Thermal inactivation of the frozen thawed traditional meat starter culture, Pediococcus pentosaceus, in a meat model system

The equation, y_(t) = y₍₀₎e^kt, was fitted (R = 0.9281, 0.9220 and 0.9117, respectively) to thermal inactivation data (55, 60 and 65 °C) of the traditional meat starter culture Pediococcus pentosaceus (10⁷ cfu/ml) in a meat model system. The population reduction constant (‘k’) increased (about 2.5- and 3-fold) with an increase in the treatment temperature (from 55 to 60 °C and from 60 to 65 °C, respectively). The Q₁₀ (55–65 °C) for ‘k’ was 7.63. Thermal treatments of 19.1, 9.0 and 3.1 min (55, 60 and 65 °C, respectively) reduced the population of P. pentosaceus by 2.0 logs. The value of ‘k’ and the duration of the thermal treatment played an important role in the extent of the inactivation of the culture. The “zero inactivation” temperature (T₀) for P. pentosaceus was 49.9 °C. About 5 logs of the culture would be destroyed at 63 and 68 °C within about 15.5 and 6.5 min, respectively.     

The effect of post-exsanguination infusion on the composition, exudation, color and post-mortem metabolic changes in lamb

Twenty-four lamb carcasses were assigned to three treatment groups: (1) control (Ctr), (2) infused with 10% (vol/wt) of a tenderizing blend (NCa), and (3) NCa plus 0·015 CaCl₂ (WCa). Results indicated that the infused carcass solution was retained in the following order: shoulder > lion > leg. Infusion had no effect (P > 0·05) on drip and cooking losses in refrigerated samples. Samples frozen and then thawed from infused carcasses had greater thaw drip (P < 0·05) and cooking losses (P < 0·01) than control samples. The amounts of drip and cooking losses were in the order: WCa > NCa > Ctr. Frozen storage preserved the red color but lowered the lightness and yellowness of ovine muscles; the opposite effect was observed following refrigerated storage. Infused samples were lighter and yellower than control in both fresh and frozen samples (P < 0·01). WCa had less red color (P < 0·01) than NCa and Ctr at all times and storage conditions. Infusion lowered (P < 0·05) the temperature of carcasses over the first 3 h postmortem (pm) compared with Ctr. The rate of glycolysis was higher in infraspinatus (IS) than in longissimus thoracis et lumborum muscle (LTL or longissimus). In both IS and LTL, glycolysis was completed within the first 6 h postmortem in NCa, whereas in Ctr and WCa, it took 12–24 h for glycolysis to be completed. The rate of glycolysis was in the order: NCa > WCa > Ctr.     

Variation in post-mortem rate of glycolyis does not necessarily affect drip loss of non-stimulated veal

In this study the effect of the rate of post mortem pH fall on the water-holding capacity of meat from moderately chilled veal carcasses was investigated. Also the relationship between muscle protein denaturation and drip loss of veal was examined. Three groups of 10 Friesian Holstein male veal calves each were selected on the basis of their pH in M. longissimus thoracis et lumborum (LTL) at 3 hr post mortem (pH₃): (1) fast pH-fall, pH₃ < 6.2; (2) intermediate pH-fall, 6.5 < pH₃ < 6.6; (3) slow pH-fall, pH₃ > 6.7. After 48 hr of chilling the LTL was excised from the carcass and sampled for determination of drip loss, filter paper wetness, sarcomere length, protein solubility and transmission value. Differences in pH₃ were not associated with differences in drip loss, filter paper wetness or differences in protein denaturation. It is suggested that at the relatively high veal carcass chilling rate the effect of rate of pH-fall on protein denaturation and thus on drip loss is negligible. Drip loss of veal was highly correlated with both solubility of sarcoplasmic (r = −0.67; p < 0.001) and total muscle protein (r = −0.54; p < 0.01) and with transmission values (r = 0.66; p < 0.001). These results indicate that protein denaturation measurements may be a good predictor for drip loss of veal.     

The effects of electrical stimulation and ageing on beef tenderness

Seventeen beef carcasses from cattle with a range of breeds, ages and body conditions were used in this trial. The four treatments applied to each carcass were control (C), electrical stimulation (ES), ageing for 28 days (A) and electrical stimulation plus ageing for 28 days (ES + A). Post-mortem muscle pH was measured at 0, 0·5, 4 and 24h post-stimulation. Significantly lower muscle pH values (P < 0·01) were achieved by the stimulated carcass side sompared to the unstimulated side at 0·5 (pH 6·47 vs. 6·91) and 4 h (pH 5·96 vs. 6·44) post-stimulation.

Warner-Bratzler shear and taste panel methods were used to assess the tenderness of Longissimus dorsi muscle samples from each of the four treatments. The ES, A and ES + A treatments were significantly more tender (P < 0·01) than the control treatment. The ES and the A treatments resulted in a similar improvement in tenderness compared to the control. The ES + A treatment was significantly more tender (P < 0·01) than the ES treatment alone, but there was no significant difference in tenderness between the A and the ES + A treatments.     

Some influences of storage fungi, temperatures and relative humidity on the germinability of grass seeds

Seeds of Poa pratensis, Festuca rubra, F. arundinacea, and Lolium multiflorum were stored at 10, 20, 30, or 35°C, and at 35, 55, 75, or 95 per cent r.h. for up to 12 months. Samples stored at 30°C and 95 per cent r.h. and 35°C and 75 or 95 per cent r.h. decreased in germinability after 2 months of storage. At 20°C and either 75 or 95 per cent r.h., seeds decreased more slowly in germinative ability than at the higher temperatures but this decrease was appreciable. Seeds stored at 10°C and at 35, 55, 75, or 95 per cent r.h. germinated well after 12 months.

Equilibrium moisture content of the seeds after storage at 35 to 75 per cent r.h. for 2, 4, and 8 months varied little among the four species at each relative humidity level and was not affected by temperature in the range of 10–35°C.

Fungi of the Aspergillus glaucus group could not always be isolated from large numbers of seeds in lots that had declined in germinability. Seeds of all four grasses apparently carried superficially-borne species of the A. glaucus group (primarily A. amstelodami) in a ‘dormant’ state at harvest. Members of this group were isolated from substantial numbers of seeds that had been stored for 3 months at 30°C and 75 per cent r.h. These fungi were not isolated from seeds stored for the same length of time at 30°C and 35 per cent r.h.; however, field fungi grew from many of these seeds.     

Effect of cooling rate upon processing characteristics of pork meat of different glycolysis type during post mortem ageing

Rapid chilling was applied to porcine longissimus dorsi muscles at 1 h post mortem in order to observe its effect on the quality of canned products prepared from those of different pH₁ values.

The muscle from one side of each animal was removed from the carcase 50 minutes post mortem and divided into two longitudinal strips. One was chilled immediately to 13–15°C (1 h post mortem): the other after a further hour (2 h post mortem) acted as control. After the centre temperature had reached 10°C the muscles were stored in a refrigerator at 3–5°C.

Compared with the control samples (chilled at 2 h p.m.), rapid chilling from 1 h p.m. caused an improvement in the water-holding capacity and the texture of pork meat, which had higher pH₁ values and was processed at 2, 4 and 48 h p.m. There was minimum brine retention and texture score if samples—both rapidly chilled and control—were processed at 24 h p.m.

Although brine retention of PSE pork meat could not be increased even by rapid chilling, the texture of heat treated PSE pork showed an improvement during storage, which was more pronounced after ageing for 48 h, if PSE samples were chilled at 1 h p.m.     

Effects of halothane genotype and pre-slaughter treatment on pig meat quality. Part 1. Post mortem metabolism, meat quality indicators and sensory traits of m. Longissimus lumborum

Forty-eight castrated F₂ offspring of Piétrain and Large White pigs were allocated to a 3 × 2 factorial design in order to study the interactive effect of halothane genotype (NN, Nn and nn) and pre-slaughter treatment [referred to as ‘Experimental’ (EXP) and ‘Commercial-like’ (COL) conditions; the latter combining short transportation, mixing unfamiliar pigs and slaughtering shortly after transport] on muscle post mortem changes and meat quality. The pigs were slaughtered over 4 days. Pre-slaughter glycogen depletion in M. longissimus lumborum (LL) was greater in the nn pigs, compared with the two other genotypes. Lactate accumulation post mortem in LL muscle was greater and the pH value at 40 min post mortem was lower in nn compared with NN pigs. Nn pigs were close to nn pigs for lactate accumulation and showed intermediate pH values in the LL muscle. In the M. semimembranosus (SM), NN and Nn pigs showed the same rate of post mortem changes, as evidenced by similar glycogen, lactate, creatine phosphate and ATP levels, and pH values at 40 min post mortem. Pre-slaughter treatment did not affect the rate of post mortem changes in both muscles and no interactive effect with halothane genotype was found. The pigs slaughtered under the ‘COL’ conditions had a significantly higher ultimate pH in the LL and SM muscles than those slaughtered under the ‘EXP’ conditions. The LL muscle from nn pigs was paler (higher L*) than that of NN and Nn pigs. In SM muscle, Nn pigs showed a significantly higher L* value than NN pigs. Drip loss of the LL muscle was significantly higher in nn compared with NN pigs, the heterozygous pigs being intermediate. Sensory evaluation of the LL muscle showed that nn pigs had a lower colour intensity and colour homogeneity of raw meat than NN and Nn pigs. Tenderness was significantly lower in nn compared with NN pigs, the Nn pigs being intermediate. Pre-slaughter treatment significantly increased ultimate pH in both muscles (LL and SM) but did not affect significantly the rate of pH fall (pH₄₀). It did not affect any of the meat quality traits and no interactive effect with halothane genotype was found. These results confirmed the influence of the halothane gene on the kinetics of muscle post mortem changes and related meat quality traits. They also confirmed the intermediate position of heterozygous pigs in terms of meat quality.     

Edible films made from gelatin, soluble starch and polyols, Part 3

The thermal and mechanical properties of edible films based on blends of gelatin with soluble starch plasticized with water, glycerol or sugars were investigated. Two different methods, known as ‘the high temperature’ and ‘the low temperature’ methods, consisting of casting aqueous solutions of blends at 60 and 20 °C, respectively, were employed for the preparation of films. With increasing water, glycerol or sorbitol content, a drop of elasticity modulus and tensile strength (up to 50% of the original values for 30% plasticizer) was observed. The tensile strength and percentage elongation increased with high gelatin contents (> 20% w/w). The development of a higher percentage renaturation of gelatin (reaching 70% for 5% water content) by the ‘low temperature’ method caused a reduction in gas and water permeabilities. The former decreased by one or two orders of magnitude for O₂ and CO₂, respectively. The semi-empirical model for calculation of gas permeability and the semi empirical equations for upper and lower limits of tensile moduli of composites were applied with limited success and the obtained values were compared to those experimentally determined.     

The colour and colour stability of beef Longissimus dorsi and Semimembranosus muscles after effective electrical stimulation

The influence of effective low voltage electrical stimulation (ES) of beef on the colour and colour stability of longissimus dorsi (LD) and semimembranosus (SM) muscles, during storage and retail display was studied by tristimulus colorimetry and reflectance spectrophotometry. ES had no significant effect on the colour of the LD muscles, but some significant effects on SM muscles of ultimate pH 5·5-5·7. Three hours after slicing into steaks at 5 days post mortem, stimulated SM muscles had a paler/lighter colour than non-stimulated controls. During a retail display of 3 days, all steaks exhibited a loss of colour quality manifested in loss of redness and decreases in both hue and chroma (saturation). These changes were most marked in the stimulated SM muscles, and analysis indicated that they were due almost exclusively to the formation of metmyoglobin (metMb). Ageing the meat, as primals cuts, for 33 days at 0°C led to no significant differences in the perceived colour three hours after slicing. The colour changes observed during the 3-day retail display of steaks occurred more rapidly in both (ES and non-ES) 33 day-aged samples than in the 5 day-aged ones. The result of this was that the colour stability of non-stimulated steaks prepared at 33 days was similar to that of ES steaks prepared fresh (5 day post mortem). In SM muscles of pH 5·8-6·0 the apparent differences in colour of the ES and non-ES samples were not significant. However, meat of pH > 5·8, although darker than meat of lesser pH, had less tendency to form metmyoglobin during retail display.

The present work also confirmed that seemingly small differences in display conditions, especially temperature, have a marked effect on metmyoglobin formation.     

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca²⁺ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca²⁺ specific electrode at 35°C. Significant differences (P < 0·001) in deterioration (%) of Ca²⁺ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice.

Predictions of meat quality in live pigs (n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN (n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn (n = 13). The Nn pigs (n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH₁ and fibre optic probe (FOP) measurements.

The extent of deterioration (%) in Ca²⁺ accumulation showed high correlations with fluid (r = −0·861) and pH (fluid) (r = −0·831) in the biopsy LD samples, and with pH₁ (r = 0·663), FOP (r = −0·812), and drip (%) loss (r = −0·777) in the post-mortem LD samples.     

Addition of grape seed extract and bearberry to porcine diets: Influence on quality attributes of raw and cooked pork

The effect of supplementation of pig diets with grape seed extract (GSE) (100, 300, 700 mg/kg feed) and bearberry (BB) (100, 300, 700 mg/kg feed) for 56 days pre-slaughter, on the oxidative stability and quality of raw and cooked M. longissimus dorsi (LD) was examined. Susceptibility of porcine liver, kidney and heart tissue homogenates to iron-induced (1 mM FeSO₄) lipid oxidation was also investigated. In raw LD steaks, stored in modified atmosphere packs (75% O₂:25% CO₂) (MAP) for up to 16 days at 4 °C, surface lightness (CIE ‘L’ value), redness (CIE ‘a’ value), lipid stability (TBARS, mg MDA (malondialdehyde)/kg muscle) and pH were not significantly affected by supplemental GSE or BB. Similarly, the oxidative stability and sensory properties of cooked LD steaks, stored in MAP (70% N₂:30% CO₂), for up to 28 days at 4 °C, were not enhanced by dietary GSE or BB. Iron-induced lipid oxidation increased in liver, kidney and heart tissue homogenates over the 24 h storage period and susceptibility to oxidation followed the order: liver > heart > kidney. Dietary GSE or BB did not significantly reduce lipid oxidation in tissue homogenates. Potential reasons for the lack of efficacy of supplemental GSE and BB on pork quality were explored.     

Evaluation of the antioxidant potential of grape seed and bearberry extracts in raw and cooked pork

The effect of grape seed extract (GSE) and bearberry (BB), on lipid oxidation (TBARS, mg malondialdehyde (MDA)/kg muscle), colour (CIE ‘a’ redness value), pH, microbial status (log₁₀CFU colony forming units/g pork) and sensorial properties of cooked pork patties was investigated. GSE (0–1000 μg/g muscle) and BB (0–1000 μg/g muscle) were added to raw pork (M. longissimus dorsi) patties which were stored in modified atmosphere packs (MAP) (75% O₂:25% CO₂) for up to 12 days at 4 °C. Cooked pork patties were stored in MAP (70% N₂:30% CO₂) for up to 4 days at 4 °C. Mesophilic plate counts and pork pH were unaffected by GSE and BB. GSE and BB addition decreased (P < 0.05) lipid oxidation (TBARS) in raw pork patties on days 9 and 12 of storage, relative to controls. Antioxidant activity of GSE and BB was observed in cooked pork patties demonstrating the thermal stability of GSE and BB. The ‘a’ redness values of raw and cooked pork patties marginally increased with increasing GSE concentration. The sensory properties of cooked pork patties were unaffected by GSE and BB addition. Results obtained demonstrate the potential for using health promoting nutraceuticals in meat and meat products.     

The protective effect of electrical stimulation and wrapping on beef tenderness at high pre rigor temperatures

A three factorial experimental design involving electrical stimulation (ES/NES), wrapping (wrapped/unwrapped) and pre rigor temperature (15 °C or 35 °C) was applied to 70 beef M. longissimus lumborum muscles to obtain a wide variation in shear force and drip loss. The shear force of all treatment groups decreased during ageing. As anticipated, wrapping and electrical stimulation had positive effects on shear force. However, high pre rigor temperature (35 °C) did not result in higher shear force values if the muscles were electrically stimulated, wrapped or both. The results suggested that electrical stimulation protects against the negative effects of high pre rigor temperatures. The drip loss of all treatment groups increased during ageing in a manner that was unrelated to treatment but was correlated to tenderness (r² = 0.70; p < 0.0001). It was concluded that the application of electrical stimulation, whatever the pre rigor temperature, protects beef from toughening through the prevention of rigor shortening and the avoidance of inhibition of ageing enzymes.     

Growth and development of water buffalo and Friesian crossbred cattle, with special reference to the 'entire' and 'boneless' cuts

Twelve buffaloes, nine Friesian × Baladi and nine Friesian × (Friesian × Baladi) bulls were slaughtered over the live weight ranges 161–560 kg for buffaloes and 176–448 kg for cattle. Right sides of all carcasses were jointed and dissected and the increase in the weight of ‘entire’ and ‘boneless’ cuts and cut groups (i.e. pistol; BLRC) relative to the ‘entire’ and ‘boneless’ side weights, respectively, were examined using covariance analyses.

Increasing distoproximal and dorsoventral growth gradients were found in both species. Most noticeably, the sticking was early developing in buffaloes and late developing in cattle, whereas the shortloin developed approximately at an average rate in buffaloes and at a lower rate in cattle. Statistically significant but relatively slight differences were recorded between buffaloes and cattle in the adjusted means of the ‘entire’ and ‘boneless’ hind shank, sirloin (favouring buffaloes) and brisket (favouring cattle). Buffaloes were superior to cattle in weight of pistol. At an equal side weight of 73 kg buffaloes had significantly higher weight of pistol (maximum difference = 1·4 kg). At a 115 kg side weight, the maximum difference in ‘entire’ and ‘boneless’ pistol reached 3·58 and 5·04 kg, respectively.     

The effect of chilling, electrical stimulation and conditioning on pork eating quality

The effect of three different post-slaughter treatments and subsequent conditioning times on the eating quality of pork was studied, using a total of 72 pigs (80–90 kg live wt). The treatments were: (A) holding in air at > 10°C for 3 h, followed by chilling in air at 1°C; (B) chilling in air at 1°C; (C) high voltage electrical stimulation (ES) at 20 min post-slaughter, followed by Treatment B. The quality attributes were measured in M. longissimus thoracis et lumborum (LTL) and in M. semimembranosus (Sm).

There was little difference in cooling rate between the three treatments; the major effect on quality came from the use of ES in Treatment C. ES reduced pH at 45 min by approximately 0·3 units, and achieved pH values at 3 h post-slaughter of 5·64 (LTL) and 5·87 (Sm) but did not produce PSE meat. Drip losses were generally low, but were slightly higher with Treatment C. By all three instrumental texture parameters, LTL from Treatment C was significantly more tender than from A and B at 4, 7 and 12 days post-slaughter, suggesting that either some cold toughening with A and B was overcome by ES in treatment C or that ES had some other beneficial action. Conditioning at 1°C improved the tenderness of LTL from 4 to 7 days and further to 12 days. Taste panelling of loin chops and Sm roasts confirmed that Treatment C gave significantly more tender meat than A and B, and that ageing from 4 to 7 days and further to 12 days significantly improved tenderness. High voltage electrical stimulation at 20 min post-slaughter followed by cooling in air at 1°C (Treatment C) produced loin muscle which was more tender at 4 days than at 12 days with the other treatments.     

Sarcomere shortening of prerigor muscles and its influence on drip loss

Detailed studies of muscle shortening post mortem at incubation temperatures between −2°C and +38°C revealed that the sarcomeres in unrestrained, excised red bovine muscle (M. sternomandibularis) shortened less than 10 % in the prerigor state between 6°C and 18°C. Below 6°C, sarcomeres contracted up to 70%. Between 20°C and 38°C sarcomere shortening of 40% was observed. In the red porcine M. cleidooccipitalis the minimum of shortening was measured at about 10°C, a higher degree of shortening—up to 50%—being obtained above and below this temperature. The drip loss of both muscle types increased linearly with increasing prerigor shortening.

This latter relationship is discussed with regard to changes within the muscle post mortem. The influence of three events on water movement from the interfilamental space into the interfibrillar fluid and from there into the extracellular space is critically evaluated. These events are: (1) the prerigor contraction of sarcomeres depending on the temperature of storage, (2) the changes due to the falling pH post mortem and (3) the onset of rigor mortis, with its irreversible association of actin and myosin.     

Sensory, chemical and gas chromatographic evaluation of five raspberry cultivars

Five raspberry cultivars, ‘Chilcotin’, ‘Chilliwack’, ‘Meeker’, ‘Skeena’ and ‘Tulameen’, were evaluated for sensory attributes, and chemical and flavor volatile compounds. ‘Chilliwack’ and ‘Tulameen’ received high ratings in sweetness and overall impression with high soluble solids, total sugars and sugar:acid ratio. ‘Chilcotin’ rated low in overall impression and sweetness, and high in sourness and astringency, with low soluble solids, sugar:acid ratio and total sugars, and high titratable acidity. Principal factor analysis (PFA) of the sensory results separated the cultivars based on desirable (appearance, color, texture, aroma and sweetness) and less desirable (sourness, bitterness, astringency and off-flavor) attributes. Twenty-eight volatile compounds were analyzed by dynamic headspace and 18 identified by gas chromatography-mass spectrometry (GC-MS), most of which were terpenes which included -pinene, sabinene, γ-terpinene, - and β-ionone and caryophyllene. Volatile compounds varied among cultivars, with benzaldehyde (11·1–31·8%), -pinene (4·0–11·5%), ethyl heptanoate (6·9–15·2%), β-myrcene (13·2–19·6%) and γ-terpinene (12·2–20·0%) as the predominant volatiles. Correlation analysis established no relationships between sensory and chemical data with volatile compounds.     

Design, fabrication, and testing of a returnable, insulated, nitrogen-refrigerated shipping container for distribution of fresh red meat under controlled CO2 atmosphere

In today's market, fresh red meat is cut and packaged at both the wholesale and retail level. Greater economies could result if the wholesaler prepared all consumer cuts centrally, but the short storage life of meat limits distribution. Use of CO₂-controlled atmosphere, master packaging, and strict temperature control (−1.5±0.5°C) can enhance storage life and, therefore, distribution ease. An insulated shipping and storage container was designed and tested for its suitability to distribute master-packaged meat. Shelves in the container supported 36 master trays (508 × 381 × 60 mm), with the source of refrigeration being injected liquid nitrogen (N₂). Electric fans dispersed the N₂ gas throughout the container. To reduce costs, 36 saline water bags (10% w/v NaCl) were used to thermally simulate the meat. Temperatures of 20 bags were recorded during storage experiments. The container was tested at outside temperatures of 15, 0 and −15°C with 4 internal fans and at 30°C with 2, 4 and 6 fans. In all instances, bags cooled from 10°C to an equilibrium temperature of −1.5°C within 5.5 h. Minimum equilibrium temperatures during any 8 h trial were −2.6, −2.0 and −2.0°C for 2, 4 and 6 fans, respectively. Correspondingly, maximum temperatures were −0.2, −0.7 and −0.3°C. Initial chilling of the product required, on average, 19 kg of N₂, while equilibrium was maintained at a N₂ consumption rate of 5.5, 4.0, 2.6 and 0.93 kg/h at outside temperatures of 30, 15 0 and −15°C, respectively, with 4 fans. The N₂ use for 2 and 6 fans was 5 and 6.3 kg/h, respectively, at an outside temperature of 30°C. During simulated power failure or when the N₂-tank ‘ran dry', temperatures in the container rose 0.9 and 2.0°C/h, respectively. When the door to the container was opened long enough to remove three trays, temperature was restored within 5 min. Convective heat transfer coefficients between saline water bags and circulating N₂ were in the range of 80–100, 115–135, and 140–155 W/(m²·K) for 2, 4 and 6 fans, respectively. Heat transfer to meat will be limited by conduction in master packaged meat if similar convection coefficients prevail.     

The effects of antifreeze proteins on chilled and frozen meat

The effects of cryoprotectant proteins, trivially termed ‘antifreeze proteins’, from the Antarctic Cod and the Winter Flounder were assessed in meat during chilling and freezing. In light-microscopy studies, bovine muscle (Sternomandibularis) samples were soaked in phosphate buffered saline with and without 0·1 mg/ml antifreeze protein. Samples were then held frozen (−20°C) or chilled (2°C) for 3 days. Samples were freeze-substituted, embedded in resin and sectioned. With antifreeze protein present, transverse sections of frozen samples had many small intracellular spaces, probably representing ice crystals. Frozen controls had much larger intracellular single spaces. Antifreeze protein had no effect on chilled samples.

Similarly treated samples were examined by scanning electron microscopy using a cryostage attachment. Chilled ovine muscle samples (Peroneus longus) were soaked for various periods (0–7 days) in 0·9% saline containing various concentrations of antifreeze proteins (0–1 mg/ml). Samples were then held frozen (−20°C) or chilled (2°C) for 5 or 7 days. With frozen samples, antifreeze proteins reduced the size of ice crystals, compared to the control. This effect depended upon the concentration used and the period of soaking before the samples were frozen, but was independent of source. Antifreeze proteins had no effect on chilled samples.     

Changes in histamine and microbiological analyses in fresh and frozen tuna muscle during temperature abuse

Temperature abuse of tuna (Thunnus alalunga) was carried out in order to assess the histamine buildup in fish-processing facilities where fish can be exposed to high temperatures for short periods of time. Histamine production was studied in tuna loins under different storage and abuse conditions. Tuna was stored at 0-2°C, 3-4°C, and 6-7°C, and abused for 2 h daily at 20°C and 30°C for 7-12 days. Loins abused at 30°C for 2 h daily contained potentially toxic histamine concentrations (67-382 mg kg^-1) when stored at a low refrigeration temperature (0-2°C), whereas when stored at 6-7°C, the loins contained highly toxic histamine concentrations (544.5-4156.6 mg kg^-1). Lower histamine concentrations (23-48 mg kg^-1 in loins stored at 0-2°C and 124.7-2435.8 mg kg^-1 in loins stored at 6-7°C) were observed in temperature-abused loins that were initially frozen. An increase over time was observed in most microbial counts tested. Bacteria isolated from the temperature-abused loins showed a varied ability of histamine production, with Morganella morganii, Klebsiella oxytoca, Staphylococcus hominis, and Enterococcus hirae being the most active histamine-producing bacteria.