Effect of thermal treatment on the texture and microstructure of abalone muscle (Haliotis discus)

The texture and microstructure of edible abalone meats were studied during heat treatments from 50 to 100°C for 60 min. No increase in extractable soluble collagen content was observed below 80°C, but a 9-fold increase was observed at 100°C. SDS-PAGE showed that extractable myosin heavy chains and paramyosin contents reduced significantly at 80°C, and disappeared completely at 100°C. The shear force increased slowly from 50 to 70°C, but relaxed back to the initial level at 100°C. Rapid reduction of hardness was observed at 50°C, minimum hardness was obtained at 100°C. Springness, cohesiveness, chewiness, and resilience were enhanced to maximum levels at 70, 90, 70, and 90°C, respectively. Optical micrographs and transmission electron microscope showed a significant increase of intermyofibrillar gaps at 90°C and broken fibers at 100°C. Results suggested that 80°C might be a suitable temperature to produce ready-to-eat abalone products.     

Effect of pH on aqueous Se(IV) reduction by pyrite

Interaction of aqueous Se(IV) with pyrite was investigated using persistently stirred batch reactors under O2-free (<1 ppm) conditions at pH ranging from 4.5 to 6.6. Thermodynamic calculations, an increase in pH during the experiments, and spectroscopic observation indicate that the reduction of aqueous Se(IV) by pyrite is dominated by the following reaction: FeS2+3.5HSeO3?+1.5H+=2SO4(2?)+Fe2++3.5Se(0)+2.5H2O. The released Fe(II) was partitioned between the bulk solution and pyrite surface at pH≈4.5 and 4.8, with the Fe2+ density at pyrite-solution interface about 4 orders of magnitude higher than that in the bulk solution, while iron oxyhydroxide precipitated at pH≈6.6, resulting in the decrease of dissolved iron. In the Se(IV) concentration range of the experiments, aqueous Se(IV) reduction rate follows the pseudofirst order which is in the form of ln mSe(IV)=?k′t+ln mSe(IV)0, where k′ is apparent rate constant combining the rate constant k and pyrite surface area to mass of solution ratio (A/M). And the aqueous Se(IV) reduction rate constant for a standard system (k) with 1 m2 pyrite surface area per 1 kg solution was obtained to be 1.65×10(?4) h(?1), 3.28×10(?4) h(?1), and 4.76×10(?4) h(?1) at pH around 4.5, 4.8, and 5.1, respectively. The positive correlation between reaction rate and pH disagrees with the theories that protons are consumed when HSeO3? is reduced to Se0, and negative charge density on pyrite surface increases as pH increases. Thus, a ferrous iron mediated electron transfer mechanism is proposed to operate during the reduction of aqueous Se(IV) by pyrite. pH and iron concentration affect significantly on Se(IV) reaction rate and reaction product.     

Effect of bleeding treatment and perfusion of yellowtail on lipid oxidation in post-mortem muscle

The present study investigated the effects of bleeding treatment and perfusion of antioxidant compounds on lipid oxidation in ordinary and dark muscles of yellowtail in the early stage of ice storage. The lipid hydroperoxide contents of dark muscles obtained from yellowtails with and without bleeding treatment were higher and increased more rapidly than those of ordinary muscles. There were no significant differences in the rates of change of the lipid hydroperoxide content (up to 48 h), fatty acid composition and metmyoglobin formation between dark muscles with and without bleeding treatment. Physiological saline containing ascorbic acid or 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox^®) was perfused into live yellowtail or added to minced dark muscle. Trolox^® significantly (P < 0.01) delayed the accumulation of lipid hydroperoxide in dark muscle compared to ascorbic acid in perfusion experiment. These results indicate that simply removing a portion of the blood from live yellowtail by bleeding is not sufficient to prevent lipid oxidation in the early stage of ice storage. Contrary to this, addition of antioxidants into fish flesh is effective to delay lipid oxidation in post-mortem muscle.     

Effect of pH on technological parameters and physicochemical and texture characteristics of the pasta filata cheese Telita

The objective of this study was to determine the effect of stretching pH on technological parameters and physicochemical and texture characteristics of the pasta filata cheese Telita. A no-brine cheese-making method was used to control both melting and stretching temperatures. Six vats of cheese, each with a different stretching pH (5.2, 5.3, 5.4, 5.5, 5.6, and 5.7), were made in 2 h. Cheese-making was replicated using 2 different lots of milk. Differences in stretching pH significantly affected all variables evaluated; stretching temperature and pH were positively correlated. Technological parameters showed an inverse relationship between pH and acidity and a direct relationship between melting and stretching temperature. The yield was highest as the pH increased and ranged from 11.4 to 12.9 kg of cheese/100 kg of milk. Physicochemical characteristics showed the following: moisture 48.1 to 53.5% (soft and semi-hard cheese), fat 46.3 to 54.9% (dry basis, full-fat cheese), minerals 2.8 to 3.5% (dry basis), calcium content 0.5 to 1.0% (dry basis), sodium 0.38 to 0.78% (dry basis), and whiteness index 77.2 to 84.5. Texture parameters showed that as the stretching pH increased, hardness increased, adhesiveness decreased, cohesiveness decreased, springiness increased, and chewiness increased. Samples were grouped based on principal component analysis. Group 1 contained cheeses at pH 5.2 and 5.3 and were better in terms of retention of components. Group 2 contained cheeses at pH 5.6 and 5.7. These cheeses attained the highest yields, were whitest, and presented the highest values for texture parameters except for adhesiveness and cohesiveness. The third group of cheeses at pH 5.4 and 5.5 were considered the best because they showed a good balance among all variables evaluated.     

微波处理对白切鸡肌肉质构的影响

对白切鸡微波杀菌后的质构特性进行了感官评定和机械测定,发现其硬度、弹性、粘聚性、恢复性的感官评定值和机械测定值均呈线性相关,且相关极显著,而咀嚼性不显著.根据质构测定的结果,确定了微波杀菌后对白切鸡质构保存较好的杀菌工艺为:白切鸡重量800±20g(每次1只),微波频率2450MHz,微波功率670W,微波时间7min.     

Effect of slaughter method on the progress of rigor of rainbow trout (Salmo gairdneri) as measured by an image processing system

Rainbow trout ( Salmo gairdneri ) were slaughtered by AC and DC electrocution, exposure to elevated concentrations of carbon dioxide and by a blow to the head. The fish were subsequently bled and placed in ice.
At regular intervals after slaughter the fish were taken from the ice and placed on a horizontal table with the posterior half of the fish overhanging the edge. The angle which the fish's tail formed with the vertical was used as an index of rigor and was measured by an image processing system. It was found that the stages of rigor were statistically the same for the four different treatments except that the onset of rigor for fish given a blow on the head was delayed.     

热烫处理对麻竹笋质构特性的影响

以大叶麻竹笋为实验原料,研究了热烫处理对麻竹笋的质构特性的影响,同时分析了麻竹笋各质构参数间的相关性。结果表明:热烫处理使麻竹笋的硬度、凝聚性、弹性、咀嚼性和回复性等质构特性显著下降,但热烫10 min以后对麻竹笋的质构特性的下降不再显著;同时相关性分析表明麻竹笋的硬度、弹性、凝聚性、咀嚼性和回复性均能很好反映麻竹笋的质地变化。     

Adsorption and cosorption of tetracycline and copper(II) on montmorillonite as affected by solution pH

Land application of wastes generated from concentrated animal feeding operations may result in accumulation of tetracyclines (TCs) and metals in agricultural soils. Adsorption of TCs and metals on soil minerals strongly affects their mobility. This study was conducted to evaluate the interaction between tetracycline (TC) and Cu(ll) with regard to their adsorption and cosorption on montmorillonite as affected by solution pH. When solution pH was below 6.5, the presence of TC increased Cu(ll) adsorption on montmorillonite, which could be due to increasing Cu(II) adsorption via the TC bridge, or due to the stronger affinity of TC-Cu(II) complex to the mineral than Cu2+ ion itself. Zeta potential of the montmorillonite significantly decreased after the adsorption of TC, suggesting a strong interaction between TC and montmorillonite. Addition of Cu(ll) ions increased TC adsorption on the mineral in a wide range of pH. The experimental data were well fit with the weighted sum model. The complexes of TC and Cu(II) (CuH2L(2+), CuHL+, and CuL) had higher sorption coefficients (K(d)) than that of the corresponding TC species (H3L+, H2L, and HL-). Increasing adsorption of TC and Cu(II) on montmorillonite as they coexist in the normal pH environment may thus reduce their mobility.     

Effect of processing on the texture and structure of raspberry (cv. Heritage) and blackberry (cv. Thornfree)

This paper reports separate studies of the effect of pre-treatments (CaCl₂, low methoxyl pectin (LMP), and combined solutions) and the effect of freezing method (at four different rates) and thawing mode (at two different rates) on objective parameters, structure and sensory characteristics of fresh raspberries and blackberries. After that, the effect of a complete freezing process combining the best pre-treatments with the best freezing/thawing conditions found for each fruit was investigated. Kramer Shear Cell (KSC), back extrusion, compression and multiple penetration tests were used to measure fruit texture objectively. For calcium and LMP pre-treatments, which were applied separately, texture parameters were significantly higher in samples treated at the highest concentrations (100 mM of CaCl₂ for both fruits and 0.3 and 3% of LMP for raspberry and blackberry, respectively) compared to fresh controls. Blackberry structure was more susceptible than raspberry structure to the effect of pre-treatments. For the combined pre-treatments, the highest texture parameters were found in the samples treated with CaCl₂ (100 mM) and LMP (0.1%) in the case of raspberries and CaCl₂ (100 mM) and LMP (3%) in the case of blackberries. Combined pre-treatment did not increase firmness with respect to that of samples treated only with calcium, which indicates that CaCl₂ preserved the raspberry structure more efficiently during processing. Fruits frozen by forced convection with liquid nitrogen vapour at –40 °C were significantly firmer. Raspberries should be thawed at 5 °C, whereas blackberries may be thawed at room temperature. Sensory analysis showed that the blackberry structure was more resistant to freezing. In both fruits, over the complete process parameter values were again highest in the samples treated with 100 mM CaCl₂, applied either separately or in combination with LMP. In raspberry, panellists detected no significant differences between sensory texture parameters of the different samples, and in blackberry, panellists found no significant differences between any of the sensory characteristics. Multiple penetration maximum force (F _MP) was the parameter that best expressed product firmness for both fresh and frozen raspberries, whereas compression slope (S _C) best reflected changes in blackberries. SEM mainly corroborated results from objective texture parameters.     

毛霉发酵对豆制品的质构和微观结构的影响

利用质构仪和扫描电子显微镜研究毛霉发酵豆腐的质构和微观结构,通过电泳分析豆腐的蛋白质水解情况,并与未发酵豆腐进行对比。结果表明,与未发酵豆腐相比,发酵豆腐的硬度和黏性增大,内聚性和弹性减小。其微观结构较均匀致密。电泳分析和微结构分析均显示出大分子量的蛋白质在豆腐发酵过程中的降解。     

The effect and mechanism of ultrasonic treatment on the postharvest texture of shiitake mushrooms (Lentinula edodes)

Fresh shiitake mushrooms (Lentinula edodes) are prone to texture softening and quality decline during storage. We investigated the effects of prestorage ultrasonic treatment on the textural changes of the mushrooms during storage. We monitored physiological parameters, such as respiration intensity, weight loss, cell wall composition and resistance‐related enzymes activity. The hardness of the ultrasonic‐treated (40 kHz, 80 W L^?1, 20 min) mushrooms after 12 days of storage (0.461 N) was significantly higher than the untreated control group (0.286 N). The weight loss and respiration intensity of the ultrasonic‐treated group were significantly lower, whereas the cell wall contents, including glucan and chitin, were significantly higher. The ultrasonic‐treated mushrooms also had higher phenylalanine ammonia lyase, superoxide dismutase and catalase activities. Thus, ultrasound preserves the texture of mushrooms by reducing metabolic rate, maintaining cell wall compositions, activating the activity of SOD and maintaining the activity of PAL and CAT.     

热处理与均质压力对扣碗酪凝乳质构的影响

热处理与均质是牛奶处理的必须工艺,这两个因素对凝乳形成、蛋白变性等方面都有影响,这些因素也影响到扣碗酪的凝乳质构性质。本文应用物性测定的方法,对热和均质扣碗酪的凝乳质构中的硬度、粘着性和凝聚性的影响进行了分析,发现牛奶的均质压力与热处理温度之间对扣碗酪的凝乳质构性质没有交互作用,选择低温热处理以及低均质压力能够得到比较好的凝乳质构。硬度和粘着性对整体饱满度的影响比较大,相关系数分别达到0.679和0.743。凝聚性对扣碗酪的整体饱满度影响不大。     

菊粉对Labneh浓缩酸乳微观结构和质构的影响

研究了添加菊粉对脱脂乳制备的Labneh(一种浓缩酸乳)物理和感官性质的影响。将市售菊粉按不同比例( 1%、3%、5 %和7% )加入至复配脱脂乳粉(reconstitutedskimmilkpowder,RSMP)制作Labneh样品。通过对酸乳宏观和微观结构的分析发现,添加菊粉后,Labneh凝胶结构和凝胶强度都有所改善。实验表明,与未加菊粉的酸乳相比,含有脂肪替代品的酸乳的微观结构比较均匀、疏松且开放度较高。感官评定的结果表明,5 %菊粉复配脱脂乳粉制作的酸乳与全脂牛乳制作的Labneh相比具有相似的特征,对全脂牛乳制作的样品和添加3%、5 %、7%菊粉的样品的统计分析结果没有显著的差别     

Effect of hydrothermal treatment and pH on the formation of aglycones in soybean

This study aims to investigate the effect of hydrothermal treatment at different pH values on the formation of aglycones in soybean grains and flour. Thermal degradation of the aglycones was also examined after the baking of cakes at 175 and 210 °C for 35 min. The results showed that the hydrothermal treatment, when applied at pH 6.0 and 7.5, at 50 °C, favored the formation of aglycones in the soybean flour, in relation to the soybean grain. Under the baking conditions, loss of aglycones reached up to 70%.     

Effect of canning process on texture of Faba beans (Vicia Faba)

The effects of different treatments such as traditional cooking, sterilizing at different time–temperature combinations and the addition of different brines on instrumental texture were evaluated. Previously, a comparison of different texture-measuring devices and optimisation of instrumental texture analysis were carried out. The results showed that all the texture-measuring devices used differentiated perfectly among the different products tested. Regarding heat treatments assayed, different sterilization treatments affected skin texture but had no significant effect when whole grain was considered. Finally, the addition of chelation agents to the brine did not affect the textural parameters but the commercial quality related to the production of Faba beans under a “Geographical Indication” had an important effect on the firmness of both the pericarp and whole seed and on pectin content.     

Impact of flavour solvent on biscuit micro-structure as measured by X-ray micro-Computed Tomography and the distribution of vanillin and HMF (HPLC)

The influence of flavour solvent, propylene glycol (PG) and triacetin (TA), was investigated on the micro-structure (as measured by X-ray micro-Computed Tomography, X-ray μCT) and aroma compound distribution (as measured by HPLC) within shortcake biscuits. X-ray μCT scanning showed biscuits made with PG had smaller pores and higher porosity than biscuits made with TA. Vanillin distribution across the biscuits was not homogeneous and was found at higher concentrations in the centre of the biscuits than the edge or bottom. The baked aroma compound 5-hydroxymethyl-furfural (HMF) was present at higher concentrations at the surface of the biscuits where Maillard chemistry is presumed to occur at its highest rate. The type of solvent had a significant effect on the total concentration and distribution of aroma compounds (p?<?0.05). TA biscuits retained greater vanillin and more HMF was formed during baking when compared to PG biscuits. The core of TA biscuits had (on a relative scale) a much greater vanillin and lower HMF concentration than PG biscuits when compared to their periphery. Although this may be due to different physicochemical properties of the two solvents and varying levels of interactions with other ingredients, the micro-structure differences indicated by X-ray μCT image analysis illustrate one potential route by which the flavour solvent may be influencing the generation and stability of biscuit aroma compounds.     

Effect of temperature, pressure and calcium soaking pre-treatments and pressure shift freezing on the texture and texture evolution of frozen green bell peppers (Capsicum annuum)

The firmness of green bell pepper (Capsicum annuum) was studied under different processing conditions. Thermal texture degradation kinetics of pepper tissue between 75 and 95 °C could be accurately described by a fractional conversion model. The firmness of pre-processed pepper increased when the samples were submitted to several heat, pressure, and combinations of heat/pressure and calcium soaking pre-treatments. Pre-heating at 55 °C during 60 min and mild heat/high-pressure treatments (200 MPa at 25 °C, 15 min) yielded the best results, which were further improved when combined with calcium soaking. These pre-treatments significantly slowed down thermal texture degradation of pepper at 90 °C, a typical temperature used for pepper blanching prior to freezing. The above-mentioned pre-treated samples showed a significant reduction in firmness when frozen by regular freezing at 0.1 MPa. The same samples showed no changes in firmness when frozen by high-pressure shift freezing at 200 MPa. When freezing was carried out by high-pressure shift and after frozen storage (−18 °C) for 2.5 months, pressure pre-treated pepper showed a better retention of texture than thermal pre-treated pepper.     

pH对丙烯酸-丁烯醛共聚物与明胶相互作用的影响

以明胶为皮胶原的模型化合物，研究了pH对丙烯酸-丁烯醛共聚物与明胶相互作用的影响。实验结果表明，丙烯酸-丁烯醛共聚物与明胶的相互作用大小与介质的pH值有关，在pH=4．5附近，相互作用最强。