The retention and recovery of amino acids from pork longissimus muscle following cooking to either 60 °C or 75 °C

Samples of pork longissimus muscle (n = 16) cooked to either 60 °C or 75 °C in a water bath for 90 min were assessed for amino acid composition. Recovery of protein in the cooked meat plus the cooking juice was > 93% and was slightly higher at 60 °C (P = 0.031), but retention in the meat was only 89% and 82% for the lower and higher temperatures (P < 0.0001). Individual amino acids varied in recovery and retention with retention being particularly low for taurine and histidine. The balance of indispensable amino acids was less than ideal, with leucine and valine being the limiting amino acids by about 30% for both raw and cooked pork. Cooking had no detrimental effect on amino acid balance. Some examples of small effects of genotype and sex on amino acid composition of pork were shown.     

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).     

Effect of cooking on protein oxidation in n-3 polyunsaturated fatty acids enriched beef. Implication on nutritional quality

The effect of cooking on protein oxidation was investigated in M. Longissimus thoracis of eight Normand cows fed during a 100 days finishing period with two different diets: a conventional diet (concentrate/straw based diet) and a diet rich in n-3 polyunsaturated fatty acids (PUFAs), obtained by addition to the conventional diet of a mixture of extruded linseed and extruded rapeseed. After 11 days storage, at 4 °C under vacuum, meat was cooked by applying jets of steam. Three experimental heating treatments were tested: two with constant surface temperatures of 65 and 96 °C during 300 s, and one with a continuous increasing surface temperature up to 207 °C. Protein oxidation was evaluated by the measurement of carbonyls, aromatic amino acids, and free thiols content. The formation of Schiff bases due to the reaction of proteins with aldehydic products of the lipid oxidation was also evaluated. Cooking resulted in a significant increase of carbonyl groups and Schiff bases as well as a significant degradation of tyrosine and tryptophan. Nevertheless, enrichment of the animal diet in n-3 PUFAs had minor effects on protein oxidation induced by cooking which are unlikely to be of nutritional significance.     

Strategy to inactivate Clostridium perfringens spores in meat products

The current study aimed to develop an inactivation strategy for Clostridium perfringens spores in meat through a combination of spore activation at low pressure (100–200 MPa, 7 min) and elevated temperature (80 °C, 10 min); spore germination at high temperatures (55, 60 or 65 °C); and inactivation of germinated spores with elevated temperatures (80 and 90 °C, 10 and 20 min) and high pressure (586 MPa, at 23 and 73 °C, 10 min). Low pressures (100–200 MPa) were insufficient to efficiently activate C. perfringens spores for germination. However, C. perfringens spores were efficiently activated with elevated temperature (80 °C, 10 min), and germinated at temperatures lethal for vegetative cells (≥55 °C) when incubated for 60 min with a mixture of l-asparagine and KCl (AK) in phosphate buffer (pH 7) and in poultry meat. Inactivation of spores (∼4 decimal reduction) in meat by elevated temperatures (80–90 °C for 20 min) required a long germination period (55 °C for 60 min). However, similar inactivation level was reached with shorter germination period (55 °C for 15 min) when spore contaminated-meat was treated with pressure-assisted thermal processing (568 MPa, 73 °C, 10 min). Therefore, the most efficient strategy to inactivate C. perfringens spores in poultry meat containing 50 mM AK consisted: (i) a primary heat treatment (80 °C, 10 min) to pasteurize and denature the meat proteins and to activate C. perfringens spores for germination; (ii) cooling of the product to 55 °C in about 20 min and further incubation at 55 °C for about 15 min for spore germination; and (iii) inactivation of germinated spores by pressure-assisted thermal processing (586 MPa at 73 °C for 10 min). Collectively, this study demonstrates the feasibility of an alternative and novel strategy to inactivate C. perfringens spores in meat products formulated with germinants specific for C. perfringens.     

Temperature- and pH-dependent effect of lactate on in vitro redox stability of red meat myoglobins

Our objective was to evaluate the influence of lactate on in vitro redox stability and thermostability of beef, horse, pork, and sheep myoglobins. Lactate (200 mM) had no effect (P > 0.05) on redox stability at physiological (pH 7.4, 37 °C) and meat (pH 5.6, 4 °C) conditions. However, lactate increased (P < 0.05) metmyoglobin formation at a condition simulating stressed live skeletal muscle (pH 6.5, 37 °C). The redox stability of myoglobins at stressed live skeletal muscle and meat conditions was species–specific (P < 0.05). Myoglobin thermostability at 71 °C was lower (P < 0.05) in the presence of lactate compared with controls and was influenced (P < 0.05) by species. The results of the present study indicate that the effects of lactate on myoglobin are temperature and pH dependent. The observed lack of influence of lactate on myoglobin redox stability at meat condition suggests that the color stability of lactate-enhanced fresh meat is not due to direct interactions between the ingredient and the heme protein.     

Effect of different temperature–time combinations on physicochemical,microbiological, textural and structural features of sous-vide cooked lamb loins

Lamb loins were subjected to sous-vide cooking at different combinations of temperature (60, 70, and 80 °C) and time (6, 12, and 24 h). Different physicochemical, histological and structural parameters were studied. Increasing cooking temperatures led to higher weight losses and lower moisture contents, whereas the effect of cooking time on these variables was limited. Samples cooked at 60 °C showed the highest lightness and redness, while increasing cooking temperature and cooking time produced higher yellowness values. Most textural variables in a texture profile analysis showed a marked interaction between cooking temperature and time. Samples cooked for 24 h showed significantly lower values for most of the studied textural parameters for all the temperatures considered. Connective tissue granulation at 60 °C and gelation at 70 °C were observed in the SEM micrographs. The sous-vide cooking of lamb loins dramatically reduced microbial population even with the less intense heat treatment studied (60 °C–6 h).     

Changes in actomyosin dissociation and endogenous enzyme activities during heating and their relationship with duck meat tenderness

The objectives of this study, were to examine the relationship between duck meat tenderness, actomyosin dissociation and endogenous enzyme activities when heating the duck breast muscle, to the internal temperature of 30, 40, 50, 60, 70, 80, 90 °C. The shear force increased in the temperature range of 30–50 °C and 70–90 °C and decreased from 50 to 70 °C, which was negatively related with liberated actin (P < 0.05). The activity of cathepsin B and L was stable while heating the meat to a temperature below 50 °C, then it decreased rapidly with temperature increase. The calpain activity kept decreasing with the temperature increase. There was no significant change in the cathepsin D activity below 70 °C but it declined rapidly thereafter, and its activity was strongly correlated with actomyosin dissociation (P < 0.05). The results suggest that actomyosin dissociation and cathepsin D, could contribute to the tenderness of duck meat during the cooking process.     

Occurrence of heterocyclic amines in cooked meat products

Heterocyclic amines (HCAs), potent mutagens and a risk factor for human cancers, are produced in meats cooked at high temperature. The aim of this study was to determine the HCA content in cooked meat products (beef, chicken, pork, fish) prepared by various cooking methods (pan frying, oven broiling, and oven baking at 170 to 230 °C) that are preferred by U.S. meat consumers. The primary HCAs in these samples were PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine) (1.49-10.89 ng/g), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline) (not detected-4.0 ng/g), and DiMeIQx (2-amino-3,4,8-trimethyl-imidazo [4,5-f]quinoxaline) (not detected-3.57 ng/g). Type and content of HCAs in cooked meat samples were highly dependent on cooking conditions. The total HCA content in well-done meat was 3.5 times higher than that of medium-rare meat. Fried pork (13.91 ng/g) had higher levels of total HCAs than fried beef (8.92 ng/g) and fried chicken (7.00 ng/g). Among the samples, fried bacon contained the highest total HCA content (17.59 ng/g).     

Effects of Trolox and ascorbic acid on the riboflavin photosensitised oxidation of aromatic amino acids

The effects of 0, 100, 250, 500, 750 or 1000 ppm Trolox and ascorbic acid on the singlet oxygen oxidation of aromatic amino acids viz. phenylalanine, tryptophan, tyrosine in the presence of 25 ppm riboflavin were determined by measuring depleted headspace oxygen by gas chromatography and aromatic amino acid content by high performance liquid chromatography. The coefficients of variations (CVs) for headspace oxygen analysis and HPLC analysis of aromatic amino acids were 1.4% and 4.7%, respectively. Samples were stored under light (1000 lux) at 30 °C for 10 h. Both Trolox and ascorbic acid acted as antioxidants. As the concentration of Trolox and ascorbic increased from 0 to 1000 ppm, the head space oxygen depletion increased. This was due to the oxidation of Trolox and ascorbic acid along with amino acids in the presence of riboflavin. High performance liquid chromatography analysis of the samples clearly indicated that both Trolox and ascorbic acid minimised the degradation of phenylalanine, tryptophan, tyrosine significantly (p < 0.05), but did not prevent their oxidation completely. Trolox acted as a better antioxidant than ascorbic acid in protecting phenylalanine, tryptophan and tyrosine. Type-I mechanism was mainly responsible for riboflavin photosensitised degradation of aromatic amino acids.     

Effect of cooking method on carnosine and its homologues, pentosidine and thiobarbituric acid-reactive substance contents in beef and turkey meat

Commercial samples of beef and turkey meat were prepared by commonly used cooking methods with standard cooking times: (1) broiled at 200 °C for 10 min, (2) broiled at a medium temperature (140 °C) for 10 min, (3) cooked by microwave (MW) for 3 min and then grilled (MW/grill) for 7 min, (4) cooked in a domestic microwave oven for 10 min, and (5) boiled in water for 10 min. The raw and cooked meats were then analysed to determine the carnosine, anserine, homocarnosine, pentosidine, and thiobarbituric acid-reactive substance (TBARS) contents. It was observed that boiling beef caused a loss of approximately 50% of the carnosine, probably because of the high water solubility of carnosine and its homologues; cooking by microwave caused a medium loss of the anti-oxidants of approximately 20%; cooking by MW/grill led to a reduction in carnosine of approximately 10%. As far as the anserine and homocarnosine contents were concerned, a greater loss was observed for the boiling method (approximately 70%) while, for the other cooking methods, the value ranged from 30% to 70%. The data oscillate more for the turkey meat: the minimum carnosine decrease was observed in the cases of MW/grill and broiling at high temperature (25%). Analogously, the anserine and homocarnosine contents decreased slightly in the case of MW/grill and broiling at a high temperature (2-7%) and by 10-30% in the other cases. No analysed meat sample showed any traces of pentosidine above the instrumental determination limits. The cooked beef showed an increased TBARS value compared to the raw meat, and the highest values were found when the beef was broiled at a high temperature, cooked by microwave or boiled in water. The TBARS value of the turkey meat decreased for all the cooking methods in comparison to the TBARS value of the fresh meat.     

Influence of meat exudates on the quality characteristics of fresh and freeze-thawed pork

The influence of the accumulated exudates released from pork loin of itself on the quality characteristics of fresh and freeze-thawed pork during cold storage was investigated. Pork loins were divided into four groups (fresh pork with exudates, fresh pork without exudates, freeze-thawed pork with exudates and freeze-thawed pork without exudates) and stored at 1.0 °C for 7 days. Exudate amount increased due to freeze-thawing and with storage, and most quality traits such as drip loss, cooking loss, tenderness, lightness, redness, and moisture content were affected by freeze-thawing (p < 0.05). Freeze–thaw increased drip loss but decreased moisture content, cooking loss, tenderness, lightness and redness of meat (p < 0.05). Microbial growth was solely affected by exudate removal and the removal of initial exudates decreased microbial growth (p < 0.05). Exudates were positively correlated with total protein content and total plate count but negatively correlated with pH and cooking loss. Therefore, removing meat exudates and avoiding freeze can slow down the quality deterioration of pork during cold storage.     

Colour and sarcoplasmic protein evaluation of pork following water bath and ohmic cooking

The objective of this study was to investigate the effects of ohmic (OH) and waterbath (WB) cooking on colour attributes and sarcoplasmic changes of porcine longissimus dorsi muscle at the same endpoint temperatures (EPTs; range 10 °C–80 °C). The OH treatment was carried out at 10 V cm^− 1, and the WB temperature at 85 °C. The colour parameters, deoxymyoglobin% (DeoMb) and metmyoglobin% (MetMb) of the OH-cooked meat were significantly lower (P < 0.05) than those obtained by WB-cooking at the same EPTs (range 60 °C–80 °C). SDS-PAGE analysis showed that the meat treated with WB-cooking had a lower sarcoplasmic protein solubility (5.97 mg/g vs.14.89 mg/g, P < 0.05) and fainter protein bands than that of OH-cooking thus, indicating paler colour, and lower water-holding capacity especially in WB-cooked meat at EPTs above 40 °C. Strong correlations among lightness, browness, metmyoglobin% and soluble proteins were observed in meat following OH-cooking.     

Influence of type of muscles on nutritional value of foal meat

The effect of type of muscle on nutritional characteristic (fatty acid profile, amino acid content, cholesterol and major and minor mineral) of foal meat was investigated. Six muscles: longissimus dorsi (LD), semimembranosus (SM), semitendinosus (ST), biceps femoris (BF), triceps brachii (TB) and psoas major & minor (PM) from twelve foals slaughtered at 15 months from an extensive production system in freedom regimen were extracted for this study. Horse meat is characterized by low fat, low cholesterol content, rich in iron and in vitamin B. Statistical analysis showed that the cholesterol content did not show significant differences (P > 0.05) among muscle with mean value range between 0.62 and 0.57 mg/100 g. Most fatty acid presented significant differences (P < 0.05) with respect to the type of muscle. The obtained results showed that except for the polyunsaturated linoleic acid, the highest contents of fatty acids were found in the hindquarter muscles. Regarding amino acid profile, significant differences (P < 0.05) were observed among muscles and our results indicated that, 100 g of foal meat covered from 80.6 to 86.7% for the daily requirement for an adult man weighing 70 kg for essential amino acids for ST and LD muscles, respectively. Statistical analysis showed significant differences (P = 0.050) for the EAA (essential amino acids) index, which was highest for TB muscle, followed by BF and SM muscles, while the lowest values were reported by ST muscle. Finally, foal meat seems to be a very good nutritional source of major and minor minerals. The higher nutritional value of foal meat will be of great importance in the promotion of this meat.     

Decomposition kinetics of umami component during meat cooking

We developed a kinetic model for the decomposition reaction of inosine monophosphate (IMP), which is a umami component, and obtained kinetic parameters based on the amount of IMP in an isothermal experiment. The amount of remaining IMP decreased with heating time, and its reduction rate was the highest at 40 °C. We assumed that the activity of IMP decomposition enzyme is temperature-dependent above 40 °C, and constant below 40 °C. The predicted results using this kinetic model are in good agreement with the experimental ones. Unsteady-state three-dimensional heat transfer analysis of meat during sous-vide cooking was conducted, and the distribution of remaining IMP was predicted. By the end of sous-vide cooking, the ratio of the amount of IMP in the interior of the meat decreased, whereas at the surface region, it was almost the same as the initial value, because the surface temperature reached the inactivation temperature immediately.     

Aroma development in high pressure treated beef and chicken meat compared to raw and heat treated

Chicken breast and beef muscle were treated at 400 and 600 MPa for 15 min at 5 °C and compared to raw meat and a heated sample (100 °C for 15 min). Vacuum-packed beef meat with a smaller fraction of unsaturated fatty acids showed better oxidative stability during 14 days of cold storage, as shown by a low steady-state level of hydroperoxide values, than vacuum-packed chicken meat. Accordingly, the critical pressures of 400 MPa and 600 MPa for chicken breast and beef sirloin, respectively, were established. Volatiles released after opening of the meat bags or during storage of open meat bags, simulating consumer behaviour, were measured under conditions mimicking eating. Quantitative and olfactory analysis of pressurised meat gave a total of 46 flavour volatiles, mainly alcohols (11), aldehydes (15), and ketones (11), but all in low abundance after 14 days of storage. Overall, beef meat contained less volatiles and in lower abundance (factor of 5) compared to chicken meat. The most important odour active volatiles (GC-O) were well below the detection thresholds necessary to impart a perceivable off-flavour. Lipid oxidation was significantly accelerated during 24 h of cold storage in both cooked chicken and beef when exposed to oxygen, while the pressurised and oxygen-exposed chicken and beef meat remained stable. Pressure treatment of beef and chicken did not induce severe changes of their raw aroma profiles.     

Non-volatile taste active compounds in the meat of Chinese mitten crab (Eriocheir sinensis)

The non-volatile taste active compounds, including soluble sugars, succinic acid, free amino acids and flavour 5′-nucleotides in the meat of Chinese mitten crab (Eriocheir sinensis) were analyzed, and their taste impacts were evaluated by taste active values (TAVs) and equivalent umami concentration (EUC) methods. The total free amino acid content of crab meat was 20.9 mg/g. Arginine, glycine and alanine were the major free amino acids, accounting for more than 70% of the total free amino acids. 5′-Adenosine monophosphate (AMP) was the main flavour 5′-nucleotide (75.3 mg/100 g), followed by 5′-inosine monophosphate (IMP) (34.4 mg/100 g) and 5′-guanosine monophosphate (GMP) (2.3 mg/100 g). Arginine, glycine, alanine, glutamic acid, IMP and AMP were of high TAV (greater than one), and they had strong taste impacts on the crab meat flavour. Glycine and alanine contributed to the major sweet taste, while glutamic acid, IMP and AMP contributed to the strong umami taste. As the TAVs of soluble sugar, succinic acid and bitter free amino acids were lower than one, thus those compounds are likely to have insignificant impact on the taste of the crab meat. The EUC was 4.2 g MSG/100 g crab meat, which meant that the umami taste of the crab meat was very intense.     

Effect of precooking time and drying temperature on the physico-chemical characteristics and in-vitro carbohydrate digestibility of taro flour

Achu is a thick porridge obtained by cooking and pounding taro (Colocasia esculenta) corms and cormels in a mortar. This study was undertaken with the objective of producing precooked taro flour that can be used in the preparation of achu. Taro slices were precooked to times of 0, 20, 45 and 90 min and dried in an air convection oven at varying temperatures of 50, 60, 70 or 80 °C before milling into flour which was then analysed for its water absorption capacity (WAC), water solubility index, emulsion activity and stability, bulk density, foam capacity and least gelation concentration (LGC). Achu made from the flours were equally analysed for their relative penetrometric index, bulk density and colour. The results showed that precooking induced significant (P<0.05) decrease in foam capacity, penetrometric index, and increase in LGC, emulsion stability and WAC. The drying temperature also induces significant reduction in emulsion capacity and stability, penetrometric index, and increase in LGC, WAC. Long precooking time (>45 min) and drying temperature (>60 °C) induced significant reduction of the in-vitro carbohydrate digestibility of taro achu.     

Effect of cooking methods on fatty acids,conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat

The effect of boiling, microwaving and grilling on the composition and nutritional quality of beef intramuscular fat from cattle fed with two diets was investigated. Longissimus lumborum muscle from 15 Alentejano young bulls fed on concentrate or pasture was analyzed. Cooking losses and, consequently, total lipids, increased directly with the cooking time and internal temperature reached by meat (microwaving > boiling > grilling). The major changes in fatty acid composition, which implicated 16 out of 34 fatty acids, resulted in higher percentages in cooked beef of SFA and MUFA and lower proportions of PUFA, relative to raw meat, while conjugated linoleic acid (CLA) isomers revealed a great stability to thermal processes. Heating decreased the PUFA/SFA ratio of meat but did not change its n−6/n−3 index. Thermal procedures induced only slight oxidative changes in meat immediately after treatment but hardly affected the true retention values of its individual fatty acids (72–168%), including CLA isomers (81–128%).     

Effect of salt,kinnow and pomegranate fruit by-product powders on color and oxidative stability of raw ground goat meat during refrigerated storage

Effects of salt, kinnow and pomegranate fruit by-product powders on color and oxidative stability of raw ground goat meat stored at 4 ± 1 °C was evaluated. Five treatments evaluated include: control (only meat), MS (meat + 2% salt), KRP (meat + 2% salt + 2% kinnow rind powder), PRP (meat + 2% salt + 2% pomegranate rind powder) and PSP (meat + 2% salt + 2% pomegranate seed powder). Addition of salt resulted in reduction of redness scores. Lightness increased in control and unchanged in others during storage. Redness scores declined and yellowness showed inconsistent changes during storage. Thiobarbituric acid reactive substances (TBARS) values were higher (P < 0.05) in MS followed by control and KRP samples compared to PRP and PSP samples throughout storage. The PSP treated samples showed lowest TBARS values than others. Percent reduction of TBARS values was highest in PSP (443%) followed by PRP (227%) and KRP (123%). Salt accelerated the TBARS formation and by-products of kinnow and pomegranate fruits counteracted this effect. The overall antioxidant effect was in the order of PSP > PRP > KRP > control > MS. Therefore, these powders have potential to be used as natural antioxidants to minimize the auto-oxidation and salt induced lipid oxidation in raw ground goat meat.