Effect of comminution temperature on the quality and shelf life of buffalo meat nuggets

Buffalo meat nuggets were prepared after equilibrating the ingredients to temperatures of 4, 10, 25 and 37 °C. Following comminution for 6 min, the temperatures of the batters were 16.3, 19.3, 27.4 and 34.8 °C and their pH and emulsion stability ranged from 6.18 to 6.29 and 88.76 to 95.33%, respectively. Increasing temperature of comminution led to increased cooking losses and TBARS values. However, even at 37 °C, complete emulsion breakdown did not occur as the cooking losses were still only about 12%. Texture profile analysis revealed an inverse relationship between chopping temperature and shear force. Sensory evaluation indicated that, at least up to comminution temperatures of 27.4 °C, the nuggets were acceptable. The aerobic mesophilic bacterial counts were higher for the nuggets made from batters with higher temperatures but, even at the 21st day of storage, the counts were well below the levels likely to cause spoilage in meat products. Results suggested that comminuted buffalo meat products can be manufactured in conditions where refrigeration is not available, by a preservation system (mostly chemical) to decrease microbial and chemical spoilage and also by devising an efficient marketing system for their early distribution (preferably 14 days).     

Effects of salt reduction on the rheological and gelation properties of beef, pork and poultry meat batters

The gelation and rheological properties of beef, pork and poultry meat batters as affected by salt reduction (2·50, 1·25 and 0·00%) were studied by using a Haake rotational viscometer and a thermal scanning rigidity monitor. Beef batters showed a decrease in shear stress with the decrease in salt levels at both high and low shear rates. Pork batter showed a mixed behavior (no definite trend in shear stress versus shear rate) and the poultry meat batters showed a Bingham pseudoplastic behavior, except for the no-salt treatment. During heating the beef batters showed the highest G values followed by the pork and the poultry meat batters. The rigidity modulus profiles exhibited two major transition temperatures at 47-53°C and at 64-76°C. Beef batter with 2·50% salt developed the highest average G value (16·6 kPa) and the poultry batter with 2·50% salt the lowest (7·3 kPa).     

Effect of processing conditions on the quality of naturally fermented Turkish sausages (sucuks)

Effects of temperature and different fat levels on the quality of Turkish sausages (sucuks) were studied during the ripening period. Sausage batters prepared at 10%, 20% and 30% fat levels were processed at 20-22 and 24-26 °C. A high ripening temperature and low fat level caused fast dehydration. Fat level affected water activity, colour, total viable and lactic acid bacteria counts of the sausages. Increasing fat content and ripening temperature resulted in high lightness (L*) and yellowness (b*) and low redness (a*) at the end of ripening. The sausages with 10% fat resulted in higher redness values. Growth of total viable and micrococci-staphylococci bacteria was affected by ripening temperature. Sausages ripened at 24-26 °C had a rapid increase in micrococci-staphylococci counts.     

Color changes in irradiated cooked pork sausage with different fat sources and packaging during storage

Pork sausages were prepared with lean pork meat, fat from different sources [backfat (BF), corn oil (CO) or flaxseed oil (FO); 10% of lean meat], NaCl (2%), and ice water (10%). The emulsified meat batters were stuffed into casings (3 cm in diameter) and cooked to an internal temperature of 72°C. Cooked sausages were sliced and vacuum- or aerobic-packaged individually. Sausages were irradiated at a 0, 2.5, or 4.5 kGy dose and stored in a 4°C refrigerator for 8 days. Aerobic-packaged, irradiated cooked sausages prepared with BF and FO showed higher Hunter L-values than nonirradiated controls at day 0, but the difference disappeared at day 8. Irradiation increased the Hunter a-value in vacuum-packaged cooked pork sausages regardless of the fat source used, and the increase of the Hunter a-value was dose-dependent. In contrast, the Hunter a-value decreased by irradiation in aerobic-packaged cooked pork sausages prepared with BF or FO. The Hunter a-value of cooked pork sausage with aerobic packaging was significantly reduced at day 8. Hunter b-values increased at Day 8 in irradiated cooked pork sausages except for the sausage prepared with CO at 2.5 kGy. Cooked pork sausages prepared with CO were lighter, and sausage prepared with FO was redder and more yellow (p<0.05) in vacuum packaging.     

Modelling the yield and texture of comminuted pork products using color and temperature. Effect of fat/lean ratio and starch

Practices to control the processing of finely comminuted meat products are proposed. The objective was to test the practical value of both temperature and light reflection measurements made during emulsification as potential indicators of cooking losses and resulting gel texture in pork sausages emulsified within a wide range of temperatures and starch and fat levels. Prior to cooking, pork batters were chopped for different times to ensure final emulsion temperatures ranging from 5 to 50°C. The effects of the fat/lean ratio (0.25 and 0.67) and starch addition (0.8 and 3.2% w:w) on temperature and optical reflection were also investigated. The chopping increased the temperature and decreased the light reflection of fresh meat emulsion. There was no relevant loss of emulsifying capacity at emulsion temperature below 30°C and lightness values over 70 CIE units. The losses and textural parameters of cooked emulsions could be predicted by means of non-linear regression equations based on the temperature and color of the raw emulsion. The determination coefficients obtained ranged from 0.89 to 0.99. The prediction models needed to be fitted to each batter formulation, especially in the presence of reduced levels of gelation agents (meat protein and starch). Lightness was a better predictor than chromaticity, since it decreased constantly with chopping in the range of final emulsion temperatures studied (5-50°C). This confirms previous studies that lightness could be used for monitoring emulsion stability in meat batters.     

The effect of preheated tendon as a lean meat replacement on the properties of fine emulsion sausages

Tendon from beef hind leg muscles was used to replace some of the lean in a conventional emulsion formulation. The tendon was homogenized and either used raw or preheated for 2·5 h at a range of temperatures (50, 60, 70, 80°C) before use. Texture analysis and sensory evaluation were performed on cylinders of cooked sausage. Texture analysis was carried out on formulations which had 20% of meat protein replaced by 20% tendons which were raw or had been preheated to 50, 60, 70, or 80°C. Fracturability decreased by about 40% with raw tendon, but was restored to within 20% of the no-replacement control if the tendon had been preheated. Hardness was approximately doubled by replacement with raw tendon or tendon heated at 50°C. At temperatures higher than that, hardness returned to approximately no-replacement levels. For sensory evaluation (0-25% replacement; preheating at 70°C), sausages were assessed by a 12-member panel for texture, flavour and overall acceptability. All attributes decreased with increasing collagen content, the decrease being less marked with preheated tendon. Thus more connective tissue could be added for the same panel score if the tissue was preheated. Comparison of the texture profile and the panel scores for texture at the same lean replacement level suggested that reduced fracturability was the texture parameter that panellists objected to when heated tendon replaced some of the lean. Other researchers have shown that connective tissue preheated to 100°C before addition in emulsion sausages results in improved yields and better sensory attributes, but the present results show that temperatures as low as 60°C can be effective for beef tendon.     

Nonprotein Nitrogen (NPN) and Free amino acid contents of dry, fermented and nonfermented sausages

Fermented and nonfermented sausages were analyzed for concentration changes in total and nonprotein nitrogen (NPN) and in free amino acid profiles during processing. Sausages fermented by Pediococcus pentaceous at 38°C and heated to 60°C had increases (p < 0·05) in total N and NPN contents and increases in concentration (≥5 mg per 100 g dry sample) for 14 of 20 free amino acids. Nonfermented sausages had no increase (p > 0·05) of NPN content and increases in only 6 of 20 free amino acids after heating to 60°C. When the effects of three starter cultures were compared, NPN concentrations after fermentation and heating and after drying were highest to lowest in the following order: P. pentaceous >P. acidilactici with M. varians >P. acidilactici. Variations of free amino acid patterns in the fermented, dried sausages were found which indicated differences in metabolic activity between the cultures. These variations did not (p > 0·05) affect sensory scores for the dried sausages. Overall, these results for rapidly fermented and mildly heated dry sausages were similar to results previously reported for 'European-style' dry sausages processed with prolonged low temperature fermentations.     

Influence of freezing method on thaw drip and protein loss of low-voltage electrically stimulated and non-stimulated sheeps' muscle

South African Mutton Merino wethers (n = 32) were slaughtered, yielding carcasses with a mean weight of 22·18 ± 2·11 kg. Sixteen carcasses were electrically stimulated (ES) (21 V, 60 Hz, 120 s) immediately and all carcasses were chilled at room temperature (16°C) for 3 h and then overnight at 4°C, 95% RH. Both left and right Mm. longissimus lumborum et thoracis were excised and cut into six portions (77 g ± 7·8 g), each placed separately in a polyethylene bag and randomly allocated to five freezing treatments. These were: (1) cryogenic, -65°C; (2) cryogenic, -90°C; (3) walk-in-freezer, -21°C; (4) blast freezer, -21°C; (5) domestic freezer, -25°C. The respective freezing rates were 4·4, 6·4, 0·55, 0·35 and 0·51 cm h(-1) to -2·2°C at core depth of 1 cm below the surface. Samples were frozen to core temperatures of -20°C, removed and placed in a storage freezer (-20°C) for 48 h and 2·5 months. Samples were then suspended in perforated bags in a chiller (4°C) to thaw, and drip was collected in outer bags over the periods 0-24, 24-48, 48-72 and 72-96 h and expressed as g (100 g)(-1). Freezing methods had significant (P < 0·01) influences on drip loss in both ES and NES samples. Following storage for 48 h post-freezing at -20°C, total drip (g (100 g)(-1)) over 96 h of both ES and NES samples for the five freezing treatments were respectively: (1) 7·61 and 4·61; (2) 7·35 and 3·29; (3) 9·44 and 4·68; (4) 9·07 and 5·43; (5) 10·58 and 5·15. Following storage for 2·5 months, the total ES and NES drip were respectively, (1) 11·25 and 9·38; (2) 10·36 and 9·15; (3) 13·72 and 12·65; (4) 13·70 and 12·26; (5) 11·92 and 11·29. Total protein in the drip did not differ between freezing treatments. Differences between ES and NES samples did occur in the 48 h storage group. It is concluded that cryogenic freezing results in less thaw drip than the vapour compression systems. This advantage of cryogenic freezing disappears if meat is stored for long periods at -20°C. Electrical stimulation increases the drip loss in samples frozen for 48 h, but the differences are not significant after 2·5 months frozen storage. Protein losses parallel the drip.     

Comparison of various types of starch when used in meat sausages

Technological and sensory properties of meat sausages formulated with 4·0% of either potato flour, modified (acetylated distarch phosphate) potato starch, wheat, corn or tapioca starch were compared. Sausages were analyzed after cooking at temperatures between 65 and 85°C followed by storage at 5°C and -25°C. Characteristics evaluated were weight loss during cooking and storage, instrumentally and sensory assessed firmness, taste and smell of sausages. The results revealed differences in the suitability of starches for use in meat sausages. Part of the differences could be ascribed to differences in gelatination properties of the starches. With the criteria used for evaluating quality, potato flour was rated as the best suited starch followed by wheat starch while tapioca was rated as the least suited. Corn starch required cooking temperatures above 75°C and showed relatively low freeze/thaw stability. The modified potato starch stored well both above and below the freezing point.     

Chilling pig carcasses: Effects on temperature, weight loss and ultimate meat quality

Effects of conventional (4°C, air velocity 0·5 m/s) and forced chilling at -5°C (120 min) or -30°C (30 min) with air velocities of 1, 2 or 4 m/s, followed by conventional chilling till 24 h post mortem on temperatures, meat quality and weight losses, were studied. Experiments were carried out in six batches of six slaughter pigs each (crossbred gilts, weighing 105-110 kg. The subcutaneous temperature decreased very rapidly to values below 0°C when 'ultra' rapid chilling (-30°C) at high air velocities (4 m/s was used. Immediately after rapid chilling, when the carcasses were railed into a conventional chiller, the subcutaneous temperature increased above the air temperature, after which the decline in temperature was continued. Temperature inside the biceps femoris muscle decreased from the start of chilling rather slowly according to an asymptotic curve until ultimate values of 4°C were reached. Theoretically calculated temperatures during slaughter and chilling were comparable with the measured values; indicating that a finite-element calculation method in combination with a cylindrical model for heat transport can be used to predict muscle temperatures for various chilling regimes. Losses in carcass weight, 24 h after conventional and forced chilling at -5°C, were about 2%. After 'ultra' rapid chilling (-30°C) the losses were reduced to 1·3% when air velocity was increased to 4 m/s. Meat quality of the longissimus lumborum muscle was not significantly affected by the various chilling regimes except for the variables related to tenderness. The Warner-Bratzler shear forces were higher (P < 0·05) together with shorter sarcomere lengths (P < 0·10) after 'ultra' rapid chilling at a high (4 m/s) air velocity, indicating an increased risk of cold shortening.     

The effect of cooking conditions on the eating quality of pork

Two experiments were conducted to examine the effects of cooking parameters, including final internal temperature (65, 72·5 or 80°C), on the eating quality of pork. Assessments were made by a 10-member trained taste panel. In Experiment 1 on loin steaks (m. longissimus) from 28 carcasses weighing 66 ± 1·9 (SD) kg, increasing the final internal temperature from 65 to 80°C had the following effects on mean scores (1-8): tenderness -1·0; juiciness -1·5, pork flavour +0·6 and abnormal flavour -0·5. The medium temperature of 72·5°C was suggested as ideal. In Experiment 2 on leg roasts (m. gluteobiceps) from 96 carcasses weighing 65 + 2·7 (SD) kg, increasing the final internal temperature from 65 to 80°C had the following effects on mean scores (1-8): tenderness -0·2 (not significant), juiciness -0·6, pork flavour +0·3 and abnormal flavour -0·5. The effects of final internal temperature were therefore smaller in roasts and temperatures towards the upper end of the range would be recommended for ideal eating quality, balancing small losses in tenderness and juiciness against gains in flavour scores. Although the experiments were not designed to examine source and sex effects there was evidence that tenderness can be improved through the use of Duroc genes and pelvic suspension of carcasses and no evidence of differences in eating quality between entire males and females.     

Utilization of chickpea flour in sausages

'English' type fresh skinless sausages were prepared in which some of the meat (mutton, pork or beef) was replaced on a protein to protein basis by chickpea flour. The acceptability of mutton sausages containing chickpea flour was not affected at levels of substitution up to 40%, whereas pork and beef sausages were significantly less acceptable at substitution levels above 30%. In all the sausages incorporation of chickpea flour led to increased cooking losses and softer textures. Incorporation of chickpea flour caused discoloration of the raw sausages which became more prominent during storage at 0°C.     

The effect of cooking temperature on the functional properties of beef proteins: The role of ionic strength, pH, and pyrophosphate

This study examined the effect of ionic strength (0·12 to 0·52), pH (5·50 and 6·00), pyrophosphate (PP) concentration (0 and 0·31%) and cooking temperature (52 to 87°C) on the cook yield (CY) and tensile strength (TS) of beef homogenates. Increasing the ionic strength, pH and pyrophosphate concentration increased the temperature at which cooking loss first occurred and decreased the temperature required for maximum TS. For most treatments, ionic strengths between 0·32 and 0·42 prevented cooking loss at all temperatures; the lower ionic strengths were required at the higher pH and PP concentration. Maximum TS occurred at 66°C for treatments that had no cooking loss between 60° and 75°C. For treatments that had cooking loss in this temperature range, TS increased linearly with increasing temperature; however, the TS values of these treatments were much lower than those in the former category. CY and TS were optimized by heating to 66°C. PP had a positive effect on both functional properties at ionic strengths >0·25 but a negative effect at ionic strengths <0·25.     

Effect of post-slaughter processing and freezing on the functionality of hot-boned meat from young bull

The effects of variation in the times of mincing post mortem (2, 4, or 6 h), pre-rigor salting (1.5% wt wt ) and freezing rate [fast (10 min, liquid nitrogen); medium (4-6 h at -40 °C and 0.8 m s(-1) air velocity); or slow (36-38 h at -10 °C and 0.1 m s(-1) air velocity followed by 12 h at -20 °C and 0.1 m s(-1) air velocity)] on the functionality of young bull meat were examined using hot-boned forequarters. At 52 h post packaging, the meat was thawed (72 h at 4 °C), its pH measured, and it was used to make finely comminuted batters. Cook yield and stress and strain of the cooked batters were measured. Time of mincing had no effect on meat pH, cook yield or stress and strain. There was a significant interaction (P < 0.05) between pre-rigor salting and freezing rate for pH. Freezing rate did not affect the pH of pre-rigor salted meat whereas the pH of unsalted pre-rigor meat was highest at the fastest freezing rate. Meat salted pre-rigor had a significantly (P < 0.05) higher pH than the post-rigor chilled control. Pre-rigor salting decreased the stress values of cooked batter whereas the slowest freezing rate increased stress. Stress and strain values for cooked batters from thawed meat were not significantly different from the values for batters made from the unfrozen control. Cook yields of batters made from pre-rigor frozen meat were higher than that of the postrigor control but not significantly so. The results indicate that suppliers can use pre-rigor salted and frozen meat when manufacturing comminuted products without major detrimental effects on the cook yield and texture of the finished product.     

Water distribution in porcine M. longissimus dorsi in relation to sensory properties

The water distribution in M. longissimus dorsi (LD) from purebred Hampshire and Swedish Yorkshire pigs was recorded by proton-pulse-NMR. Three domains of water were seen with this type of method, designated as free, extracellular and intracellular water, respectively. The relative proton population for the free water increased from 1·8% in raw, to 3·3% in fried, samples from Hampshire and to 4·2% for the Yorkshire samples. The relaxation time of the extracellular water increased for Hampshire samples from 100 ms, when raw, to 108 ms and 114 ms for samples fried to centre temperatures of 68°C and 80°C, respectively. For Yorkshire samples it decreased from 122 to 108 and 109 ms, respectively. The relative proton population of the extracellular water decreased after frying (raw: 24·5%, 68°C: 18·6% and 80°C: 13·9%) for Hampshire samples, whereas the corresponding populations of protons for those of Yorkshire were 16·5%, 19·2% and 16·6%. The intracellular water had relaxation times of about 40 ms (raw), 30 ms (68°C) and 28 ms (80°C) for both breeds. The relative proton populations were: for Hampshire, 74·1% (raw), 77·7% (68°C), 83·4% (80°C) and, for Yorkshire, 81·6% (raw), 75·5% (68°C) and 77·2% (80°C). On average, the samples of Hampshire were more juicy and tender than those of Yorkshire. The sensory properties were related to the water distribution, but obvious influences of breed and end-point temperature at frying were noted for the relationships. In general, the juiciness and tenderness of fried LD samples could fairly well be predicted by the water distribution in raw meat. However, due to the influence of breed and temperature, different variables are best for the prediction. Also, when the sensory properties were related to the water distribution in fried samples, the influences of breed and end-point temperatures were noted.     

Modelling post-mortem tenderisation-I: Texture of electrically stimulated and non-stimulated beef

Texture in electrically stimulated and non-stimulated beef M Pectoralis profundus, stored under a range of temperatures from 0 to 30°C, while avoiding muscle shortening, was measured from 1 to 21 days after stunning. The pre-rigor temperature (from 0 to 30°C), maintained until the pH had fallen to 6·4 and then held at 15°C, had no effect on the toughness nor on the rate of tenderisation after rigor. Modelling toughness prior to 24 h suggested that toughness of all muscles could be rationalised and that first-order tenderisation began when the muscles reached pH 6·1 when the toughness of all the muscles was projected to be 12·5 kg. After pH 6·1, the rate of tenderisation at 30°C was 10-fold higher than at 1°C and was not affected by variations in pH from 6·1 to 5·5. At the higher temperatures, the ultimate toughness of aged meat was slightly higher than at the lower temperatures.     

Modelling post-mortem tenderisation-II: Enzyme changes during storage of electrically stimulated and non-stimulated beef

Levels of calpains I and II, cathepsins B and L and β-glucuronidase were determined in extracts of electrically stimulated and control beef M. Pectoralis profundus stored at temperatures between 0 and 30°C and varied to avoid muscle shortening. The level of lysosomal enzymes remained essentially unchanged throughout storage. The levels of calpain II were largely unaffected by the early treatments and decreased slightly throughout ageing. The level of calpain I, in both stimulated and control meats, was unaffected by temperature prior to the attainment of about pH 6·2 and thereafter the loss was accelerated at higher temperatures. In the extreme case studied, that of stimulated meat held at 15°C, 73% of the activity was lost in the first 24 h. After ageing, the level was about 11% of the initial when stored at 1°C and 25% when stored at 15°C. The exponential decay constants for the decrease in the levels of calpain I were 0·01 h(-1) at 1°C and 0·06 h(-1) at 15°C, and were the same as those for the previously determined rate of tenderisation. This suggested that the rate of proteolysis by calpain I was linked to the rate of tenderisation.     

Effect of fat level and storage conditions on quality characteristics of traditional Greek sausages

Traditionally-processed Greek sausages were produced with three different fat levels (10, 20 and 30% fat). Some sausages were air dried (23-28°C, 64-76% RH) for 2h and stored at 3-7°C and 65-75% RH. The rest were immediately stored in a ripening room at 13-15°C, 85-95% RH and 0.1m(-1)s air velocity. Fat level affected the composition of the sausages, their weight loss, brine concentration, water activity, colour and sensory attributes. Sausages with 20% fat had the highest scores for all sensory attributes. Sausages with 30% fat were very light, yellow, soft and too fatty when grilled, whereas those with 10% fat were dark and very hard after grilling. Storage conditions affected the microflora, pH, weight losses and water activity, but had no effect on composition, colour and sensory attributes. Sausages stored in the ripening room had a rapid increase in lactic acid bacteria count and lower pH than those in cold storage. Storage of traditional sausages for up to 7 days in a ripening room, similar to that used for fermented sausages, is considered beneficial. ?     

The effects of spray-chilling carcasses on the shrinkage and quality of beef

After slaughter, alternate beef carcass sides (left, right) were allocated to an intermittent spray-chilling cooling treatment using water (4 cycles per hour; 60 s/cycle) and conventional air chilling (1-2°C; air velocity 0·5 m/s), or conventional air chilling only. Experiments 1, 2, and 3 (n = 19, 26 and 16 carcasses) involved spray-chilling for 4, 8, 12 h in shrouded sides, whereas experiment 4 (n = 16 carcasses) involved 8 h of spray-chilling in unshrouded sides. At 24 h post-slaughter all sides were ribbed (12 13 th ribs ), and assessed for meat and fat colour. Half the treatment and control sides in each experiment were aged for 6 days, while the boneless ribs and inside rounds were removed from the remaining sides, vacuum packaged and held for 6 days. After 6 days of storage, retail packs of rib steaks and round roasts were prepared and assessed for colour and drip losses over a 4-day period. Spray-chilling significantly reduced carcass shrinkage at 24 h post slaughter in experiments 1-4 by 0·48, 0·69, 0·89 and 1·48%, respectively. After 6 days of cooler storage, spray-chilling significantly reduced carcass shrinkage in experiments 3 and 4 only (0·47 and 0·94%). Weight and drip losses for vacuum packaged ribs and inside rounds were not influenced by spray-chilling over 6 days of storage. Spray-chilling had no influence on rate of pH decline, but reduced loin and round muscle temperatures by 1-2°C. Loin eye muscle colour and shear force were not affected by treatment, but in experiments 2, 3 and 4, fat colour was significantly lighter in spray-chilled compared to conventionally chilled sides. Colour changes and drip losses in retail packs over 4 days for rib steaks and round roasts were not related to spray-chilling. It was concluded that spray-chilling could provide a moderate reduction in carcass shrinkage during cooling without having a detrimental influence on muscle quality.     

Retail colour display life of chilled lamb as affected by processing conditions and storage temperature

This study explored the impact of i) processing conditions (electrical stimulation and pre rigor temperatures), and ii) storage temperature prior to retail display on the colour stability of lamb which had been vacuum-packaged for seven weeks before retail packaging in high-oxygen modified atmosphere (80% O(2)/20% CO(2)). A high pre rigor temperature (42°C) reduced colour stability while differences in colour stability between pre rigor temperatures of 5°C, 15°C and 25°C were limited. It was not affected by electrical stimulation, and did not interact with pre rigor temperature. In contrast, an increase in the storage temperature from the ideal temperature of -1.5°C to 2°C significantly decreased the colour stability of lamb loins. Even one week at 2°C at the end of the storage period had a substantial negative impact on the retail colour display life. The variability in colour increased over time, and the variability increased more for the temperature abuse treatments.