PHYSICAL AND SENSORY CHARACTERISTICS OF COMMERCIALLY AVAILABLE FRANKFURTERS

This study's objective was to identify the range of physical and sensory properties of commercially available frankfurters. Twenty-five types of frankfurters were evaluated by a six-member sensory panel and subjected to Instron texture profiling. A wide range of sensory and textural characteristics was observed for acceptable frankfurters. Salty flavor and juiciness were correlated with fat content, but salt and fat content were inversely correlated. Negative correlations occurred between fat content and Instron fracturability and compression; fat content decreased resistance to force from mechanical stress. Firmness was positively correlated with Warner-Bratzler shear force. The development of an accurate regression equation to predict sensory hardness was not possible with this data set.     

PREDICTION OF THE SENSORY TEXTURE OF A YAM THICK PASTE (AMALA) USING INSTRUMENTAL AND PHYSICOCHEMICAL PARAMETERS

Amala is a traditional thick paste consumed in West Africa (Nigeria, Bénin, Togo). It is prepared from blanched dried yam flour and has a particular texture. The texture attributes of amala pastes obtained from market and prepared in laboratory were sensorily evaluated. Both compression and extrusion tests were done from which maxima force and slope were calculated. The physical (particle size), starch characteristics and functional properties (solubility, swelling power [Sp], viscosity) of yam flours were also determined to establish a predictive model for amala sensory texture attributes. The main amala sensory attributes were stickiness, firmness and smoothness. Stickiness and firmness could be assessed by uniaxial extrusion test: These attributes were highly correlated with the maximum extrusion slope (r = ?0.60 and r = 0.53, respectively). Stickiness was associated with yam flour Sp, which in turn was related to gelatinization temperature and enthalpy changes. In addition, soluble matter and soluble amylose were found to be indicators of amala sensory stickiness. No clear relationships were observed between sensory firmness and yam flour physicochemical characteristics or functional properties.     

STRESS RELAXATION DURING FORCE-COMPRESSION STUDIES ON FOODS WITH THE INSTRON UNIVERSAL TESTING MACHINE AND ITS IMPLICATIONS

Abstract. The time required to apply the force in force-compression studies with the Instron Universal Testing Machine is long enough for short time relaxation processes to operate, possibly via intermolecular attraction forces. A theoretical analysis is presented whereby stress relaxation can be determined for the stress-strain region in which the Boltzmann Superposition Principle is valid. Application of the analysis is demonstrated using force-compression data obtained on cheeses of different textural properties. After correction for stress relaxation, the calculated and experimental relaxation modulus-time curves agree satisfactorily over a much longer time interval for Edam cheese than for Cheddar cheese. The latter cheese becomes non-linear at much smaller compressions than does Edam cheese, possibly by the propagation of cracks through the sample during compression. Firmness is one of the textural properties evaluated during the first bite of mastication. Since the time associated with the first bite is longer than that required for application of force during the first compression of a sample with the Instron in this study, it is possible that the sensory evaluation of firmness is made under conditions involving stress relaxation.     

SENSORY AND MECHANICAL ATTRIBUTES OF GEL TEXTURE

Eighteen experienced judges evaluated the texture of gels varying in gelatin concentration (22-45 g/L) in terms of firmness by oral and manual shear and compression, cohesiveness, and extent of breakdown in the mouth. Manual compression and biting with the front teeth discriminated well across gel concentrations. All sensory measures except extent of breakdown increased with gelatin concentration. Instron (IUTM) measurements showed that increasing gelatin concentration resulted in an increase in maximum force and force/deformation, but had little effect on deformation at yield and rupture or in elasticity and cohesiveness. Results from mechanical measurements varied with the type of force applied (compression, shear or puncture), the loading rate (50 or 200 mm/min), and the extent of deformation attained (40–90%). The highest discrimination across gel concentrations was achieved with shear force at a rate of 200 mm/min and at greater deformations. Sensory responses correlated most highly with the following IUTM measurements: (1) Compression forces at yield and at deformations of 70 and 85% at the higher crosshead speed; (2) Compression forces below the yield point at the lower crosshead speed; and (3) Shear forces measured at maximum deformation (90%) at 200 mm/min.     

UNIAXIAL COMPRESSION OF UF-FETA CHEESE RELATED TO SENSORY TEXTURE ANALYSIS

Rheological characteristics of seven Feta cheeses with different textures and produced from ultrafiltered milk (UF-Feta cheeses) were evaluated by uniaxial compression and sensory texture analysis. The effect of uniaxial deformation rate (50–2500 mm/min) on four rheological parameters: Stress at fracture s?_f), Hencky strain at fracture (?_f), deformability modulus (E) and work to fracture (W_f) was examined. Three Principal Components (PC) described 76, 16 and 4% respectively, of the variation in the uniaxial compression data set (4 parameters at 12 deformation rates). Statistically α_f, E and W_f described the same type of information in the data set. Six sensory texture attributes of the UF-Feta cheeses were evaluated by a sensory texture panel: nonoral firmness, nonoral brittleness, nonoral spreadability, oral crumbliness, oral firmness and oral stickiness. One PC described 93% of the variation in the sensory texture data and grouped the sensory variables into two negatively correlated groups: nonoral firmness nonoral brittleness, oral firmness and oral crumbliness versus nonoral spreadability and oral stickiness. Correlations and Partial Least Squares regression (PLS) between instrumental and sensory texture variables showed that nonoral and oral firmness were the nonoral and oral sensory variables best predicted from instrumental measurements. α_f, E and W_f were all able to predict nonoral and oral firmness. Of the instrumental parameters, α_f generally gave the best correlation to nonoral firmness at all deformation rates. Above a deformation rate of 50 mm/min correlations between α_f and nonoral firmness were almost independent of deformation rate, and at any deformation rate correlations between α_f and oral firmness     

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).     

Influence of dietary oils and protein level on pork quality. 2. Effects on properties of fat and processing characteristics of bacon and frankfurter-style sausages

Palm kernel oil (PKO) and palm oil (PO) are used in tropical countries as cheaper substitutes for conventional feed sources such as soya bean oil (SBO) but little is known about their effects on meat quality. This study, therefore, evaluated the effects of these three dietary oils on the fatty acid composition (FA) of pork fat and the qualities of belly bacon and frankfurter sausage. The 3×2 factorial design also included high and low dietary protein. Total cooking loss, water loss and fat losses were determined in frankfurter sausages at chopping temperatures from 2 to 24°C. PKO resulted in a poor P:S ratio (0.34) and a relatively hard fat (slip point 32.8°C), but resulted in bacon with a higher tensile cohesive force and more high quality slices, judged subjectively. PO had a fatty acid composition closer to the SBO control, a better P:S ratio than PKO (0.48) and softer fat. There was a trend for total cooking losses and fat losses to be higher in PKO compared with PO and SBO at all chopping temperatures, suggesting that the firmest, most saturated fat (PKO) was least suitable for frankfurter production. The low protein diet increased the concentration of saturated fatty acids and increased fat firmness but its effect on fatty acid composition and other properties were less marked than those of oil type.     

SENSORY TEXTURE PROFILE, GRAIN PHYSICO-CHEMICAL CHARACTERISTICS AND INSTRUMENTAL MEASUREMENTS OF COOKED RICE

Three samples of raw-milled rice, and 4 differently parboiled rices were used to study and to relate sensory perception to instrumental measurements. Variance analysis showed that some physico-chemical characteristics indicated great differences among rice samples: thickness of cooked grain, length/width ratio, water uptake, elastic recovery, white core rate and amylose and protein contents. The most discerning sensory attributes were: elasticity, stickiness, pastiness, mealiness, length of grain, firmness, crunchiness, time in mouth, brittle texture and juiciness. The correlation circle of the principal component analysis (PCA) showed high correlation between some sensory characteristics and instrumental measurements. Melting texture, surface moistness, juiciness, were positively correlated with water uptake (r = 0.70, 0.61, 0.71). Granular texture, crunchiness, brittleness and mealiness were significantly affected by white core presence (r = 0.81, 0.74, 0.86, 0.83). Elasticity was dependent upon elastic recovery and firmness measured by the Viscoelastograph, but not linearly. Length of cooked grain was correlated with the length/width ratio of raw grain (r = 0.83). Pastiness, compactness, stickiness were slightly influenced by the thickness of raw grain (r = 0.81, 0.67, 0.72). To a weaker extent, the sensory firmness was associated with the firmness measured by extrusion force using an Ottawa cell (r = 0.58). PCA showed greatdifferences in texture between rices. Two of the parboiled rices were very elastic, another was firm, granular, crunchy and mealy. The remaining two, cooked longer, were moister and more melting. Among the 3 samples of raw-milled rices, differences in grain length feeling and melting-granular-brittle characteristics. were distinguished.     

Compositional and instrumental firmness variations within fresh pork bellies

Fresh pork bellies (n=24) were cut into 15 sections to measure the intra-belly variation in compositional and mechanical firmness characteristics. Length and width of each belly was measured before the belly was divided into 3 rows (D = dorsal; C = central; and V = ventral) and 5 columns (labeled 1, 2, 3, 4, and 5 from cranial to caudal), resulting in 15 belly sections of equal dimensions. The belly section with the greatest compression value was D-1, whereas the lowest compression value was found in the V-4 section (column×row, P<0.001). Conversely, the greatest and least puncture values were observed in the C-2 and V-5 locations, respectively (column×row, P=0.016). The D-3 section had the lowest proportion of lean and the greatest proportion of fat, but the greatest lean and lowest fat percentages were found in the V-1 and C-4 sections, respectively (column×row, P<0.001). The greatest proportions of saturated fatty acids (SFA) were found in the V-4 and V-5, and the lowest proportions of SFA were in D-1 (column×row, P<0.001). Moreover, C-4 and V-1 had the greatest percentages of monounsaturated fatty acids (MUFA), whereas the lowest MUFA content was observed in D-1, D-2, and D-3 (column×row, P<0.001). The D row (columns 1, 2, 3, and 5) also had the greatest proportion of polyunsaturated fatty acids (PUFA), but the lowest proportions of PUFA were located in C-4, V-4, and V-5 (column×row, P<0.001). Consequently, the iodine value was greatest in D-1 and lowest in V-4, V-5, and C-5 (column×row, P<0.001). It is apparent from these results that there is an obvious fatty acid composition gradient within bellies, which results in considerable intra-belly variation in composition and firmness.     

Relationships between dietary fatty acid composition and either melting point or fatty acid profile of adipose tissue in broilers

Data on the fatty acid composition of the diet and that of the adipose tissue in broilers were collected from the literature. The linear regression between the dietary and the adipose tissue unsaturated to saturated fatty acids ratio (U/S ratio) was calculated because the U/S ratio of adipose tissue fat determines its melting point, which is an indicator of the consistency of poultry fat. For 54 data points from three different experiments, the linear correlation coefficient of the relationship between dietary and adipose tissue U/S ratio was 0.77. The regression equation for linoleic acid in adipose tissue as a function of dietary linoleic acid was calculated. The linoleic acid content of adipose tissue was expressed as weight percentage of total fatty acids. Intake was expressed as either weight percentage of total fatty acids or as energy percentage of total dietary metabolizable energy. The linear correlation coefficients were 0.68 and 0.78 as based on 116 or 91 data points from 15 or 12 different experiments. Significant correlations were also found for α-linolenic acid. The linoleic acid content of adipose tissue was found to be correlated (r=0.87) for 25 data points with that in consumable broiler meat, which may affect serum cholesterol concentrations in humans. With the help of the regression formulas presented it may be possible to formulate broiler diets in relation to consumer health and product quality.     

THE RELATIONSHIP OF FATTY ACID COMPOSITION AND CARCASS CHARACTERISTICS TO MEAT FLAVOR IN LAMB1

The relationship of 20 fatty acids and carcass quality characteristics to meat flavor in lamb was studied. Subcutaneous fat samples obtained from 64 lamb carcasses were analyzed for fatty acid composition. A taste panel evaluated flavor of a ground lean-fat mixture of meat. Flavor was most highly correlated with amounts of fatty acids 18:1 and 18:3 (r =—0.33 and r = 0.33, respectively). The remaining fatty acids were not associated with flavor. Quality grade, carcass weight, fat softness, maturity and fat color were not associated with lamb flavor. Carcass softness was not associated with quality grades. Greater quantities of 17:0, 18:1, and 18:2 were associated with increased carcass fatness.     

A Puncture Testing Method for Monitoring Solid Substrate Fermentation

Meitauza, an indigenous Chinese food made from fermented okara (soymilk residue), was used as a model system for monitoring solid substrate fermentations. The Instron Universal Testing machine and Chatillon hand operated force gauge were used to measure the force to penetrate meitauza as an estimation of mycelial binding. Increased firmness during fermentation was caused by fungal growth and not by water loss and surface crusting. Puncture force readings with the Instron were werll correlated (r = 0.86) with Chatillon measurements. The results of this study indicate that textural measurements using puncture force may have valuable application in monitoring the degree of mycelial growth or fermentation in a solid substrate.     

EVALUATION OF GOUDA CHEESE FIRMNESS BY COMPRESSION TESTS

Cheese maturity, test temperature, crosshead speed, sample shape, sample height and surface area influence the force-compression behaviour of Gouda cheese in an Instron Universal Testing Machine. Introducing mineral oil or Emery paper between the sample's surfaces and the compression plates affects the shape of the compressed samples. Cine-film records indicate that deformation is barrel-shaped (convex) with Emery paper and under normal test conditions, and concave with mineral oil. In the first two test situations friction prevents the cheese surfaces from spreading to the same extent during sample compression as when using mineral oil. Compression as modified by friction may be the principal factor associated with the subjective evaluation of firmness by squeezing samples between the fingers. Firmness evaluation by chewing involves still higher percent compressions which, in Instron tests, lead to sample breakdown and crack propagation.     

The influence of diets containing either conventional corn, conventional corn with choice white grease, high oil corn, or high oil high oleic corn on belly/bacon quality

The objectives of this study were to evaluate diets possessing different fatty acid profiles (as influenced by corn type) with regard to fatty acid profile and firmness of pork bellies. Crossbred barrows (n=196) were fed one of four corn-based diets consisting of conventional corn (CONV), CONV with choice white grease (CWG), high oil corn (HOC), or high oleic, high oil corn (HOHOC). Following 98 days on test, two animals representing the average pen weight (118 kg) were selected for harvest (n=56). A 50-g fat sample was removed from each belly for fatty acid profile analysis. Lateral and vertical flex tests were performed to determine belly firmness. Bellies were pumped and cooked according to a commercial protocol. Total saturated fatty acids increased (P<0.001) and total unsaturated fatty acids decreased (P<0.05) when CWG was added to the CONV diet or when HOC or HOHOC were substituted for CONV corn. Pigs fed CONV corn had firmer bellies, while those fed HOC were softer. No differences were observed across treatment for percentage pump retention, smokehouse yield, or slicing yield (P>0.05). Based on the results of this study, corn type influences fatty acid profile, and belly firmness, but does not affect pump retention, or slicing yields.     

Effects of fatty acid supplements on milk yield and energy balance of lactating dairy cows

Saturated and unsaturated fatty acid supplements (FS) were evaluated for effects on yield of milk and milk components, concentration of milk components including milk fatty acid profile, and energy balance. Eight ruminally and duodenally cannulated cows and 8 noncannulated cows were used in a replicated 4 × 4 Latin square design experiment with 21-d periods. Treatments were control and a linear substitution of 2.5% fatty acids from saturated FS (SAT; prilled, hydrogenated free fatty acids) for partially unsaturated FS (UNS; calcium soaps of long-chain fatty acids). The SAT treatment did not change milk fat concentration, but UNS linearly decreased milk fat in cannulated cows and tended to decrease milk fat in noncannulated cows compared with control. Milk fat depression with UNS corresponded to increased concentrations of trans-10, cis-12 conjugated linoleic acid and trans C18:1 fatty acids in milk. Milk fat profile was similar for SAT and control, but UNS decreased concentration of short- and medium-chain FA. Digestible energy intake tended to decrease linearly with increasing unsaturated FS in cannulated and noncannulated cows. Increasing unsaturated FS linearly increased empty body weight and net energy gain in cannulated cows, whereas increasing saturated FS linearly increased plasma insulin. Efficiency of conversion of digestible energy to milk tended to decrease linearly with increasing unsaturated FS for cannulated cows only. Addition of SAT provided little benefit to production and energy balance, whereas UNS decreased energy intake and milk energy yield.     

INFLUENCE OF PARBOILING AND FREEZING CONDITIONS ON TEXTURAL PROPERTIES OF CALIFORNIA COOKED RICE

The textural properties of thawed samples of cooked parboiled, long (Cal Belle) and short (S201) grain rice varieties were evaluated using an Instron Universal Testing Instrument (Model 1122). In general, the parboiling treatments resulted in a significant increase of hardness but a significant decrease in stickiness of both long and short grain cooked rice when freezing conditions were pooled. Freezing increased hardness and decreased stickiness of long grain cooked parboiled rice significantly regardless of parboiling conditions, however, it did not decrease the stickiness of short grain cooked parboiled rice significantly. The long grain rice was harder and less sticky than the short grain rice when cooked regardless of treatments used. Hardness was negatively correlated with stickiness indexes (r =?0.819, P < 0.001).     

Turgor Pressure Effects on Textural Behavior of Honeydew Melon

ABSTRACT: Melon samples were equilibrated with solutions of increasing mannitol concentration in the range 0.00 to 0.80 M for the purpose of evaluating turgor pressure through volume change measurement. Melon compression and relaxation behaviors were evaluated with an Instron Testing machine, and structural characteristics were observed through microscopy. Immersion in mannitol solutions affected tissue firmness, reducing its value in all studied cases. After plasmolysis and plasmotypsis, samples became less elastic and more viscous, and firmness reduced more than 50%. Textural parameters obtained and microscopy results indicated that, in general, fracture might be associated with cell-wall integrity, and residual relaxation force might be associated with tissue turgor pressure.     

Texture and mechanical properties of prok backfat

A puncture test for measuring the firmness of backfat is described for use in studies of the effects of changes in animal production, and meat processing on the quality of fatty tissue. The operating and recording conditions were chosen from sensory deformation characteristics used in firmness evaluation when pressing fat with the index finger. On average, assessors exerted aaaximum force of about 30 N and caused a deformation of 4 mm in 2 sec and the best predictor of firmness was the maximum deformation they applied. Mechanical properties of the fats were determined by stress relaxation and the modulus 2.5 sec after compression was about 80 × 10⁴ for hard and < 3 × 10⁴ N/m² for soft fat at 3°C and the logarithm of the modulus was linearly related to the subjective firmness rating.
In the puncture test, the forces required to drive a stainless steel punch (3.5 mm in diameter) 2.5 or 4.0 mm into backfat at 3°C at 2 mm/sec correlated well (r > 0.8) with firmness rating and five replicate determinations using the punch proved more discriminating than a panel of four assessors. A combination of the forces required on inner and outer layers of fat accounted for 93% of variation in firmness assessments.     

LIQUID HOLDING CAPACITY AND INSTRUMENTAL AND SENSORY TEXTURE PROPERTIES OF HERRING (CLUPEA HARENGUS L.) RELATED TO BIOLOGICAL AND CHEMICAL PARAMETERS

Instrumental texture measurements done on raw herring fillets only partly describe the sensory texture of marinated herring fillets. Sensory texture parameters of marinated fillets were related to instrumental texture measurements of raw fillets by three different data analysis approaches. Uniaxial compression measurements were used as a single parameter, as compression curves or fitted to polynomials. Data from all three methods were related to sensory firmness (r = 0.310–0.366, P < 0.05). Elasticity could be predicted from the maximum compression force (r = 0.181, P < 0.05). The compression curve contained information correlating with all the measured sensory texture parameters (r = 0.102–0.310, P < 0.05), while the fitted polynomials, in addition to firmness, could predict fatty mouthfeel (r = 0.201, P < 0.05). The most information about the sensory texture was obtained from the compression curves. This study shows that the texture properties of herring are highly intercorrelated and can be regarded as a multivariate complex of parameters. The liquid holding capacity (LHC), defined as the moisture held after a low centrifuge speed expressible moisture measurement, and the texture of herring are influenced by a variety of factors, e.g., spawning time of year, gonad maturity, body size, age and lipid content (P < 0.05). Increases in body weight, age and lipid content are intercorrelated and result in marinated fillets being more firm, elastic, juicy and fatty. Decreases in these factors will give marinated fillets that are perceived to be gritty and with low intensities of firmness, elasticity, juiciness and fatty mouthfeel.