Quality maintenance of minimally processed Chinese cabbage with low temperature and citric acid dip

Chinese cabbage (Brassica campestris L pekinensis group) was minimally processed using best preparation techniques and stored at 0 and at 5°C with and without dips in either citric acid, calcium chloride or ascorbic acid, all at 10 g litre⁻¹. The visual quality, degree of chilling injury, pH and taste were evaluated. The most deleterious effects on quality were produced by black speck (gomasho) and browning. Citric acid inhibited the development of black speck and extended storage life from 10 days of the control to 14 days at 5°C. At 0°C the storage life was not extended by any dip, but citric acid improved quality by reducing black speck. Minimally processed Chinese cabbage treated with citric acid showed only a slight reduction of pH from 6·3 of the control to 6·1 (P⩽0·05) and taste was not significantly affected (P>0·05). Microbial spoilage was not apparent during storage at 0°C for 35 days and 5°C for 21 days under any treatment. © 1997 SCI.     

Processing, Microbial and Sensory Characteristics of Cooler and Freezer Stored Hot-Boned Beef

Weiners were prepared from preblended hot-boned (prerigor) beef raw materials stored up to 21 days at 2°C and up to 28 days at -10°C. The addition of salt was necessary for maintenance of desirable sausage-making characteristics of hot-boned beef stored at 2°C for 7 days. The addition of salt for the maintenance of desirable functional properties does not appear to be necessary, if the prerigor materials are stored at freezer temperatures (-10°C). Flavor problems may develop in products from preblended raw materials stored at -10°C beyond 14 days postmortem.     

Sodium Lactate Effects on Shelf-Life, Sensory, and Physical Characteristics of Fresh Pork Sausage

The objective of our study was to evaluate the effects of various levels (0%, 1%, 2%, 3%) of sodium lactate on selected physical, sensory, and microbiological characteristics of fresh pork sausage stored at 4°C for 28 days. Samples containing 0% and 1% SL reached 10⁸ CFU/g after 10 days refrigerated storage. Addition of 2% or 3% SL to fresh pork sausage delayed microbial deterioration, pH decline, and development of sour- and off-flavors 7 days at 4°C. Samples containing 2% SL did not reach total plate counts of 10⁸ CFU/g until 24 days storage. SL appeared to protect red color, and to “enhance” pork-and salty-flavors in sausage. TBA, L-, a-, and b-values were unaffected by SL level.     

Centralized Packaging of Beef Loin Steaks with Different Oxygen-Barrier Films: Physical and Sensory Characteristics

Vacuum packaged beef strip loins (n = 72) were stored (2 ° 1°C) for either 0, 12 or 24 days before fabrication; steaks were packaged and displayed (2°C or 7°C) up to 6 days in oxygen-permeable film or up to 30 days in vacuum packages (medium or high oxygen-barrier film). Steaks displayed at 2°C, rather than 7°C, tended to have higher overall appearance scores especially when steaks were from 12 or 24 day subprimals. Overall palatability of vacuum packaged steaks was unacceptable after 10–15 days of display. Vacuum packaged steaks can be displayed for 10 days if: (1) steaks are from relatively fresh subprimals, (2) steaks are vacuum packaged with high oxygen-barrier film, and (3) steaks are displayed at 2°C. Although visual scores for vacuum packaged steaks were acceptable for 20–30 days, off-odors and off-flavors were limiting factors in determining shelf-life.     

The development,fecundity and longevity of Dermestes ater Degeer (Coleoptera: Dermestidae)

Larvae of Dermestes ater Deg. were bred on a diet of fishmeal, wheat germ, yeast and cholesterol at 15, 20, 25, 30 or 35°C with a constant 65% r.h. and at 25°C with 40, 50, 60, 70 or 80% r.h. Whenever possible emerging adults were paired and kept under the same conditions to determine longevity and fecundity. Eggs laid at 25°C and placed at 15°C failed to hatch. The egg period at 25, 30 and 35°C averaged 4–5 days and at 37.5°C it was about 3 days. Egg hatch was low approximating to about 40% except at 37.5°C where it was only just above 10%. No viable adults emerged at temperatures below 25°C. Development was completed in about 40 days at 30 and 35°C and at all humidities tested at 25°C (taking about 50 days at 80% r.h. and 65–70 days at 40% r.h.). Mortality was low at 25 and 30°C (less than 30%) but high at 35°C (90%). Fifty per cent of adults were dead after about 100 days at 25°C, after about 30 days at 30°C; the two adults at 35°C survived just over 20 days. A pre-oviposition period averaging about 33 days at 25°C and 4 days at 30°C was followed by an oviposition period of about 2 months. The number of eggs laid was very variable (0–135) as was the percentage hatch (0–69%). The results are compared with those obtained by other authors.     

The tentative recognition of psychrotrophic Gram-negative bacteria in 48 h by their surface growth at 10°C

Employing 153 species and strains of Gram-negative bacteria representing 20 genera, 79 produced visible growth on brain heart infusion agar (BHIA) at 7°C in 10 days and thus conformed to the definition of psychrotrophs. All but 5 of the 79 (93.7%) grew on BHIA plates at 10°C in 2 days. At 12°C, 13 psychrotrophs did not grow in 24 h while in 2 days 28 nonpsychrotrophs grew. Surface plating for colony enumeration generally required 3 days, and pour plating 4 days for countable colonies. It is suggested that those bacteria that grow rapidly at 7°C but not at 40°C be designated stenopsychrotrophs while those that can grow at 40°C or above and generally more slowly at 7°C be designated eurypsychrotrophs. The use of 10°C for 2 days may be used to make a rapid and tentative designation of Gram-negative psychrotrophs when turbid broth cultures are streaked on BHIA plates.     

Temperature and NaCl Affect Growth and Survival of Escherichia coli 0157:H7 in Poultry-Based and Laboratory Media

In tryptic soy broth (TSB) and a poultry extract broth (PB) with 0 to 10% (w/v) NaCl incubated at 37°C, growth of E. coli 0157:H7 was inhibited at 28% NaCl whereas at 10°C, growth was inhibited at 24% NaCl in TSB and at 26% NaCl in PB. The bacterium did not grow at 4°C. Increased NaCl-sensitivity observed at 10°C was a bacteriostatic effect that was ineffective with increasing incubation temperature. At 10°C, E. coli 0157:H7 was more salt-tolerant in PB than in TSB, although PB growth rates were lower. Findings suggest that PB may be a more suitable medium for testing E. coli 0157:H7 in poultry products. Cells of E. coli 0157:H7 that were exposed to refrigeration (4°C) and/or NaCl for 24 days did not grow on MacConkey agar with 1% sorbitol.     

Survival and Growth of Listeria monocytogenes on Lettuce as Influenced by Shredding, Chlorine Treatment, Modified Atmosphere Packaging and Temperature

The effects of shredding, chlorine treatment and modified atmosphere packaging on survival and growth of Listeria monocytogenes, mesophilic aerobes, psychrotrophs and yeasts and molds on lettuce stored at 5°C and 10°C were determined. With the exception of shredded lettuce which had not been chlorine treated, no significant changes in populations of L. monocytogenes were detected during the first 8 days of incubation at 5°C; significant increases occurred between 8 and 15 days. Significant increases occurred within 3 days when lettuce was stored at 10°C; after 10 days, populations reached 10⁸-10⁹ CFU/g. Chlorine treatment, modified atmosphere (3% O₂, 97% N₂) and shredding did not influence growth of L. monocytogenes. It was concluded that L. monocytogenes is capable of growing on lettuce subjected to commonly used packaging and distribution procedures used in the food industry.     

Thermal Destruction of Listeria monocytogenes in a Meat Slurry and in Ground Beef

Thermal destruction of Listeria monocytogenes cells was determined in phosphate buffer, a meat slurry (20% ground beef/80% water) and in ground beef. D-values at 60°C, 65°C and 70°C in phosphate buffer, and in the meat slurry were 0.63, 0.29 and 0.15, and 2.54, 0.75 and 0.23 min, respectively. Heating of ground beef (80% lean) in a 75°C water bath to 50°C, 60°C or 65°C required 6.2, 8.4 and 10.6 min, respectively, and resulted in 0.2-0.9, 1.6-3.4 and 4.4-6.1 log reductions in L. monocytogenes cells, from the initial inoculation level of 8.08 log CFU/g. Viable cells were also detected after cold (21 days) or selective enrichment (24 hr) in eight out of nine samples of ground beef inoculated with 7.84-8.08 log CFU/g and cooked to 70°C.     

Banana Shrimp, Penaeus merguiensis, Quality Changes During Iced and Frozen Storage

Shelf life of banana shrimps, Penaeus merguiensis, were studied along with formaldehyde changes in their muscles during iced and frozen storage. K-value, timethylamine oxide nitrogen (TMAO-N), trimethylamine nitrogen (TMA-N), volatile basic nitrogen (VB-N) and sensory quality were determined. Shelf life was 4 days in ice, 6 days at -3°C and 9 wk at ??10°C. They remained acceptable after 6 mo at ?20°C. Formaldehyde was a good indicator in shrimp shelf life assessment.     

RELATIONSHIP OF TREATMENT OF FRESH STRAWBERRIES TO THE QUALITY OF FROZEN FRUIT AND PRESERVES1

‘Cardinal’ strawberries were hand picked and stored 1 day at 21°C to enhance softening. Three separate preprocessing experiments were conducted to determine the effects of style of pack, 0.18% calcium (Ca) dips, 0.3% low methoxyl pectin (LMP), 40° Brix sucrose dips, heat of 70°C, vacuum at 172 mm Hg and drying to 70% moisture on quality and firmness of frozen-then-thawed and preserved strawberries. The greatest firming effect on frozen-then-thawed fruit was due to Ca and pectin. Sliced fruit was firmed more than whole fruit by the Ca and pectin treatments. Drained weight loss was reduced by pectin, Ca, sucrose, heat and vacuum in frozen-then-thawed fruit. Drained weight losses were the same or greater among treatments in preserves. The firmness and wholeness of preserves was increased by Ca, vacuum, 40° Brix sucrose, heat and to a lesser extent drying, but individual effects were not additive. The drying treatment reduced color quality.     

Shelf Life and Quality of Freshly Squeezed, Unpasteurized, Polyethylene-Bottled Citrus Juice

Florida's chief orange and grapefruit cultivars were used to produce five freshly squeezed, unpasteurized, polyethylene-bottled juices using commercial conditions. Juices were stored at different temperatures. Shelf life depended primarily on storage temperature: ?1.7°C, 20–23 days; 1.1°C, 16–22 days; 4.4°C, 10–16 days; and 7.8°C, 5–8 days. Staleness was the primary off-flavor limiting shelf life at the three lower temperatures while spoilage with diacetyl was primarily responsible at 7.8°C. At the three lower temperatures, microbial counts generally decreased markedly during storage, while at 7.8°C, an increase was generally noted. Ascorbic acid retention after 2 wk of storage at the three lowest storage temperatures was about 91–93% for two orange juices and 86–88% for the grapefruit juice.     

Microbiology of a Ham-Type Product Made from Soy-Extended Cured Beef and Inoculated with Clostridium sporogenes PA3679

The microbiological stability of a new ham-type product made from soy-extended cured beef was examined under wholesale (2–4°C) and retail (5°C) refrigerated storage conditions, and during abuse-temperature holding for 24 and 48 hr at 24-25°C after inoculation with Closrridium sporogenes PA3679. No microbiological effects (P >0.05) could be attributed to the level of soy protein isolate in the injection brine (0, 5, 7.5 or 9%) on the basis of mesophilic, psychrotrophic, anaerobic and lactic bacterial counts. Samples held at 2-4°C did not exceed 10⁴ CFU/g after 4 wk for any bacterial type examined. Product shelf-life was > 3 wk at 5°C and 2 wk at 8–10°C. Inoculated PA3679 did not grow in the product during 24 or 48 hr simulated mishandling (24-2°C).     

Effect of Heat Treatment and Selected Antimicrobials on the Shelf-life and Safety of Cooked, Vacuum-Packaged, Refrigerated Pork Chops

The shelf-life of refrigerated (2–4°C) pork chops inoculated with Clostridium sporogenes PA3679 and Staphylococcus aureus Z88 was examined in products sliced from loins cooked to 66°C (150°F), dipped in 5% polyphosphate blend, 2.5% potassium sorbate or 2% acetic acid solutions, vacuum-packaged and stored at 2–4°C. The effect of a second in-the-bag cooking step to 66°C (150°F) after vacuum packaging was also studied. Pork chops not reheated after packaging showed incipient spoilage after 15 days at 2–4°C, depending on surface treatment. The second cooking increased the shelf-life of refrigerated product to more than 60 days and reduced counts of inoculated cultures to undetectable levels. However, on exposure of the chops to simulated mishandling (24–25°C), clostridial growth was detected in all samples except those dipped in polyphosphate or acetic acid solutions.     

Comparison of Shelf Life and Quality of Mullet Stored at Zero and Subzero Temperature

The shelf life and quality of mullet (Mugil spp.) caught off the Southeast Atlantic coast were evaluated during storage at subzero temperature (-2°C) either unpackaged or vacuum packed in iolon film. Subzero temperature was maintained by storing fish in either 2% NaCl- or 7% propylene glycol-ice. Shelf life of fish stored in -2°C ice was 10 days, compared to 7 days for the fish stored in 0°C ice. Extension of shelf life was attributed to delayed microbial growth and slow biochemical changes. Structural changes due to ice crystals at subzero temperature storage appeared to be minor compared to those which occurred during freezing at -20°C as revealed by microscopic examination. The minor structural changes along with insignificant biochemical changes resulted in products having acceptable eating quality for 10 days.     

Comparison of High Hydrostatic Pressure,High-PressureCarbon Dioxide and High-Temperature Short-Time Processing on Quality of Mulberry Juice

Changes of microbial, physicochemical and sensory properties of mulberry juice processed by high hydrostatic pressure (HHP) (500 MPa/5 min), high-pressure carbon dioxide (HPCD) (15 MPa/55 °C/10 min), and high-temperature short time (HTST) (110 °C/8.6 s) during 28 days of storage at 4 °C and 25 °C were investigated. Total aerobic bacteria (TAB) and yeast and mold (Y&M) were not detected in HHP-treated and HTST-treated mulberry juices for 28 days at 4 °C and 25 °C, but were detected more than 2 log₁₀ CFU/ml in HPCD-treated mulberry juice for 21 days at 4 °C and 14 days at 25 °C, respectively. Total anthocyanins were retained after HHP and reduced by 4 % after HTST while increased by 11 % after HPCD. Total phenols were retained by HHP, while increased by 4 % after HTST and 16 % after HPCD. The antioxidant capacity was retained by HTST and HHP and increased by HPCD. Both total phenols and antioxidant capacity were decreased during the initial 14 days but then increased up to 28 days regardless of storage temperature. The value of polymeric color and browning index decreased and a* increased in HHP-treated and HPCD-treated mulberry juices, while HTST-treated mulberry juice had a reverse result. The viscosity of mulberry juice increased in HHP-treated and HPCD-treated juices, while decreased in HTST-treated juice. During storage, total anthocyanins, total phenols, and antioxidant capacity and color in all mulberry juices decreased more largely at 25 °C than that at 4 °C. Better quality was observed in HHP- and HPCD-treated mulberry juices, and a longer shelf life was observed in HHP-treated samples compared to HPCD-treated ones.     

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.     

Population dynamics of Salmonella spp. and Shigella spp. in ready-to-eat Mediterranean vegetable salads

This study evaluated the behavior of Salmonella and Shigella (5–6 log CFU/g) in tomato–cucumber (TC) salad without additives (control), TC with 1.0% lemon juice and 0.5% salt, TC with 10% wt/wt tahini, coleslaw, and toum sauce at 4, 10, or 24°C for 5 days. At 4°C, both pathogens survived well in all salads, with a 0.2–1.6 log CFU/g reduction after 5 days (except for toum sauce with >3.5 log CFU/g reduction after 4 days). At 10°C, Salmonella in the different TC salads remained constant, whereas Shigella numbers significantly increased by 1.0–1.7 log CFU/g after 5 days. Yet, both pathogens significantly decreased by 1.2–1.4 log CFU/g in coleslaw after 5 days and by >3.5 log CFU/g in toum sauce after 3 days. At 24°C, Salmonella significantly increased in TC salad without additives by 1.4 log CFU/g after 5 days and were below the detection level in the other types of salad after 5 days. However, Shigella numbers significantly increased by 1.0 log CFU/g in TC with tahini, but they significantly declined by 1.9–2.9 log CFU/g in TC salads after 5 days, and the pathogen was not detected in coleslaw and toum sauce after 4 days.     

Mangosteen Oil-In-Water Emulsions: Rheology, Creaming, and Microstructural Characteristics during Storage

The rheological properties and physical stability of mangosteen (Garcinia mangostana L.) extract in oil-in-water (MIO/W) emulsions were investigated. Rheological study on the emulsions exhibited Newtonian flow behavior. The 20?wt.% emulsion showed higher apparent viscosity than 10?wt.% MIO/W sample. The effects of salt (NaCl) concentration (0, 50, 100, and 200?mM) and heat treatment (70?°C) on the stability of the emulsions were also examined. Heat (70?°C)- and NaCl (100 and 200?mM)-treated emulsions showed creaming and droplet aggregation on storage for a period of 60?days. The 10?wt.% MIO/W emulsions stored at 4?°C showed a homogeneous distribution of oil droplets with good stability to creaming and viscosity independent of shear stress (i.e., a Newtonian liquid).     

The effect of temperature upon the longevity,fecundity and circannual development of Anthrenus sarnicus Mroczkowski (Coleoptera: Dermestidae)

Eggs of Anthrenus sarnicus Mroczkowski, laid at 25°C and placed at temperatures ranging from 15 to 32.5°C when 0–1 day old, hatched over the range 20–30°C, incubation taking about 11 days at 30°C and about 25 days at 20°C. Reduction in relative humidity to as low as 25% at 25°C did not affect the duration of the egg period but egg fertility was slightly reduced. When eggs were laid in the conditions at which they were to hatch the range was lower (15–25°C) than when they were laid at 25°C.When bred on a mixture of fishmeal, yeast and cholesterol in the dark at 65% r.h. development took approx 1 yr at both 20 and 25°C. At 15°C, some larvae also took just over 1 yr to develop and others took approx 2 yr. There was a little evidence to suggest the possibility of some larvae taking approx 3 yr.Adults laid eggs at temperatures from 15 to 30°C, but some pairings at all temperatures were infertile. The mean pre-oviposition period at 15°C was 30 days reducing to about 14 days at higher temperatures. The mean oviposition period fell from 21 days at 15°C to 5 days at 30°C and during this period 30–40 eggs were laid at 15–25°C but fewer than 20 at 30°C. There was a post-oviposition period of about 10 days. Total longevity of males averaged 53 days at 15°C and 18 at 30°C. Adult life for laying females averaged 66 days at 15° reducing to 30 days at 30°C; non-laying females lived a little longer.