Effect of temperature of comminution on the stability and eating quality of 'English' sausages

Sausages were prepared after equilibrating the ingredients to temperatures in the range 2° to 37°C. Following comminution for 6·5 min the temperatures of the batters ranged from 15 to 33°C and their pHs from 6·25 to 6·48. During storage at -20°C sausages prepared from the high temperature batters lost more weight than those made from batters prepared at the lower temperatures (0·3% compared to 1·2%). Increasing temperature of comminution led to increased cooking losses, softening in texture and darkening in colour. However, even at the highest temperatures complete emulsion breakdown did not occur as cooling losses were still only about 20%. Subjective assessment indicated that at least up to comminution temperatures of 25°C the sausages were acceptable. At temperatures above 30°C off-flavours developed. It is suggested that comminuted meat products can be manufactured in situations where refrigeration is not available, provided a preservation system can be devised to inhibit microbial and chemical spoilage.     

Determination of aromatic amino acid content in cooked meat by derivative spectrophotometry: Implications for nutritional quality of meat

The technique of second derivative spectrophotometry was used to determine the level and the heat stability of the three aromatic amino acids (tryptophan, tyrosine and phenylalanine) in bovine meat (M. Longissimus thoraci). This paper presents a method which measures the second derivative absorbance values at a wavelength specifically assigned to each aromatic amino acid with corrections for the interference from other amino acids at the same wavelength. Three cooking temperatures were tested in this study (60, 100 and 140 °C). Due to important cooking losses, results differ slightly according to the method of calculation (level expressed by gram of wet meat or by gram of proteins). Whatever the calculation method, heating at 60 °C had little effect on aromatic acid levels while higher temperatures had a dramatic effect on aromatic amino acids stability. The stability of the three aromatic amino acids during cooking decreased in the order tryptophan > phenylalanine > tyrosine.     

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.     

Effect of Gradual Heating and Fat/Oil Type on Fat Stability,Texture, Color,and Microstructure of Meat Batters

The effects of endpoint cooking temperature (40, 50, 60, 70, 80, and 90 °C) on emulsion stability, texture, color, and microstructure of meat batters prepared with different fats/oils were studied. Canola oil treatments showed the highest cooking loss whereas hydrogenated palm oil provided the most stable meat batters. Rendered beef fat was less stable than regular beef fat. Increasing endpoint cooking temperatures resulted in a progressive reduction of water holding capacity in all treatments. As temperature was raised, meat batters showed higher hardness and cohesiveness values, but no appreciable changes in cohesiveness above 60 °C. Canola and hydrogenated palm oil treatments showed the highest hardness and chewiness values. Lightness (L^*) values of all meat batters increased significantly with increasing temperature from 40 to 60 or 70 °C; no major changes observed above 70 °C. Light microscopy revealed no substantial changes in the microstructure of all the stable meat batters cooked to between 50 and 70 °C. Heating to 90 °C changed the microstructure in all meat batters except the hydrogenated palm oil treatments, which still showed nonround fat particles and a less aggregated protein matrix.     

Oxidative Stability of Batter-Breaded Restructured Nuggets Processed from Prerigor Pork

Restructured pork slices made with either prerigor or postrigor meat, with or without 1.5% of defatted glandless cottonseed flour (GCF). were batter-breaded with or without GCF in predust and batter-mix: Prerigor products had less cooking losses than postrigor products; GCF in the meat or coating reduced cooking losses. Prefried prerigor products were more susceptible to lipid oxidation and warmed-over flavor development than prefried postrigor products. GCF in the meat or coating markedly reduced the oxidative deterioration in nuggets stored at 4°C or ?20°C regardless of the rigor state of meat used for restructuring. Little lipid oxidation occurred in vacuum-packaged raw nuggets stored at ?20°C.     

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).     

The spoilage characteristics of Brochothrix thermosphacta and two psychrotolerant Enterobacteriacae in vacuum packed lamb and the comparison between high and low pH cuts

The spoilage potential of Brochothrix thermosphacta, Serratia proteamaculans and Rahnella aquatilis was investigated in vacuum packaged high (5.9 to 6.4) and low (5.4 to 5.8) pH lamb. Vacuum packaged fore shank (m. extensor carpi radialis) and striploins (m. longissimus dorsi) (n = 306) inoculated with ~ 100 CFU of individual bacteria were stored for twelve weeks at temperatures − 1.5, 0, 2 and 7 °C. Spoilage characteristics and bacterial numbers were recorded and analysed in comparison to un-inoculated control samples. All three bacterial species were shown to grow in vacuum packaged lamb of pH values between 5.4 and 6.4, when stored at chilled temperatures (− 1.5 to 7 °C) for up to 84 days. B. thermosphacta and S. proteamaculans caused spoilage to the meat under these conditions whilst R. aquatilis spoiled high pH meat at 7 °C. These results go against previous beef models stipulating that Brochothrix and Enterobacteriacae species cannot grow on or cause spoilage of low pH meat in the absence of oxygen.     

Biochemical activities of Brochothrix thermosphacta

Activities of 19 hydrolases were estimated in cell suspensions of 40 Brochothrix thermosphacta strains, isolated from meat and meat products packaged under various conditions, by using API ZYM® test. These strains produced: acidic phosphatase, esterase C4, esterase/lipase C8, α-chymotrypsin, leucine arylamidase, β-glucosidase and α-glucosidase. The predominating biotype produced only the first four of the listed enzymes. The extracellular lipolytic activity for bromo-chloro-indolyl-caprylate was detected only in culture broth supernatants of 4 strains thereby indicating that esterase/lipase C8 is cell-bound. 13 of the strains displayed proteolytic activity for albumin at 4 °C (0.31-2.07 U) while 9 strains showed this activity at 25 °C (0.11-1.21 U). Only 4 strains digested albumin at both temperatures. Thus the meat spoilage potential of B. thermosphacta strains results not only from digestion of carbohydrates but also from their proteolytic activity.     

Effects of protein level and fat/oil on emulsion stability,texture, microstructure and color of meat batters

Beef meat batters formulated with increasing protein level (10–15%) and containing 25% beef fat were compared to batters prepared with 25% canola oil. Emulsion stability of the canola oil treatments was higher (less separation during cooking) at the 10–13% protein level compared to the beef fat treatments. However, above 13% protein this was reversed and the canola oil treatments showed high fat and liquid separation, which did not occur at all in the beef fat treatments. This indicates differences in stabilization of fat versus oil in such meat emulsions. Hardness of the cooked meat batters showed significantly (P < 0.05) higher values when the protein level was raised, and was higher in canola oil than in beef fat meat emulsions at similar protein levels. Products’ chewiness were higher in the canola oil treatments compared to the beef fat emulsions. Lightness decreased and redness increased in canola oil batters as the protein level was raised. The micrographs revealed the formation of larger fat globules in the beef fat emulsions compared to the canola oil meat emulsions. The canola oil treatment with 14% protein started to show fat globule coalescence, which could be related to the reduced emulsion stability.     

Changed dynamics in myofibrillar protein aggregation as a consequence of heating time and temperature

The kinetics of protein aggregation induced by cooking were investigated in pig M. Longissimus dorsi. The 4 day aged muscles were cooked either in water or under dry heat conditions for 30 min. Four temperatures from 50 to 100 °C were tested for the “in water” cooking mode and an additional temperature of 140 °C was tested in the dry condition. Raw and cooked meat specimens were ground in a KCl solution. After delipidation of the meat extract, protein aggregation was evaluated with a laser granulometer (Sysmex FPIA-3000) which enabled reliable and reproducible characterization of particle number, size, and shape distribution using automated imaging techniques. The cooking mode (dry/“in water”) did not affect the granulometry measurements. But, increasing cooking time and temperature affected the number, the size, and the shape of particles. An important decrease in particle number was observed during cooking in parallel with a reduction in particle size and a change in circularity. From these data a model with intermediary fibrillar aggregates and final amorphous aggregates was proposed.     

Protein-Protein Interaction and Fat and Water Binding in Comminuted Flesh Products

The possible role of protein-protein interaction in influencing the water and fat binding capacity of comminuted flesh products was studied. Water and fat binding by meat batters diminish when temperatures exceed 16°C during comminution. The loss of binding capacity was partially reversible, and cooling the batters to 0°C by addition of dry ice and rechopping allowed a partial recovery of the fat and water binding capacity. A cause and effect relationship between the change in fat and water binding by meat batters on chopping and protein-protein interaction in actomyosin solutions was demonstrated. Protein-protein interaction results in molecular aggregation and when measured as an increase in light scattering absorbance at 320 nm by a protein solution, the reaction was shown to be reversible between 4 and 30°C. When actomyosin solutions extracted from meat samples showed reduced protein-protein interaction in the temperature range used in chopping, the batters made from these meats also showed the least loss in fat and water binding capacity with prolonged chopping. Controlling temperatures during chopping within a range where protein-protein interaction in actomyosin solutions was found to be minimal, allowed prolonged chopping without loss in fat and water binding.     

Spoilage characteristics of Brochothrix thermosphacta and campestris in chilled vacuum packaged lamb,and their detection and identification by real time PCR

The spoilage potential of Brochothrix campestris and Brochothrix thermosphacta was investigated in vacuum-packed lamb. Striploins (n = 338) were inoculated and stored for twelve weeks at temperatures − 1.5, 0, 2 and 7 °C. Growth around 5–6 log₁₀ CFU/cm² was recorded after six weeks at 0, 2 and 7 °C, and ~ 3 log₁₀ CFU/cm² after nine weeks at − 1.5 °C. B. campestris was shown to cause spoilage by nine weeks at temperatures above 0 °C by the presence of green drip and unacceptable odours. Molecular based assays for the detection and differentiation of B. thermosphacta and B. campestris were developed and validated. A TaqMan assay was designed to target a unique single-nucleotide polymorphism in the Brochothrix 16 s rRNA gene with a sensitivity of < 7 CFU per reaction. Secondly a specific PCR was designed for B. campestris targeting the structural genes, brcA and brcB. These testing regimes offer a rapid and cost effective method for the detection and screening of Brochothrix species in meat products and processing environments.     

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.     

Monitoring quality loss of pasteurized skim milk using visible and short wavelength near-infrared spectroscopy and multivariate analysis

Visible and short wavelength near-infrared diffuse reflectance spectroscopy (600 to 1,100 nm) was evaluated as a technique for detecting and monitoring spoilage of pasteurized skim milk at 3 storage temperatures (6, 21, and 37°C) over 3 to 30 h (control, t = 0 h; n = 3). Spectra, total aerobic plate count, and pH were obtained, with a total of 60 spectra acquired per sample. Multivariate statistical procedures, including principal component analysis, soft independent modeling of class analogy, and partial least squares calibration models were developed for predicting the degree of milk spoilage. Principal component analysis showed apparent clustering and segregation of milk samples that were stored at different time intervals. Milk samples that were stored for 30 h or less at different temperatures were noticeably separated from control and distinctly clustered. Soft independent modeling of class analogy analysis could correctly classify 88 to 93% of spectra of incubated samples from control at 30 h. A partial least squares model with 5 latent variables correlating spectral features with bacterial counts and pH yielded a correlation coefficient (R = 0.99 and 0.99) and a standard error of prediction (0.34 log₁₀ cfu/mL and 0.031 pH unit), respectively. It may be feasible to use short wavelength near-infrared spectroscopy to detect and monitor milk spoilage rapidly and noninvasively by correlating changes in spectral features with the level of bacterial proliferation and milk spoilage.     

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 inulin, β-Glucan and their mixtures on emulsion stability,color and textural parameters of cooked meat batters

The effects of fat level (20.0, 12.5 and 5.0%), Inulin (gel-IG, and powder-IP) and β-Glucan (βG) on emulsion stability, color, textural characteristics and microstructure of cooked meat batters were investigated. Reducing fat to 5.0% increased cooking loss and decreased emulsion stability, lightness, hardness and fracturability of cooked emulsions. Inulin, βG, and their mixtures were used as fat replacers in low fat formulations. Adding IP provided better emulsion stability compared to IG, which had no significant effect on stability. IP also produced harder (27–34 N) low fat products with a high fracturability (26–29 N). On the contrary, emulsions containing IG resulted in creamy and softer characteristics. The results were supported by light micrographs, which indicated that appropriate addition of IG and βG mixtures (3%-IG & 0.3%-βG, 6%-IG & 0.6%-βG) could compensate for some of the changes brought about by fat reduction, and maintained several of the textural characteristics of the product as well as reducing cook loss.     

Effects of batters containing different protein types on the quality of deep-fat-fried chicken nuggets

The effects of soy protein isolate (SPI), whey protein isolate (WPI) and egg albumen (EA) on the quality of deep-fat-fried chicken nuggets were studied. Batter without protein addition was used as a control. Batter pickup and moisture content, oil content, texture, porosity and colour of the nuggets were determined for 3, 6, 9 and 12 min of frying at 180 °C. Additionally, the rheological properties of batters were studied. SPI (3%) provided the highest apparent viscosity and coating pickup. All the batters showed shear-thinning behaviour except EA-added batter. Addition of different proteins to the batter formulation decreased the oil content of the final product. EA reduced the oil content of chicken nuggets significantly but yielded softer products. WPI (3%) was found to be the most effective ingredient on improving quality parameters of deep-fat-fried chicken nuggets. WPI (3%) added batters provided the hardest and crunchiest product with the darkest colour and also significantly reduced the oil content of the fried nuggets.     

Effect of hot-boned pork on the quality of hurdle treated pork sausages during ambient temperature (37 ± 1 °C) storage

The study was aimed at evaluating the suitability of hot-boned pork and pork fat for processing shelf-stable pork sausages using hurdle technology and the different hurdles incorporated were low pH, low water activity, dipping in potassium sorbate solution, vacuum-packaging and post-package reheating. Emulsion stability and cooking yield did not Izatnagardiffer significantly among hot- and cold-processed sausages. Despite the same emulsion pH, the sausages from hot-boned pork had significantly higher fat content. Colour and texture profiles of pork sausages were significantly (P < 0.05) influenced by hot processing. During storage at ambient temperature (37 ± 1 °C), various physico-chemical characteristics, namely pH, TBARS and tyrosine values, of hot- and cold-processed sausages, did not differ. Hot-processing markedly increased the total plate counts of the sausages, but a significant difference was absent for anaerobic counts between treatments at any particular storage interval. Cold-processed sausages had the higher lactobacillus counts throughout the storage period. Sensory evaluation revealed that hurdle-treated pork sausages from hot-boned pork were equally suitable as those from cold-boned pork up to day 6 at ambient temperature.     

Reduction of spoilage of chilled vacuum-packed lamb by psychrotolerant clostridia

Methods for the reduction of spoilage, of lamb, by psychrotolerant clostridia were investigated including exposure to air, hot and cold water spray washing and tyndallisation. Initially vegetative cells of psychrotolerant clostridia associated with spoilage of chilled vacuum-packed meat were exposed to aerobic cooked meat medium at room temperature (21 °C) to determine how long they remained viable. Survival of strains varied from 2 h to 3 days. Vegetative cells of Clostridium estertheticum subsp. estertheticum survived 7 days at 10 °C with little reduction in viable numbers. This ruled out exposure to air as a practical method for reducing spoilage. Trials were also carried out on chilled vacuum-packed lamb inoculated with spores of Cl. estertheticum subsp. estertheticum. The time until inoculated packs reached the loss of vacuum stage varied from 38 to 53 days. Hot and cold water washing extended the shelf life by 12 to 13 days in comparison to untreated packs.