Anaerobic Plate Counts Research Articles

Application of lavender and rosemary essential oils improvement of the microbiological quality of chicken quarters

The aim of the present work was monitoring of chicken quarters microbiological indicators after treatment by ethylenediaminetetraacetate (EDTA), lavender (Lavandula angustifolia L.) and rosemary (Rosmarinus officinalis L.) essential oil, stored under vacuum packaging, at 4 ±0.5°C for a period of 16 days. The following treatments of chicken quarters were used: Air-packaging control samples, control vacuum-packaging samples, vacuum-packaging with EDTA solution 1.50% w/w, control samples, vacuum-packaging with Lavandula angustifolia essential oil at concentrations 0.2% v/w and vacuum-packaging with Rosmarinus officinalis essential oil at concentration 0.2% v/w. The quality assessment of all samples was established by microbiological analysis. Sampling was carried out after certain time intervals: 0, 4, 8, 12 and 16 days. Chicken quarters were stored under vacuum packaging, at 4 ±0.5°C during experiment. Microbiological analyses were conducted by using standard microbiological methods. Anaerobic plate count were determined using Plate Count Agar, after incubation for 2 days at 35°C under anaerobic condition. Pseudomonas spp. were determined on Pseudomonas Isolation agar after incubation at 48 h at 25°C. For lactic acid bacteria were inoculated into Rogosa and Sharpe agar after incubation 48-78 h at 37°C in an aerobic atmosphere supplemented with carbon dioxide (5% CO2). For members of the family Enterobacteriaceae violet red bile glucose agar were used and samples were incubated at 37°C for 24 h. The initial APC value of chicken quarter was 3.00 log CFU.g-1 on 0 day. The number of anaerobic plate count ranged from 3.00 log CFU.g-1 in all tested group on 0 day to 6.11 log CFU.g-1 on 16 day in control group stored in air condition. The initial LAC value of chicken quarter was 3.00 log CFU.g-1 on 0 day. The number of lactic acid bacteria ranged from 3.00 log CFU.g-1 in all tested group on 0 day to 3.58 log CFU.g-1 on 16 day in control group stored in air condition. The initial Enterobacteriacea genera value of chicken quarter was 2.00 log CFU.g-1 on 0 day. Presences of these bacteria were found on all groups at 16 days. The results of this present study suggest the possibility of application the Lavandula angustifolia and Rosmarinus officinalis essential oil as natural food preservatives and potential sources of antimicrobial ingredients for food industry.

The microbes we eat: abundance and taxonomy of microbes consumed in a day’s worth of meals for three diet types

Far more attention has been paid to the microbes in our feces than the microbes in our food. Research efforts dedicated to the microbes that we eat have historically been focused on a fairly narrow range of species, namely those which cause disease and those which are thought to confer some “probiotic” health benefit. Little is known about the effects of ingested microbial communities that are present in typical American diets, and even the basic questions of which microbes, how many of them, and how much they vary from diet to diet and meal to meal, have not been answered.We characterized the microbiota of three different dietary patterns in order to estimate: the average total amount of daily microbes ingested via food and beverages, and their composition in three daily meal plans representing three different dietary patterns. The three dietary patterns analyzed were: (1) the Average American (AMERICAN): focused on convenience foods, (2) USDA recommended (USDA): emphasizing fruits and vegetables, lean meat, dairy, and whole grains, and (3) Vegan (VEGAN): excluding all animal products. Meals were prepared in a home kitchen or purchased at restaurants and blended, followed by microbial analysis including aerobic, anaerobic, yeast and mold plate counts as well as 16S rRNA PCR survey analysis.Based on plate counts, the USDA meal plan had the highest total amount of microbes at 1.3 × 109 CFU per day, followed by the VEGAN meal plan and the AMERICAN meal plan at 6 × 106 and 1.4 × 106 CFU per day respectively. There was no significant difference in diversity among the three dietary patterns. Individual meals clustered based on taxonomic composition independent of dietary pattern. For example, meals that were abundant in Lactic Acid Bacteria were from all three dietary patterns. Some taxonomic groups were correlated with the nutritional content of the meals. Predictive metagenome analysis using PICRUSt indicated differences in some functional KEGG categories across the three dietary patterns and for meals clustered based on whether they were raw or cooked.Further studies are needed to determine the impact of ingested microbes on the intestinal microbiota, the extent of variation across foods, meals and diets, and the extent to which dietary microbes may impact human health. The answers to these questions will reveal whether dietary microbes, beyond probiotics taken as supplements—i.e., ingested with food—are important contributors to the composition, inter-individual variation, and function of our gut microbiota.

Effects of Gas Composition in the Modified Atmosphere Packaging on the Shelf-life of Longissimus dorsi of Korean Native Black Pigs-Duroc Crossbred during Refrigerated Storage.

This study was conducted to observe the effects of gas composition in modified atmosphere packaging (MAP) on the shelf-life of Longissimus dorsi of Korean Native Black Pigs-Duroc Crossbred (KNP×D) during refrigerated storage. Muscle sample was obtained from the left side of carcass of seven months old of KNP×D barrow. The sample was sliced into 1 cm in thickness, placed on trays (two slices/tray) and filled with different gas composition, i.e. 0:20:80/O2:CO2:N2 (MAP1), 30:20:50/O2:CO2:N2 (MAP2) and 70:20:10/O2:CO2:N2 (MAP3). Other slices of sample were vacuum packed (VP) as a control. All packs were stored at 5±1°C. At 12 d of storage, pH value of MAP2 and MAP3 were higher (p<0.05) than that of MAP1 and pH value of MAP1 was higher (p<0.05) than that of VP. At 6 d of storage, redness (a*) value of MAP2 and MAP3 were higher (p<0.05) than that of VP and MAP1 and, at 9 and 12 d of storage, redness value of MAP3 was higher (p<0.05) than that of VP, MAP1, and MAP2. At 3, 6, 9, and 12 d of storage, the 2-thiobarbituric acid reactive substances (TBARS) value of MAP3 was higher than that of MAP2 and TBARS value of MAP2 was higher than that of VP and MAP1. At 3, 6, 9, and 12 d of storage, volatile basic nitrogen values of MAP2 and MAP3 were higher (p<0.05) than those of VP and MAP1. At 3 d of storage, total aerobic plate counts of MAP2 and MAP3 were higher (p<0.05) than those of VP and MAP1 and, at 6 d of storage, total aerobic plate counts of MAP3 was higher (p<0.05) than that of MAP1 and MAP2. However, there was no significant different total aerobic plate count among MAP1, MAP2, and MAP3 at 9 and 12 d of storage. There was no significant different total anaerobic plate count among MAP1, MAP2, and MAP3 during storage. It is concluded that the MAP containing 30:20:50/O2:CO2:N2 gas composition (MAP2) might be ideal for better meat quality for KNP×D meat.

Quality of olive oil reformulated MRE entrée packaged in oxygen-absorbing film

An iron-based oxygen absorber (ABSO2RB®) activated by moisture was incorporated into a retort laminate and used to package chicken pesto with noodles. The effect of packaging material (regular MRE and oxygen-absorbing pouches) and reformulation with olive oil on the quality and shelf life of the entrée were investigated. Physical properties (color, texture, moisture, water activity), chemical properties (pH, TBARS), and microbiological quality (Total aerobic, coliforms, Escherichia coli, Yeast and Molds, Anaerobic plate counts) were measured in triplicates in an accelerated shelf-life study for 6 months at 37.8 °C. Samples stored at 26.7 °C for 12 months served as calibrated controls. Consumer and trained panel tests were carried out using a 9-point hedonic scale. The ABSO2RB® pouches performed well in terms of seal integrity and strength and limited the formation of rancid fatty acids in olive oil throughout the shelf-life study. Soybean formulations in ABSO2RB® pouches had the lowest (p < 0.05) Thiobarbituric Acid Reactive Substances (TBARS) value. Consumer and trained panelists accepted the olive oil formulations, in both packages. Results from this study will help MRE developers to expand the number of items using healthier oils. If future considerations to replace MRE packaging are needed, the ABSO2RB® film will be a suitable alternative.

Safety and intestinal microbiota modulation by the exopolysaccharide-producing strains Bifidobacterium animalis IPLA R1 and Bifidobacterium longum IPLA E44 orally administered to Wistar rats

Bifidobacterium animalis subsp. lactis IPLA R1 and Bifidobacterium longum IPLA E44 strains were tested for their safety and ability to modulate the intestinal microbiota in vivo. Chemically simulated gastrointestinal digestion showed considerably lower survival of E44 than R1 strain, the first microorganism also being more sensitive to refrigerated storage in 10% skimmed milk at 4°C. Harmful glycosidic activities were absent, or at low levels, in the strains R1 and E44. Both strains were sensitive to most antibiotics and resistant to aminoglycosides, a common feature in bifidobacteria. Similar to several other bifidobacteria strains, B. animalis subsp. lactis IPLA R1 displayed a moderate resistance against tetracycline which correlated with the presence of tet(W) gene in its genome. The general parameters indicating well-being status, as well as translocation to different organs and histological examination of the gut tissues, revealed no changes induced by the administration of bifidobacteria to rats. Twelve-week-old male Wistar rats were distributed into three groups, eight rats in each. Two groups were administered daily over 108cfu of the corresponding strain suspended in 10% skimmed milk for 24days, whereas rats in the placebo group received skimmed milk without microorganisms added. The microbiota and short chain fatty acids (SCFA) were monitored in faeces at different time points during treatment and in caecum content at the end of the assay. Quantitative PCR (qPCR) showed that faecal and caecal Bifidobacterium levels were higher in bifidobacteria-fed rats than in the placebo rats at the end of the intervention, whereas total anaerobic plate counts did not show significant differences. Quantification of B. animalis and B. longum by qPCR showed that, independent of the microorganism administered, treatment with bifidobacteria resulted in higher levels of B. animalis in the caecum. PCR-DGGE analysis of microbial populations revealed a higher diversity of bands in caecum content of rats fed B. animalis IPLA R1 than in the placebo group and rats fed B. longum IPLA E44. Remarkably, although no variations in the proportion of acetate, propionate and butyrate were found, at the end of the assay the total SCFA concentration in the faeces of rats fed bifidobacteria was significantly higher and those in caecum content significantly lower, than that of the placebo group. This suggests a displacement of the SCFA production to parts of the colon beyond the caecum in rats receiving bifidobacteria. Therefore, the oral administration of B. animalis IPLA R1 and B. longum E44 can be considered safe, these microorganisms having the ability to modulate the intestinal microbiota of rats by influencing SCFA and the bifidobacterial population levels.

Evaluation of 0.1% Ammonium Hydroxide to Replace Sodium Tripolyphosphate in Fresh Meat Injection Brines

Paired USDA Select beef strip loins (n = 10), aged 2 d, were injected with either an alkaline-based (3.6% sodium chloride, 1% Herbalox seasoning, adjusted to pH 10 with ammonium hydroxide [approximately 0.1%, FFC grade]) or a phosphate-based (3.6% sodium chloride, 1% Herbalox seasoning, 4.5% sodium tripolyphosphate) brine. Steaks were evaluated for 19 d. Overall, phosphate-injected steaks performed better than alkaline-injected steaks with respect to cook yield, water holding capacity, lipid oxidation, color stability, tenderness, and juiciness. Phosphate-injected steaks also had less purge than alkaline-injected steaks, as confirmed by composition analysis. Phosphate-injected steaks were higher in moisture and ash content, and were nearly 2% lower in protein content. Alkaline-injected steaks had significantly lower aerobic (approximately 1 log lower) and anaerobic (approximately 2 log lower) plate counts. Final meat pH probably contributed to the differences observed between treatments. The final pH of phosphate-injected steak was 5.99 while that of alkaline-injected steak was 5.73. Further research should be conducted to determine the concentration of ammonium hydroxide needed in the alkaline-based brine to increase the final meat pH to similar levels found in the phosphate-injected steaks.

EFFECT OF FLAXSEED FLOUR AND PACKAGING ON SHELF LIFE OF REFRIGERATED PASTA

ABSTRACT The effects of flaxseed (Linum usitatissimum) flour (FF) and packaging conditions on microbial counts, lipid stability and cooking quality were determined for fresh pasta stored 7 weeks at 4C. Fresh pastas made from semolina or semolina blended with 15% (w/w) FF (FF-pasta) were packaged in metallized bags under three conditions: ambient air, nitrogen and vacuum. Packaging conditions did not affect aerobic or anaerobic plate counts. Mold and yeast counts were lower for pasta packaged under vacuum than under ambient air or nitrogen. Compared with traditional fresh pasta, FF-pasta had lower microbial counts during storage. Free fatty acid content in FF-pasta increased from 1.9 to 2.4% during storage. Lipid oxidation was lowest with vacuum-packaged pasta. Packaging conditions had little or no effect on cooking quality. Compared with traditional pasta, FF-pasta had lower cooked firmness and cooking loss. Cooked firmness was found to decrease only during the first week of storage; no further decrease occurred during the subsequent weeks. PRACTICAL APPLICATIONS This research would have practical applications to the fresh, refrigerated pasta industry. Although limited in scope, the results indicate that flaxseed flour (FF) has some bacteriostatic and fungistatic activity that may be useful in extending shelf life of fresh, refrigerated pasta/noodle products, and that further research to improve and maintain the cooking quality of FF-pasta during storage is needed.

Incidence of spore-forming bacteria in unsweetened evaporated milk brands in Nigeria

A total of forty-five samples of three most commonly consumed unsweetened evaporated milk brands purchased from retail outlets in South-western Nigeria were examined for occurrence of spore-forming bacteria. All the samples had high numbers of spore-forming bacteria of the genera Bacillus spp and Clostridium spp. with mean total aerobic viable counts of 2.15x105cfuml-1 for br and A, 0.95x105cfuml-1 for brand B and 0.69x105cfuml-1 for brand C. Total anaerobic plate counts ranged from 0.13x105 for brand C, to 0.54x105 for brand B and 1.67x105 for brand A. The organisms isolated from the three brands were identified as Bacillus cereus, Bacillus licheniformis, Bacillus coagulans, Bacillus stearothermophilus, Bacillus subtilis and Clostridium perfringens, with B. subtilis having the highest frequency of occurrence (93.33%). Samples were subjected to four different pasteurization treatments: 550C for 30 min, 800C for 15 min, 900C for 10 min and 1200C for 30 sec, to determine a more efficient process. No growth was observed on culture plates of samples pasteurized at 1200C for 30 sec, except on aerobic plates of brand A. However the milk samples treated under this regime curdled. Samples pasteurized at 800C for 15 min recorded the least counts next to samples treated at 1200C for 30 sec, without causing the samples to curdle. Keywords: Evaporated milk, pasteurization, sporeforming bacteria, viable counts. Nigerian Food Journal Vol. 25 (1) 2007: pp. 137-144

A comparative study of high pressure sterilisation and conventional thermal sterilisation: Quality effects in green beans

Experiments were conducted to compare the colour, texture and microbiological quality of green beans that had been either high pressure sterilised (HPS) using commercially achievable pressures (a pre-heat to 86 °C followed by two treatments of 2 min at 700 MPa) or were conventionally thermally sterilised (Fo 1 to 3 min with a retort temperature of 115 °C). Samples were assessed immediately after processing and after 7 months of ambient storage. HPS treated samples were generally darker in appearance (L⁎ values shifted downwards) compared with heat treated (F0 3 min) samples. The a⁎ values for HPS samples were significantly (P 0.05). HPS treated samples were typically twice as firm as F0 3 min treated samples (P < 0.05). There was some softening over storage but this differential in firmness was maintained after 7 months. Total aerobic and anaerobic plate counts and spore counts after storage were below the limits of detection in all samples apart from one canned sample where leaker spoilage had occurred. Industrial relevance Thermal sterilisation technologies are used to produce ambient stable products but frequently these products suffer deleterious quality changes such as colour and texture modification as a result of processing. There is industrial interest in any technologies with the potential to produce ambient stable products with improved retention of ‘fresh’ characteristics. High pressure sterilisation is a promising method for the production of ambient stable products with improved quality.

Use of Carbon Monoxide Combined with Carbon Dioxide for Modified Atmosphere Packaging of Pre- and Postrigor Fresh Pork Sausage To Improve Shelf Life

Fresh pre- and postrigor pork sausage patties were manufactured in the Iowa State University Meat Laboratory and packaged either in modified atmosphere (MAP) with 0.4% carbon monoxide (CO) and 99.6% carbon dioxide (CO2) or on foam trays overwrapped with oxygen-permeable film (OW). Packages were stored at 2 to 4°C under fluorescent lights for up to 31 days. Aerobic, anaerobic, and psychrotrophic plate counts, raw and cooked color, purge, and lipid oxidation were measured during storage. Results indicated that both pork sausage products in MAP had lower aerobic and psychrotrophic counts and less lipid oxidation throughout storage (P < 0.05). Raw color of both products in MAP was redder than the OW patties (P < 0.05), but the prerigor pork sausage in MAP benefited more from the CO atmosphere in terms of raw color than the postrigor pork sausage in MAP. Cooked color of the prerigor pork sausage in MAP was significantly redder than cooked color of the postrigor pork sausage. Both pork sausage products in MAP were also lighter (L* value) than the OW patties for raw and cooked color. Therefore, the combination of CO and CO2 in MAP was beneficial in extending the shelf life of preand postrigor fresh pork sausage by reducing aerobic and psychrotrophic microbial growth and improving oxidative stability and color, compared to conventional OW packaging. However, increased purge, increased anaerobic growth, and changes in cooking behavior were also observed for the products in MAP during storage (P < 0.05).

Contaminación microbiológica y actividad antimicrobiana del azúcar de caña cristalizado sobre algunos agentes de interés médico en Costa Rica

Microbiological contamination and antimicrobial activity of cristalised cane sugar on some medically important microorganisms in Costa Rica. Unrefined cristalised cane sugar, obtained after the filtration and evaporation of sugar cane juice, is a nutritional product of traditional consumption in Costa Rica and other Neotropical countries. It has been used in the topic treatment of infected wounds, with satisfactory results even with some antibiotic-ressistant bacteria. We studied the microbiological quality of 50 commercial samples. The analyses included total aerobic and anaerobic bacteria plate count; aerobic and anaerobic spore count; mold and yeast count; total and fecal coliforms; and presence of Clostridium botulinum. The antimicrobial effect was tested for Staphylococcus aureus (ATCC 25923), S. epidermidis (UCR 2902), Pseudomonas aeruginosa (ATCC 9027), Escherichia coli (ATCC 25922), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (ATCC 19116) and Aspergillus niger (Asni 06). Most of the samples (76%) presented counts lower than 100 CFU/g especially for sporulated forms (90% lower than 20 CFU/g), the mold and yeast count was higher (38% higher than 10(2) CFU/g), demonstrating the importance of these microorganisms in the spoilage of the product; 76% of the samples presented fecal contamination; C. botulinum was not isolated with the methodology employed. No inhibitory effect was observed for A. niger, but all samples han an inhibitory effect over the other species, especially for P. aeruginosa and S. aureus.

Shelf-life and Microbiological Profiler of Chicken Wing Products Following Sous vide Treatment

Chicken wings were vacuum-packaged and cooked (sous vide) at 75 and 90 C until the internal o temperature reached 73.8 C was reached. The cooked samples were stored at 2 and 7 C, separately. The o o TBA values, aerobic plate count, aerobic and anaerobic plate counts and Warner-Bratzler (WB) shear force of the samples were evaluated weekly for 7 wk. The sous vide treatment chicken wings had lower TBA values, aerobic and anaerobic plate counts throughout the 7 wk of storage when compared with the control. The sous vide treatment did not affect the WB shear force of chicken wings. At 2 C, the sous vide cooked o chicken wings had a shelf life of at least 7 wk. Results demonstrate that sous vide treatment was an effective method to prevent lipid oxidation during storage and enhance shelf life of chicken wing products.

Inhibition of Nonproteolytic, Psychrotrophic Clostridia and Anaerobic Sporeformers by Sodium Diacetate and Sodium Lactate in Cook-in-Bag Turkey Breast ,

A nonproteolytic, psychrotrophic Clostridium isolate, designated strain OMFRI1, was recovered from cook-in-bag turkey breasts (CIBTB) that displayed an intense pink discoloration and an off-odor following extended refrigerated storage. The viability of strain OMFRI1 in CIBTB containing sodium diacetate (at 0, 0.25, and 0.5%) and/or sodium lactate (at 0, 1.25, and 2.5%) was subsequently evaluated. Raw CIBTB batter was inoculated with 9 to 30 spores of strain OMFRI1 per g, vacuum packaged, cooked to an instantaneous internal temperature of 71.1°C, chilled, and incubated at 4°C for up to 22 weeks. In the absence of food-grade antimicrobial agents, spoilage (i.e., an off-odor) occurred within 6 weeks, and anaerobic plate counts reached 6.6 log10 CFU/g. The CIBTB containing sodium diacetate (0.25%) and that containing sodium lactate (1.25%) required 12 weeks for spoilage to occur and for anaerobic plate counts to reach 7.0 and 6.0 log10 CFU/g, respectively. When sodium diacetate (0.25%) and sodium lactate (1.25%) were used in combination, no off-odor was detected and anaerobic plate counts did not exceed 2.3 log10 CFU/g over 22 weeks of storage at 4°C. In related experiments, sodium diacetate (at 0, 0.25, and 0.5%), sodium lactate (at 0, 1.25, and 2.5%), and combinations of both ingredients were evaluated in uninoculated CIBTB incubated at 25°C for up to 22 days. In the absence of antimicrobial agents and in CIBTB containing sodium diacetate (0.5%), spoilage occurred within 8 days and anaerobic plate counts reached 6.8 and 6.6 log10 CFU/g, respectively. Samples of CIBTB containing sodium lactate (2.5%) showed signs of spoilage within 22 days, and anaerobic plate counts for these samples ranged from ≤1.0 to 6.3 log10 CFU/g. In CIBTB containing both sodium lactate (2.5%) and sodium diacetate (0.25%), spoilage was not evident and anaerobic plate counts were ≤1.0 log10 CFU/g within 22 days. These data validate the efficacy of sodium lactate and sodium diacetate in extending the shelf life of CIBTB.

Screening and selection of Lactobacillus strains for use as adjunct cultures in production of semi-hard cheese.

Thirty-three Lactobacillus strains were tested as adjuncts in a cheese model system. Eighteen strains originated from cheese (nine Lactobacillus spp. and nine Lb. paracasei/casei) and 15 from human intestinal mucosa (11 Lb. rhamnosus; three Lb. paracasei; one Lb. plantarum). Model cheeses weighing 120 g were made of cheese grains from full-scale production of washed curd semi-hard cheese (Herrgård). The model system was reproducible and similar to full-scale production with respect to moisture, salt content, pH and microbial flora. The model cheeses were sampled for aerobic and anaerobic plate count and viable counts of Lactobacillus and Lactococcus. The presence of adjuncts in the model cheeses was confirmed by typing isolates with Randomly Amplified Polymorphic DNA (RAPD). The sensory properties of model cheeses were described. In a first trial 23 of the 33 adjuncts were re-isolated from the corresponding model cheeses after 9 or 13 weeks. Adjuncts of Lb. paracasei were re-isolated more frequently than adjuncts of Lb. rhamnosus. Nine strains were selected, on the basis of their ability to grow and be a dominating part of the microflora of model cheese with interesting sensory properties. These strains were further studied together with two commercial cultures. The sensory influences on model cheeses of six of the adjuncts were confirmed, and flavour scores were in the range of 2.9-7.1 for model cheeses with different adjuncts while the control had a flavour score of 5.6 (0-10 scale). Survival and growth of seven out of the nine strains correlated with the results of the first trial. Growth and influence on flavour of four adjunct cultures were confirmed in experimental cheese manufactured in a 400-1 open vat.

A semiconducting metal-oxide array for monitoring fish freshness

An array of semiconducting metal-oxide (SMO) chemiresistive sensors can quantitatively measure the freshness of Atlantic salmon ( Salmo salar), haddock ( Melanogrammus aeglefinus), and Atlantic cod ( Gadus morhua). A variety of SMO films were tested, including films containing oxides of copper and tin, and commercially available tin-based SMO films. Analytical testing of the fish samples was performed in conjunction with SMO sensor testing of the volatile gases emitted from the degrading fish. Testing included the use of a sensory evaluation panel and tests incorporating amine colorimetric methods, pH analyses, and bacterial aerobic and anaerobic plate counts. Sensory analysis, trimethylamine (TMA) content, pH, and aerobic and anaerobic plate counts provided results that correlated well with each other and with SMO sensor results. A radial basis function (RBF) neural network was designed and used to classify the day of fish degradation (1–15) from the SMO sensor array response.

Effect of dietary fish oil on fatty acid composition, lipid oxidation and sensory property of chicken frankfurters during storage

Broilers fed with three levels of fish oil (0, 2 and 4%) for 6 weeks were used in the manufacture of chicken frankfurters. The meat samples were vacuum-packed and stored at 0°C for 0, 10, 20 and 30 days. Cooking yield, proximate and fatty acid composition, lipid oxidation, microbial and sensory properties of the meat products were measured. Cooking yield, moisture, fat, protein, ash and cholesterol contents of frankfurters were not affected ( P>0.05) by levels of dietary fish oil. Frankfurters processed from chickens fed diets enriched with 2 and 4% of supplemental fish oil had a higher ( P<0.05) level of n-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), but had a lower level of n-6 fatty acids ( P<0.05) than the controls (0% fish oil). TBA values and pH values of meat samples were not affected ( P>0.05) by levels of supplemental fish oil in the diets, however, pH values of the vacuum-packaged chicken frankfurters decreased ( P<0.05) as the storage time increased. No differences ( P>0.05) in total anaerobic plate counts were observed among the fish oil treatments during storage. Supplementation of 2 and 4% fish oil in the diets did not increase ( P>0.05) the intensity of fishy flavor in chicken frankfurters.

Evaluation of Botulinal Toxin Production in Packaged Fresh-Cut Cantaloupe and Honeydew Melons

The ability of Clostridium botulinum to produce toxin on cubed, packaged melons was investigated relative to microbial spoilage at various incubation temperatures and in different packaging systems. Freshly cut cubes (approximately 2.5 cm3) of cantaloupe and honeydew melons were surface inoculated with a 10 strain mixture of proteolytic and nonproteolytic spores of C. botulinum (10 to 15 cubes per package; approximately 100 total spores per package). To initially evaluate toxin production and spoilage in a passively modified atmosphere, melon cubes were loosely packaged in air in polyethylene pouches, sealed, and incubated at 7 or 15°C for up to 21 days. At various sampling intervals, samples were tested for headspace oxygen and carbon dioxide levels, pH, presence of botulinal toxin, aerobic and anaerobic plate counts, and counts of yeasts and molds. During incubation, headspace oxygen levels decreased, headspace carbon dioxide levels increased, aerobic and anaerobic plate counts increased, and the pH remained constant or decreased slightly. Botulinal toxin was not detected in any cantaloupe samples or in honeydew samples incubated at 7°C. Botulinal toxin was detected in some honeydew samples at 15°C after 9 days of incubation, but the toxic honeydews were severely spoiled and considered organoleptically unacceptable. A similar second experiment was performed in which half of the melon cubes were treated with UV light to inactivate vegetative organisms before packaging, and these were incubated at 7, 15, or 27°C. In this second experiment, toxin production occurred in the UV-treated samples at 15°C with gross spoilage and at 27°C with only marginal spoilage. These data indicate that inhibition of spoilage organisms with UV light could result in botulinal toxin formation in packaged melons before overt spoilage.

Comparison of aerobic and anaerobic methods for the microbiological monitoring of chilled packaged meat during storage

Aerobic and anaerobic plate counts were compared for routine monitoring of the microflora, dominated by lactic acid bacteria, developing on vacuum- and carbon dioxide-packaged raw meat during chilled storage. No statistical differences were observed between aerobic and anaerobic enumerations, made on plate count and blood agar plates, of the microflora developing on beef striploins packaged under vacuum or carbon dioxide during 14 weeks' storage at 0 degree C. With both techniques the spoilage microflora development differed between the two packaging regimes. The results indicate that there is no necessity for aerobic plate counts to be replaced by anaerobic plate counts in the routine microbiological examination of the spoilage microflora developing on chilled meats packaged under anoxic modified atmospheres.

Microdistribution of sulfate‐reducing bacteria in sediments of a hypertrophic lake and their response to the addition of organic matter

AbstractTo clarify the ecological significance of the association of sulfate‐reducing bacteria (SRB) with sediment particle size, SRB utilizing lactate (l‐SRB), propionate (p‐SRB) and acetate (a‐SRB) were examined with different sizes of sediment particles in a hypertrophic freshwater lake using the anaerobic plate count method. The numbers of l‐SRB and a‐SRB were 104–105 colony forming units (CFU) per ml in the 0–3 cm layer and 102–103 CFU ml−1 in the 10–13 cm layer while the numbers of p‐SRB were one or two orders lower than those of l‐SRB and a‐SRB. A sediment suspension was fractionated into four fractions (&lt;1, 1–10, 10–94 and &gt;94 μm). The highest proportions of l‐SRB and a‐SRB were found in the 10–94 μm fraction: 66–97% for l‐SRB and 53–98% for a‐SRB. The highest proportion of p‐SRB was found in the &gt;94 μm fraction (70–74%). These results indicate that most SRB were associated with sediment particles. One isolate from an acetate‐utilizing enrichment culture was similar to Desulfotomaculum acetoxidans, a spore‐forming sulfate‐reducing bacterium. When lactate and sulfate were added to sediment samples, l‐SRB and a‐SRB in the &lt;10 μm‐fraction grew more rapidly than those in whole sediment for the first 2 days. This result suggests that nutrients uptake by free‐living and small particle‐associated (&lt;10 μm) SRB is higher than that by SRB associated with larger particles.

EFFECT OF PROCESSING VARIABLES ON MICROBIAL QUALITY AND SHELF‐LIFE OF BLUE CRAB (CALLINECTES SAPIDUS) MEAT

ABSTRACTThe effects of cooking time, cooking method, season, and storage condition on the microbiological quality, sensory characteristics, and shelf‐life of crabmeat were determined under commercial processing conditions. Microbial flora content of the meat was inversely proportional (p 0.05) to the cooking time in both total aerobic and anaerobic plate counts after 6 and 9 days at 2.2C during summer. Boiled cooked crabmeat showed higher microbial count (1–2 log cycle) and shorter shelf‐lives than 10 and 12 min retort cooked meat. During summer, the shelf‐life of the meat as determined by a sensory evaluation, was: 15.5 days at 0.0C; 12.5 days at 2.2C; and 8.5 days at 5.6C.