Shelf life of fresh sausages stored under modified atmospheres

The aim of this study was to investigate differences in modified atmosphere packaging (MAP) for the improvement of the shelf life of fresh meat products. Three different conditions for preserving fresh sausages were tested: MAP1 (20% CO2, 70% O2, and 10% N2), MAP2 (40% CO2 and 60% O2), and MAP3 (40% CO2, 30% O2, and 30% N2). Samples from the MAP2 group had fewer spoilage bacteria, stable red color (no change of a* value), and good physical attributes (high water-holding capacity, little loss from cooking, and low shear force needed for cutting) compared with samples from other treatment groups. Thus, high concentrations of CO2 (40%) and O2 (60%) resulted in a longer shelf life for fresh sausages.     

Microflora changes in peanuts (groundnuts) stored under modified atmospheres

These pilot scale experiments were designed to determine if long-term storage of U.S. No. 1 peanuts (groundnuts) is practical in modified atmospheres with minimal deterioration through molding, aflatoxin contamination, and insect infestation, without use of refrigeration or pesticides. Two lots of U.S. No. 1 peanuts (248 kg) were stored at 26±2°C for 1 year, in 1978–79 and in 1980–81, in atmospheres either of ca. 60% CO₂, simulated burner gas, ca. 99% N₂ or in refrigerated and non-refrigerated ambient air. In two larger tests, the CO₂ atmosphere was used with 1996 and 6451 kg of peanuts in different non-refrigerated bins. When the CO₂ was not recirculated in the 1996 kg bin the humidity and moisture increased and moisture migration occurred. The peanuts at the top molded, predominantly with yeast species and Penicillium roqueforti Thom. Species of the genus Eurotium (Aspergillus glaucus group), the A. flavus group and various other Penicillium spp. were also isolated. These mycofloral changes were different from those seen in ambient air or refrigerated storage when moisture increases occurred. No molding and only minor change in the microflora was observed in the bin with 6451 kg of peanuts with CO₂ recirculation and humidity control. Only minor changes in the microflora occurred in the other treatments. No aflatoxins accumulated in any treatment.     

Nonproteolytic Clostridium botulinum toxigenesis in cooked turkey stored under modified atmospheres

The ability of nonproteolytic Clostridium botulinum type B spores to grow and produce toxin in cooked, uncured turkey packaged under modified atmospheres was investigated at refrigeration and mild to moderate abuse temperatures. Cook-in-bag turkey breast was carved into small chunks, surface-inoculated with a mixture of nonproteolytic C. botulinum type B spores, packaged in O2-impermeable bags under two modified atmospheres (100% N2 and 30% CO2:70% N2), and stored at 4, 10, and 15 degrees C. Samples were analyzed for botulinal toxin and indigenous microorganisms, as well as subjected to sensory evaluation, on days 0, 7, 14, 28, 42, and 60. Given sufficient incubation time, nonproteolytic C. botulinum type B grew and produced toxin in all temperature and modified atmosphere treatment combinations. At moderate temperature abuse (15 degrees C), toxin was detected by day 7, independent of packaging atmosphere. At mild temperature abuse (10 degrees C), toxin was detected by day 14, also independent of packaging atmosphere. At refrigeration temperature (4 degrees C), toxin was detected by day 14 in product packaged under 100% N2 and by day 28 in product packaged under 30% CO2:70% N2. Reduced storage temperature significantly delayed toxin production and extended the period of sensory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum. At all three storage temperatures, toxin detection preceded or coincided with development of sensory characteristics of spoilage, demonstrating the potential for consumption of toxic product when spoilage-signaling sensory cues are absent.     

Production of zearalenone in vitro and in corn grains stored under modified atmospheres

The production of zearalenone by an isolate of Fusarium equiseti was studied in chemically defined medium and in corn grains stored under modified atmospheres. An increase in the concentrations of sucrose or xylose in Czapek's medium resulted in increased toxin production, while no toxin was produced when lactose was present in the medium. Methionine (10(-2) and 10(-3) M) and cystine (10(-3) M) added to Czapek's medium inhibited zearalenone production. When amino acids or nitrogen salts were added as the sole nitrogen source, only alanine, tryptophan and NH4Cl totally inhibited zearalenone production. Zearalenone production was inhibited almost completely in high-moisture corn grains (27%) kept under atmospheres enriched with high CO2 levels (60%, 40% or 20%) with either 20% or 5% O2. However, a lower amount of CO2 was needed to inhibit fungal development and toxin formation when a reduced O2 level was applied.     

Sensory characteristics of Galician chorizo sausage packed under vacuum and under modified atmospheres

One of the most widely used methods for conservation of Galician chorizo sausage is vacuum packing. Recently, some manufacturers have begun to implement packaging under modified atmospheres. We compared the sensory characteristics, over about 7 months of storage, of chorizos packed under vacuum or under a modified atmosphere (100% CO(2), 100% N(2), or 50:50 CO(2)/N(2)). Most of the 29 variables considered differed significantly between samples packed under vacuum and samples packed under the modified atmospheres. Nineteen of the variables varied significantly over the storage period. Parallel studies of gas permeabilities confirmed that the aluminum-polyester-polyethylene laminate used for packing under modified atmospheres showed very low permeability to both CO(2) and N(2).     

The shelf-life of beef steaks treated with dl-lactic acid and antioxidants and stored under modified atmospheres

Beef steaks were treated with 1.5% lactic acid alone or supplemented with antioxidants (0.1% rosemary extract and 0.05% ascorbic acid). The steaks were stored under modified atmospheres containing either 60% O₂/40% CO₂ or 70% O₂/20% CO₂/10% N₂. Both the 40% CO₂ atmosphere and the lactic acid treatment significantly (P<0.05) inhibited growth of lactic acid bacteria, Brochothrix thermosphacta and Pseudomonas spp. Neither CO₂ in the pack atmosphere, treatment with lactic acid, nor a combination of both, affected formation of thiobarbituric acid reactive substances, myoglobin oxidation, or CIE a^* values. However, treatment with antioxidants significantly (P<0.05) delayed oxidation of both myoglobin and lipids, and so extended the storage-life.     

Probability of growth and toxin production by nonproteolytic Clostridium botulinum in rockfish stored under modified atmospheres

The potential risk of C. botulinum growth in fresh fish stored under modified atmospheres remains unclear. Few studies have identified qualitatively certain conditions leading to toxigenesis. This paper is the First of a series attempting to quantify the effect of a variety of parameters on the probability (P) of toxigenesis by one spore in fish. The factorial design experiments included red snapper tissue homogenate inoculated with a pool of nonproteolytic spores (5 type E, 4 type B and 4 type F strains) at 7 levels (10⁴−10⁻² per 3 g sample) and incubated at 4, 8, 12, 17 and 30°C under 3 modified atmospheres (vacuum, 100% CO₂ and 70% CO₂+30% air) for up to 21 days. At the 10⁰ spore/sample level the earliest time to detect toxin production at 4, 8, 12, 17 and 30°C under all modified atmospheres was > 21, 12, 9, 6 and 2 days, respectively. At the 10¹ spores/sample level the earliest times for the same temperatures were > 21, 9, 6, 3–6 and 1–2 days, respectively. The probability of toxigenesis was affected significantly (P < 0.005) by temperature, storage time, atmosphere×temperature, and temperature×time but not by atmosphere (P > 0.1). Using linear and logistic regression models, equations were derived which can predict the P of 1 spore initiating growth and toxigenesis by a particular day and at a particular temperature of storage. Studies involving other fish substrates are in progress.     

Physical characteristics of lamb primals packaged under vacuum or modified atmospheres

Lamb primals (shoulders) were packaged under vacuum, 80% O(2)/20% CO(2), 50% CO(2)/50% N(2) or 100% CO(2) and stored at 5 or 0 °C. Pack contents were examined at 7 day intervals to determine the composition of the pack atmosphere, drip loss, colour (muscle and fat) and pH (surface and internal). The composition of the gas atmospheres changed very little during storage. The only significant differences between developed head space compositions above primals stored at the two different temperatures (5 and 0 °C) were noted in packs stored for 28 days under 80% O(2)/20% CO(2). Low levels of drip loss (<0.5%) were noted in all packs stored under the modified gas atmospheres. In contrast, significantly higher levels of drip loss (0.5-1.1%) were noted in vacuum packaged lamb stored at 5 and 0 °C. Acceptable muscle colour was observed 2 hr after opening of all packs. The only significant differences between atmospheres for lean muscle colour were noted after 28 days storage. Fat colour did not generally change during storage in any of the atmospheres, apart from a slight bleaching effect at 7 days. There were no significant differences between the surface or internal pH values noted after storage under any of the atmosphere/temperature combinations. In general, higher pH values were observed at the surface of the meat than in the interior. This pattern was noted before and after storage.     

Quality of chilled ready-to-bake pizza stored in air and under modified atmospheres: Microbiological and sensory attributes

Modified atmosphere packaging (MAP) studies on microbiological and sensory analysis were conducted to extend the shelf life of ready-to-bake pizza stored at 7±1°C. The gas combinations used were: atm1: air (control), atm2: CO₂ (100%), atm3: N₂ (100%), atm4: 50% CO₂/50% N₂. Total plate count (TPC), yeasts/molds (Y/M), coliforms, lactic acid bacteria (LAB), psychrotrophs, and anaerobic spore formers were estimated at time intervals of 0, 5, 10, 15, and 20 days. TPC and LAB of pizza samples (atm1) reached 7.10 and 8.14 log CFU/g after 10 days of storage, respectively. Coliforms, psychrotrophs, and Y/M were significantly higher (p<0.05) for pizza samples stored in atm1 than other storage conditions of MAP. Finally, counts of anaerobic spore formers were low (<3 log CFU/g) irrespective of the packaging conditions throughout the entire storage period. It was concluded that among the 4 atmospheres examined, atm2 (100% CO₂) was the best, followed by atm4>atm3>atm1 respectively, in descending order. MAP conditions under this study may extend shelf life of pizza to considerable amount of time.     

Probability of growth and toxin production by nonproteolytic Clostridium botulinum in rockfish fillets stored under modified atmospheres

Whether toxin production by Clostridium botulinum precedes or follows spoilage of fish stored under modified atmospheres (MA), remains unclear. In this factorial design study we inoculated a pool of nonproteolytic C. botulinum spores (5 type E, 4 type B, and 4 type F strains) at 6 levels (10⁴ to 10⁻¹) between two rockfish fillets and then incubated the fillets at 4, 8, 12 and 30°C under vacuum, 100% CO₂ and 70% CO₂+30% air for 21 days. The probability of toxigenesis by one spore was significantly affected (P<0.005) by temperature (T) and storage time (S_t), and not (P>0.1) by MA, MA×T or MA×S_t. At the 10° spore/sample level, the earliest time to detect toxin production at 4,8,12 and 30°C under all MAs was >21, 15–21, 6–9 and 2 days, respectively. No toxin production was detected at 4°C. Only type B toxin was present in the toxic samples. At 30°C storage, spoilage of fillets followed toxigenesis. Using linear and logistic regression models, equations were derived that could estimate the lag phase and predict the probability of one spore initiating growth under a particular storage condition.     

Microbiological,physicochemical and sensory characteristics of Cameros cheese packaged under modified atmospheres

This study evaluated the shelf-life quality of Cameros cheeses packaged under modified atmospheres. Five different modified atmosphere conditions were studied (carbon dioxide/nitrogen mixtures and vacuum). Control cheeses were packaged in air. The product stored at 3–4°C was evaluated periodically to investigate its sensory quality, microbiological condition and physicochemical characteristics. Weight loss and pH evolution were similar in vacuum and air packaging. Cheeses packaged in 100% CO₂showed the greatest weight losses and lower pH values. CO₂reduced proteolysis and lipolysis during storage in all conditions studied. Fat acidity and NPN/TN values were slightly higher in vacuum than in CO₂, but lower than in air. Modified atmosphere packaging presented an extended shelf life. Those containing CO₂reduced the growth rate of mesophiles, psychrotrophs, Enterobacteriaceae and coliforms, which was lower when the CO₂concentration increased. The lowest microbial counts were at 100% CO₂while vacuum conditions presented microbial counts only slightly lower than the controls. Salmonella spp.,Staphylococcus aureus and Listeria spp. were not found in any of the samples. Faecal coliforms, moulds and yeasts were not detected under CO₂atmospheres or in vacuum. After 7 days of storage, the sensory characteristics of the control cheeses were unacceptable in all the parameters studied. However, the overall score for cheeses stored in 40% and 50% CO₂did not change substantially, retaining a reasonable acceptability until the end of the storage period. The 100% CO₂atmosphere had a very negative effect on sensory quality. With regard to Cameros cheese, packaging in 50%CO₂/50%N₂and 40%CO₂/60%N₂are the most effective for extending shelf life and retaining good sensory characteristics.     

Effects of transport age and calf and maternal characteristics on health and performance of veal calves

The objective of this study was to investigate effects of calf transport age (14 vs. 28 d) and calf (e.g., sex and breed) and dam characteristics (e.g., parity and ease of birth) on health and performance of veal calves until slaughter age. Calves (n = 683) originated from 13 dairy farms in the Netherlands and were transported at either 14 or 28 d of age from the dairy farm to 8 Dutch veal farms. A health assessment of calves was performed on a weekly basis at the dairy farm and in wk 2, 10, 18, and 24 at the veal farm. Body weight of calves was measured on a weekly basis at the dairy farm and upon arrival at the veal farm. At the veal farm, use of antibiotics and other medicines during the rearing period (both at herd and individual level) was recorded and carcass weights were obtained from the slaughterhouse. Body weight upon arrival (Δ = 11.8 kg) and carcass weight at slaughter (Δ = 14.8 kg) were greater, and mortality risk (Δ = ?3.1%) and prevalence of animals treated with medicines other than antibiotics (e.g., antiinflammatories, multivitamins, and anticoccidial drugs; Δ = ?5.4%) were lower in calves transported at 28 d compared with calves transported at 14 d. Crossbreds other than Belgian Blue × Holstein Friesian received a higher number of individual treatments with antibiotics and other medicines (Δ = 14.8% and Δ = 15.1%, respectively) at the veal farm compared with Belgian Blue × Holstein Friesian calves. These findings suggest that calves transported at 28 d were more robust compared with calves transported at 14 d.     

Microbiological quality of foods packaged under modified atmospheres

The microbiological quality of various sandwiches and meats packaged under modified atmosphere was evaluated. Samples were analyzed both on the day of manufacture and at the end of shelf life. On day 0, around 60% of products examined contained ≤10⁵ total aerobic counts g⁻¹, while at the end of the shelf life approximately 63·3% of samples contained ≥10⁷ cfu g⁻¹.Listeria spp. were found in eight of the 58 lots examined, withL. monocytogenes being present in five of the eight samples. One lot was found to containAeromonas hydrophila, while another one containedStaphylococcus aureus. Clostridium botulinum andSalmonella spp. were not found in any of the samples.     

Effect of stunning systems on meat quality of Manchego suckling lamb packed under modified atmospheres

The effects of the type of stunning (TS) [electrically vs. gas] and packing in modified atmospheres (MA) [MA-A: 30% CO₂/70% O₂; MA-B: 30% CO₂/69.3% N₂/0.7% CO; MA-C: 40% CO₂/60% N₂] on meat quality (pH), drip losses (DL), water holding capacity (WHC), shear force (SF) and instrumental colour (L^∗, and C^∗chroma) of suckling lamb of the Spanish Manchego breed at 7, 14 and 21 d post-packing was studied. Acceptance of meat samples (on the basis of colour and odour) was determined. In general neither the TS nor the MA affected the pH values. Meat from the gas stunned lambs had the lowest DL (P < 0.001 at 14 d post-packing), but lower WHC (more water expelled; P < 0.01 at 14 and 21 d post-packing), was more tender (P < 0.01) and had higher L^∗ (P < 0.001 at 14 d post-packing) and C^∗ values (P < 0.001) than the electrically stunned group. Similar values of WHC and SF were observed for all MA types but the use of CO in the packs (MA-B) caused less DL, gave the highest C^∗ values, acceptability and colour stability with time of storage.     

The use of modified atmospheres to control Sitophilus zeamais and Sitophilus oryzae on stored rice in Portugal

This study reports the efficacy of using CO₂ against Sitophilus zeamais and Sitophilus oryzae as an alternative treatment to fumigation for rice stored in a rice mill in Portugal. The trials were conducted in a silo containing 40 tonnes of polished rice and in four hermetic big bags of 1 tonne capacity; two with paddy and two with polished rice. The composition of the atmosphere ranged from 90 to 95% CO₂ and 0.7–2.1% O₂. Three trials were carried out at different temperatures and treatment times; stored rice in the silo at 29.6 ± 0.1 °C for 26 days (first trial), at 34.1 ± 0.2 °C for 10 days (second trial), and in big bags at 22 °C for 26 days (third trial).To evaluate the efficacy of each treatment, metal cages with 16 g of infested rice where placed at bottom, middle, top and surface of the polished rice in the silo. Four replications of each type of infested rice containing one-week-old S. zeamais adults, or eggs of S. zeamais or S. oryzae, were incubated in the laboratory, at the same temperature as in the silo, to serve as a control.In all modified atmosphere treatments adults of S. zeamais, and eggs of both S. oryzae and S. zeamais, showed mortality close to 100% and no F1 emergence was recorded in any treatment sample. This was the first time that a Portuguese rice mill used modified atmospheres.     

Shelf-life of a chilled precooked chicken product stored in air and under modified atmospheres: microbiological, chemical, sensory attributes

This study evaluated the effect of modified atmosphere packaging on shelf-life extension of a precooked chicken meat product stored at 4 degrees C using microbiological, physico-chemical and sensory analyses. The following gas mixtures were used: M1: 30%/70% (CO2/N2), M2: 60%/40% (CO2/N2) and M3: 90%/10% (CO2/N2). Identical chicken samples were aerobically packaged and used as control samples. Sampling was carried out at predetermined time intervals namely: 0, 4, 8, 12, 16 and 20 days. Total viable counts (TVC), Lactic acid bacteria (LAB), Brochothrix thermosphacta, pseudomonads, yeasts and molds, and Enterobacteriaceae were monitored. TVC of precooked chicken product reached 7 log cfu/g, after days 12 and 16 of storage (air and M1 samples), respectively. The M2 and M3 gas mixture packaged samples did not reach this value throughout the 20 days storage period under refrigeration. LAB and to a lesser degree B. thermosphacta, constituted part of the natural microflora of precooked chicken samples stored in air and under MAP reaching 7.0-8.1 log cfu/g at the end of storage period. Of the remaining bacterial species monitored, both pseudomonads and yeasts/molds were significantly higher (P<0.05) for chicken samples stored in air than under MAP (M1, M2, M3) throughout the entire storage period under refrigeration. Finally, counts of Enterobacteriaceae were low (<2 log cfu/g) in all chicken samples irrespective of the packaging conditions throughout the entire storage period. Of the chemical indices determined, thiobarbituric (TBA) values in all cases remained low, equal or lower than 3.0 mg malonaldehyde (MA)/kg during the entire storage period. Results of the present work show that the limit of sensory acceptability was only reached for the aerobically stored and M1 gas mixture chicken samples somewhat before days 16 and 20 of storage, respectively. This limit coincided with high TVC and LAB populations (>6.8 log cfu/g), increased lipid oxidation (aerobic storage only) and apparent growth of yeasts/moulds on the surface of chicken samples. The use of MAP as shown in the present study, resulted in an extension of shelf-life of precooked chicken by ca. 4 days (M1 gas mixture), and by more than 6 days (M2 and M3 gas mixtures), respectively. Precooked chicken meat was better preserved under M2 and M3 mixtures maintaining desirable odor/taste attributes even on final day of storage tested.     

Calf and dam characteristics and calf transport age affect immunoglobulin titers and hematological parameters of veal calves

This study aimed to investigate effects of transport age of calves (14 vs. 28 d), and of calf and dam characteristics, on immunoglobulin titers and hematological variables of veal calves. Calves (n = 683) were transported to a veal farm at 14 or 28 d of age. Natural antibodies N-IgG, N-IgM, and N-IgA against phosphorylcholine conjugated to bovine serum albumin (PC-BSA) were measured in serum of the dams 1 wk before calving and in first colostrum. These antibodies were also measured in serum of calves 1 wk after birth, 1 d before transport, and in wk 2 and 10 posttransport at the veal farm. Hematological variables were assessed in calves 1 d before transport and in wk 2 posttransport. One day before transport, titers of N-IgG, N-IgM, N-IgA, and neutrophil counts were higher, and lymphocyte counts were lower in 14-d-old calves compared with 28-d-old calves. In wk 2 at the veal farm, calves transported at 14 d of age had higher N-IgG titers and neutrophil counts, but lower N-IgM and N-IgA titers, and lymphocyte counts than calves transported at 28 d. In wk 1 and 1 d before transport, N-Ig in calves were positively related to N-Ig in colostrum. In wk 2 and 10 at the veal farm, N-IgG in calves was positively related to N-IgG in colostrum. The N-IgG titers in calves at the dairy farm were negatively related to the likelihood of being individually treated with antibiotics or other medicines at the veal farm. Our results suggest that calves transported to the veal farm at 28 d of age showed a more advanced development of their adaptive immunity than calves transported at 14 d of age. Quality of colostrum might have long-term consequences for N-IgG titers and immunity in veal calves.     

Efficacy of mint and eucalyptus leaves on the physico-chemical characteristics of stored wheat against insect infestation

Wheat treated with mint and eucalyptus leaves powder was stored for six months in four different storage structures viz., jute bags, peru (made from bamboo strips), metal bins and polythene bags. Samples were analysed at monthly intervals for physico-chemical characteristics. After six months of storage, per cent damage increased, whereas weight and density decreased in untreated wheat, but no significant (P < 0.05) changes were observed in treated grains. Proximate principles increased signficantly (P < 0.05) in untreated grains except crude fat which decreased, but no significant changes were observed in their treated counterparts. Mint leaves powder was able to protect wheat stored in different storage structures for 6 months, whereas eucalyptus leaves had their protective effects only for 5 months.