Quality and Nutritional Changes in Frozen Breaded Shrimp Stored in Wholesale and Retail Freezers

Chemical, microbiological, and sensory changes were monitored in breaded fantail shrimp held in upright and coffin style freezers at two retail markets and in a large warehouse freezer. Quality and nutritional changes in a test lot of shrimp were followed for 13 months. Significant sensory deterioration can be detected as early as 3 - 4 months after production when shrimp are stored in a retail freezer. Minimum retail freezer temperatures reached ≤-20°C between 1% and 36% of the monitored days and had daily temperature variations of 12 - 18°C. Storage at the wholesale level below -20°C with maximum daily temperature variations of 2 - 3°C proved to be an effective method to maintain the quality of frozen shrimp for at least 13 months of storage.     

Storage Changes of Fresh and Pasteurized Blue Crab Meat in Different Types of Packaging

We investigated pasteurization and storage of blue crabmeat in steel cans, aluminum cans, plastic cans, nonbarrier pouches, and barrier pouches. Fresh meat was packed in copolymer polyethylene/polypro-pylene cups, Saran® over-wrapped or vacuum skin packaged polystyrene trays, and nonbarrier pouches. Meat pasteurized in plastic and aluminum cans had better sensory and microbiological quality and longer shelf life than meat packed in steel cans. Oxygen-barrier pouches had the lowest quality and shortest shelf life. Nonbarrier pouches had product with quality similar to meat in steel cans, but with an extended shelf life. No packaging materials improved the microbiological shelf life of freshly cooked meat. Vacuum skin packaging resulted in improved sensory qualities of freshly cooked and picked meat.     

INTROGRESSING PHEROMONE QTL BETWEEN SPECIES: TOWARDS AN EVOLUTIONARY UNDERSTANDING OF DIFFERENTIATION IN SEXUAL COMMUNICATION

As a first step toward understanding how noctuid moths evolve species-specific pheromone communication systems, we hybridized and backcrossed two closely related moth species, Heliothis virescens (Hv) and H. subflexa (Hs), which differ qualitatively and quantitatively in their multi-component sex pheromone blends. We used amplified fragment length polymorphism (AFLP) marker-based mapping of backcross families to determine which of the 30 autosomes in these moths contained quantitative trait loci (QTL) controlling the percentages of specific chemical components in the pheromone blends. In two previous backcrosses to Hs, we found a strong depressive effect of Hv-chromosome 22 on the percentage of three acetate components in the pheromone gland. These acetates are present in Hs and absent in Hv. Here, we describe how we introgressed Hv-chromosome 22 into the genomic background of Hs. Selection for Hv-chromosome 22 started from backcross 3 (BC₃) females. All females that had Hv-chromosome 22 and a low percentage of acetates (< 3% of the total amount of pheromone components present) were backcrossed to Hs males. In BC₅ to BC₈, we determined whether Hv-chromosome 22 was present by a) running only the primer pairs that would yield the markers for that chromosome, and/or b) determining the relative percentages of acetates in the pheromone glands. Either or both genotype and phenotype were used as a criterion to continue to backcross these females to Hs males. In BC₉, we confirmed the isolation of Hv-chromosome 22 in the Hs genomic background, and backcrossed the males to Hs females to eliminate the Hv-sex chromosome as well as mitochondrial DNA. The pheromone composition was determined in BC₃, BC₅, and BC₁₁ females with and without Hv-chromosome 22. All backcross females with Hv-chromosome 22 contained significantly less acetates than females without this chromosome. In addition, BC₃ females with Hv-chromosome 22 contained significantly more Z11-16:OH than BC₃ females without Hv-chromosome 22. However, in BC₅ and BC₁₁ females, the correlation between Z11-16:OH and Hv-chromosome 22 was lost, suggesting that there are separate QTL for the acetates and for Z11-16:OH, and that the relative amount of the alcohol component is only affected in epistasis with other (minor) QTL. Now that we have succeeded in isolating the chromosome that has a major effect on acetate production, we can test in behavioral experiments whether the presence of acetates may have been a driving force for a shift in pheromone composition. Such tests are necessary to move towards an evolutionary understanding of the differentiation in sexual communication in Heliothis spp. moths.     

EFFECT OF ATTACHMENT TIME FOLLOWED BY CHLORINE WASHING ON THE SURVIVAL OF INOCULATED LISTERIA MONOCYTOGENES ON TOMATOES AND SPINACH

ABSTRACT

The effect of attachment time (30 min, 24, 48 and 72 h) followed by chlorine washing (200 ppm) on the survival of inoculated Listeria monocytogenes on the surface and subsurface of tomatoes and spinach were studied. The work was done to determine the efficacy of chlorine to decontaminate surface and subsurface pathogens that may have come into contact with produce during preharvest. Tomatoes and spinach leaves were inoculated with a 6 log cfu/mL 18 h culture of L. monocytogenes ATCC 7644 (LM) on the surface and subsurface and incubated at 20C for either, 30 min, 24, 48 or 72 h. LM attached and survived on the surface and subsurface structures of both control and chlorine‐washed vegetables after each attachment time, up to 72 h. Higher levels of LM attachment and survival was however noticed on the subsurface structures. Chlorine had a greater effect on the LM on the surface structures compared to those in the subsurface structures, possibly because chlorine was not able to access the subsurface structures where the pathogens were located. Chlorine was not effective in totally inactivating the surface LM on spinach and tomato. This research indicated that LM could attach to both surface and subsurface structures of both tomatoes and spinach within 30 min and that even after 72 h, it still remained viable.

PRACTICAL APPLICATIONS

This study will inform the produce industry on the ability of L. monocytogenes ATCC 7644 to attach and grow on the surface and subsurface structures of tomato and spinach during post harvest. More attention should be given to this phenomenon because the use of fresh or minimally processed fruits and vegetables are recommended as part of a healthy diet. It also indicates that minimal processors should avoid using vegetables with wounds since L. monocytogenes attached more to the subsurfaces structures of the produce. Moreover, the use of sanitizers such as chlorine is less effective under these conditions. It has also brought to light the inability of chlorine to effectively decontaminate pathogens making it imperative for the produce industry to implement Hazard Analysis Critical Control Point, Good Agricultural Practice and Good Hygiene Practice.     

On Combining Artificial Neural Nets

This paper reviews research on combining artificial neural nets, and provides an overview of, and an introduction to, the papers contained in this special issue, and its companion (Connection Science, 9, 1). Two main approaches, ensemble-based, and modular, are identified and considered. An ensemble, or committee, is made up of a set of nets, each of which is a general function approximator. The members of the ensemble are combined in order to obtain better generalization performance than would be achieved by any of the individual nets. The main issues considered here under the heading of ensemble-based approaches are a how to combine the outputs of the ensemble members, b how to create candidate ensemble members and c which methods lead to the most effective ensembles? Under the heading of modular approaches, we begin by considering a divide-and-conquer approach by which a function is automatically decomposed into a number of subfunctions which are treated by specialist modules. Other modular approaches are also identified and considered, for while the divide-and-conquer approach is designed to improve performance, the term modularity can be given a wider interpretation. The broadly defined topic of modularity includes the explicit decomposition of a task based on the designer's understanding, and the exploitation of specialist modules in order to accomplish tasks which could not be performed by a monolithic net.     

Modularity,Combining and Artificial Neural Nets

In this paper, the modular combination of artificial neural nets is considered. A modular approach to combining can be contrasted with an ensemble-based approach in that it implies individual modules, each responsible for some specialist aspect of a task, as opposed to each approximating the same function. It is possible to characterize modular systems in terms of (i) reasons for the task decomposition, (ii) the method for accomplishing the decomposition and (iii) the relationship between the modules. These characteristics are considered in brief outlines of the papers in the issue. Reasons for task decomposition include the exploitation of specialist capabilities of individual nets, performance improvement, and making the system easier to understand and modify. Task decomposition may be either automatic (based on the blind application of a data partitioning algorithm) or explicit (based on prior knowledge of the task or the specialist capabilities of the modules), and the relationship between the modules may be successive, cooperative or supervisory.     

Characterization of Minced Meat Extracted from Blue Crab Picking Plant By-Products

Blue crab meat was mechanically extracted from picking-room byproducts to produce the following minced meat yields: 3.18%, white; 10.71%, mixed; 6.39%, claw, and 2.62%, leg. Each meat had distinct visual, textural, and flavor attributes. Aerobic plate counts of unpasteurized minced meat ranged from 10⁵ to 10⁷ CFU/g. Extraction within 1.5 hours of picking or icing of by-products prior to mechanical extraction stabilized microbial levels. Meat pasteurized at 80.6°C darkened or blued significantly less than meat processed at 83.3°C. Addition of citric acid-phosphate buffer to meat pasteurized at 80.6°C further reduced darkening of meats.     

Grapevine genetics after the genome sequence: Challenges and limitations

The publication of the genome sequences of inbred grapevine plant PN40024 and the cultivar Pinot Noir has provided a new generation of molecular tools and has opened the way to functional genomics in grapevine. Establishing gene biological function is now a major challenge requiring the parallel development of molecular and genetic information. New massive pyrosequencing technologies will ensure no shortage of nucleotide sequence information. However, genetic analysis and genetic tools in grapevine still require additional development. Exploiting the existing natural genetic variation in Vitis vinifera L. and other inter-fertile Vitis species should be a priority to focus functional analyses on genes contributing to phenotypic variation because their genetic variation constitutes the basis for genetic improvement of classical cultivars and for the development of new ones. In this review, we discussed the current molecular and genetic tools available in grapevine and considered those that need to be developed to exploit natural genetic variation in the analyses of gene function. We also reviewed the scarce information on the genetic and molecular structure of relevant grapevine traits and proposed future directions.