Pacific shrimp (Pandalus jordani) was washed repeatedly and the eluted bacteria were enumerated and identified. Selected isolates were tested for their adhesive properties. Washing reduced the microbial load by 3.84 to 42.04%. The bacteria which most resisted wash-off were Staphylococcus and Pseudomonas spp. The easiest to wash off was Flavobacterium spp. In higher-count samples, Moraxella and/or Lactobacillus spp. washed off readily, but they still constituted large proportions of the residual bacteria on shrimp. Adhesiveness, measured by hydrophobic interaction with octane, showed 43.3% change in absorbance by Staphylococcus spp., followed by 21.5% by Moraxella spp., and Arthrobacter spp. at 13.5%. Pseudomonas spp. showed only 5.7% change in absorption. Attachment, measured by hanging glass cover slips in broth, however, showed Pseudomonas and Staphylococcus spp. to have the greatest ability to adhere, with 0.47 and 0.46% attachment, respectively. Moraxella spp. showed the least ability to adhere to glass (.02%), followed by Lactobacil lus spp. at 0.11%. Arthrobacter and Flavobacterium spp. adhered at 0.30 and 0.37% levels, respectively. Attachment of Pseudomonas spp. to glass was the least affected by media composition, temperature, or presence of a surface-active agent (sodium hexametaphosphate). Staphylococcus spp., on the other hand, attached most strongly under optimum growth conditions but were most affected by varying growth conditions, temperature, and presence of a metabolic inhibitor (sodium hexametaphosphate). This indicates that the adhesive ability of Staphylococcus spp. is directly related to its metabolic activity, while Pseudomonas spp. is less sensitive to changes in metabolism and may depend on motility for adhesion. Bacteria that could adhere strongly on solid surfaces (Pseudomonas and Staphylococcus spp.) tend to be found in greater proportions and, hence, contribute more to the spoilage of shrimp. / Graduation date: 1983

No description available.

No description available.

Bakery products are important sources of nutrients in our diet. However, spoilage occurs shortly after baking. After microbial spoilage, the main spoilage problem is staling. / Therefore, methods to control staling are of great importance to the bakery industry since staling results in millions of dollars annually in lost revenues. / Initial studies using a one variable at a time approach showed that enzymes, guar, algin and pectin gums and high fructose corn syrup could delay staling and resulted in an organoleptically acceptable product. Subsequent optimization studies using a Response Surface Methodology (RSM) approach show the appropriate levels of enzyme (Novamyl), guar gum and HFCS resulted in bagels with a textural and sensorial shelf life of 6 weeks at ambient temperature. / Furthermore, the cost of reformulating ($ sim$0.5 cent/bagel) is minimal and could easily be recovered through reduced production costs, reduced losses due to staling and additional sales and market areas.

During storage of grain, there may have significant damage to its quality due to unfavorable physical and biological interactions and thus requires continuous monitoring. Therefore, an easy, cost-effective and environmentally friendly method is necessary for efficient monitoring of stored-grain. Arrays of sensors are being used for classifying liquors, perfumes, quality of food products mimicking mammalian olfactory systems. Monitoring of stored grain is a new application of sensor arrays. The main objective was to fabricate a carbon black polymer sensor array which can easily monitor incipient grain spoilage by detecting spoiling stored grain volatiles (benzene derivatives and aliphatic hydrocarbon derivatives) with minimum interference from relative humidity. Various aspects of a good sensor were analyzed using statistical analysis (RSD, LDA, PCA, t-test). The developed sensor array can identify red flour beetle-infected and uninfected wheat and fungal volatiles at ambient conditions as well as some stored grain conditions (MC 16%, RH 52%).

No description available.

Black spot development or "melanosis" is a common defect in fresh shrimp which results in product being devalued and rejected by consumers. Currently, sulfiting agents are used to control melanosis in shrimp. However, with increasing regulatory and consumer concerns about the safety of sulphites as a method of melanosis control, the shrimp processing industry is actively seeking alternative methods to control melanosis on, and extend the shelf life of, fresh shrimp. One method which has the potential to fulfill both objectives is glucose oxidase (GOX)/glucose dipping solutions in conjunction with Modified Atmosphere Packaging (MAP). / Preliminary studies have shown that black spot development can be controlled for 14 days at 4$ sp circ$C in white shrimp (Pandalus occidentalis) and pink shrimp (Pandalus borealis) using GOX/glucose or GOX/glucose/ascorbic acid in conjunction with gas packaging (60% CO$ sb2$: 40% N$ sb2$). This dipping/packaging treatment also improves the physical, chemical and microbiological changes in white shrimp compared to samples dipped only in water and air packaged. This study has shown that the combined use of two or more "barriers" can be used to extend the shelf life of, and control melanosis on, fresh shrimp. This novel process of "dipping" shrimp in GOX/glucose solutions in conjunction with MAP will have a significant effect in the area of shrimp hygiene and will have the potential to minimize shrimp spoilage incurred through melanosis.

Four meat spoilage organisms were grown at 4$ sp circ$C for 7 d, in an aqueous extract of meat (Meat Juice Medium), and the levels of various nutrients in the extracts were measured. At an agitation rate of 50 rev$ cdot$min$ sp{-1},$ the four species reached viable counts of 10$ sp8$ Colony Forming Units (CFU)$ cdot$ml$ sp{-1},$ and the order of nutrient utilization was as follows: (1) glucose, (2) gluconate and urea, (3) glycerol, (4) glucose-6-phosphate. Several substrates were still present in the growth medium at the end of the growth period, namely lactate, glucose-6-phosphate and the two unknowns. At a higher agitation rate (100 rev$ cdot$min$ sp{-1}),$ the non-fluorescent pseudomonad reached final counts of ca. 10$ sp{10}$ CFU$ cdot$ml$ sp{-1},$ 2 logs higher than those of the other three organisms present in the mixed culture. The order of nutrient utilization was: (1) glucose, (2) gluconate, urea and glycerol, (3) lactate and glucose-6-phosphate, (4) unknowns 1 and 2. At day 7, none of the nine substrates studied remained in the growth medium.

Dekkera and the closely related Brettanomyces are important yeasts in food and beverage production in part due to the metabolism of hydroxycinnamic acids (HCAs). There is a dearth of information concerning the role Brettanomyces spp. play in the food or beverage from which they are isolated and although Dekkera spp. have been investigated further there are discrepancies and questions yet to be answered. Representatives of both genera were examined to define growth and metabolism of individual HCAs in synthetic media. In addition, growth with combinations of HCAs was investigated for the first time. The results provide a comprehensive overview of HCA metabolism and volatile product formation for these genera. Furthermore, results have been confirmed in a semidefined wine medium that more closely resembled the physio-chemical parameters found in the typical wine environment. The enzymes responsible for the metabolism of HCAs were examined in Dekkera and Brettanomyces. Dekkera yeasts are known to enzymatically convert HCAs into vinylphenols (VPs) and ethylphenols (EPs). These products are indicative of Dekkera contamination. The first enzyme in the two-step HCA ─ VP ─ EP biochemical pathway is a hydroxycinnamic acid decarboxylase (HCD). This enzyme has been previously characterised from a single Dekkera strain. The second enzyme, vinylphenol reductase (VPR) has never been isolated or characterised from any microorganism. In order to further elucidate the HCA ─ VP ─ EP pathway, cell extracts were prepared from all five Dekkera and Brettanomyces spp. to evaluate activity against HCAs and VPs. Brettanomyces spp. were unable to metabolise HCAs indicating that these yeast do not have a functional HCD enzyme. Both Dekkera spp. have substrate inducible HCD activity. Temperature and pH optima were 40ºC and 5.75-6.00, respectively. The active protein was purified from cell extracts of D. anomala CBS 77 and a partial sequence was obtained. 3’RACE PCR was performed and a near complete gene sequence determined. This sequence does not have homology to HCA decarboxylase enzymes previously characterised from yeasts and bacteria and thus may represent a novel enzyme not previously described. Biochemical characterisation of the vinylphenol reductase (VPR) enzyme was also undertaken. VPR activity was found for all 5 Dekkera and Brettanomyces spp. Activity was greatest at pH 6 and between 40-50ºC and was induced by both VPs and HCAs. Data obtained during growth experiments indicated that HCAs, and in particular ferulic acid, inhibited the growth of Dekkera and Brettanomyces spp. On this basis a more detailed study was carried out to determine the concentrations required to prevent growth in various media. In a modified red wine a concentration 0.1 mM ferulic acid inhibited growth and 2 mM prevented cultures of both D. anomala and D. bruxellensis from becoming established even when re-inoculated into to a fresh HCA-free medium. Scanning electron micrographs revealed that ferulic acid caused physical damage to Dekkera cells upon exposure. This work could lead to the development of an alternative method for the control of Dekkera in wine or other food products. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1454852 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 11, 2008) Includes bibliographical references.