CHALLENGE STUDIES WITH PROTEOLYTIC CLOSTRIDIUM BOTULINUM IN YEAST AND CHEMICALLY LEAVENED CRUMPETS PACKAGED UNDER MODIFIED ATMOSPHERES

Challenge studies were done with proteolytic Clostridium botulinum (10³ spores/g) in yeast-and chemical-leavened crumpets (50-g) packaged in air with an ethanol vapor (2-G Ethicap®) generator or in 100% CO₂ and stored at ambient temperature (25C) for 30 days. Neurotoxin was detected in all gas- (CO₂) packaged crumpets after 5 days regardless of the method of leavening. While neurotoxin was delayed for 10 days in chemical-leavened Ethicap®-packaged crumpets, it was not detected in any similarly packaged yeast-leavened crumpets throughout storage. This inhibition of growth and neurotoxin production by C. botulinum was attributed to the production of ethanol by Saccharomyces cerevisiae in the yeast leavened crumpets, in conjunction with the ethanol vapor generated by the Ethicap® sachets (2-G), to levels to inhibitory to the growth of C. botulinum (>2.8% v/v). Subsequent challenge studies in sterile crumpets inoculated with either C. botulinum (10³ spores/g) or a co-inoculum of C. botulinum (10³ spores/g) and S. cerevisiae (10⁵ CFU/g) confirmed the significant role (p<0.001) of S. cerevisiae in enhancing the antibotulinal efficacy of ethanol vapor. These studies showed that the method of crumpet leavening could have a profound effect on the growth of and neurotoxin production by C. botulinum in crumpets packaged under modified atmospheres.     

GROWTH/SURVIVAL OF NATURAL FLORA AND LISTERIA MONOCYTOGENES ON REFRIGERATED UNCOOKED PORK AND TURKEY PACKAGED UNDER MODIFIED ATMOSPHERES

Listeria monocytogenes was inoculated onto fresh pork and turkey slices. Inoculated and control samples were packaged under modified atmospheres (100% N₂, and 20%/80% and 40%/60% CO₂O₂) or air in plastic bags of low gas permeability. Samples were stored at 1 and 7C. Samples stored in air showed a similar microbiological pattern to that usually observed in fresh meat stored aerobically. Packaging under modified atmospheres extended the meat shelf-life. Bacterial growth was strongly inhibited at 1C, particularly in samples stored under CO₂/O₂ enriched atmospheres. Temperature and pH were critical factors for L. monocytogenes growth. This pathogen grew only on pork (initial pH 5.3) packaged in air and stored at 7C. No L. monocytogenes growth was observed at 1C in any atmosphere assayed. However, growth on turkey (initial pH 6.0) was marked at 7C in all atmospheres tested, while at 1C, this bacterium grew weakly only on samples stored in air .     

CO/CO2/N2三种气体协同对冷却猪肉保鲜及护色效果的研究

为了延长冷却肉的货架期,采用添加一定浓度CO的方法进行护色处理,CO能与肌红蛋白(Mb)强烈结合形成碳氧肌红蛋白(MbCO).使肉在货架期内呈现樱桃红色.研究在混合气体中添加低浓度的CO气调包装对冷却猪肉的保鲜效果,测定贮存过程中的微生物、理化和感官指标(特别是色泽)的变化,确定适合的冷却猪肉气调包装混合气体比例为1%CO/50?2/49%N2,不但延长了货架期,而且使冷却肉在整个货架期内呈现诱人的亮红色.     

THE SHELF-LIFE EXTENSION OF HADDOCK IN CARBON DIOXIDE-OXYGEN ATMOSPHERES WITH AND WITHOUT POTASSIUM SORBATE

Fresh haddock, whole fish or fillets, treated or not with various potassium sorbate dips, were sealed in gas impermeable bags containing gas atmospheres of 60% CO₂, 20% O₂ and 20% N₂, air or vacuum, stored on ice in insulated AIRBOX containers at 0°C and subsequently assessed using the Torry freshness scale after 11 to 18 days storage. The trends in the data suggested higher freshness scores for gas and gas plus dip compared with the air and vacuum packs. The dip alone was not effective. It was important to maintain the fish at 0° C.     

PROLONGING THE SHELF-LIFE OF FRESH GREEN CHILE PEPPERS THROUGH MODIFIED ATMOSPHERE PACKAGING AND LOW TEMPERATURE STORAGE

The postharvest quality of green chile fruit was compared after storage in 3 types of packages at 2 temperatures (24C and 8C). Package types were corrugated cardboard boxes, pressed cardboard trays overwrapped with VF-71 polyethylene, or low-density polyethylene (LDPE) bags. Fruit packaged in boxes or overwrapped trays had 24.8% and 10.1% weight loss, respectively, after 1 week of storage at 24C. Fruit packaged in polyethylene bags lost 0.3% weight and remained green. After 1 week at 8C, the weight losses were 3.8%, 1.8% and 0% for the boxed, overwrapped and bagged treatments, respectively. Postharvest quality was maintained up to 4 weeks when fruit were packaged in LDPE bags and stored at 8C. In a second study, steady state O₂ and CO₂ levels were determined inside the LDPE packages as fruit weight and temperature were varied. Storage temperatures were 24C, 16C and 8C. At 8C, steady state O₂ levels ranged from 12.0 kPa to 0.9 kPa, and CO₂ levels ranged from 2.0 kPa to 4.6 kPa as fruit weight was increased from 120 to 480 g. At 24C and 16C, fruit packaged in 480 g units had slower ripening rates than fruit packaged in smaller units; however, fruit stored at 8C remained green the longest, regardless of fruit weight.     

THE UTILIZATION OF MODIFIED GAS ATMOSPHERE PACKAGING FOR FRESH MEAT: A REVIEW

Distribution and packaging methods that are used for fresh meats have changed drastically over the past decade from primarily the shipment of carcasses to vacuum packaged primal cuts. Research efforts are now being directed at the replacement of vacuum packaging with modified gas atmospheres which may be more cost efficient and reduce trim losses. This paper reviews some of the more current research which has been conducted in modified gas atmosphere packaging.     

FISH SAUCE PRODUCTS AND MANUFACTURING: A REVIEW

Fish sauce, due to its characteristic flavor and taste, is a popular condiment for cooking and dipping. Biochemically, fish sauce is salt-soluble protein in the form of amino acids and peptides. It is developed microbiologically with halophilic bacteria, which are principally responsible for flavor and aroma. This review article covers the manufacturing methods of fish sauce, factors affecting the quality of fish sauce, nutritional values of fish sauce, microorganisms involved with fermentation, and flavor. In addition, rapid fermentation to reduce time and new parameters to estimate the quality of fish sauce are reviewed. Along with a new approach for estimating the quality of fish sauce, the quantitative analysis of degradation compounds from ATP and other specific protein compounds in fish sauce are discussed.     

SHELF-LIFE AND MICROBIAL GROWTH KINETICS OF FRESH CITRUS JUICES: SHAMOUTI ORANGE

The paper deals with the shelf-life and endogenous microbial growth kinetics of freshly squeezed unpasteurized Shamouti orange juice. Microbial and organoleptic data was evaluated for seven temperatures (range of 2.0 to 14°C). Microbial lag-time was more sensitive to temperature change in the lower range (E _a = 42.4 Kcal/mol). The effect of temperature on growth rate was quite moderate in the lower range but in the order of 12.1 Kcal/mol at the upper end. Organoleptic data kinetics indicated that unpasteurized Shamouti juice can maintain its initial quality for 4 days if kept a 2°C and about 2 days if kept at 7°C. The kinetics data (both microbial and taste) was used successfully for the prediction of microbial growth and for taste deterioration under variable time-temperature conditions (i.e., simulation of cold chain path).     

FISH SAUCE PRODUCTS AND MANUFACTURING: A REVIEW

Fish sauce, due to its characteristic flavor and taste, is a popular condiment for cooking and dipping. Biochemically, fish sauce is salt-soluble protein in the form of amino acids and peptides. It is developed microbiologically with halophilic bacteria, which are principally responsible for flavor and aroma. This review article covers the manufacturing methods of fish sauce, factors affecting the quality of fish sauce, nutritional values of fish sauce, microorganisms involved with fermentation, and flavor. In addition, rapid fermentation to reduce time and new parameters to estimate the quality of fish sauce are reviewed. Along with a new approach for estimating the quality of fish sauce, the quantitative analysis of degradation compounds from ATP and other specific protein compounds in fish sauce are discussed.     

MICROBIOLOGICAL AND SENSORY EVALUATION OF COOKED ROAST BEEF PACKAGED IN A MODIFIED ATMOSPHERE

Sliced cooked roast beef was packaged in a modified atmosphere (MA) consisting of 75% CO2, 15% N2 and 10% 02 and stored at 4.4°C for 42 days to evaluate the MA's effectiveness at controlling the outgrowth of Pseudomonas fragi, Clostridium perfringens, Staphylococcus aureus and Salmonella typhimurium after inoculation. Additionally, a taste panel was conducted to monitor the effects of modified atmosphere packaging (MAP) on sensory parameters of uninoculated samples. P. fragi was able to grow only to a limited extent in the MA, but grew to high numbers in air. The three pathogens were unable to grow in the MA, probably due to the effects of temperature. Numbers in S. typhimurium and C. perfringens declined more rapidly in the MA than in air but S. aureus numbers did not decrease in either atmosphere. High numbers of molds were recovered from the uninoculated samples stored in air but none were recovered from MAP samples. Sensory analysis indicated that most product deterioration occurred within the first 7 days of storage.     

VACUUM PACKAGING OF FRESH BEEF: A REVIEW

Vacuum packaging is a method of distributing beef primal cuts in oxygen impermeable bags under vacuum. Increased technology in the application of vacuum packaging has verified that it provides a means of prolonging the shelf-life and palatability of beef during extended periods of shipment and storage. Additional advantages of vacuumized storage include reduction in weight loss from evaporation and trimming, preservation of color, increased hygienic control and enhanced palatability due to controlled aging. Such benefits have been achieved by intensified research efforts directed towards improving packaging systems. The objective of this review is to discuss these research efforts and identify those factors associated with the quality of vacuum packaged beef.     

FACTORS ASSOCIATED WITH FRESH MEAT COLOR: A REVIEW

The color of fresh meat is important to every aspect of the meat industry. The basic explanations for various colors and intensities of color need to be understood in order to minimize off-colors which ultimately result in product loss. This review discusses the various color forms of myoglobin in muscle and their relationship to species, atmospheric conditions, antemortem factors and storage characteristics.