Rheological changes during thermal processing of low-fat meat emulsions formulated with different texture-modifying ingredients

The rheological behaviour of high-fat (22%) and low-fat (8%) meat emulsions during thermal processing in the presence (3%) of various texture-modifying non-meat ingredients, namely maltodextrin, starch, wheat flour, egg white and apple fibre, was analysed. Rheological properties of emulsions were assessed using non-destructive measurements (thermal scanning rigidity monitor, TSRM). The lower the fat content, the lower were the rigidity values of meat emulsions throughout the temperature range studied. Emulsions made with maltodextrin proved less rigid. Addition of starch and egg white favoured the formation of more rigid structures in low-fat meat emulsions at temperatures over 55 °C. Low-fat meat batters containing wheat flour and apple fibre exhibited the highest rigidity values over the given temperature range. The presence of wheat flour caused variations in the modulus of rigidity at all stages of the thermal gelation process, very similar to those observed in high-fat emulsions.     

Effects of levels of fat,surimi from sardine (Sardina pilchardus) and heat processing on thermal gelation of meat batters

The object of the study was to analyse the Theological behaviour occurring during heat-induced gelation (measured by thermal scanning rigidity monitor) of meat batters containing various proportions of fat (48, 106, 147 and 208 g kg^?1) and sardine surimi (0, 100, 200 and 300 g kg^?1 fish protein added with respect to total protein present) and subjected to different heat treatments (A, heating from 14 to 76?C at a rate of 1?C min^?1; B, gradual temperature increase at a rate of 1?C min^?1 up to 40?C, maintenance at this temperature for 30 min, then heating from 40 to 76?C at 1?C min^?1; C, samples kept at 4?C for 20 h and then heated in the same way as process A). The results indicate that differences in levels of fat content significantly affect the gelation patterns of pork batters, gels being stiffer the higher the fat content and the lower the water content. A highly significant correlation (r = 0.78, P < 0.01) has been established between fat content and maximum values of G, which occur at the final experimental temperature of 76?C. In contrast, in general, neither addition of surimi nor variation in the heat treatment applied has any major effect on the gelation process in the system as formulated.     

Characteristics of low-fat meat emulsion systems with pork fat replaced by vegetable oils and rice bran fiber

The effects of vegetable oils prepared from olive, corn, soybean, canola, or grape seed, and rice bran fiber on the composition and rheological properties of meat batters were studied. Pork fat at 30% in the control was partially replaced by one of the vegetable oils at 10% in addition to reducing the pork fat to 10%. The chemical composition, cooking characteristics, texture properties, and viscosity of low-fat meat batters were analyzed. The moisture, protein, ash content, uncooked and cooked pH values, b^∗-value, hardness, cohesiveness, gumminess, chewiness, and viscosity of meat batters with vegetable oil and rice bran fiber were all higher than the control. In addition, batters supplemented with vegetable oil and rice bran fiber had lower cooking loss and better emulsion stability. Low-fat meat batters with reduced pork fat content (10%) and 10% vegetable oil plus rice bran fiber had improved characteristics relative to the regular fat control.     

Effects of different levels of fat on rheological changes and microstructure of meat batters during heat processing

Summary The effect of differences in fat content (5.3% and 20.8%) on the rheological characteristics and microstructure of meat batters in the course of heating was studied. Rheological properties were assessed using nondestructive measurements (thermal scanning rigidity monitor) and structural failure (penetration test) analyses. Microstructure was studied by scanning electron microscopy (SEM). The influence of fat content on the modulus of rigidity (G) only became evident as gel structures began to form, giving higher G values for meat batters the higher the fat content of the sample. As the temperature was raised in the product (between 40 and 70° C), penetration stress and elasticity increased. The work of penetration, on the other hand, increased between 40 and 60° C, remaining steady at higher temperatures. Analysis of the results on the basis of different treatments indicates that an increase in fat content significantly raises penetration stress, elasticity and work of penetration. Increased temperature causes the formation of a matrix structure typical of heat-induced protein gels, which became compact and determine the formation of stronger, more elastic structures. Differences in microstructure caused by fat content were more evident at low temperature (40° C).

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Auswirkungen verschiedener Fettgehalte auf die rheologischen Veränderungen und Mikrostruktur von Fleischmischungen während des Erwärmungsprozesses

Zusammenfassung Es wurde die Wirkung verschiedener Fettgehalte (5,3% und 20,8%) auf die rheologischen Eigenschaften und Mikrostruktur von Fleischbräten während des Erwärmungsprozesses untersucht. Die rheologischen Eigenschaften wurden mittels nicht zerstörender Messungen (thermal scanning rigidity monitor, TSRM) und Penetrationstests bewertet. Die Untersuchungen der MikroStruktur wurde durch Raster-Elektronenmikroskopie (REM) durchgeführt. Der Einfluß des Fettgehalts auf den Festigkeitsgleitmodul (G) wird im gleichen Ausmaß ersichtlich, in welchem die Gelstrukturen beginnen, sich zu bilden. Je höher der Fettgehalt des Bräts ist, desto größer werden die G-Werte in den Bräten. Je mehr die Temperatur des Erzeugnisses gesteigert wurde (zwischen 40 °C und 70 °C), um so mehr stiegen Penetrationdruck und Elastizität an. Obwohl sich die Penetration zwischen 40 °C und 60 °C erhöhte, blieb diese bei höheren Temperaturen konstant. Die Analyse der Ergebnisse aufgrund der Behandlungen zeigt, daß ein größerer Fettgehalt den Penetrationdruck, die Elastizität und Eindringungseffekt bedeutend erhöhen. Die Erhöhung der Temperatur verursacht die Bildung von Matrix-Strukturen, die typisch für die durch Hitze herbeigeführten Proteingele sind, deren stärkere Verdichtung die Bildung von stärkeren und elastischeren Strukturen bedeutet. Die durch die Einwirkung des Fettgehalts in der Mikrostruktur entstandenen Unterschiede scheinen bei niedriger Temperatur (40 °C) klarer hervorzutreten.

     

Pressure-assisted gelation of chemically modified poultry meat batters

Changes were induced in the characteristics of poultry meat protein using specific chemical modifiers to investigate the effect of pressurization, prior to heating, on gelation, texture and thermal behaviour of meat batters. Values of hardness and chewiness were higher in cooked meat batters treated with urea than in a salt-only sample, but cohesiveness was similar. The β-mercaptoethanol treatment produced a heat-induced gel with very similar properties to the salt-only gel. The rheological behaviours of salt-only and β-mercaptoethanol samples were very similar, but storage modulus values were higher in samples with urea, which accelerated gelation. The pressure-induced reduction of differences in the textural properties of meat batters suggests that hydrophobic interactions play an important role in heat-induced gelation. Differential scanning calorimetry showed that urea clearly destabilized chicken meat batters, while β-mercaptoethanol had very little influence on their thermal behaviour. Pressurization tended to equalize batters and final cooking definitively equalized them.     

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

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

EFFECTS OF SALT REDUCTION ON THE RHEOLOGICAL AND GELATION PROPERTIES OF WHITE AND DARK POULTRY MEAT BATTERS

The rheological and gelation properties of poultry dark and white meat batters prepared with average and reduced NaCl levels (2%, 1% and 0%) and with 0.5% hexametaphosphate (HMP) added to the 1% salt batters were studied. Lowering the salt content decreased the shear stress in both the white and dark meat at the same shear rates. HMP addition to the 1% NaCl treatments increased the shear stress in the dark meat but not in the white meat at the same shear rates using a concentric cylinder viscometer. The relationship between the rotor angular velocity and shear stress of the raw batters was nonlinear and resembled a pseudoplastic behaviour with yield stress in all cases. Plots of the modulus of rigidity (G) versus cooking temperature indicated that white meat always exhibited higher G than that of dark meat. The highest G was observed in the white meat with 2.0% NaCl and the lowest in the dark meat with no salt. The batters with no salt also exhibited gel formation, however with lower G values.     

Rheological changes during thermal gelation of meat batters containing surimi from alaska pollack (Theragra chalcogramma) or sardine (Sardina pilchardus)

The objective of this study was to use a thermal scanning rigidity monitor to analyse the changes occurring in rheological behaviour during thermal gelation induced by the presence of surimi in meat batters. These studies were conducted on systems prepared with pork meat to which varying proportions of surimi from Alaska pollack (Theragra chalcogramma (Pallas)) or sardine (Sardina pilchardus) (Walb) were added. The results indicated that gelation in pork proteins did not occur in the same way as in fish proteins. Whereas the addition of Alaska pollack surimi to the meat preparations produced scarcely any change with respect to the meat alone, the sardine surimi caused major alterations. These changes depended upon the proportion of protein from surimi added: addition of 100 g kg^?1 caused a protein matrix to form, inducing the formation of stiffer gels and the appearance of the setting phenomenon, although at higher temperatures than are found with fish proteins. Such behaviour was not apparent when the proportion of protein from surimi was raised to 200 g kg^?1.     

Physicochemical Effects of the Lipid Phase and Protein Level on Meat Emulsion Stability,Texture, and Microstructure

ABSTRACT: The effects of beef fat (25%) substitution with rendered beef fat, canola oil, palm oil, or hydrogenated palm oil at varying meat protein levels (8%, 11%, and 14%) were studied in emulsified beef meat batters. There was no significant difference in fat loss among meat batters made with beef fat, rendered beef fat, or palm oil. Hydrogenated palm oil provided the most stable batters at all protein levels. Increasing meat protein to 14% resulted in high fat loss in batters prepared with canola oil, which did not occur in the other formulations. This indicates that the physicochemical characteristics of fat/oil affect emulsion stability. Cooked batter hardness was higher (P < 0.05) when protein level was raised; highest in hydrogenated palm oil batters when compared at similar protein levels. As protein level was raised springiness values were increased in all the meat treatments. Springiness was higher in the canola oil treatments. Light microscopy revealed fat globule coalescence in canola oil meat batters prepared with 14% protein, as well as the development of fat channels and more protein aggregation; both seem to result in lower emulsion stability. Hydrogenated palm oil batters showed fat particles with sharp edges as opposed to the round ones seen in all other treatments.     

Konjac gel fat analogue for use in meat products: Comparison with pork fats

The paper reports a study of the characteristics of konjac gel fat analogue as compared to types of pork fat for use in fat reduction strategies for meat products. Various characteristics—colour, mechanical/rheological behaviour and thermal properties—of pork fats (backfat-PBF and trimmed fat-PTF) and konjac gel (KFG) with different physical structures (intact or ground to 4 and 8 mm) were studied. Pork fat melting processes were evaluated by differential scanning calorimetry (DSC) at above- and below-zero temperature ranges with PBF and PTF always showing similar net results. KFG did not show any thermal event in the range from −40 to 100 °C except the freezing/melting of its constitutional water. While water and fat binding properties of pork fats were affected by fat type and structural disintegration (ranging between 0 and 77%), in all cases KFG presented excellent thermal water binding (<1%). As compared to KFG, PBF showed greater (P < 0.05) hardness, chewiness, penetration force, gel strength, extrusion force and work of extrusion. These differences were minimized after grinding. Kramer shear values in KFG were greater (P < 0.05) than in PBF when this was ground to 4 mm, but lower (P < 0.05) at 8 mm. The highest Kramer shear values (P < 0.05) were recorded in PTF irrespective of the degree of disintegration. Rheological analyses indicate that the behaviour of KFG, which is thermally stable, is predominantly elastic during heating and exhibits rheological thermal behaviour (at over 40 °C) similar to that of pork backfat.     

添加成分对外裹糊流变性能及外裹糊鱼块油炸过程油脂渗透的影响

将分别添加黄原胶（0.4%）、大豆纤维（2%）、乳清蛋白（4%）的外裹糊制作油炸外裹糊鱼块,通过测定外裹糊的黏性模量（G”）和弹性模量（G’）以及油炸外裹糊鱼块的水分和油脂含量、微观结构、苏丹红染色水平和油脂分布,探讨添加成分对外裹糊流变性能及外裹糊鱼块深度油炸过程油脂渗透的影响。结果显示：4 种外裹糊（包括对照组,即外裹糊中未添加黄原胶、大豆纤维或乳清蛋白）的G”值和G’值随温度升高先减小后增大,最后趋于稳定,黄原胶组外裹糊的G”值和G’值最大。油炸后黄原胶组的外壳结构紧密,鱼块孔隙小且数量少,具有较高的水分含量和较低的油脂含量。苏丹红染色幅度最大的是对照组,油脂已通过外壳渗入鱼块;黄原胶组染色幅度最小,只出现在外壳中。油脂主要分布在外壳孔隙周围,黄原胶组的荧光强度最低,其次是乳清蛋白组和大豆纤维组,对照组的荧光强度最高。研究结果表明外裹糊中分别添加黄原胶、大豆纤维、乳清蛋白明显影响了外裹糊的流变性能,抑制了外裹糊鱼块深度油炸过程的油脂渗透。     

Effects of two types of soy protein isolates,native and preheated whey protein isolates on emulsified meat batters prepared at different protein levels

The effects of substituting 1.5% of the meat proteins with low gelling soy protein isolate (LGS), high gelling soy protein isolate (HGS), native whey protein isolate (NWP), and preheated whey protein isolate (PWP) were compared at varying levels of proteins (12, 13 and 14%), with all meat control batters prepared with canola oil. Cooking losses were lower for all the non-meat protein treatments compared to the all meat controls. When raising the protein level from 12 to 14%, cooking losses increased in all treatments except for the NWP treatments. Using LGS increased emulsification and resulted in a more stable meat batters at the 13 and 14% protein treatments. Textural profile analysis results showed that elevating protein level increased hardness and cohesiveness. The highest hardness values were obtained for the PWP treatments and the lowest for the HGS, indicating a strong non-meat protein effect on texture modification. Non-meat protein addition resulted in lighter and less red products (i.e., lower red meat content) compared to the all meat controls; color affected by non-meat protein type. Light microscopy revealed that non-meat proteins decreased the frequency of fat globules' agglomeration and protein aggregation. The whey protein preparations and HGS formed distinct “islands” within the meat batters' matrices, which appeared to interact with the meat protein matrix.     

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.     

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.     

Rheology and microstructure of cross-linked waxy maize starch/whey protein suspensions

The objective of the present work was to investigate the effect of the heating process on the structural and rheological properties of whey protein isolate/cross-linked waxy maize starch (WPI/CWMS) blends depending upon the concentration and the starch/whey protein ratio. Starch concentration ranged from 3 to 4% (w/w) and the protein content was of 0.5, 1 and 1.5% (w/w). The blend (pH 7, 100 mM ionic strength) was heated using a jacketed vessel at two pasting temperatures: 90 and 110 °C. The particle size distribution of the WPI suspension (1.5%) displayed three distinct classes of aggregates (0.3, 65 and 220 μm), whereas the size of swollen starch granules varied from 48 to 56 μm according to the pasting temperature. When the two components were mixed together, the peak attributed to swollen starch granules was attenuated and broadened towards higher values (up to 88 μm) due to protein aggregates (260–410 μm). This effect was more pronounced as the protein concentration increased. When compared to starch alone, the rheology of the mixed system was dramatically modified for the flow behaviour as well as for the viscoelastic properties which changed from a solid-like (3–4% starch) to a liquid-like behaviour (3–4% starch/1.5% protein). Microscopic observations showed aggregated proteins located in the continuous phase and swollen starch granules as the dispersed phase. Protein aggregates were of different sizes, part of them appeared adsorbed onto swollen starch granules while another part was unevenly distributed in the continuous phase, yielding discontinuous network which could explain the peculiar viscoelastic behaviour of such suspensions.     

Front-face fluorescence spectroscopy as a tool to classify seven bovine muscles according to their chemical and rheological characteristics

Potential of front-face fluorescence spectroscopy was evaluated to classify muscles according to their chemical and rheological characteristics. Seven bovine muscles (Semitendinosus, Semimembranosus, Tensor fasciae latae, Rectus abdominis, Longissimus thoracis et lumborum, Triceps branchii and Infraspinatus) were taken from 14 animals of the Charolais breed. Chemical characteristics and rheological properties of the meat were determined including dry matter, fat, collagen, protein, peak load, energy required to rupture and cooking loss. Emission spectra in the 305–400 nm, 340–540 nm and 410–700 nm ranges were recorded using front-face fluorescence spectroscopy by fixing the excitation wavelengths at 290, 322 and 382 nm, respectively. Analysis of variance (ANOVA) applied on chemical and rheological parameters showed that these muscles were significantly different (P < 0.01) from each other. Chemical and rheological data were divided into low, medium and high range groups for each variable. The results of PLSDA showed that 305–400 nm spectra were responsible for 67% (calibration), 53% (validation), 96% (calibration) and 55% (validation) of good classification for protein and cooking loss, respectively, while 340–540 nm spectra allowed 75% of good classification (validation samples) for fat content.     

Rheological study of layer cake batters made with soybean protein isolate and different starch sources

The study of new gluten-free foods suitable for celiac people is necessary since people allergic to wheat proteins are more and more frequent. This study examined the effect of using different starch sources (rice, corn, potato and wheat) and protein types (soy protein isolate, wheat protein) at different percentages (0%, 10%, 20%), on the rheological properties of batters (flow, viscoelastic and stickiness behaviour) and on batter density and cake volume. The highest consistency, viscous and elastic moduli, and adhesive force corresponded to batters made of rice starch and soy protein isolate, which showed the most similar rheological behaviour to wheat flour batters. The batters obtained showed adequate characteristics in processing and in achieving high quality products. However, the percentages of starches and proteins should be experimentally optimized in each case.     

Rheological properties and microstructure of Cheddar cheese made with different fat contents

Reduced- and low-fat cheeses are desired based on composition but often fall short on overall quality. One of the major problems with fat reduction in cheese is the development of a firm texture that does not break down during mastication, unlike that observed in full-fat cheeses. The objective of this investigation was to determine how the amount of fat affects the structure of Cheddar cheese from initial formation (2 wk) through 24 wk of aging. Cheeses were made with target fat contents of 3 to 33% (wt/wt) and moisture to protein ratios of 1.5:1. This allowed for comparisons based on relative amounts of fat and protein gel phases. Cheese microstructure was determined by confocal scanning laser microscopy combined with quantitative image analysis. Rheological analysis was used to determine changes in mechanical properties. Increasing fat content caused an increase in size of fat globules and a higher percentage of nonspherical globules. However, no changes in fat globules were observed with aging. Cheese rigidity (storage modulus) increased with fat content at 10°C, but differences attributable to fat were not apparent at 25°C. This was attributable to the storage modulus of fat approaching that of the protein gel; therefore, the amount of fat or gel phase did not have an effect on the cheese storage modulus. The rigidity of cheese decreased with storage and, because changes in the fat phase were not detected, it appeared to be attributable to changes in the gel network. It appeared that the diminished textural quality in low-fat Cheddar cheese is attributed to changes in the breakdown pattern during chewing, as altered by fat disrupting the cheese network.     

The effect of butter grains on physical properties of butter-like emulsions

Milk fat exists as globules in its natural state in milk. The potential of using globular fat to modulate the rheological properties and crystallization behavior in butter-like emulsions was studied in the present work. We conducted a comparative study of butter-like emulsions, with a fat phase consisting of 0, 10, 25, 50, or 100% anhydrous milk fat (AMF), the remaining fat being butter grains, and all samples containing 20% water, to obtain systematic variation in the ratio of globular fat. All emulsions were studied over 4 wk of storage at 5°C. By combining small and large deformation rheology, we conducted a detailed characterization of the rheological behavior of butter-like emulsions. We applied differential scanning calorimetry to monitor thermal behavior, confocal laser scanning microscopy for microstructural analysis, and low-field pulsed nuclear magnetic resonance spectrometry to measure solid fat content. By combining these techniques, we determined that increasing the fraction of globular fat (by mixing with butter grains) decreases the hardness of butter-like emulsions up to an order of magnitude at d 1. However, no difference was observed in thermal behavior as a function of butter grain content, as all emulsions containing butter grains revealed 2 endothermal peaks corresponding to the high (32.7°C ± 0.6) and medium (14.6°C ± 0.1) melting fractions of fatty acids. In terms of microstructure, decreasing the amount of butter grains in the emulsions resulted in formation of a denser fat crystal network, corresponding to increased hardness. Moreover, microstructural analysis revealed that the presence of butter grains resulted in faster formation of a continuous fat crystal network compared with the 100% AMF sample, which was dominated by crystal clusters surrounded by liquid oil. During storage, hardness remained stable and no changes in thermal behavior were observed, despite an increase in solid fat content of up to 5%. After 28 d of storage, we observed no difference in either microstructural or rheological properties, indicating that formation of primary bonds occurs primarily within the first day of storage. The rheological behavior of butter-like emulsions is not determined solely by hardness, but also by stiffness related to secondary bonds within the fat crystal network. The complex rheological behavior of milk fat-based emulsions is better characterized using multiple parameters.     

Effect of fat level and ripening temperature on biochemical and sensory characteristics of naturally fermented Turkish sausages (sucuk)

Changes in chemical and sensory characteristics of naturally fermented Turkish sausages during ripening were evaluated for three fat levels (10, 20 and 30%) and two different ripening temperatures, i.e. 20–22 and 24–26 °C. Fat level, ripening temperature and time affected total acidity, free fatty acids (FFA) and thiobarbituric acid (TBA) values. Both higher fat content and higher temperature resulted in higher FFA and TBA values during ripening, indicating high lipolytic and oxidative activity. TBA values showed an increase from the first to the ninth day, but were lower at 20–22 °C than at 24–26 °C. High fat level and temperature adversely affected rancid flavor and overall acceptability.