Browsing by Author "Webster, Janet B."
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- Changes in Aromatic Chemistry and Sensory Quality of Milk Due to Light WavelengthWebster, Janet B. (Virginia Tech, 2006-11-09)Gas chromatography (GC) and gas chromatography olfactometry (GCO) was used to determine the effect of specific light wavelengths on light oxidation in milk. The most damaging wavelengths to milk quality appear to be the UV (200-400 and 395 nm) and short visible (463 nm) wavelengths. However, exposure to 610 nm also appears to be damaging. GC and GCO were also used to look at the efficacy of film over-wraps made from iridescent films. Single-layer over-wraps were not as effective in reducing light oxidation as multi-layer film over-wraps. Single-layer over-wrap treatments had higher numbers of odor-active compounds than multi-layer over-wrap treatments with a number of odor-active compounds detected consistently in single-layer over-wrap treatments but not in the multi-layer over-wrap treatments. Concentrations of volatile compounds were slightly lower in the multilayer treatments. Multi-layer film over-wrap treatments were tested for light oxidation flavor intensity with a balanced incomplete block multi-sample difference test using a ranking system and a trained panel. Packaging over-wraps limited the production of light oxidation flavor in milk over time but not to the same degree as the complete light block. Blocking all visible riboflavin excitation wavelengths was better at reducing light oxidation flavor than blocking only a single visible excitation wavelength. A method to determine light oxidation in oil using Fourier Transform Infrared (FTIR) spectroscopy was established and preliminary data is presented.
- Identification and characterization of a psychotrophic Clostridium sp. isolated from spoiled pasteurized crabmeatWebster, Janet B. (Virginia Tech, 1994)A number of crab processors in the Maryland and Virginia region experienced an abnormally high incidence of spoilage in their pasteurized product in the fall of 1989. The spoilage was only seen in cans that were processed either shortly before or after hurricane Hugo and the majority of spoilage occurred in machine picked meat only. All processors pasteurized the meat at least to an Fi~5 of 32 minutes, which is the minimum National Blue Crab Industry Association (NBCIA) recommendation. Spoiled pasteurized crabmeat, processed in 1989 and 1990, were analyzed for their microbial content. Several cans that had spoiled in 1972 were also analyzed for microbial content Isolated organisms were tested for heat tolerance, and those organisms able to survive an F11~5 of 32 minutes or longer were identified. Can seams were evaluated to determine if the spoilage was due to post processing contamination. Approximate D-values were determined for the heat tolerant organisms. A psychrotrophic Clostridium sp. was found in all cans tested from a Maryland processor, Processor B. This processor only had spoilage in machine picked meat pasteurized after hurricane Hugo. Spoilage was seen in cans which had received a F 16/185 of 80 to 100 minutes. Spores from this organism had an approximate D-value of 6.5 minutes at 85 C in brain heart infusion broth (BHI). Cans from Processor B did not show any seam defects, and it was concluded that spoilage was due to the survival of spores, during pasteurization, from the Clostridium sp. that were able to outgrow at the temperature at which crabmeat is stored commercially. A Bacillus sp., possibly Bacillus pasteuranii, was found in one can from Processor B. Spores from this organism have an approximate D-value of 26.5 minutes in BHI broth at 85 C. This organism is unable to grow at refrigeration temperatures and it is not felt to have caused spoilage in the crabmeat. The Clostridium sp. found in cans from Processor B, pasteurized in 1989 and 1990, was also found in a can of jumbo lump meat from Processor D, processed in 1989, and a can of claw meat from Processor E, pasteurized around 1972. Cans from Processor A, who saw small amounts of spoilage before hurricane Hugo and in some hand- picked meat as well as machine piced meat had can seam measurements which did not meet specifications. It was concluded that spoilage from this processor was due to post-processing contamination. Crab processors must be aware that spores, from organisms that are able to outgrow at refrigeration temperatures, are able to survive pasteurization. The Clostridium sp. isolated in this study is one example. Processors will need to make sure their product is receiving sufficient heat to kill all spores of these organisms, while still maintaining a product with good sensory characteristics. It appears, from this study, that crab processors may want to increase the F-value that a lot of crabmeat receives after major storms, since the Clostridium sp. seemed to show up after hurricanes. Finally, crab processors need to be stringent in their sanitation and cleanliness so as to minimize the numbers of these types of organisms in their product.
- Photochemical Protection of Riboflavin and Tetrapyrroles with Light Scattering TechnologyHamilton, Jeffrey Hunt (Virginia Tech, 2012-06-18)The effectiveness of titanium dioxide (TiO?) in polyethylene films at preventing the photooxidation of riboflavin in a model solution was evaluated. Five different TiO? loads (0.5-8.0 wt%), each at 3 different thicknesses (50-100 um) were evaluated. A photochemical reactor, equipped with a 350W mercury lamp, provided full spectrum light or narrow bandwidth wavelength exposure, using filters allowing transmission at 25 nm wavebands at maximum peak height at 450, 550, or 650 nm. Riboflavin concentration was measured by HPLC over 8 hours of exposure. Increased TiO? load and thickness significantly affected riboflavin photooxidation (p<0.05). TiO? load had more influence on protection provided to riboflavin than did film thickness. Film opacity correlated linearly with decreased photooxidation (R2 of 0.831 & 0.783 for full spectrum and 450 nm bandpass-filter sets, respectively). Riboflavin photooxidation proceeded most rapidly with the full spectrum exposure (light intensity 118 ° 17.3 mW). Photooxidation occurred in the 450 nm bandpass-filter, but not for 550 & 650 nm sets (light intensities of 2.84 °0.416, 3.36 °0.710, and 0.553 ° 0.246 mW, respectively). Effect of fluorescent light-exposure (2020-1690 lux) on the same system was monitored over 2 days. Riboflavin degradation in the photoreactor proceeded ~300 times faster than under fluorescent lighting. Riboflavin degradation was found to significantly increase with the addition of chlorophyll-like tetrapyrroles (p<0.05). Riboflavin was found to significantly decrease the degradation rate of the tetrapyrroles pyropheophytin a and pheophytin a (p<0.05). The decrease in rate was not significant for chlorophyll a (p>0.05).
- Protecting soymilk flavor and nutrients from photodegradation.Bianchi, Laurie M.; Duncan, Susan E.; Webster, Janet B.; Johnson, Daryan S.; Chang, Hao-Hsun; Marcy, Joseph E.; O'Keefe, Sean F. (Wiley, 2015-07)Five different packaging treatments were studied over a 36-day period to determine if they protected soymilk from photo-oxidation. Soymilk was packaged in high-density polyethylene (HDPE) bottles with and without light protective additives (LPA). Two controls [(1) no LPA (translucent appearance); (2) a light-protected control (foil overwrap over no LPA control)] and three LPA-containing treatments, Low (0.6% TiO2), Medium (1.3% TiO2), High (4.3% TiO2) were studied. Bottles were stored in a lighted refrigerated display case (average light intensity between 800 to 2200 lux; 3°C) for 36 days and evaluated weekly. Soymilk packaged in high LPA bottles was protected from developing light-oxidized off-flavors and odors for a minimum of 15 days. High LPA bottles provided protection for riboflavin and controlled development of photooxidative products for approximately 29 days.