EFFECTS OF SOY PROTEIN AND FREEZING TREATMENTS ON COOKING LOSS AND COMPOSITION OF BEEF PATTIES

All-beef and soy-extended patties were frozen to −18°C in either 24, 48, 72 or 96h and stored at −23, −18 or −7°C for 6, 9, 12, 18 or 24 months. The addition of soy resulted in a substantial reduction in cooking loss for patties cooked from the frozen state with a greater retention of moisture in cooked patties. Freezing reduced cooking loss for soy-extended patties, but increased cooking loss for all-beef patties. Faster freezing (-18°C in 24 h vs. −18°C in 96 h) reduced cooking loss and produced higher moisture values in all-beef patties. Patties stored at –7°C lost more moisture during cooking. Increased frozen storage time had a minimal effect on cooking losses, moisture and fat levels. Where it is essential for frozen patties to sustain minimal cooking losses with maximal moisture in cooked patties, the inclusion of soy protein concentrate, faster freezing, and storage at –18°C or colder are suggested.     

Effect of preslaughter fasting on the characteristics of pig livers

Seventy-seven pigs of about 60 kg liveweight were killed in two experiments, which examined the influence of food deprivation preslaughter on the chemical composition, physical characteristics and eating quality of liver. In the first experiment pigs were fasted for 0, 24 or 48 hr before slaughter. Livers from fasted animals were lighter in weight ( P < 0.001) and contained proportionally slightly more water ( P < 0.001), fat ( P < 0.001) and protein ( P < 0.001) but very much less glycogen ( P < 0.001) and less lactate ( P < 0.001). They had higher pH values ( P < 0.001) both just after slaughter and during storage at 2°C for up to 72 hr. They were darker in colour initially ( P < 0.05) and after chilling for 72 hr ( P < 0.01) partly due to the higher ( P < 0.05) concentrations of haem pigments. The second experiment examined how these differences influenced eating quality. It included a control group killed 2 hr after food withdrawal and groups fasted for 12, 24 and 48 hr. After frying, livers from pigs fasted longer were found to be darker in appearance ( P < 0.001), less tender ( P < 0.001), less juicy ( P < 0.001) and, overall, less acceptable ( P < 0.001). Livers from pigs fasted longer also lost less weight during cooking ( P < 0.05) and were tougher ( P < 0.05) based on instrumental measurements. Livers from half of the pigs in each fasting group were stored at 2°C prior to assessment of eating quality; the remaining livers were frozen at −20°C. Freezing had small deleterious effects on the texture ( P < 0.01) and juiciness ( P < 0.05) of livers but did not influence mean overall acceptability.     

Effect of grass or concentrate feeding systems on lamb carcass and meat quality

Thirty-two male Ile de France lambs were divided into four equal groups at age 37 days. Two groups were allowed to graze a natural pasture in France each at a different growth rate (grass high and grass low groups). The other two groups were raised in stalls and fed concentrates to achieve the same growth rates (stall high and stall low groups, respectively) as from the grass groups. The animals were slaughtered when they attained 35 kg and their carcass and meat quality were evaluated. Animals from the two high growth rate groups were slaughtered at an average age of 129 days while those from the low growth rate groups were slaughtered at 163 days. Carcasses from stall-fed lambs were heavier than those from grass-fed lambs as the digestive tract percentage was higher in the grass lambs. Carcasses from stall lambs had better muscular conformation score (P <0.05) and were fattier than those from grass-fed animals. Subcutaneous fat was more yellow and harder in grass-fed lambs (P <0.05). Meat from grass-fed lambs was darker (P <0.05) in colour (lower L*) than meat from stall animals up to 24 h of display. Meat from stall fed animals was more tender and juicier than meat from grass-fed animals (P <0.01), as judged by a trained panel of assessors. Typical lamb flavour was higher in stall-fed lambs (P <0.01). Meat from grass-fed animals had more pronounced liver flavour (P <0.05) and less fatty flavour (P <0.01) than stall-fed lambs. Overall the difference in meat quality between the two different growth rates was minimal.     

Interrelationships amongst carcass and meat quality characteristics of sheep

The relationships between various carcass and meat quality characteristics of sheep were studied. Relationships were determined by regression, using data obtained from sheep belonging to a wide range of breeds, sex types and slaughter weight (32-62 kg). The chilling rate of the M. longissimus dorsi (LD) post-mortem was negatively correlated with carcass weight (r=-0.42, P<0.01), back fat thickness (r=-0.54, P<0.001) and the cooking loss of the M. infraspinatus (IS) muscle (r=-0.44, P<0.001). Correlation between chilling rate and shear force of the IS muscle was not significant, which was also the case between chilling rate and the cooking loss and shear force of the LD and M. triceps brachii muscles. A positive relationship was observed between total collagen and cooking loss (r=0.34, P<0.05) and between heat-insoluble collagen and cooking loss of the LD muscle (r=0.37, P<0.01). Generally collagen content was positively correlated with lean content and negatively with fat content. Carcass weight was significantly (P<0.001) correlated with intramuscular fat (r=0.61), moisture (r=-0.76), cooking loss (r=-0.49), shear force (r=-0.41) and hue angle (r=-0.41). Shear force was positively associated with cooking loss (r=0.42, P<0.001), but negatively with intramuscular fat content (r=-0.55, P<0.001). Cooking loss was positively correlated with moisture content (r=0.55, P<0.001).     

HEAT-INDUCED CHANGES IN EXTRACTABILITY OF BEEF MUSCLE COLLAGEN

Alterations in the extractability of collagen due to heating of beef muscle were determined and compared with shear and penetrometer values. Strips were heated in a water bath programmed to reproduce the internal temperature curve of a roast in a 163°C oven. Samples were removed at internal temperatures of 58, 67, 75 and 82° C. Data were collected on weight of raw and heated meat, amount of juice expressed during heating, moisture, fat and nitrogen content of the meat and juice, total and extractable collagen, and shear force and depth of penetrometer penetration. Solubilized collagen in the heated meat was determined by extraction with water at 40°C. The amount of soluble collagen increased with increasing internal temperature. Comparison of the solubilized collagen data with shear and penetrometer readings suggested that the changes in the contractile fibers influenced texture more than did the changes in the collagen of these muscles under these heating conditions.     

The variation in pig muscle glycolytic potential during lairage-an in-vivo study

The variations in glycolytic potential (GP, very close to glycogen content) were studied during lairage in pig m. longissimus dorsi using biopsy sampling. Pigs were sampled on arrival at the abattoor and after treatment. Post-mortem measurements including pH(1), pH(u) and FOP(u) were performed on both longissimus dorsi (LD) and biceps femoris (BF) muscles. The animals underwent one of the following treatments: 2 h lairage mixed or unmixed; 24 h lairage mixed or unmixed with access to water only; 24 h lairage mixed or unmixed with access to a sugar solution. A significant depletion in GP occurred during lairage except when pigs were fed liquid sugar. The extent of this depletion was irrespective of lairage duration or mixing. Pigs lairaged 24 h with access to water only exhibited a significantly lower pH(1) in m. BF suggesting a higher propensity to develop PSE meat. Values of pH(u) were low (pH < 5·5), and did not vary significantly between the treatments since muscle GP remained high, despite the depletion induced by lairage. This was attributed to the high level of muscle glycogen characterizing the Hampshire crossbred pigs used in this experiment. These results suggest that interaction between breed and handling procedure may be important regarding meat pH(u).     

Halothane genotype and pork quality. 1. Carcass and meat quality characteristics of three halothane genotypes

The carcass and meat quality characteristics of three halothane genotypes in pigs were evaluated. Sixty crossbred Landrace×Large White pigs (NN=25, Nn=19, nn=16) of ±86 kg live weight were slaughtered, the carcasses chilled for 24 h at 2°C, certain carcass and meat quality traits determined and the shoulder and leg cuts deboned and cut into primal cuts. Dressing percentage of the Nn pigs was higher (P<0.05) than that of the NN and nn pigs. Carcass length was the longest (P<0.05) for the nn pigs. Midline fat measurements as well as measurements at the 2nd-3rd last rib (45 mm from the midline) indicated that the nn pigs had less fat (P<0.05) and a larger eye muscle width (P<0.05), depth (P<0.001) and area (P<0.001) than the NN or Nn pigs. This resulted in the nn pigs having the highest (P<0.05) percentage predicted carcass lean content. Fat, bone and lean yield of the shoulder identified the nn pigs with the least bone (P<0.05) and fat (P<0.001) and the highest lean yield (P<0.05), expressed as a percentage of total shoulder weight. Yield from the legs identified the nn pigs as having the lowest fat (P<0.001) and highest lean (P<0.05), expressed as a percentage of total leg weight. The primal lean cuts (topside, silverside, thickflank and rump) from the legs showed that the nn pigs had the highest values (P<0.05) for lean as a fraction of cold carcass weight. This resulted from the higher weight of these cuts (P<0.05) in the nn pigs. Calculation of bone yield in the legs showed that the femur weights were highest (P<0.05) for the Nn pigs, also when expressed as percentage of leg weight (P<0.05) and as a fraction of cold carcass weight (P<0.05). Comparison of meat quality traits show that the nn pigs had poor quality with regard to pH(45) (P<0.001), pH(24) (P<0.05), drip loss (P<0.001) and reflectance values (P<0.05).     

PRELIMINARY OBSERVATIONS ON EFFECTS OF FAT CONTENT AND DEGREE OF FAT EMULSIFICATION ON THE STRUCTURE-FUNCTIONAL RELATIONSHIP OF CHEDDAR-TYPE CHEESE

Cheddar type cheeses of different fat contents were produced and denoted: full-fat (FFC), 306g/kg; half-fat (HFC), 174 g/kg; and low fat (LFC, 13 g/kg). Full-fat Cheddar cheese (FFCH) was also prepared from milk which had been homogenized at first and second stage pressures of 25 and 5 MPa, respectively. The cheeses were held at 4C for 30 days and at 7C for the remainder of the 190-day ripening period. Reducing the fat level from 174 to 13 g/kg resulted in decreases in contents of moisture in nonfat substance and pH 4.6 soluble N as a percentage of total N (pH4.6SN), and increases in the contents of moisture, protein and intact casein. Homogenization of cheesemilk resulted in a slight increase in moisture content and an increase in pH4.6SN. Confocal laser scanning microscopy revealed that the extent of fat globule clumping and coalescence in both the unheated and heated (to 95C) cheeses decreased with homogenization of the cheesemilk and with fat reduction. Homogenization of the cheesemilk and reducing the fat content of the cheese resulted in a decrease in the flowability and stretchability of the melted cheese. Dynamic measurement of the viscoelastic changes on heating the cheese from 20 to 90C showed that reduction of fat content resulted in a decrease in the magnitude of the phase angle, δ, at temperatures >50C. At temperatures<∼60C, the storage modulus, G', increased on reducing the fat content from 306–174 g/kg to 13 g/kg. Homogenization resulted in a marked decrease in δ at temperatures>45–50C, with δ_max typically decreasing from ∼65–70° in the FFC to ∼35° in the FFCH.     

The behaviour and blood profile of bulls which produce dark cutting meat

Thirty British Friesian bulls (12 months old), in groups of 6 or 12, were mixed with unfamiliar animals for 16 h preslaughter. Before and during mixing, blood samples were collected and behaviour was monitored. The ultimate pH (pHu) was measured in the m. Longissimus dorsi (LD) 24 h after slaughter. Thirteen carcasses were dark cutting (DC, pHu≧6) and 17 were normal (pHu<6). DC carcasses came from animals which exhibited over twice the total number of agonistic interactions (P<0.001) and showed more dominant behaviour (P<0.001) than animals producing normal carcasses. There was no difference in the blood profile of DC and normal bulls before mixing. However, DC bulls had higher levels of creatine phosphokinase (P<0.001), free fatty acids (P<0.001) and β-hydroxybutyrate (P<0.01) in the blood samples collected after mixing. Overall, pHu was correlated with total activity (r=0.71, P<0.001) and dominance scores (r=0.70, P<0.001). The conclusion is that the cause of DC in mixed groups of bulls is primarily behavioural. Muscle glycogen stores are depleted when blood-borne metabolites are inadequate to fuel the intense or prolonged muscular activity associated with agonistic behaviour.     

EFFECTS OF TENTH RIB FAT THICKNESS ON MOISTURE, LIPID AND CHOLESTEROL CONTENT OF SUBCUTANEOUS, INTERMUSCULAR AND INTERNAL FATS

Samples from subcutaneous, intermuscular and internal fat depots of 30 crossbred pig carcasses with tenth rib fat thickness ranging from 1.5 to 4.3 cm were used to evaluate the relationships of backfat thickness and fat depot composition (moisture, lipid and cholesterol contents). Moisture and cholesterol were highest and lipid content was lowest in intermuscular fat while cholesterol was lowest (P < 0.05) in subcutaneous fat when compared to the other fat depots. Significant (P < 0.01) linear effects of tenth rib fat depth on moisture and lipid contents of all fat depots were observed. Linear effects (P < 0.05) of tenth rib fat thickness on cholesterol content of subcutaneous and internal fat depots were observed on both a wet and dry bases. However, the linear effect (P < 0.05) of tenth rib fat depth on cholesterol content in the intermuscular fat depot was observed only on a dry basis. When the three fat depots were combined, increased tenth rib fat depth resulted in decreased moisture and cholesterol contents on a dry basis while percentage lipid increased (P < 0.05).     

Formula Optimization of a Low-fat Food System Containing Whey Protein Isolate- Xanthan Gum Complexes as Fat Replacer

Whey protein isolate‐xanthan gum complexes (WPXC) have the potential to significantly reduce fat use in various products. However, their stability and functionality have not been extensively studied, particularly in neutral pH products. The objective of this study was to evaluate WPXC as a fat replacer in cake frostings and sandwich cookie fillings with reduced‐fat content (160 or 80 g/kg fat). Response surface methodology was used to analyze the effect of WPXC on the viscosity and textural response attributes of samples and to optimize the low‐fat formulations. It was found that WPXC had a positive effect (P > 0.001), providing acceptable viscosity and texture attributes to the low‐fat samples. A significant moisture‐WPXC interaction (P > 0.001) revealed that the optimum moisture‐WPXC ratio varied, depending on the targeted texture. This ratio was about 8:1 for cake frostings and about 5:1 for sandwich cookie fillings. Optimal formulations were found, and samples meeting the desirability specifications presented textural and melting profiles similar to those of the control products. However, for the production of sandwich cookie fillings, the use of other ingredients (for example humectants and emulsifiers) must be considered to maintain a low water activity (A_w) and prevent moisture migration to the cookie shell.     

PREPARATION AND PROPERTIES OF LOW TEMPERATURE EXTRACTED ANIMAL PROTEIN CONCENTRATES

Protein concentrate prepared by extraction of fish, deboned poultry by-products, pork back fat, and beef scraps with isopropyl alcohol (IPA) had good functional properties when the extraction was carried out at 45° C and below. Salt soluble protein extracts from the low temperature extracted protein concentrates had the capacity to emulsify oil and water when tested in a model system. The emulsions gelled when heated. When added to meat batters, the protein concentrate showed the capacity to add to the water- and oil-binding capacity of the system. The solvent requirement of the low temperature extraction process using IPA was determined from the solubility curves of fat in mixtures of water and IPA. The higher the fat content the more solvent was required; for the same fat content, an increase in the moisture content resulted in an increase in the solvent requirement.     

The sorption isotherms of maize meal

Summary. The equilibrium moisture contents of the three main grades of South African maize meal over a range of 1.4-90.7% relative humidity (r.h.) were determined at 30°C. It was found that the fat content of maize meal influenced the moisture content at equilibrium, i.e. the higher the fat content, the lower the equilibrium moisture content for a specific relative humidity. Both desorption and adsorption isotherms for maize meal were found to be sigmoid and the effects of hysteresis were encountered in all cases. On prolonged storage mould growth occurred in maize meals held in an atmosphere of 84% r.h. and higher. From the sorption isotherms the maximum r.h. at which maize meal could be stored without the danger of mould contamination could be predicted.     

Rheological, texture and sensory properties of low-fat mayonnaise with different fat mimetics

Application of whey protein isolate and low-methoxy pectin-based fat mimetics in mayonnaise was studied. Fat was partially substituted by different fat mimetics at levels of 50%, respectively, which the fat mimetics were referred to as PFM1 (microparticulate pectin gel), PFM2 (pectin weak-gel), and PFM3 (microparticulated combination of WPI and pectin). The full fat (Ff) (100% oil) mayonnaise without fat mimetic was used as a control experiment. Physicochemical, rheological, texture analysis, and sensory evaluation of the Ff and low fat (Lf) mayonnaises were performed. The results indicated that all Lf mayonnaises had significantly lower energy content, but higher water content than their Ff counterpart. In terms of texture, the formulation with pectin weak-gel as fat mimetic showed similar texture values as those of the Ff sample. Both Ff and Lf mayonnaises exhibited thixothopic shear thinning behaviour under steady shear tests and were rheologically classified as weak gels under small amplitude oscillatory shear tests. Sensory evaluation demonstrated that mayonnaises substituted with low-methoxy pectin were acceptable. This study shows good potential for pectin weak-gel and microparticulated pectin gel to be used as a fat mimetic in mayonnaise.     

INSTRUMENTAL AND SENSORY MEASUREMENT OF BEEF PATTY AND SAUSAGE TEXTURE

Beef sausages and beef patties of different texture were produced by varying the fat content in the raw mix over the range 5–30%. Batter shear stress and strain increased linearly with increased fat level (P<0.09 and 0.001, respectively). Although batter shear stress was not related to sensory scores, shear strain was directly related to moistness and inversely related to grittiness scores (P<0.05). Batter sensory moistness increased and firmness and grittiness deceased linearly with fat content (P<0.001). Changes in fat content did not affect the peak force of cooked patties, and there were poor correlations between patty peak force and sensory scores. Patty juiciness and softness increased and patty cohesiveness and chewiness decreased with fat content (P<0.001). Batter cook yield increased and patty cook yield decreased with increasing fat level (P<0.001). Sensory scores, using trained panelists, were more sensitive to the effect of fat content on patty and sausage texture than instrumental measurements.     

EXTRUSION PROCESSING OF TRITICALE

Whole triticale kernels were extruded using a Brabender Plasti-corder extruder with 3/4-in. rifled barrel and 1:1 flight depth ratio screw. Samples were extruded at initial moisture contents of 15% and 20% using barrel temperatures of 350 °F, 400 °F and 450 °F through nozzle openings of 1/8 in. and 1/16 in. The products were measured for pH, final moisture content, color, trypsin hydrolysis, torque during extrusion, and texture and flavor as evaluated by a taste panel. From the results it was concluded that an acceptable product could be produced at 20% initial moisture using either the small nozzle and operating at 350 °F or the larger nozzle and operating at 400 °F.     

Effect of pre-fry drying of oil uptake and distribution in potato crisp manufacture

Microwave, hot air (40 and 105°C) and freeze drying were used to remove varying amounts of moisture from 1.3 mm thick potato slices. The partially dried slices were then fried in oil at 165°C either for a constant 2 min or a variable frying time based on the amount of pre-drying. The microwave and hot air treatments resulted in a reduction in the final oil content, which was related to the degree of pre-fry drying. Freeze drying resulted in an increase in the oil content, again related to the initial moisture reduction. Oil distribution at the microscopic and macroscopic level was determined and found to be related to the initial moisture distribution in the slice. It is suggested that pre-fry drying may be a more successful point of influence than post-fry treatment in the manufacture of a'lower fat crisp'.     

Response surface optimization and characteristics of rambutan (Nephelium lappaceum L.) kernel fat by hexane extraction

Response surface methodology (RSM) was used to study the effect of moisture content (1.59-18.41 g/100 g), extraction time (2.3-10.7 h) and particle size (0.09-2.11 mm) on the fat yield from rambutan kernels using hexane extraction. The physical and chemical characteristics of rambutan fat were also determined. The optimum conditions obtained from response surface analysis was 4.99 g/100 g moisture, 1.05 mm particle size and 9.2 h extraction time. Under these optimum conditions, the maximum fat yield was 37.35 g/100 g. The extracted fat was a white solid at room temperature. The physical and chemical characteristics of the extracted fat compared well with those of conventional fats. The high level of arachidic acid (∼ 34.3 g/100 g fat) and low iodine value in rambutan kernel fat permits the use of the fat, especially where oxidation may be a concern, without its being subjected to hydrogenation.     

EFFECTS OF FAT TRIM ON THE COMPOSITION OF BEEF RETAIL CUTS – 2. FAT AND MOISTURE CONTENT OF THE SEPARABLE LEAN

Thirty beef carcass sides varying in USDA quality and yield grade were fabricated into various steaks and roasts. The retail cuts were assigned serially to the following treatments: (A) raw, trimmed to 0.6 cm external fat; (B) trimmed to 0.6 cm external fat, cooked; (C) trimmed to 0.0 cm external fat, cooked. The 0.0 cm and 0.6 cm, cooked treatments were prepared by appropriate cookery methods, and the separable lean and separable fat were analyzed for chemical fat and moisture content. Regression analyses were used to predict values for the percentage chemical fat and moisture content at each treatment as influenced by marbling and USDA yield grade. Retail cuts that were braised had the lowest (P < 0.05) predicted moisture content of the separable lean, while roasted cuts had the highest (P< 0.05) predicted percentage moisture content of the lean. Trimming retail cuts to 0.0 cm external fat before cooking decreased the predicted percentage chemical fat of the lean as compared to retail cuts trimmed to 0.6 cm before cooking.     

The effects of castration, preslaughter stress and zeranol implants on beef: Part 2-Cooking properties and flavor of loin steaks from bovine males

A total of 144 male crossbred calves were allocated to four castration or implant treatments (unimplanted bulls; unimplanted steers; bulls implanted with zeranol at 100 days of age and reimplanted at intervals of 69, 93 and 56 days thereafter; bulls implanted with zeranol at 168 days of age and reimplanted at intervals of 93 and 56 days thereafter) and two preslaughter shipping treatments (minimum preslaughter stress, with cattle shipped and slaughtered within 4 h of leaving the feedlot pen; normal preslaughter stress, with cattle mixed, trucked 160 km, and slaughtered up to 24 h after leaving the feedlot pen). These cattle were slaughtered and striploin steaks were removed after 6 days of post-mortem aging. Evaluations of these steaks were then conducted using both an experienced laboratory taste panel and a highly trained professional flavor profile panel. Results indicated that: (1) steaks from bulls had higher cooking losses than their counterparts from steers, when minimum preslaughter stress was applied; and required longer cooking times under both preslaughter handling treatments; (2) steaks from unimplanted bulls had greater cooking losses and required longer cooking times than their counterparts from implanted bulls under normal preslaughter stress, but not under minimum preslaughter stress; (3) higher proportions of bull steaks than steer steaks contained inappropriate flavor character notes, under both minimum and normal levels of preslaughter stress; (4) both castration and preslaughter handling affected the intensity and order of appearance of specific flavor character notes; (5) the level of preslaughter stress significantly influenced the detection of specific flavor character notes in steaks from both bulls and steers; (6) steaks from steers under minimum preslaughter stress were rated significantly higher in flavor amplitude than their counterparts from bulls when under normal preslaughter stress, and steaks from steers under minimum preslaughter stress received higher flavor desirability scores than steaks from bulls under both minimum and normal preslaughter stress; (7) zeranol implants influenced the appearance and the order of appearance of specific flavor character notes under both minimum and normal levels of preslaughter stress; (8) both zeranol implants and the length of time animals were implanted appeared to increase the intensity of certain inappropriate character notes, and to decrease the intensity of certain appropriate character notes; (9) steaks from implanted bulls received lower flavor amplitude ratings than their counterparts from unimplanted bulls under normal preslaughter stress, but not under minimum preslaughter stress; (10) the level of preslaughter stress influenced both the appearance and order of appearance of specific flavor character notes in both implanted and unimplanted bull steaks; (11) the intensities of certain flavor character notes were influenced by differences in the level of preslaughter stress in both implanted and unimplanted bull steaks, and higher levels usually resulted in inappropriate character notes being more intense; (12) steaks from bulls in both implant groups received lower flavor amplitude ratings when normal preslaughter stress was applied, clearly indicating the deleterious effect of the combination of zeranol implants and normal preslaughter stress on bull beef flavor; and (13) the deleterious effect of the combination of zeranol implants and normal preslaughter stress on bull beef flavor could not be explaind on the basis of greater production of 'dark cutting' beef.