Acid Adaptation Enhances Tolerance of Escherichia coli O157:H7 to High Voltage Atmospheric Cold Plasma in Raw Pineapple Juice.

Pathogens that adapt to environmental stress can develop an increased tolerance to some physical or chemical antimicrobial treatments. The main objective of this study was to determine if acid adaptation increased the tolerance of Escherichia coli O157:H7 to high voltage atmospheric cold plasma (HVACP) in raw pineapple juice. Samples (10 mL) of juice were inoculated with non-acid-adapted (NAA) or acid-adapted (AA) E. coli to obtain a viable count of ~7.00 log10 CFU/mL. The samples were exposed to HVACP (70 kV) for 1-7 min, with inoculated non-HVACP-treated juice serving as a control. Juice samples were analyzed for survivors at 0.1 h and after 24 h of refrigeration (4 °C). Samples analyzed after 24 h exhibited significant decreases in viable NAA cells with sub-lethal injury detected in both NAA and AA survivors (p < 0.05). No NAA survivor in juice exposed to HVACP for 5 or 7 min was detected after 24 h. However, the number of AA survivors was 3.33 and 3.09 log10 CFU/mL in juice treated for 5 and 7 min, respectively (p < 0.05). These results indicate that acid adaptation increases the tolerance of E. coli to HVACP in pineapple juice. The potentially higher tolerance of AA E. coli O157:H7 to HVACP should be considered in developing safe juice processing parameters for this novel non-thermal technology.

Beef Handling Practices Among Consumers in the U.S. Virgin Islands.

U.S. Virgin Islands (USVI) imports more than 95% of its food. Transportation limitations throughout the territory's supply chain can make temperature control of protein foods challenging for consumers. This study aimed to characterize the beef handling practices used by consumers in USVI to determine any educational needs. Printed and online surveys (n = 620 total) were disseminated in USVI through extension agents and local media sources. Three hundred and thirty-four consumers completed a 30-question food handling questionnaire on consumption patterns and food handling from purchasing to their kitchen. Frequencies and Pearson chi-square tests of independence were performed. Beef ranked second among the different meat types consumed, 92% of consumers bought beef from grocery stores, and 55% removed beef from shelves immediately after entering the store. When shopping, 59.1% of respondents always checked the use-by/freeze-by dates of beef, 46.3% always separated beef from other foods, but only 27.5% always used insulated bags. Eighty-three percent of consumers returned home within 1 h of shopping, 92% took less than 30 min to store groceries in either a freezer or refrigerator (98%) and during power outages, 45.1% maintained cold temperatures of beef. Seventy-two percent of consumers washed their hands for more than 10 s, but 33% of those from households with a vulnerable person did not use soap to wash their hands and dried them with reusable towels. When cooking, 44.6% of consumers thawed beef within the temperature danger zone, 80.1% did not check the temperature of beef for doneness, and 34 respondents cooked hamburgers below 160°F. Future consumer food safety education initiatives in the USVI should address hand hygiene among food preparers in homes with vulnerable persons, temperature control practices by promoting the use of insulated bags, safe meat thawing techniques, and the use of thermometers during cooking.

Effects of Pro-Oxidants and Antioxidants on the Total Antioxidant Capacity and Lipid Oxidation Products of Milk During Refrigerated Storage.

Oxidized flavor is a major problem that affects the dairy industry because of its adverse effect on milk acceptability. The objectives of this research were to examine the roles of pro-oxidants and antioxidants on the oxidative stability of whole milk. In the 1st experiment, the effect of light (2300 Lux) and/or cupric sulfate (0, 0.5, and 1.0 mg/kg) as pro-oxidants in milk were investigated during an 11-d refrigerated storage period. The effects of added retinyl palmitate (1.16 mg/L; 2113 IU Vitamin A/L) and tocopheryl acetate (100 mg/kg milk fat; 5.02 IU Vitamin E/L) as antioxidants in the presence of light (2300 Lux) and light with cupric sulfate (0.05 mg/kg) during a 7-d study were investigated in the 2nd experiment. The presence of pro-oxidants significantly (P < 0.05) decreased the total antioxidant capacity (TAC) and increased the lipid oxidation products in milk during storage. Light had a greater effect in the decrease of TAC, although cupric sulfate in the presence of light significantly increased the formation of lipid oxidation products. The addition of antioxidants resulted in a significant (P < 0.05) increase in TAC on day 0. However, with exposure to light and light with cupric sulfate, the antioxidants did not result in a higher TAC in comparison to the treatments without added antioxidant. Analysis of lipid oxidation products by instrumental and sensory methods showed that the presence of light and cupric sulfate significantly (P < 0.05) increased the oxidized flavor from the control, but no significant (P > 0.05) difference in oxidized flavor intensity was detected between milk with and without added antioxidants. PRACTICAL APPLICATION: Production and processing variables can affect the content of pro-oxidants and antioxidants in milk, which has an impact on flavor. An understanding of the role of these components in contributing to or minimizing off-flavor formation in milk, will help dairy producers to provide quality products to consumers.

Resistant starch: promise for improving human health.

Ongoing research to develop digestion-resistant starch for human health promotion integrates the disciplines of starch chemistry, agronomy, analytical chemistry, food science, nutrition, pathology, and microbiology. The objectives of this research include identifying components of starch structure that confer digestion resistance, developing novel plants and starches, and modifying foods to incorporate these starches. Furthermore, recent and ongoing studies address the impact of digestion-resistant starches on the prevention and control of chronic human diseases, including diabetes, colon cancer, and obesity. This review provides a transdisciplinary overview of this field, including a description of types of resistant starches; factors in plants that affect digestion resistance; methods for starch analysis; challenges in developing food products with resistant starches; mammalian intestinal and gut bacterial metabolism; potential effects on gut microbiota; and impacts and mechanisms for the prevention and control of colon cancer, diabetes, and obesity. Although this has been an active area of research and considerable progress has been made, many questions regarding how to best use digestion-resistant starches in human diets for disease prevention must be answered before the full potential of resistant starches can be realized.

Viability of bifidobacteria strains in yogurt with added oat beta-glucan and corn starch during cold storage.

Probiotics must be consumed at a level of 10(7) CFU/mL for successful colonization of the gut. In yogurts containing beneficial cultures, the survival of probiotic strains can quickly decline below this critical concentration during cold storage. We hypothesized that beta-glucan would increase the viability of bifidobacteria strains in yogurt during cold storage. Yogurts were produced containing 0.44% beta-glucan (concentrated or freeze-dried) extracted from whole oat flour and/or 1.33% modified corn starch, and bifidobacteria (B. breve or B. longum) at a concentration of at least 10(9) CFU/mL. All yogurts were stored at 4 degrees C. Bifidobacteria and yogurt cultures, Streptococcus thermophilus and Lactobacillus delbureckii subsp. bulgaricus, were enumerated from undisturbed aliquots before fermentation, after fermentation, and once a week for 5 wk. S. thermophilus and L. bulgaricus maintained a concentration of at least 10(8) CFU/mL in yogurts containing concentrated or freeze-dried beta-glucan regardless of starch addition, and in the control with no added beta-glucan or starch. Similarly, the probiotic, Bifidobacterium breve, survived above a therapeutic level in all treatments. The addition of beta-glucan prolonged the survival of Bifidobacterium longum at a concentration of at least 10(7) CFU/mL by up to 2 wk on average beyond the control. Further, the inclusion of concentrated beta-glucan in yogurt improved survival of B. longum above 10(7) CFU/mL by 1 wk longer than did freeze-dried beta-glucan. Study results suggest that beta-glucan has a protective effect on bifidobacteria in yogurt when stressed by low-temperature storage.

Conjugated linoleic acid content and organoleptic attributes of fermented milk products produced with probiotic bacteria.

The effect of probiotic bacteria on the formation of conjugated linoleic acid (CLA), microbial growth, and organoleptic attributes (acidity, texture, and flavor) of fermented milk products was determined. Four probiotic bacteria, Lactobacillus rhamnosus, Propionibacterium freudenreichii subsp. shermanii 56, P. freudenreichii subsp. shermanii 51, and P. freudenreichii subsp. freudenreichii 23, were evaluated individually or in coculture with traditional yogurt cultures (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus). The lipid source was hydrolyzed soy oil. L. rhamnosus, in coculture with yogurt culture, resulted in the highest content of CLA. Growth and CLA formation of propionibacteria were enhanced in the presence of yogurt cultures. Texture and flavor attributes of fermented milks produced with propionibacteria were significantly different than the fermented milks processed with yogurt cultures. The fermented milks processed with probiotic bacteria in coculture with yogurt cultures demonstrated similar acidity, texture, and flavor as the fermented milk produced with yogurt cultures.

Effect of gas environment and sorbate addition on flavor characteristics of irradiated apple cider during storage.

Apple cider, with (0.1%) and without potassium sorbate, was packaged in polystyrene containers and exposed to three different gas environments: oxygen flush, nitrogen flush, and atmospheric air. To evaluate the effects of irradiation (2 kGy) and storage on flavor and microbial quality, these irradiated apple cider samples were compared to a control, unirradiated sample exposed to atmospheric air. Volatile compounds, soluble solids, titratable acidity, and microbiological counts were determined weekly throughout 7 weeks of refrigerated (4 degrees C) storage. Cider irradiated and stored in atmospheric air or nitrogen-flush environments had lower rates of loss for characteristic flavor volatiles compared to unirradiated apple cider and cider irradiated and stored in an oxygen-flush environment. The addition of potassium sorbate to the apple cider resulted in lower counts of yeasts and aerobic microorganisms, reduced fermentation of sugars to organic acids, and improved retention of volatile compounds characteristic of apple cider.

Physical and sensory properties of dairy products from cows with various milk fatty acid compositions.

Dairy products from milk of cows fed diets rich in polyunsaturated fatty acids have a more health-promoting fatty acid composition and are softer but often have oxidized flavors. Dairy products made from cow's milk that has more- or less-unsaturated fatty acid compositions were tested for differences in texture and flavor from those made from bulk-tank milk. The milk was manufactured into butter, vanilla ice cream, yogurt, Provolone cheese, and Cheddar cheese. The products were analyzed for fatty acid composition, physical properties, and flavor. Milk of cows with a more monounsaturated fatty acid composition yielded products with a more monounsaturated fatty acid composition that were softer and had a satisfactory flavor. Thus, selection of cows for milk fatty acid composition can be used to produce dairy products that are probably more healthful and have a softer texture.

Effects of processing treatment and sorbate addition on the flavor characteristics of apple cider.

Processing treatments used to produce a microbiologically "safe" apple cider were evaluated to determine the impact of these treatments on the overall flavor characteristics. Apple cider with (0.1%) and without (0%) potassium sorbate was subjected to four processing treatments: untreated, irradiated at 2 kGy, irradiated at 4 kGy, and pasteurized. Volatile flavor compounds were isolated from the cider using solid-phase microextraction methods with gas chromatographic analysis. A trained descriptive analysis panel evaluated sensory attributes. The effects of the processing treatment were dependent on the presence of sorbate in the apple cider. Irradiation treatments resulted in a decrease in the content of esters characteristic of apple flavor and an increase in the content of alcohols and aldehydes formed through lipid oxidation reactions. The presence of sorbate reduced the effects of the irradiation treatments on these volatile flavor compounds. Sensory panelists, however, detected higher intensities of undesirable flavor attributes, including "cardboard flavor", and lower intensities of the desirable "apple flavor" in irradiated cider with added sorbate.