Department of Food Science and Technology

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Browsing Department of Food Science and Technology by Department "Fralin Life Sciences Institute"

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    Evaluation of Listeria monocytogenes and Staphylococcus aureus Survival and Growth during Cooling of Hams Cured with Natural-Source Nitrite
    Wu, Jian; Acuff, Jennifer C.; Waterman, Kim M.; Ponder, Monica A. (International Association of Food Protection, 2021-02-01)
    Growing consumer demand for clean-label “natural” products has encouraged more meat processors to cure meat products with natural sources of nitrate or nitrite such as celery juice powder. One challenge for these producers is to identify safe cooling rates in products cured with celery juice powder where extended cooling could allow growth of pathogens. The Food Safety and Inspection Service of the U.S. Department of Agriculture recently added guidelines for stabilization of meat products cured using naturally occurring nitrites based on control of Clostridium spp. However, a knowledge gap exists for safe cooling rates that prevent the growth of Listeria monocytogenes and Staphylococcus aureus, potential postlethality contaminants, in naturally cured ham. The study was conducted to investigate the temperature profiles of naturally cured hams of typical sizes during refrigerator cooling and to determine the behavior of S. aureus and L. monocytogenes on ham during these cooling periods. Whole hams (14 lb [6,300 g]), half hams (6 lb [2,700 g]), and quarter hams (3 lb [1,400 g]) were slowly cooked in a smokehouse until internal temperatures reached a minimum of 1408F (608C) and then were immediately transferred into a walk-in cooler (388F [3.38C]). Cooling times for hams of all sizes were within the requirements for cured products but not for uncured products. Worst-case scenarios of postprocessing surface contamination were simulated by inoculating small naturally cured ham samples with S. aureus or L. monocytogenes. These inoculated hams were then cooled under controlled conditions of 130 to 458F (54.4 to 7.28C) for 720 to 900 min. By the end of cooling, small decreases (0.5 to 0.6 log CFU/g) were found for each inoculum. These findings may help small ham processors evaluating production and quality control methods to determine whether recommended concentrations of natural curing agents used to prevent growth of clostridial pathogens may also prevent growth of other pathogens during meat cooling.
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    Evaluation of peanut skin and grape seed extracts to inhibit growth of foodborne pathogens
    Levy, Jason M.; Boyer, Renee R.; Neilson, Andrew P.; O'Keefe, Sean F.; Chu, Hyun Sik S.; Williams, Robert C.; Dorenkott, Melanie R.; Goodrich, Katheryn M. (Wiley, 2017-11-01)
    Peanut skin extract (PSE) and grape seed extract (GSE) are derived from waste products in the wine and peanut industries, respectively. Both have high concentrations of polyphenols, known to possess antioxidant and antimicrobial properties. PSE primarily contains “A-type” procyanidins, while GSE primarily contains “B-type” procyanidins. These differ structurally, but are both isomers of epicatechin dimers. The objective of this study was to evaluate the antimicrobial effects of PSE containing A-type procyanidins and GSE containing B-type procyanidins against select foodborne pathogens (Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium). The minimum inhibitory concentration (MIC) of the two extracts on L. monocytogenes, E. coli O157:H7, and S. Typhimurium was determined using the pour plate method. GSE had a significantly lower MIC (p ≤ .05) than PSE for L. monocytogenes (GSE = 60.6 ppm, PSE > 68.2 ppm) and S. Typhimurium (GSE = 45.7 ppm, PSE = 60.6 ppm), but no difference in inhibition of E. coli O157:H7. Since GSE contributed to greater inhibition, GSE extract was fractionated into monomer-rich (consisting primarily of catechins, epicatechins, and epicatechin gallates) and oligomer-rich (consisting of dimers, trimers, tetramers, up to decamers) components. Growth curves of all three pathogens in the presence of full extract, monomer and oligomer fractions were compared separately. None of the extracts inhibited S. Typhimurium growth. Generally, the extract containing greater oligomer components inhibited growth of L. monocytogenes and E. coli O157:H7 when compared to the control. Results indicate that an extract with type B procyanidins higher in oligomers may have greater antimicrobial properties.
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    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.