enzyme inactivated wheat flour, the rate was highest at 0.0 a_w and decreased with rise in a_w. the rate of lipid oxidation in wheat flour was lowest at 0.0 a_w whereas in enzyme inactivated wheat flour it was highest at 0.0 a_w and decreased with rise in a_w. In micro-crystalline cellulose system vitamin A degradation was least at 0.33 a_w and the rate of degradation increased both below and above this a_w. Among the wheat flour constituents, gluten provided better protection to vitamin A than starch. the role of lipoxygenase enzyme in accelerating the rate of degradation of vitamin A in wheat flour at higher a_w has been suggested.     

EFFECT OF FROZEN TEMPERATURE AND STORAGE TIME ON CALPAINS, CATHEPSINS (B, B + L, H AND D) AND THEIR ENDOGENOUS INHIBITORS IN GOAT MUSCLES

The effects of frozen storage on the biochemical properties of myofibrils, muscle proteinases (cathepsins and calpains) and their endogenous inhibitors were investigated. Longissimus dorsi, biceps femoris, semimembranosus and semitendinosus muscles from goat were frozen (?15C) and studied up to 120 days. The results showed that the percentage change in sarcomere length was 8.4–13.1. The calpain activity was determined after separation on a diethylaminoethyl–Sephacel column (Sigma, St. Louis, MO). Significantly greater percentage of calpain II activity was recovered when compared to calpain I. There was a 15–25% loss in calpastatin inhibitory activity, and the cystatin level fell by 11–16% after 80 days. Cathepsin B, B + L, H and D were very stable when compared to calpains. The calcium concentration may also be the factor for calpain activation. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis result showed the appearance of 55 kDa components. It was concluded that calpains, not cathepsins, play an important role in the proteolysis of myofibrillar proteins at the freezing temperature.     

An Integrated Approach to Factors Affecting the Shelf Life of Products in Modified Atmosphere Packaging (MAP)

The aim of this work was to analyze the main factors influencing the shelf life of peanut products in modified atmosphere packaging (MAP). Roasted and salted peanuts produced by three well-known commercial companies were presented as examples. Different types of packaging (multilayer laminated materials, cans) with different gas mixture composition (0-1% O₂, 1-3% O_2, 3-6% O₂) were compared. The main aim of shelf-life investigation is to ensure consumer acceptance of a product. Factors affecting the shelf life of products in MAP are presented as an integrated pyramid. All elements of this shelf-life pyramid should be analyzed and included during shelf-life investigations. This study indicates that estimation of the shelf life of a food is integrally related to its packaging (e.g., peanuts in MAP); both product conditions and the package as well as gas mixture composition should be considered.     

An Integrated Approach to Factors Affecting the Shelf Life of Products in Modified Atmosphere Packaging (MAP)

Abstract

The aim of this work was to analyze the main factors influencing the shelf life of peanut products in modified atmosphere packaging (MAP). Roasted and salted peanuts produced by three well-known commercial companies were presented as examples. Different types of packaging (multilayer laminated materials, cans) with different gas mixture composition (0–1% O₂, 1–3% O_2, 3–6% O₂) were compared. The main aim of shelf-life investigation is to ensure consumer acceptance of a product. Factors affecting the shelf life of products in MAP are presented as an integrated pyramid. All elements of this shelf-life pyramid should be analyzed and included during shelf-life investigations. This study indicates that estimation of the shelf life of a food is integrally related to its packaging (e.g., peanuts in MAP); both product conditions and the package as well as gas mixture composition should be considered.     

Active Packaging of Fresh Chicken Breast,with Allyl Isothiocyanate (AITC) in Combination with Modified Atmosphere Packaging (MAP) to Control the Growth of Pathogens

ABSTRACT: Listeria monocytogenes and Salmonella typhimurium are major bacterial pathogens associated with poultry products. Ally isothiocyanate (AITC), a natural antimicrobial compound, is reportedly effective against these pathogenic organisms. A device was designed for the controlled release of AITC with modified atmosphere packaging (MAP), and then evaluated for its ability to control the growth of L. monocytogenes and S. typhimurium on raw chicken breast during refrigerated storage. In order to obtain controlled release during the test period, a glass vial was filled with AITC and triglyceride. It was then sealed using high-density polyethylene film. The release of AITC was controlled by the concentration (mole fraction) of AITC in the triglyceride and by the AITC vapor permeability through the film. The fresh chicken samples were inoculated with one or the other of the pathogens at 10⁴ CFU/g, and the packages (with and without AITC-controlled release device) were flushed with ambient air or 30% CO₂/70% N₂ before sealing, and then stored at 4 °C for up to 21 d. The maximum reduction in MAP plus AITC (compared to MAP alone) was 0.77 log CFU/g for L. monocytogenes and 1.3 log CFU/g for S. typhimurium. The color of the chicken breast meat was affected by the concentration of AITC. Overall, a release rate of 0.6 μg/h of AITC was found to not affect the color, whereas at 1.2 μg/h of AITC the surface of the chicken was discolored.