Beef Jerky: Viability of Food-Poisoning Microorganisms on Jerky during its Manufacture and Storage

Beef jerky was made from slices of flank steak inoculated with Staphylococcus aureus , vegetative cells of Clostridium perfringens as well as Bacillus subtilis and a two species-composite of Salmonella . Slices were placed in a domestic food dehydrator for 4 h at 52.9±0.8°C (127.2°F) followed by 4 h at 48.2±0.4°C (118.8°F). Meat slices dried rapidly, reaching an a_w of 0.86 and a shelf-stable moisture-protein ratio of ≤1.6 within the first 2.5-3 h of drying. Samples originally contained about 68% moisture, but this dropped to about 30% by 4 h and 20% by 8 h. Some growth of inoculated S. aureus occurred initially but total numbers of all other added microorganisms decreased rapidly from the start of drying and although significantly reduced in numbers at the end of 8 h treatment, they survived processing. C. perfringens cells were not detected at the end of the heated-drying regimen but were recovered later in an inoculated sample stored at 2.5°C for a month. Contaminated jerky stored at 20°C and high relative humidity (RH) for 26-28 d did not contain detectable added bacteria, whereas identical samples stored at 2.5°C and low RH contained viable S. aureus and B. subtilis as well as C. perfringens . Domestic preparation of jerky from beef of normal retail quality would involve little risk provided initial drying is done rapidly at temperatures equal to or greater than those used in the present study.

Shelf-Life of Meat Loaves Packaged in Vacuum or Nitrogen Gas 2. Effect of Storage Temperature, Light and Time on Physicochemical and Sensory Changes

Effects of temperature, light and time of storage on the physicochemical (gas composition, pH, extract release volume (ERV), exudate and TBA) and sensory (appearance and off-odor) changes of vacuum- or nitrogen-packed meat loaves were examined at intervals during 49 d of storage at -4, 0, 3 and 7°C under dark and lighted display. Meat loaves stored at -4°C did not exhibit significant changes during 49 d of storage, but extending duration and increasing temperature above 0°C had a significant effect on the shelf-life of meat loaves, regardless of treatments. Appearance and off-odor changes were not related to those of ERV, exudate and TBA, but significant relationships were noted between CO₂, pH and sensory changes. Overall, nitrogen packaging significantly improved appearance by retarding the greenish discoloration of meat loaves. Light increased the frequency of green discoloration of vacuum-packed samples after 28 d at 0, 3 and 7°C as compared to nitrogen-packed samples.

Shelf-Life of Meat Loaves Packaged in Vacuum or Nitrogen Gas I. Effect of Storage Temperature, Light and Time on the Microflora Change

The effects of storage temperature, light and time on the microflora of vacuum- or nitrogen-packed meat loaves were examined at intervals during 49 d at -4, 0, 3 and 7°C under dark and lighted displays. Storage of cooked cured meat loaves at -4°C for 49 d produced little increase in lactobacilli numbers (from log₁₀ 5.2 to 6.3) but resulted in significant (P<0.05) increases in psychrotrophs (log₁₀ 3.9 to 5.9) and anaerobes (log₁₀ 5.1 to 6.3 under vacuum). Storage time and temperature above 0°C resulted in a significant (P<0.05) increase in lactobacilli, psychrotroph and anaerobe numbers, regardless of packaging atmospheres, but the times at which counts reached approx. 10⁸/g were deferred, i.e., day 7 at 7°C, day 21 at 3°C and day 28 at 0°C. Apart from a few exceptions in the numbers of psychrotrohs and lactobacilli, there were no significant differences in the numbers of microflora between vacuum- and nitrogen-packed meat loaves. At day 0, the dominant flora in both types of packaged samples was composed of Pseudomonas (32 to 34%), Brochothrix (24 to 38%), Micrococcus (9 to 22%) and Lactobacillus spp. (7 to 20%). By day 49, Lactobacillus spp. became a predominant part (62 to 76%) of the psychrotrophs. Few significant differences in the composition of psychrotrophs were found among different treatments. With an initial level of 10² coliforms per gram, there was no significant (P>0.05) change in coliforms counts between treatments but the numbers of yeasts and molds were lower in nitrogen-packed samples at 3 and 7°C as compared with similarly treated vacuum-packed samples.

Nematospora sinecauda sp. nov., a yeast pathogen of mustard seeds

An undescribed yeast species was recovered from oriental (Brassica juncea) and yellow (B. hirta) mustard seeds. The new species most closely resembled Nematospora coryli but its asci were rarely cylindrical. The asci and ascospores of N. sinecauda were smaller and the spores did not possess a whip-like appendage. During germination a sprout cell formed first on the smooth anterior surface of the spore above the median ridge. The posterior region of the spore was decorated with interrupted concentric ridges. A description of the new species is given.

Effects of Temperature, Light and Storage Time on the Microflora of Vacuum- or Nitrogen-Packed Frankfurters

Frankfurters were vacuum- or nitrogen- packaged and stored at -4, 0, 3 and 7°C for 49 d under light or dark display conditions. Effects of temperature, light and storage duration on microflora in vacuum- and nitrogen-packed sausages were then examined. Differences in number of lactobacilli, psychrotrophic and anaerobic bacteria in vacuum- or nitrogen-packed samples were not statistically significant during storage tests. Lactobacillus development was slightly higher in nitrogen gas compared to vacuum packages, but was also not significantly different. The effectiveness of nitrogen packaging on yeast and mold inhibition was significant, particularly at higher temperatures (3 and 7°C). Nitrogen gas packaging thus offers little advantage over vacuum to promote lactobacillus development, but it is particularly effective against growth of mold and yeast. Initially, the dominant flora of both package samples consisted of Pseudomonas and Microbacterium sp. but Lactobacillus sp. became the predominant psychrotrophs (85.2-96.3%) after 49 d of storage, regardless of different treatments. Temperature was the most important factor which influenced growth of the microflora on frankfurters; freezing temperatures of -4 and 0°C were an effective insurance against development of spoilage microflora in frankfurters for up to 49 d, regardless of packaging atmosphere. With an initial level of 10 to 10³ coliforms per gram, there was no significant change in the number of coliforms during storage. Light had no important influence on microbial growth in frankfurters, irrespective of packaging atmosphere.

Effects of Temperature, Light and Storage Time on the Physicochemical and Sensory Characteristics of Vacuum- or Nitrogen-Packed Frankfurters

Frankfurters prepacked in vacuum or nitrogen gas were stored for 49 d at -4, 0, 3 and 7°C under dark and light conditions. Effects of temperature, light and storage duration on physiocochemical (gas composition, TBA, pH, ERV, nitroso-hematin) and sensory (color and off-odor) characteristics of both package samples were then examined. The relative volume of nitrogen decreased gradually but the change was not significant (P>0.05) during the 49-d study. No significant increases in CO₂ concentration were observed between both package treatments at -4 and 0°C, whereas the largest increase in CO₂ content (4.8-16.8%) occurred at 7°C after 21 d of storage. TBA, pH, ERV and nitroso-hematin values were not differently affected by either modified atmosphere types, regardless of storage temperature and illumination used. With respect to surface discoloration and off-odor, nitrogen-packed frankfurters exhibited a lower incidence of discoloration and off-odor and were of satisfactory appearance, even after 35 d of storage at 7°C. Vacuum-packed samples, however, could not be effectively stored longer than 21 d due to formation of brown and green discolorations. Light generally had a significant effect on surface discoloration of vacuum-packed frankfurters. Data indicate that color and odor changes were not related to the values of TBA, ERV and nitro so-pigment but significant relationships were noted between pH. CO₂ and microflora counts at 7°C.

Prevention of surface mold growth on Italian dry sausage by natamycin and potassium sorbate

Inhibition of uncontrolled mold growth on three types of raw cured Italian dry salami was studied under commercial production conditions. Salami were dipped or sprayed with natamycin (pimaricin) or were given a combined organic acid-plus-potassium sorbate treatment. Acetic and citric acids potentiated the inhibitory effects of potassium sorbate significantly, but lactic and succinic acids showed little or no effect. Treatment of salami by dipping in 2.5% (wt/vol) potassium sorbate or 2,000 ppm (mg/liter) of pimaricin did not successfully prevent the growth of surface molds. At 10% potassium sorbate on all types of salami and at 2.5% sorbate on Casalingo salami, visual inhibition of mold growth was observed, but numbers of viable fungi on all salami types treated with 2.5% sorbate were not significantly (95% confidence) different from numbers found in the untreated controls. Pimaricin spray (2 X 1,000 ppm) was as good as or slightly better than 2.5% potassium sorbate, but greater concentrations of each were required to satisfactorily inhibit surface mold growth during the 25- to 50-day ripening period.

Ultraviolet Spectrophotometric Determination of Sorbic Acid in Dry Fermented Sausage

A rapid and reliable method is described for determining sorbic acid in dry fermented Italian salami (moisture &lt;50%, fat &gt;25%). Sorbic acid was extracted from the homogenized sample with metaphosphoric acid and partitioned into isooctane. The absorbance of the extract was read at 255 nm. Background UV-absorbing materials were determined by their absorbance at 255 nm after permanganate oxidation of sorbic acid. Unexpectedly, spice components contributed to the UV absorbance of permanganate-labile substances, and sorbic acid was at first overestimated. Interference caused by spice components was calculated by measuring the difference in absorbance before and after permanganate treatment of a sample extract from a salami which had not been treated with sorbic acid. Recovery of added sorbic acid (50 –600 ppm) was between 92 and 98.7%.

Ultraviolet spectrophotometric determination of sorbic acid in dry fermented sausage

A rapid and reliable method is described for determining sorbic acid in dry fermented Italian salami (moisture < 50%, fat > 25%). Sorbic acid was extracted from the homogenized sample with metaphosphoric acid and partitioned into isooctane. The absorbance of the extract was read at 255 nm. Background UV-absorbing materials were determined by their absorbance at 255 nm after permanganate oxidation of sorbic acid. Unexpectedly, spice components contributed to the UV absorbance of permanganate-labile substances, and sorbic acid was at first overestimated. Interference caused by spice components was calculated by measuring the difference in absorbance before and after permanganate treatment of a sample extract from a salami which had not been treated with sorbic acid. Recovery of added sorbic acid (50--600 ppm) was between 92 and 98.7%.

Ribosome-covered vesicles associated with synthesis and secretion of invertase in yeast

A ribosome-covered vesicle population in Saccharomyces cerevisiae M1016 shows a marked increase when invertase synthesis is derepressed. These structures have not been reported previously. It is suggested that these structures may be related to the synthesis and secretion of invertase.

Role of vacuoles and vesicles in extracellular enzyme secretion from yeast

Preliminary evidence has been obtained which suggests that the intracellular invertase of Saccharomyces cerevisiae may not be localized in the vacuole per se. Alkaline phosphatase, an intracellular enzyme, and acid protease, a typically lysosomal enzyme, both showed high specific activity in the vacuole fraction prepared by equilibrium centrifugation of lysed sphaeroplasts in Ficoll gradients. Invertase activity has been found to be associated with vacuoles only when glucose-repressed cells are derepressed. Cells derepressed for invertase biosynthesis contained a population of vesicles which were virtually absent from the repressed cells. Evidence is presented which strongly suggests that these vesicles rather than the vacuoles are the vehicle by which invertase is secreted from the cell.