Antilisterial activity of hops beta acids in broth with or without other antimicrobials.

Hops beta acids (HBA) are parts of hops flowers used to preserve wort and provide flavor in beer, and are reported as having antimicrobial properties. This study evaluated the antilisterial activity of HBA alone or in combination with other known antimicrobials in a culture broth medium. Listeria monocytogenes (10-strain mixture) was inoculated (2.6 to 2.8 log CFU/mL) into tryptic soy broth supplemented with 0.6% yeast extract (TSBYE) without (control) or with HBA (0.5 to 5.0 microg/mL), potassium lactate (1.0%), sodium diacetate (0.25%), or acetic acid (0.1%), alone or in combination with HBA (0.5 to 3.0 microg/mL). Survival/growth of the pathogen during storage at 4 degrees C (35 d), 10 degrees C (20 d), or 25 degrees C (2 d) was periodically monitored by spiral plating onto tryptic soy agar plus 0.6% yeast extract. As expected, TSBYE without antimicrobials (control) supported rapid pathogen growth with growth rates of 0.40, 2.88, and 9.58 log CFU/mL/d at 4, 10, and 25 degrees C, respectively; corresponding Y(end) values exceeded 9.0 log CFU/mL at 35, 20, and 2 d storage. HBA used alone (1.0 to 5.0 microg/mL) inhibited growth of L. monocytogenes at all 3 temperatures, with inhibition being more pronounced at higher concentrations and at the lower storage temperature (4 degrees C). The antilisterial activity of HBA (0.5 to 3.0 microg/mL) was enhanced when combined with sodium diacetate, acetic acid, or potassium lactate, achieving complete inhibition at 4 degrees C when 3.0 microg/mL HBA were used in combination with each of the above antimicrobials. Overall, HBA exhibited promising antilisterial activity in a broth medium and further studies are needed to investigate its potential antilisterial effects in food products.

Case life of seven retail products from beef cattle supplemented with alpha-tocopheryl acetate.

Packages (n = 660) of clod, strip loin, tenderloin, bottom round, eye-of-round, and top round steaks, as well as ground beef, from beef cattle fed diets supplemented with vitamin E (500 IU/d for 100 d preharvest) were compared with packages of products derived from carcasses of beef cattle fed control diets to determine the duration of acceptable muscle color during simulated retail display. In addition, the effect of storage before steak fabrication, simulating distribution time, on the acceptability of each treatment and each cut during retail display was investigated. Dietary supplementation of animals with vitamin E increased muscle alpha-tocopherol concentrations (P < .05) in all cuts. The acceptable retail display time of ground beef from vitamin E-supplemented cattle was longer (P < .05) compared to ground beef from unsupplemented cattle by 10.2, 15.6, and 17.6 h following 7, 14, and 21 d of storage in chub packages prior to final grinding and retail display, respectively. However, length of storage in a vacuum package before retail display did not have a consistent effect on retail case life of steaks. Product drip loss during retail display was not affected by storage time or vitamin E treatment. The trained panel color score during retail display of high vitamin E strip loin, bottom round, inside round, and eye-of-round steaks remained acceptable longer (P < .05) by 11.5, 25.2, 8.4, and 29.4 h, respectively, than that of control steaks. The results demonstrated that vitamin E supplementation of cattle feed can be used as a management tool to reduce the economic losses associated with beef muscle color deterioration during retail display of products.

Effects of muscle α-tocopherol level and surface microbiological contamination on retail caselife of fresh beef from the US, Japan and Australia.

This study evaluated effects of dietary supplementation of vitamin E (1000 IU vitamin E/daily for 100 days prior to harvest) to fed cattle on retail caselife performance of fresh US beef in an export market (Japan). Economic performance (monetary losses associated with color deterioration) for US beef from vitamin E supplemented cattle vs beef from non-vitamin E supplemented cattle was contrasted. An additional, controlled study was performed to compare muscle α-tocopherol concentrations, color changes and microbiological growth for fresh beef derived from vitamin E supplemented US cattle and fresh beef from cattle with an unknown history, but from other countries. Australian strip loin steaks had the highest muscle α-tocopherol concentrations (4.6 µg/g tissue), followed by US strip loin steaks derived from vitamin E supplemented cattle (3.4 µg/g tissue) and Japanese strip loin steaks (2.8 or 2.5 µg/g tissue). US strip loin steaks from non-vitamin E supplemented cattle had the lowest (p<0.05) α-tocopherol levels (1.7 µg/g tissue). Aerobic plate counts and total coliform counts were generally low at 0 days of retail display, and they changed similarly among treatments over 6 days of display, regardless of the country of origin of the beef. Vitamin E supplementation of US cattle reduced total Japanese retail store losses due to discoloration of US beef, in yen, by 5.2 percentage points (p<0.05), saving Japanese retailers US $0.24/kg. Data suggest that US beef-normally perceived, in Japan, to discolor more quickly in the retail display case than beef from Australia-would compete more favorably, in shelf-life, with beef from other countries if it was derived from cattle that had been fed supplemental vitamin E.

Bacterial growth in ground beef patties made with meat from animals fed diets without or with supplemental vitamin E.

A study was designed to determine populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, and Listeria monocytogenes during display at 4 and 12 degrees C of ground beef patties made with meat from animals fed diets supplemented daily (for 100 days) with 0, 1,000, or 2,000 IU of vitamin E. The patties (113.5 g) were either left uninoculated or were inoculated with Escherichia coli O157:H7 or L. monocytogenes and were tray-overwrapped and stored (at 4 or 12 degrees C for 8 to 10 or 4 to 6 days, respectively) while being continuously exposed to fluorescent light in a display setting. Patties were visually evaluated for overall appearance (based on color and/or discoloration) twice a day and analyzed for microbiological counts at 2-day intervals during display at 4 degrees C and at 0, 1, 2, 3, 4, and 6 days during display at 12 degrees C. Use of beef from animals fed supplemental vitamin E ("high-vitamin E beef") resulted in ground beef patties which, when stored at 4 degrees C, maintained visually acceptable color longer than did patties made from control beef (from animals not fed supplemental vitamin E), but effects on microbial growth were less pronounced. In general, use of high-vitamin E beef versus control beef in patty manufacture had no major effect on populations of aerobic bacteria, coliforms, sorbitol-negative bacteria, or L. monocytogenes in ground beef patties displayed at 4 or 12 degrees C. Listeria monocytogenes multiplied at 12 degrees C, but growth was similar among ground beef patties made from high-vitamin E beef versus control beef. Overall, changes in bacterial populations were similar in ground beef patties derived from meat from animals with or without added vitamin E in their diets, but control ground beef became visually unacceptable sooner.

Growth and fresh meat quality characteristics of pigs supplemented with vitamin E.

Crossbred pigs (n = 30) were fed to determine the influence of supplementation with vitamin E on growth and slaughter characteristics of swine and on the quality characteristics of fresh pork. Pigs received either a control diet containing no vitamin E (CON) or a diet formulated to contain 100 mg of vitamin E/kg feed (VITE). During 84 d of feeding, feed intake and weight gain were measured every 2 wk. After the feeding period, pigs were slaughtered and the loin from the left side of each carcass was removed 4 d after death. Alpha-Tocopherol concentration and proximate composition of the longissimus muscle were determined. Loins were sliced into 10-cm sections and stored under vacuum (2 degrees C) for 0, 14, 28, and 56 d. After storage, loins were sliced into 2.54-cm chops, wrapped in polyvinyl chloride film and stored in a retail case (2 to 4 degrees C) for 5 d. Thiobarbituric acid (TBA) values, Hunter L, a, and b values, total plate counts, pH, purge loss, drip loss, cook loss, taste panel characteristics, and visual panel characteristics were evaluated. Growth traits, slaughter characteristics, and proximate composition did not differ (P > .05) between dietary treatment groups. Alpha-Tocopherol concentrations were greater (P < .05) and TBA values during extended retail display were less (P < .05) for VITE chops than for CON chops. Overall palatability ratings were more desirable (P < .05, at 14 d of vacuum storage) for VITE chops than for CON chops. Color measurements, sensory characteristics, total plate counts, pH, purge loss, drip loss, and cook loss were not influenced (P > .05) by vitamin E supplementation. These results indicated that at the tissue alpha-tocopherol concentrations of the present study, vitamin E supplementation of the growing-finishing diet of hogs reduced lipid oxidation in fresh pork but did not influence pork color or tissue drip loss.