C. Vanderzant

Effect of acid decontamination of beef subprimal cuts on the microbiological and sensory characteristics of steaks.

Beef strip loins were decontaminated by spraying with solutions of various food grade acids (1.0% lactic acid, 1.0% acetic acid and an acid mixture containing 1.0% lactic acid, 2.0% acetic acid, 0.25% citric acid and 0.1% ascorbic acid) followed by vacuum packaging and storing at 4 ± 1°C. Initially and at days 3 and 6 of display in polyvinyl chloride (PVC) film, aerobic plate counts (APCs) of steaks fabricated from the acid treated loins that were stored for 0, 14, 28, 42, 56, 70 and 84 days were not significantly different (P > 0.05) from the APCs of steaks fabricated from control loins.

Attachment of Microorganisms to Pork Skin and Surfaces of Beef and Lamb Carcasses

A model system was developed to study attachment to and possibly detachment of bacteria from pork skin and thin-surface slices of beef and lamb carcasses. The technique involves embedding pork skin and beef and lamb surfaces in solidified wax with the skin surface exposed. After exposure of the skin or carcass surface to bacterial suspensions and subsequent manipulations, the sample is removed aseptically from the wax and subjected to agar plate counting methods. A direct relationship existed between bacterial counts of the skin or carcass surface and concentration of bacterial cells in the attachment medium. Much of the bacterial attachment occurred during the first minute of immersion in the attachment medium, although in some instances continued attachment occurred over a 30-min period. Gram-negative motile bacteria showed greater attachment than did gram-positive non-motile species. Temperature and pH of the attachment medium had little effect on the extent of bacterial attachment.

Microbiology of Beef Packaged in Various Gas Atmospheres

Boneless beef roasts ( longissimus muscles) were vacuum-packaged and then the bags were injected with one of six gas mixtures: 100% O2, 20% CO2 +80% N2, 50% CO2 + 50% O2, 20% CO2 +80% O2, 25% CO2 + 25% O2 +50% N2 or 51% CO2 + 30% O2 + 18% N2 + 1% CO. One group of roasts, vacuum-packaged without added gas served as controls. Roasts were stored for 0-35 days at 1-3 C. At five weekly intervals, steaks were removed from roasts in each treatment and examined after storage for 5 days under retail display conditions. Psychrotrophic plate counts of roasts stored in modified gas atmospheres were usually higher than those stored in conventional vacuum packages. Differences in lactobacillus counts between roasts stored in modified gas atmospheres and those stored in vacuum packages rarely were statistically significant. Counts of retail steaks prepared from roasts stored in various gas atmospheres were usually slightly higher than those prepared from comparable vacuum packaged roasts. In most instances these differences were not statistically significant. Initially, the microbial flora of vacuum-packaged beef roasts consisted primarily of Moraxella-Acinetobacter and Pseudomonas spp. Lactobacilli predominated on roasts at later storage intervals even on roasts stored in atmospheres initially containing 100% O2 or 20% CO2 + 80% O2. Pseudomonas spp. remained a substantial part of the microflora of roasts stored in high O2 containing atmospheres.

Identification and evaluation of volatile compounds of vacuum and modified atmosphere packaged beef strip loins.

Beef strip loins were packaged and stored for up to 28 days at 3°C in high-oxygen barrier film under vacuum and in 100% CO(2), 40% CO(2)/60% N(2) and 20% CO(2)/80% O(2). As storage progressed, loins packaged and stored in 20% CO(2)/80% O(2) developed strong off-odors. 1-hexene, methyl thiirane, ethyl acetate, benzene and 1-heptene were detected in these packaged loins beginning at 7 to 14 days of storage. With the exception of 1-hexene, these compounds were not consistently detected in loins stored in vacuum, in 100% CO(2), or in 40% CO(2)/60% N(2), and these packaged loins developed much less off-odor during storage than loins packaged and stored in 20% CO(2)/80% O(2). A large number of volatile compounds from the headspace of the packaged loins originated from the packaging material. Lactobacillus plantarum became the dominant flora on loins stored under vacuum and under 40% CO(2)/60% N(2) while Leuconostoc mesenteroides subsp. mesenteroides predominated in loins stored in 100% CO(2). Pseudomonas putida eventually dominated on loins stored in 20% CO(2)/80% O(2).

Microbiological and Chemical Changes During Storage of Swordfish (Xiphias gladius) Steaks in Retail Packages Containing CO2-Enriched Atmospheres

Swordfish ( Xiphias gladius ) steaks were held in retail packages containing 100% CO2 and in mixtures of 40% and 70% CO2 in combination with either oxygen or nitrogen. Controls were stored in air. Samples were removed for chemical and microbiological analyses after 2-22 d of storage at 3.5°C. The inhibitory effect of CO2 on psychrotrophic, aerobic gram-negative spoilage bacteria was proportional to the CO2 tension in the packages. Maximum inhibition of growth was achieved with 100% CO2. Except for steaks stored in 40% CO2:60% O2 heterofermentative Lactobacillus spp. became a dominant part of the microflora of steaks stored in CO2-enriched atmospheres. Pseudomonas spp. continued to be a major part of the microflora of steaks stored in 40% CO2:60% O2. During the first 2 d of storage, there was a decrease in the surface pH of the swordfish steaks proportional to the CO2 tension in the packages. Swordfish steaks stored in CO2-enriched atmospheres had lower total volatile nitrogen (TVN), trimethylamine (TMA) and total volatile acid (TVA) values than steaks stored in air. Oxidative rancidity was not a flavor problem of fish in any of the atmospheres after 20 d of refrigerated storage.

Storage Characteristics of Finfish Fillets (Archosargus probatocephalus) Packaged in Modified Gas Atmospheres Containing Carbon Dioxide

Sheepshead ( Archosargus probatocephalus ) fillets were stored in air and in modified gas atmospheres consisting of: 100% CO2, 80% CO2:20% O2, 60% CO2:40% O2, 30% C02:60% O2, 20% CO2:80% O2, 40% CO2:60% N2 and 44% CO2:36% O2:20% N2 At regular intervals during refrigerated storage, numbers and types of microorganisms and total volatile nitrogen (TVN) were determined. Increases in aerobic plate counts of fish fillets held in air and in 20% C02:80% O2 were greater than those for fillets stored in the other gas atmospheres. The most effective combinations of gas for limiting bacterial growth were 100% CO2 and 40% CO2:60% N2. Total volatile nitrogen values of samples stored in air and in 20% CO2:80% O2 increased similarly to those of fish held on ice. At higher CO2 concentrations, however, increases in TVN were slow and the rate of TVN production appeared inversely proportional to CO2 tension.

Examination of Turkey Eggs, Poults and Brooder House Facilities for Campylobacter jejuni

Campylobacter jejuni was not isolated from fertile turkey eggs or from newly-hatched poults. The organism was present in 16 to 76% of fecal swabs of 15-to 19-day old turkeys from two commercial brooder facilities, and was isolated from litter and drinking water. Extensive cleaning of a brooder house and application of new litter seemed to exclude litter, water, feed and grit as initial sources of contamination. Newly-hatched poults could be raised in a Campylobacter -free environment for 19 to 21 d without evidence of this organism in fecal swabs.

Role of Hafnia alvei and a Lactobacillus Species in the Spoilage of Vacuum-Packaged Strip Loin Steaks

A microbiological examination of vacuum-packaged strip loin steaks that were defective (gassy packages, hydrogen sulfide odor) revealed high total counts (107-108/cm2) with Hafnia alvei , Lactobacillus and Pseudomonas spp. as major isolates. Re-inoculation experiments indicated that H. alvei was the likely cause of the hydrogen sulfide odor. Gas formation resulted from the activity of heterofermentative lactobacilli and H. alvei . Improvements in plant practices and temperature control eliminated the problem.

Effect of temperature and ph on the survival of campylobacter fetus

Test strains of C. fetus subsp. jejuni and C. fetus subsp. intestinalis failed to survive heating in skimmilk at 60 C for 1 min. A few strains survived heating in skimmilk at 55 C for 1-3 min. D50C values for C. fetus subsp. jejuni and C. fetus subsp. intestinalis in skimmilk ranged from 1.3-4.5 and from 1.0-3.7, respectively. No survivors of C. fetus subsp. jejuni and C. fetus subsp. intestinalis were detected in beef roasts inoculated at levels of 106-107 viable cells per g when the final temperature in the center was 57 and 55 C, respectively. At an internal temperature of 50-53 C, survivors of C. fetus were detected in beef roasts. Storage of skimmilk, beef and ground beef inoculated with C. fetus at -20, 1, 10, 20, 30 or 40 C resulted in decreases in C. fetus count. Survival of C. fetus was best at 1 and 10 C. Rapid increases in C. fetus counts occurred at 37 C in Brucella broth adjusted to pH 6-8. At pH 5, no survivors were detected after 24 h. At pH 9, counts of C. fetus subsp. jejuni decreased rapidly while those of C. fetus subsp. intestinalis increased slightly.

Examination of Poultry Giblets, Raw Milk and Meat for Campylobacter fetus subsp. jejuni

An MPN procedure was used to determine the presence of Campylobacter fetus subsp. jejuni in poultry giblets. This procedure consists of (a) subculturing a sample in Brucella broth supplemented with 0.15% agar, 0.05% sodium pyruvate and the following antimicrobial agents per liter: vancomycin 10 mg, trimethoprim 5 mg, polymyxin B sulfate 2,500 IU, amphotericin B 2 mg and cephalothin 15 mg and (b) subsequent streaking of a loopful of Brucella broth held at 42 C for 48 h on plates of Brucella agar supplemented with 10% defibrinated horse blood and the concentrations of antimicrobial agents identified above. C. fetus subsp. jejuni was present in 85% of the chicken livers and in 89% of the chicken gizzards obtained immediately after evisceration. The organism was not recovered from samples treated with chlorinated water. C. fetus subsp. jejuni was not recovered from raw milk (bulk tank samples or individual cow samples) or from beef ( infraspinatus or biceps femoris muscles).