Effect of high pressure processing on batters and cakes properties

High-pressure processing (HPP) is a novel non-thermal method that has shown great potential for reducing microbial loads, at temperatures below sterilization conditions. The aim of the present study was to investigate microbial, physical and structural changes in highly pressured batters and their layer cakes as a function of pressure level (300–600 MPa) and holding time (3–6 min). Characteristics of the batter (microflora, density, microstructure, and rheological properties) and cakes (specific volume, weight loss, color, and texture) were analyzed. HPP decreased molds and yeast and aerobic mesophilic bacteria counts, especially at highest pressures, and increased the density, G′, and G″ of batters. Cakes from HP treated batters presented a lower volume, darker crust, and harder texture than cakes from untreated batters. Increased values for the specific volume were obtained when the pressure was raised. Further studies are required to minimize its negative effects on the quality of the cakes.Industrial relevanceIn view of the increasing interest in home-made baking products, food industry has developed new commercially prepared batter products, which also present the disadvantage of a short shelf life even in cool conditions. High pressure processing (HPP) reduced microbial populations of batters, at temperatures below sterilization conditions. In this study, changes in the internal structure and the physical properties of batters and their consequences in the characteristics of cakes were also studied. These results showed negative effects of HPP in some batters constituents, so further studies are required to investigate possible changes in formulation, which reduce these effects.     

高压对肌肉蛋白凝胶性的影响

高压技术对肌肉蛋白的凝胶特性的作用和在食品工业上新的应用这两个方面引起了人们的兴趣,高压对凝胶的稳定作用依赖于蛋白系统本身的特性和高压处理的条件,压力和温度是相关联的两个条件,它们会引起不同的影响,这主要依赖于温度和压力的大小以及它们的作用顺序。综述了影响高压对肌肉蛋白凝胶稳定性的4种不同的温度和压力的组合:(1)在低温和常温对原料肉的高压处理;(2)在高压条件下对原料肉的加热处理;(3)在加热前对原料肉的高压处理;(4)振动或逐步脉冲的高压。     

Mass transfer dynamics during high pressure brining of chicken breast

The objectives of this study were to investigate the changes in mass transfer, textural properties and water holding capacity of chicken breast when brine treated under different pressures. Chicken breasts were treated for up to 20 min in 4% sodium chloride solution under five pressures: 50, 100, 150, 200, and 300 MPa at 25 ± 1 °C. The results indicated that the total weight and water uptake of the chicken breast increased with increasing pressure up to 150 MPa, and then decreased with further pressure increase up to 300 MPa. Chicken breast samples brined at 150 MPa, with a sodium chloride effective diffusivity value of 2.96 × 10⁻⁸ m²/s, exhibited minimum hardness and maximum water holding capacity. In general, pressure treatment at 150 MPa was found to be the most suitable level for curing based on its higher yield, effective diffusivity and improved texture and water holding capacity.     

Compression heating influence of pressure transmitting fluids on bacteria inactivation during high pressure processing

Compression heating characteristics of different pressure transmitting fluids [three different concentrations (75:25, 50:50, 25:75) of water–glycol mix and sodium benzoate (2%) solutions] and their influence on inactivation of spores of Bacillus subtilis in phosphate buffer (0.067 M, pH 7.0) during high pressure processing (HPP) were studied. Experiments were conducted using a pilot scale food processor. Pressure transmitting fluids containing highest percentage of glycol (25:75 water–glycol mix) showed highest temperature increase while 2% sodium benzoate solution showed least temperature increase during high pressure processing. The target pressure, holding time, compressibility, initial temperature, and the rate of heat loss to the surroundings primarily influenced the apparent temperature increase of pressure transmitting fluid in a vessel during HPP. The temperature change was further influenced by the fluid properties such as viscosity, specific heat and thermal conductivity. Use of sodium benzoate solution as pressure-transmitting fluid resulted in highest inactivation of B. subtilis spores. Change in pressure transmitting fluid temperature as a result of compression heating and subsequent heat transfer should be considered in inactivation of bacterial spores by HPP.     

Gelation characteristics of tropical surimi under water bath and ohmic heating

Gelation characteristics of tropical surimi, namely threadfin bream (TB), bigeye snapper (BS), goatfish (GF) and lizardfish (LF) prepared in the absence and presence of 10 g kg^?1 egg white proteins were evaluated using either ohmic (OH) or water bath (WB) heating. LF and GF surimi exhibited higher endogenous proteolytic activity than BS and TB. Ohmic heating markedly minimized proteolysis of LF and GF surimi as evidenced by a reduction of trichloroacetic acid (TCA)-soluble oligopeptide content of gels and more retention of myosin heavy chain (MHC). Ohmic heating increased breaking force and deformation of TB and BS surimi by 1.3 and 1.6 times, respectively, as compared to water bath heating. However, TB surimi gels heated by a higher applied voltage gradient of 16.7 V cm^?1 exhibited lower breaking force than those heated at 6.7 V cm^?1. Gels heated ohmically contained lower total sulfhydryl concentration, indicating the greater extent of disulfide bond formation as compared to gels heated in a 90 °C water bath. The rapid heating method with shorter heating time could improve water holding capacity and preserve color of tropical surimi gels when compared to water bath heating.     

压致升温及其对超高压下微生物失活的影响

压力与温度的结合能有效地杀灭芽孢杆菌的芽孢。在绝热情况下,压致升温对芽孢的杀灭有很大影响。本文主要阐述了压力处理过程中介质与食品的压致升温情况,同时由于不同的绝热升温产生的热传递造成高压容器内的温度不均一。因此,在压力处理过程中,控制热效应对芽孢杀灭的效果起重要作用。     

Use of high pressure to reduce cook loss and improve texture of low-salt beef sausage batters

Methods were investigated to reduce the salt content of beef-containing smallgoods as high-salt intake has been identified as a public health risk for most individuals. Raw meat batters were manufactured from retail beef mince (4–7% fat) using various NaCl concentrations (0–2%), and were packed into casings and subjected to high pressure processing (up to 400 MPa for 2 min at 10 °C). Following pressure treatment, samples were cooked to an internal temperature of 72 °C and cooled. Cooked products were assessed for cooking loss, colour and physical consistency by texture profile analysis. Flavour and overall acceptability were assessed by sensory panels. High pressure processing (HPP) was found to produce a dramatic improvement in the moisture retention of the cooked products. Control (unpressurised) sausages containing 2% NaCl had a similar cook loss (9.3%) to pressure-treated sausages containing just 1% NaCl, whereas unpressurised samples with 1% NaCl had a cook loss of 24.9%. The hardness and gumminess of pressure-treated samples was higher compared to untreated samples, at all salt concentrations. The greatest differences in texture with pressure treatment were seen in the 1% NaCl samples. Pressure treatment generally caused no changes in the colour of either the raw or cooked product; however there was a slight increase in “whiteness” with pressure treatment. Sensory panels reported a greater acceptability in both appearance and texture of pressure-treated sausages of lower salt content compared with non-pressure-treated samples. Examination of extracted proteins using SDS-PAGE and of muscle proteins by thermal analysis indicated that pressure contributed to enhanced binding through protein solubilisation and gelation through partial protein unfolding. The application of high pressure to beef sausages with low-salt content resulted in reduced cooking losses and improved texture.

Industrial relevance

Enhanced meat binding through extraction of salt-soluble proteins is an essential step in the formulation of meat products such as sausages and emulsion-type products. The ability to reduce salt and achieve high binding and water retention through use of HPP is important in being able to produce healthier foods.     

High pressure processing of meat batters with added walnuts

Various model systems were designed in order to analyse the way in which addition of different levels of walnut (0, 10, 20%) and processing by high pressure (HPP) (400 MPa for 10 min at 10 °C) influenced the physico‐chemical properties of cooked (70 °C for 30 min) meat batters. The addition of walnut increased the fat level and decreased the moisture content in the meat batters. All of the meat batters exhibited good water and fat binding properties. The hardness, cohesiveness, springiness and chewiness of cooked products were reduced by addition of walnut but were unaffected by HPP. Incorporation of nuts in meat products can potentially be used to confer cardiac health benefits.     

High hydrostatic pressure/temperature modeling of frankfurter batters

The impact of high pressure/temperature treatment on structure modification and functional sensory properties of frankfurter batter was investigated. The degree of solubilization of meat proteins, particularly of myosin, was identified as a key process with significant effect on the batter's structural properties. The maximal solubilization level was at 200 MPa/40 °C IT for all formulations which was found to be treatment time dependent. The impact of the pressurizing gradient — PG = 40 MPa/s and PG = 2.5 MPa/s was investigated and estimated to have a significant effect on the protein network and functional properties, respectively. These were improved at low PG (2.5 MPa/s) as a phenomenon of secondary network formation parallel to the main matrix. Batter secondary-structure characteristics were found to be ionic-strength dependent. According to SDS-PAGE analysis, the major role in the solubilization, aggregation and gelation processes occurring in the aqueous phase was due to the myosin S-1 and S-2, N-terminal, C-terminals, the MLC and actin during the high pressure/temperature treatment.     

食盐添加量对海藻粉鸡肉糜品质的影响

为探究食盐对添加海藻粉(刺麒麟菜粉)鸡胸肉糜的影响,考察了食盐添加量对鸡胸肉糜的pH值、色泽、乳化稳定性、盐溶蛋白溶解度、蒸煮损失、冻融损失、质构、持水性、弛豫时间T_2及微观结构的影响。结果表明:pH值、L*和W值随食盐添加量的增加而显著下降,a*值先上升后下降,添加1.5%时达最大值;添加食盐可显著减少蒸煮损失和冻融损失,提高持水性;乳化稳定性随食盐添加量的增加而显著下降,盐溶蛋白溶解度逐渐提高;低场核磁共振表明加入食盐会使T_(22)峰面积减小;扫描电镜显示适量食盐能使肉糜形成较小的孔洞,凝胶网络结构更加均匀致密。添加海藻粉可以显著降低盐的用量,同时可以得到理想的低盐鸡肉糜产品。     

Functionality of batters containing different starch types for deep-fat frying of chicken nuggets

The effect of various starch types (amylomaize, corn, waxymaize, pregelatinized tapioca) on quality attributes (texture, moisture content, oil content, color, coating pick up, cooking yield, volume and porosity) of deep-fat fried chicken nuggets were studied. Chicken samples, 0.04 m in diameter and 0.015 m in thickness, taken from the breast portion, were coated with batters composed of a 3:5 solid to water ratio by immersion. The solid content of batter formulations contained equal amounts of corn and wheat flour, 5.0% starch, 1.0% salt and 0.5% leavening agent. As control, batter without starch addition, was used. Samples were fried at 180°C for 3, 6, 9 and 12 minutes. Crispness and oil content of chicken nuggets increased, whereas moisture content decreased with increasing frying time. Starch addition to the formulations increased crispness of the product significantly at the last stages of frying. The highest porosity and oil content was obtained when corn starch was used. Pregelatinized tapioca starch was found to provide a product with the lowest oil content, the highest moisture content, coating pick up and volume.     

Gelation properties of chicken myofibrillar protein induced by transglutaminase crosslinking

Gelation properties of chicken myofibrillar protein isolate (MPI) and the effect of microbial transglutaminase (MTG) were studied using a dynamic oscillatory rheometer and a texture analyzer. Final heating temperature had a great impact on gel stiffness and the maximum gel stiffness was obtained at 95 °C. pH and ionic strength also influenced gel stiffness and the maximum gel stiffness was achieved at pH 6, 0.9 M NaCl; however, less stiff gels were formed in 0.6 and 1.2 M NaCl. In the MPI concentration range of ∼0.5-5%, a positive correlation was observed between gel stiffness or gel peak force and MPI concentration. When MTG was included at levels of ∼0 to 12-15 U, positive linear relations were found between gel stiffness or peak force and MTG levels. However, negative correlations for these parameters were observed at higher MTG concentrations. When MTG level was greater than 15 U, gel stiffness or peak force tended to decrease. The improvement in gel strength or gel peak force for the MPI with inclusion of MTG suggested that some ε (γ-glutamyl) lysine (G-L) crosslinking occurred among myofibrillar molecules. Thus, MTG is useful in improving gelation properties of heat-induced MPI gel and provides new opportunities to expand the utilization of low value meat in muscle foods.     

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.     

Use of low-field nuclear magnetic resonance to characterize water properties in frozen chicken breasts thawed under high pressure

The state of water in high-pressure-thawed and conventionally water bath-thawed chicken breasts was analyzed using low-field nuclear magnetic resonance. The influence of high-pressure thawing on water holding capacity, including thawing loss, cooking loss and expressible fluid, was evaluated. Thawing loss was significantly reduced (p < 0.05) compared to the conventional thawing method but neither cooking loss nor total expressible fluid changed significantly (p > 0.05). Higher thawing pressures lead to the T₂₁ relaxation time being increased from 39.9 to 55.9 ms, and P₂₁ increased from 89.5 to 94.9 %. Significant negative correlations (p < 0.01) were observed between the thawing loss and T₂₁, T₂₂, P₂₁. These results indicate that high thawing pressures can transform the water from the loosely bound water fraction (T₂₂) to a more tightly bound (T₂₁) water fraction with the increase in water relaxation time.     

Modeling mass transfer during osmotic dehydration of strawberries under high hydrostatic pressure conditions

Simultaneous application of high hydrostatic pressure (200–400 MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson–Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions.Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes.     

高压浸提法提取大豆异黄酮工艺

探讨了以大豆豆粕为原料,以乙醇为溶剂常压下提取大豆异黄酮的工艺条件,并以此为根据,以高压釜为浸提罐,采用单因素优选法确定最佳大豆异黄酮得率的浸提压力。结果表明,在14atm下,大豆异黄酮的得率为1860μg/g,比常压提取提高了28.3%,这为工业化生产大豆异黄酮提高产品得率,降低成本提供了重要参考。     

谷氨酰胺转氨酶对低盐鸡肉糜保水性和蛋白质二级结构的影响

本文利用拉曼光谱技术研究谷氨酰胺转氨酶对鸡肉糜保水性、质构和蛋白质二级结构等的影响。结果表明:低盐鸡肉糜的乳化稳定性和蒸煮得率随着谷氨酰胺转氨酶添加量的增加而显著提高（p<0.05）,但0.67%和1.0%谷氨酰胺转氨酶处理组间差异不显著（p>0.05）;鸡肉糜的硬度、弹性、内聚性和咀嚼性随着谷氨酰胺转氨酶的增加而显著提高（p<0.05）;添加谷氨酰胺转氨酶,酰胺I带的波峰从1659 cm-1移动到1661、1662和1662 cm-1,β-折叠和β-转角含量显著增加（p<0.05）,α-螺旋含量显著（p<0.05）降低,无规则卷曲差异不显著。由此可见,谷氨酰胺转氨酶添加量为0.33%¹.0%时,能够改变蛋白质二级结构,提高低盐鸡肉糜的质构和保水性,且添加量为0.67%时,质构和保水性最好。      

热协同超高压处理对苹果酱品质影响的研究

40℃～60℃协同500MPa处理后，果酱中检测不到微生物。40℃协同500MPa处理后，果酱中酚类物质的含量与处理前相比没有显著差异（P〉0．05）。50℃和60℃协同500MPa处理后，除了聚原花色素外，其他酚类比处理前显著增高，果酱的L值显著升高，果酱色泽有所改善。热协同高压处理前后苹果酱可溶性固形物含量和pH值没有显著差异（P〉0．05），但还原型Vc的损失明显大于单独压力处理的。     

Significance of frictional heating for effects of high pressure homogenisation on milk

High pressure homogenisation (HPH) is a novel dairy processing tool, which has many effects on enzymes, microbes, fat globules and proteins in milk. The effects of HPH on milk are due to a combination of shear forces and frictional heating of the milk during processing; the relative importance of these different factors is unclear, and was the focus of this study. The effect of milk inlet temperature (in the range 10-50 degrees C) on residual plasmin, alkaline phosphatase, lactoperoxidase and lipase activities in raw whole bovine milk homogenised at 200 MPa was investigated. HPH caused significant heating of the milk; outlet temperature increased in a linear fashion (0.5887 degrees C/ degrees C, R2=0.9994) with increasing inlet temperature. As milk was held for 20 s at the final temperature before cooling, samples of the same milk were heated isothermally in glass capillary tubes for the same time/temperature combinations. Inactivation profiles of alkaline phosphatase in milk were similar for isothermal heating or HPH, indicating that loss of enzyme activity was due to heating alone. Loss of plasmin and lactoperoxidase activity in HPH milk, however, was greater than that in heated milk. Large differences in residual lipase activities in milks subjected to heating or HPH were observed due to the significant increase in lipase activity in homogenised milk. Denaturation of beta-lactoglobulin was more extensive following HPH than the equivalent heat treatment. Inactivation of plasmin was correlated with increasing fat/serum interfacial area but was not correlated with denaturation of beta-lactoglobulin. Thus, while some effects of HPH on milk are due to thermal effects alone, many are induced by the combination of forces and heating to which the milk is exposed during HPH.     

热协同超高压处理对苹果酱品质影响的研究

40℃～60℃协同500MPa处理后,果酱中检测不到微生物。40℃协同500MPa处理后,果酱中酚类物质的含量与处理前相比没有显著差异(P>0.05),50℃和60℃协同500MPa处理后,除了聚原花色素外,其他酚类比处理前显著增高,果酱的L值显著升高,果酱色泽有所改善。热协同高压处理前后苹果酱可溶性固形物含量和pH值没有显著差异(P>0.05),但还原型VC的损失明显大于单独压力处理的。