Solubility of Muscle Proteins as a Result of Autolysis and Microbiological Growth

Bovine Longissimus dorsi samples, collected aseptically 3 hr postmortem, were used to determine natural muscle enzyme activity. Samples of this tissue were inoculated with Pseudomonas putrefaciens or Lactobacillus casei and incubated 0, 1, 7, 14, and 21 days at 2°C and 0, 1, and 3 days at 25 and 37°C. Protein solubility, pH and microbial counts were determined after appropriate periods of storage. Only small differences were noted in the solubility of muscle proteins between the muscle treatments after 21 days of storage at 2°C compared to much larger differences noted after only 3 days of storage at higher incubation temperatures (25 and 37°C).     

Effect of Storage Temperature on Rigor-Mortis and ATP Degradation in Plaice Paralichthys olivaceus Muscle

Live specimens of the plaice Paralichthys olivaceus were spiked at the brain, stored at various temperatures ranging from 0° to 20°C and examined for changes in rigor tension and ATP degradation in the muscle. The ATP degradation rate was clearly slower at 5–15°C than at WC, resulting in retardation of rigor- mortis onset at the former temperatures. Lactic acid accumulation in the muscle correlated well with the decrease of ATP. The muscle showed an ATP concentration of 3 μmol/g and “rigor index” (full rigor = 100%) at 30% when lactic acid increased up to 30 μmol/g at most storage temperatures. The muscle showed full rigor when ATP completely disappeared and lactic acid attained the maximum plateau (40–50 μmol/g).     

Electrical Stimulation of Mutton

Electrically stimulated ovine muscles, restrained from shortening during rapid chilling at 0-1 or 15-16°C, had lower Warner-Bratzler (WB) shear force values after 1 and 2 days aging at 0-1°C than un-stimulated controls, but were not significantly different at ≥4 days aging. Direct measurement of muscle fiber length showed that contraction values obtained for muscles assigned to go into rigor at 0, 15, 30 or 40°C were significantly less for stimulated muscles than for control muscles at 0°C, but of same magnitude or at rigor temperatures ≥15°C. WB shear force values indicated that, at temperatures ≥15°C, increase in tenderness due to stimulation became small after 7 days aging at 0-1°C, whereas at 0°C aging further increased improvement due to stimulation. Results were thus consistent with electrical stimulation reducing myofibrillar shortening at rigor temperature <15°C but at temperature ≥15°C stimulation had the same effect as a few days aging.     

Changes in the lipids of turkey muscle during storage at chilling and freezing temperatures

Diced turkey leg and breast muscle stored for 22 days at 0° and —3°, and for up to one year at —10°, —20° and —60° was examined at intervals for lipid composition. Free fatty acids increased at all temperatures except —60°, with a Q₁₀ of 3-4 between 0° and —20° 90% of the fatty acids liberated were unsaturated, matching in composition the unsaturated acids of the muscle glycerophospholipids. Demonstration of linear relationships between increase in free fatty acids and decrease in phosphatidylethanolamine or increase in lysophosphatidylcholine confirmed phospholipase A₂ as the enzyme mainly responsible. The composition of the fatty acids liberated during storage at 0° and —3° showed that both lipase and phospholipase were active. A slight decrease in extractability, resulting in an apparent loss of phospholipid-P, was observed after storage at low temperatures.     

Effects of Storage Temperature, Humidity and Duration on Ostrich Fern (Matteuccia Struthiopteris (L.) Todaro) Quality

Storage of Ostrich ferns (fiddleheads) at temperatures above or below 0°C decreased storage life and marketable quality. Percent weight loss, ascorbic acid, bacterial load, yeast and mold loads generally increased and relative water content decreased with increased storage temperature above 0°C and duration. Fiddlehead absolute moisture and ascorbic acid decreased with extended storage at lower storage humidities. Marketable yields decreased with higher storage temperatures, lower storage humidity and extended storage durations. Optimum storage conditions of 0°C and 100% RH provided marketable yields of 95% and 76% after 16 and 32 days, respectively, while fiddlehead storage in water at 0°C for 15 days provided marketable yields of 97%.     

Myofibrillar protein degradation of carp (Labeo rohita (Hamilton)) muscle after post‐mortem unfrozen and frozen storage

The degradation of myofibrillar proteins of rohu carp (Labeo rohita (Hamilton)) muscle was analysed after post‐mortem storage. Muscle fillets were kept either unfrozen at 2 °C for up to 15 days or frozen at ?8 °C or ?20 °C for up to 6 months. A co‐ordinated histochemical, biochemical and electrophoretic study showed a differential response of the carp muscle, revealing clear degenerative/degradative changes specific to the post‐mortem storage temperatures. The myofibrillar protein fractions, namely myosin light chains and α‐actinin, showed degradative changes during the above storage conditions, whereas other protein fractions in the high‐molecular‐weight range fragmented to give lower‐molecular‐weight proteins. The importance of the post‐mortem storage temperature for controlling the degradation of the myofibrillar proteins was emphasised. This is the first report on this popular fish species, known for its culinary importance, showing that specific protein fractions of the myofibrils degrade during post‐mortem storage. © 2001 Society of Chemical Industry     

Optimizing storage temperature of liquid bovine semen diluted in INRA96

Temperature regulation of liquid bovine semen can be difficult in field situations. Two experiments were carried out to assess the effect of storage temperature on in vitro sperm characteristics and 60-d nonreturn rate (NRR) following artificial insemination (AI) of liquid bovine semen. In experiment 1, the effect of storage of liquid bovine semen in INRA96 diluent (IMV Technologies, L'Aigle, France) at 1 of 5 storage temperatures (5, 15, or 28°C, and fluctuating between 5 and 15°C or 5 and 28°C) on total and progressive motility and kinematic parameters was assessed objectively via computer-assisted sperm analyzer on d 0, 1, 2, 3, and 4 after collection. Fluctuating temperatures were designed to mimic day- to nighttime variation. In experiment 2, we assessed the field fertility of liquid semen stored at a constant 5 or 15°C or in an unregulated manner and compared with that of frozen-thawed semen (total of n = 106,738 inseminations). In experiment 1, we detected a linear decrease in motility with increased duration of storage. Semen stored at a constant 15°C or fluctuating between 5 and 15°C had greater total motility than semen held at 5 or 28°C or fluctuating between 5 and 28°C; however, semen stored at 15°C and fluctuating between 5 and 15°C did not differ from each other. Semen held at a constant 5 or 15°C or fluctuating between 5 and 15°C, although not differing from each other, had higher progressive motility scores than that held at 28°C or fluctuating between 5 and 28°C. Semen stored at a constant 28°C exhibited poor motility and velocity values but had high progressive motion values compared with that all other storage temperatures; however, the other storage temperatures did not differ from each other in relation to motility kinematics. In experiment 2, semen stored at a constant 5°C resulted in a lower 60-d NRR (62.5%) than storage at constant 15°C or unregulated temperature or frozen-thawed semen (73.6, 74.6, and 74.4%, respectively. In conclusion, sperm stored in IRNA96 are quite tolerant in terms of storage temperature, retaining acceptable motility between 5 and 15°C. Storing semen at a constant 15°C resulted in greater in vitro sperm motility and higher NRR rates than storage at 5°C and did not differ in NRR from frozen-thawed semen or semen stored at an unregulated temperature; however, lower storage temperatures were shown to be more detrimental to sperm in vivo than unregulated storage conditions.     

Storage Stability of Intermediate Moisture Mullet Roe

A storage stability study was performed on intermediate moisture roe (a_w= 0.84, salt content = 4%). Samples were stored at various temperatures for up to 1 month. Microbial analyses indicated that bacteria could grow from 5–25°C. Fungi grew at 15° and 25°C while their growth was inhibited at 5°C; however, a lag phase was detected at 15°C. TBA values increased linearly during storage. Microbial analyses, chemical determination of rancidity and sensory evaluations showed that the product was still acceptable after 30 days storage at 5°, 15° or 25°C.     

Effect of Postmortem Storage on Degradation of the Myofibrillar Protein Titin in Bovine Longissimus Muscle

Purified bovine longissimus muscle myofibrils were prepared from muscle at death and from muscle samples stored at 2°, 25°, or 37°C for 1, 3, and 7 days postmortem. Tbe myofibrils were analyzed by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. Titin migrated as a closely spaced doublet of very high molecular weight (M_r～ 1 × 10⁶) in myofibrils from at-death muscle samples. With increased storage time and temperature, the top band of the titin doublet gradually disappeared. the lower doublet band (putative breakdown product of upper band) remained after 7 days storage at 2° or 25°C, but disappeared by 3 days of postmortem storage at 37°C. Thus, titin is degraded in postmortem muscle, and the rate of degradation is enhanced by increases in storage time and temperature.     

Vibrio parahaemolyticus in granulated ark shell clam (Tegillarca granosas): accumulation from water and survival during cold storage and thermal process

This study investigated accumulation of Vibrio parahaemolyticus in granulated ark shell clam (Tegillarca granosas) exposed to contaminated water and survival of V. parahaemolyticus in the clams during cold storage and heating processes. Vibrio parahaemolyticus could be accumulated in clams to a level similar to that of contaminated water within 12 h of exposure of clams to contaminated water at temperatures between 9 and 33 °C. Keeping clams stored at 5 and 0 °C for 10 days resulted in 1.98 and 2.32 log MPN g^?1 reductions of V. parahaemolyticus, respectively, in the clams. Frozen storage at ?18 °C for 15 days or at ?30 °C for 30 days were capable of reducing V. parahaemolyticus from 4.05 log MPN g^?1 to non‐detectable levels (< 3 MPN g^?1). A heating process in hot water at 80 °C or higher for 1 min also reduced V. parahaemolyticus in the clams to non‐detectable levels.     

Effects of temperature on post-mortem metabolism in beef muscle

Changes in pH and in the levels of some phosphate fractions with time were examined in beef muscle stored at 1°, 15° and 37° soon after slaughter. At 15° the fall in pH of the muscle and decreases in concentration of creatine phosphate and of other acid-labile phosphate occurred more slowly than at 37° and there was also a slower increase in the concentration of inorganic phosphate. Not all of these changes occurred more slowly at 1° than at 15°, however. The alkali-labile phosphate concentration remained virtually constant at 37° but increased at each of the other two temperatures, the increase at 1° being greater than that at 15°. These changes in alkali-labile phosphate concentration were attributable to the accumulation of hexose-6-phosphate. An effect of temperature on the metabolism of an organic phosphate fraction stable to both acid and alkali was noted.     

Ensuring the best storage temperature of Egyptian pastrami based on microbiological,physico-chemical and sensory evaluation

Egyptian pastrami is among the most important and widely consumed meat products in Egypt and due to the great defects in its storage as a ready-to-eat products by retailers, distributers or even consumers, the aim of the current research is to assess the effect of storage temperatures on physico-chemical, microbiological, and sensory properties of Egyptian pastrami using autoclaved non-meat ingredients to ensure the best storage temperature of such important food. Four storage temperatures were applied including room temperature during summer (25 °C), room temperature during winter (15 °C), in fridge at 4 °C and in freezer at −18 °C for a period of 60 days using whole unsliced produced pastrami arms. The findings showed that there was no significant effect (P > 0.05) of storage temperatures on the physico-chemical and sensory properties of tested Egyptian pastrami as the four types were highly accepted based on the physico-chemical and sensory evaluation. Meanwhile, there was noticeable effect of storage temperatures on the microbiological properties of the four manufactured types of pastrami, as the samples stored at −18 °C or at 4 °C for 60 days had the lowest microbial loads and was the best from microbiological aspect.     

Low-temperature transitions in cod and tuna determined by differential scanning calorimetry

Differential scanning calorimetry measurements have revealed different thermal transitions in cod and tuna samples. Transition temperatures detected at −11°C, −15°C and −21°C were highly dependent on the annealing temperature. In tuna muscle an additional transition was observed at −72°C. This transition appeared differently than the thermal events observed at higher temperatures, as it spanned a broad temperature interval of 25°C. The transition was comparable to low-temperature glass transitions reported in protein-rich systems. No transition at this low temperature was detected in cod samples. The transitions observed at higher temperatures (−11°C to −21°C) may possibly stem from a glassy matrix containing muscle proteins. However, the presence of a glass transition at −11°C was in disagreement with the low storage stability at −18°C during practical time scales. It was proposed that freezing of cod could be associated with more than one glass transition, with a glass transition at a temperature lower than −11°C being too small to be detectable with instrument, yet governing important deterioration processes. In order to optimize frozen storage conditions, the relationship between deterioration processes important for preservation of quality and glass transition temperatures still needs to be established.     

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.     

The influence of storage temperature and storage time on color stability,retail properties and case-life of retail-ready beef

Steaks from three different muscles were either vacuum or carbon dioxide packed and stored for up to 24 weeks at three different storage temperatures (−1.5, 2, or 5 °C). Following storage, they were displayed for up to 30 h. CIE color coordinates, the oxidative states of myoglobin and pH were measured and muscle color, surface discoloration, retail appearance, and odor were evaluated prior to storage and during display (0, 1, 2, 4, 6, 24 and 30 h), and/or immediately prior to and following display. Prior to display, pH was negatively related to duration of storage, and samples stored at −1.5 °C had the highest and samples stored at 5 °C, had the lowest pH. Perception of muscle color was influenced by duration of storage and display, but lower storage temperatures appeared to produce a stabilizing effect. Both lightness of muscle color and deoxymyoglobin content were apparently not influenced by storage temperature or duration of storage or display. Both oxymyoglobin (OMB) and redness, as defined by CIE a* values, were lost progressively during storage and display, but this loss was progressively lower as storage temperature decreased. Yellowness of muscle color, as defined by CIE b* values, generally decreased as storage was prolonged, and this decrease was observed more quickly at higher storage temperatures. Surprisingly, b* values were not related to duration of display. Both surface discoloration and metmyoglobin (MMB) content increased progressively during storage and display. Samples stored at 5 °C displayed the most surface discoloration, while samples stored at −1.5 °C contained the least MMB and displayed the least surface discoloration. Retail appearance deteriorated progressively during storage in all samples stored at 2 and 5 °C and in samples stored at −1.5 °C, which were displayed for at least 24 h. Retail appearance also deteriorated progressively during display in samples stored at −1.5 and 2 °C for three weeks or longer and in samples stored at 5 °C for 0 to 15 and 24 weeks. In unstored samples, samples to be stored at −1.5 °C generally received the lowest retail appearance scores, but after prolonged storage and display, samples stored at −1.5 °C received higher retail appearance scores than samples stored at 5 °C, particularly when samples were stored for 12 weeks or longer and displayed for 1 h or more. Odor deteriorated progressively during storage when measured both prior to display and after 30 h of display. In samples stored for three weeks or longer, samples stored at −1.5 °C generally received the lowest odor scores and were perceived to have the least prevalent off-odors. Samples stored at −1.5 °C maintained a retail case-life of 30 h, when stored for up to 17 weeks, while samples stored at 2 and 5 °C maintained a retail case-life of 30 h, when stored for only eight and seven weeks, respectively. Consequently, storage life can be more than doubled by storage at subzero temperatures (−1.5 °C).     

Prediction of Quality in Frozen Cod (Gadus morhua) Fillets

Physical and chemical indices were determined on frozen cod (Gadus morhua) fillets stored for ca. 90 days at either - 12°C, - 15°C, - 22°C, - 30°C or under a set of simulated industrial fluctuating temperature conditions (SIFTC). Univariate and multivariate statistics on the quality indices gave a relationship between frozen storage textural deterioration and the chemical parameters as influenced by storage temperature. Results on the SIFTC resembled the - 12°C and - 15°C storage treatments. Chemical indices had lower activation energy values than those for the physical parameters. Ammonia, determined enzymatically, can be used as an index of frozen fish quality. The quadratic equations developed using the dependent variable of Instron raw peak force, independent of time and temperature, can predict the textural quality of frozen cod fillets.     

Changes in the quality of dehydrated broccoli stems during storage

Dehydrated broccoli stems were studied during storage at different temperatures, namely 5, 15, 25 and 40 °C. The parameters studied were rehydration capacity, texture of the rehydrated product and chlorophyll content. A diffusional model was used to study the rehydration process, yielding good agreement with the experimental data when the equilibrium moisture and the effective diffusivity were identified. Samples stored at 5 °C showed little change in any of the parameters studied during the storage time considered (427 days). At 15 and 25 °C the equilibrium moisture and the effective diffusivity varied linearly. At 40 °C, sharp changes were observed up to 115 days, the equilibrium moisture decreasing and the effective diffusivity increasing. From this time on, both values showed moderate changes. With reference to texture, samples stored at 5, 15 and 25 °C showed a similar trend without significant changes during the whole period, the textural values increasing with temperature. At 40 °C the texture suffered a sharp increase up to 145 days, then changes were negligible. Chlorophyll content degradation was increased with temperature. As a result of a calorimetric study a second‐order transition was observed at 34 ± 1 °C. This fact can contribute to the interpretation of the different tendencies observed in all the parameters studied at 40 °C. © 2000 Society of Chemical Industry     

Effect of modified atmosphere packaging on the microbial development and visible shelf life of a mayonnaise-based vegetable salad

The effect of a modified atmosphere of 20% carbon dioxide, 80% nitrogen, on the microbial development and visual shelf life of a mayonnaise-based vegetable salad is reported. The modified atmosphere delayed the spoilage of the salad at all three chosen storage temperatures. The principal organisms causing spoilage of the salads were yeasts, those spoiling the modified atmosphere packs having a fermentative ability. Modified atmosphere packaging of the vegetable salad would allow the manufacturer to increase the shelf life of the product from 40 to 54 days at 4°C storage, 12 to 22 days at 10°C storage, and 5 to 12 days at 15°C storage.     

Increased Aflatoxin Production by Aspergillus parasiticus Under Conditions of Cycling Temperatures

The effects of cycling temperatures (5°C for 12 hr and 25°C for 12 hr) on aflatoxin production by Aspergillus parasiticus NRRL 2999 in yeast extract sucrose (YES) medium were studied. Cycling temperatures, after preincubation at 25°C for various times, resulted in more aflatoxin B₁, G₁, and total aflatoxin production than did constant incubation at either 25°C, which is generally considered to be the optimum for aflatoxin production, or 15°C, which is the same total thermal input as the 5-25°C temperature cycling. With increased preincubation time at 25°C, toxin production increased and the lag phase of growth was shortened or not evident. Cultures that were preincubated at 25°C for 1, 2, and 3 days prior to onset of temperature cycling showed the greatest increase in maximum aflatoxin production over the 25°C and 15°C constant temperatures. Cultures that were not preincubated at 25°C but subjected to constantly fluctuating temperatures produced maximum amounts of aflatoxin equivalent to cultures incubated at a constant 25°C. The maximum aflatoxin production at all temperatures studied occurred during the late log phase of growth and at pH minimums. Aflatoxins were found in higher concentrations in the broth than the mycelia under temperature cycling conditions, at 15°C, and at 25°C during the first 21 days of incubation, whereas greater amounts of toxin were retained in mycelium at 25°C in the later incubation period (28-42 days).     

Color Stability and Microbial Growth Relationships in Beef as Affected by Endogenous α-Tocopherol

Longissimus muscle from Holstein steers supplemented with vitamin E at 500 or 2000 mg/head/day showed less surface metmyoglobin accumulation than controls during 12 days storage at 4°C. Temperature abuse at 25°C for 24 hr increased metmyoglobin formation; vitamin E supplementation diminished the adverse effect of temperature abuse. No differences (P > 0.05) in bacterial load were observed among the 3 vitamin E treatments during storage. Sensory panelists preferred vitamin E-supplemented beef steaks in visual acceptance. Panelist assessment of discoloration correlated highly with a value and hue angle. In general, elevated α-tocopherol concentrations in beef steaks did not affect panelist assessment of meat spoilage.