Effect of combined heat and high-pressure treatments on the texture of chicken breast muscle (pectoralis fundus)

Commercially supplied chicken breast muscle was subjected to simultaneous heat and pressure treatments. Treatment conditions ranged from ambient temperature to 70 degrees C and from 0.1 to 800 MPa, respectively, in various combinations. Texture profile analysis (TPA) of the treated samples was performed to determine changes in muscle hardness. At treatment temperatures up to and including 50 degrees C, heat and pressure acted synergistically to increase muscle hardness. However, at 60 and 70 degrees C, hardness decreased following treatments in excess of 200 MPa. TPA was performed on extracted myofibrillar protein gels that after treatment under similar conditions revealed similar effects of heat and pressure. Differential scanning calorimetry analysis of whole muscle samples revealed that at ambient pressure the unfolding of myosin was completed at 60 degrees C, unlike actin, which completely denatured only above 70 degrees C. With simultaneous pressure treatment at >200 MPa, myosin and actin unfolded at 20 degrees C. Unfolding of myosin and actin could be induced in extracted myofibrillar protein with simultaneous treatment at 200 MPa and 40 degrees C. Electrophoretic analysis indicated high pressure/temperature regimens induced disulfide bonding between myosin chains.     

Flavor release and perception of flavored whey protein gels: perception is determined by texture rather than by release

Five whey protein gels, with different gel hardnesses and waterholding capacities, were flavored with ethylbutyrate or diacetyl and evaluated by a 10-person panel to study the relation between the gel structure and the sensory perception, as well as the nosespace flavor concentration during eating. The sensory perception of the flavor compounds was measured by the time-intensity method, while simultaneously the nosespace flavor concentration was monitored by the MS-Nose. The nosespace flavor concentration was found to be independent of the gel hardness or waterholding capacity. However, significant changes in flavor intensity between the gels were perceived by the majority of the panelists, despite the fact that the panelists were instructed to focus only on flavor perception and to not take texture into account. From these observations it is concluded that the texture of gels determines perception of flavor intensity rather than the in-nose flavor concentration.     

Effects of dietary sodium selenite and selenium yeast on antioxidant enzyme activities and oxidative stability of chicken breast meat

The effects of sodium selenite (SS) and selenium yeast (SY) alone and in combination (MS) on the selenium (Se) content, antioxidant enzyme activities (AEA), total antioxidant capacity (TAC), and oxidative stability of chicken breast meat were investigated. The results showed that the highest (p < 0.05) glutathione peroxidase (GSH-Px) activity was found in the SS-supplemented chicken breast meat; however, SY and MS treatments significantly increased (p < 0.05) the Se content and the activities of catalase (CAT), total superoxide dismutase (T-SOD), and TAC, but decreased (p < 0.05) the malondialdehyde (MDA) content at 42 days of age. Twelve days of storage at 4 °C decreased (p < 0.05) the activity of the GSH-Px, but CAT, T-SOD, and TAC remained stable. SY decreased the lipid oxidation more effectively in chicken breast meat. It was concluded that SY and MS are more effective than SS in increasing the AEA, TAC, and oxidative stability of chicken breast meat.     

Effect of red wine marinades on the formation of heterocyclic amines in fried chicken breast

Genotoxic heterocyclic amines (HAs) are formed via the Maillard reaction and free radical reaction mechanisms when meat or fish is cooked at usual cooking conditions. In this paper, the effect of the addition of red wine was tested to study if it interferes in HA formation. Fried chicken breast was the food item chosen, and three different red wines, characterized in terms of grape varieties, free amino acids, antioxidant properties, and metallic composition, were used to marinate meat prior to the heating process. Unmarinated samples and samples marinated with an ethanol-water mixture provided reference HA levels. The frying experiments were performed under well-controlled temperature and time conditions. The samples were analyzed for HA content using solid-phase extraction and LC-MS/MS. DMIP, PhIP, MeIQx, 4,8-DiMeIQx, IFP, TMIP, harman, and norharman were identified in fried chicken breast. Red wine marinades were found to reduce the formation of some of the HAs formed. PhIP, with a reduction of up to 88%, was the most minimized amine, although the formation of harman was enhanced.     

Role of the soluble and micelle-bound heat-induced protein aggregates on network formation in acid skim milk gels

Gel formation was monitored by low amplitude rheometry during acidification at 40 degrees C with 1.5% glucono-delta-lactone in combined milk systems containing soluble and/or micelle-bound heat-induced (95 degrees C/10 min) aggregates of denatured whey proteins and kappa-casein and in heated dairy mixes with varying micellar casein/whey protein ratio (CN/WP). Both soluble and micelle-bound aggregates increased gelation pH and gel strength. Micelle-bound aggregates seemed to modify the micelle surface so that micelles were destabilized at a pH of 5.1 (instead of 4.7), while soluble aggregates precipitated at their calculated pI of approximately 5.3, and initiated an early gelation by interacting with the micelles. Decreasing the CN/WP ratio produced larger aggregates with higher whey protein: kappa-casein ratio, which gave more elastic gels. The specific effects of the micellar and soluble aggregates on gel strength are discussed with respect to their relative proportions in the heated milk.     

Influence of pH and ionic strength on heat-induced formation and rheological properties of soy protein gels in relation to denaturation and their protein compositions

The influence of pH and ionic strength on gel formation and gel properties of soy protein isolate (SPI) in relation to denaturation and protein aggregation/precipitation was studied. Denaturation proved to be a prerequisite for gel formation under all conditions of pH and ionic strength studied. Gels exhibited a low stiffness at pH >6 and a high stiffness at pH <6. This might be caused by variations in the association/dissociation behavior of the soy proteins on heating as a function of pH, as indicated by the different protein compositions of the dissolved protein after heating. At pH 3-5 all protein seems to participate in the network, whereas at pH >5 less protein and especially fewer acidic polypeptides take part in the network, coinciding with less stiff gels. At pH 7.6, extensive rearrangements in the network structure took place during prolonged heating, whereas at pH 3.8 rearrangements did not occur.     

电解质对热应激肉鸡生产性能和屠体品质的影响

试验研究了热应激对肉鸡的影响以及电解质添加剂对肉鸡生产性能和屠体品质的影响。结果表明 ,(1 )热应激可显著降低肉仔鸡采食量、日增重和饲料利用率 ;(2 )与高温对照组相比 ,在日粮中添加抗热应激添加剂的 1 4～ 3 1日龄肉鸡 ,其平均日增重提高了 6.43 % (P<0 .0 5 ) ;3 8～ 46日龄肉鸡 ,平均日增重和饲料利用率分别提高了 2 7.5 4% (P<0 .0 5 )和 2 0 .1 9% (P<0 .0 5 ) ;但这种抗热应激添加剂对肉鸡采食量无显著效果。此外 ,热应激能显著地增加肉鸡腹脂率 ,而添加抗热应激添加剂能显著降低腹脂率。     

Analysis of genotypic and environmental effects on rice starch. 1. Apparent amylose content, pasting viscosity, and gel texture

Eight rice varieties with wide diversity in apparent amylose content (AC) were selected and planted in the early season and late season of Hangzhou and in the winter season of Hainan for two consecutive years to study the genotype x environment effects on the starch properties of the grain. Analyses of variance showed that AC, cool paste viscosity, breakdown viscosity, setback viscosity, peak time, gel hardness, adhesiveness, and cohesiveness were mainly affected by genotypic variation, whereas peak viscosity and hot paste viscosity were mainly affected by environmental variation. The year x season, year x variety, seasonx variety, and year x season x variety effects were significant for most traits, indicating significant genotype x environment interactions. AC was significantly correlated with all other parameters except PV. Because the Wx gene controls the synthesis of amylose in rice, the mechanism of how the environment affects starch properties is discussed in relation to Wx expression and regulation. The implications of the results for rice breeders and starch-based food manufacturers are discussed.     

电子鼻和电子舌单独与联合检测掺大豆蛋白或淀粉的鸡肉糜

为实现掺杂掺假鸡肉的快速、客观评价,该研究利用电子鼻和电子舌联合检测技术对掺杂鸡肉糜进行快速检测,通过对采集的数据进行主成分分析和偏最小二乘法分析,所得结果表明,采用主成分分析,电子鼻和电子舌联合检测掺大豆蛋白鸡肉糜和掺淀粉鸡肉糜的主成分总贡献率分别为99.8%和99.1%;采用偏最小二乘法分析,电子鼻和电子舌联合检测鸡肉糜中掺杂大豆蛋白含量的预测值与真实值之间的决定系数为0.992,均方根误差为2.8%;联合检测鸡肉糜中掺杂淀粉含量的预测值与真实值之间的决定系数为0.996,均方根误差为2.4%。表明电子鼻和电子舌联合检测对鸡肉糜的掺杂情况具有良好的区分和预测能力,并且是一种有效、高精度的肉类掺假检测方法。     

Chemical reactions in cottonseed protein cross-linking by formaldehyde, glutaraldehyde, and glyoxal for the formation of protein films with enhanced mechanical properties

Amino acids involved in cottonseed protein cross-linking by formaldehyde, glutaraldehyde, and glyoxal during protein film formation were identified by an original technique. The entire HPLC amino acid profile (after acid hydrolysis) was studied, along with variations in reactive lysine contents, in films cross-linked or not with increasing quantities of formaldehyde, glutaraldehyde, and glyoxal. This strategy highlighted the formation of acid-resistant lysine derivatives that a simple reactive lysine determination would not have detected. The results-which agree with previously published data-enhance the overall understanding of cross-linking activities that occur in aqueous alkaline solutions during the formation of protein films made with cottonseed flour. Lysine was found to have a key role in protein cross-linking by dialdehydes, with the involvement of tyrosine in the presence of formaldehyde and of arginine in the presence of glyoxal. These results could provide valuable chemical tools for adjusting the mechanical properties of cottonseed protein films.     

风干牦牛肉加工过程中水分状态变化及质构相关性分析

为研究风干牦牛肉在加工过程中水分迁移规律,以及与组织结构和质构之间的相关性,该文选取甘肃甘南公牦牛半膜肌,在自然风干60 d中采集样本,采用直接干燥法分析风干牦牛肉含水率的变化,水分活度仪、低场核磁共振仪研究水分活度和水分状态,(hematoxylin-eosinstaining,HE)染色法观察组织结构变化,物性测试仪分析质构特性。结果显示,牦牛肉在风干加工60 d过程中,含水率降低了约60.27%,最终水分活度约达到0.308,降低了约66.73%。30 d时不易流动水峰积分面积降低了约98.12%,40 d后无峰出现,而结合水含量基本不变。随含水率的降低,肌原纤维横截面积、肌纤维直径以及肌间距离均显著降低(P0.05),分别降低了约42.65%、67.15%和61.22%。硬度、内聚性、胶着性和咀嚼性显著升高(P0.05),其中咀嚼性增加了约1 229.16 g,弹性及回复力则显著降低(P0.05)。不易流动水的变化与组织结构及质构各指标间均表现出极显著相关关系(P0.01)。表明牦牛肉在自然冷冻风干过程中不易流动水不断向外扩散蒸发,引起牦牛肉肌纤维收缩和聚集,导致其质构特性发生变化。研究结果可为传统风干牦牛肉加工过程中水分迁移机制以及产品品质控制提供参考。     

Influence of sodium polyacrylate on the water-holding capacity of three different soils and effects on growth of wheat

Abstract. The effectiveness of sodium polyacrylate to increase soil water retention and to enhance growth of wheat under water deficit was evaluated. Water-holding capacity of the soils was considerably increased only when the soil was amended with the polymer at a rate 3 g L⁻¹. The effect on plant-available water was greater at soil matric potentials up to −1000 hPa. The biomass and grain yield of plants without water deficit were increased by the polymer amendment, but decreased under severe water deficit stress. The polymer had no significant affect on plant N, grain N or grain Na content.     

Cold-set globular protein gels: interactions,structure and rheology as a function of protein concentration

We identified the contribution of covalent and noncovalent interactions to the scaling behavior of the structural and rheological properties in a cold gelling protein system. The system we studied consisted of two types of whey protein aggregates, equal in size but different in the amount of accessible thiol groups at the surface of the aggregates. Analysis of the structural characteristics of acid-induced gels of both thiol-blocked and unmodified whey protein aggregates yielded a fractal dimension (2.3 +/- 0.1), which is in line with other comparable protein networks. However, application of known fractal scaling equations to our rheological data yielded ambiguous results. It is suggested that acid-induced cold-gelation probably starts off as a fractal process, but is rapidly taken over by another mechanism at larger length scales (>100 nm). In addition, indications were found for disulfide cross-link-dependent structural rearrangements at smaller length scales (<100 nm).     

Enzymatic and mechanistic studies on the formation of N-phenylglycolohydroxamic acid from nitrosobenzene and pyruvate in spinach leaf homogenate

The biotransformation mechanism of an unknown metabolite formed enzymatically from nitrosobenzene (NOB) and pyruvate in spinach (Spinacea oleracea L.) was investigated using spinach leaf homogenate. The unknown metabolite was identified as N-phenylglycolohydroxamic acid (PGA). The activity of PGA formation was decreased by l-alanine, increased by l-serine, and completely inhibited by aminooxyacetic acid, an inhibitor of transaminases. These results indicate that the transaminase participates in PGA formation. Indeed, hydroxypyruvate and alanine were produced in the transamination between pyruvate and serine. Hydroxypyruvate served as a direct-acting glycoloyl donor for PGA formation. A good correlation between the activities of the 200 g supernatant of spinach homogenate and commercial yeast transketolase for PGA formation from several glycoloyl donors was obtained. These results suggest the following mechanism for PGA formation from NOB and pyruvate: transamination of l-serine into hydroxypyruvate, which serves as a glycoloyl donor to NOB.     

Effect of electron beam irradiation and storage at 5 degrees C on thiobarbituric acid reactive substances and carbonyl contents in chicken breast meat infused with antioxidants and selected plant extracts

This study evaluated the effectiveness of synthetic and natural antioxidants, green tea, commercial grape seed extracts/combinations, and TBHQ, with varying concentrations of lipid oxidation of nonirradiated and irradiated chicken breast meats stored at 5 degrees C for 12 days. Fresh boneless and skinless chicken breast meats were vacuum-infused with varying concentrations of antioxidants: green tea, grape seed extracts alone/in combination, and TBHQ. The irradiation dosage was 3.0 kGy. Carbonyl values of raw chicken meat and thiobarbituric acid reactive substances (TBARS) values of raw and cooked chicken meat were determined for 0-12 days at 5 degrees C storage. TBARS values for 0-12 days of storage at 5 degrees C ranged from 1.21 to 7.3 and 1.22 to 8.51 mg malondialdehyde/100 g chicken for nonirradiated and irradiated raw chicken, respectively. TBARS values of cooked chicken ranged from 2.19 to 35.83 and 2.45 to 45.72 mg malondialdehyde/100 g chicken for nonirradiated and irradiated chicken, respectively. Irradiation increased TBARS values of both controls and plant extracts. The carbonyl content in meat lipid ranged from 1.7 to 2.9 and 1.7 to 4.41 micromol acetophenone/10 g of nonirradiated and irradiated chicken meat, respectively, and meat protein ranged from 1.4 to 2.07 and 1.41 to 2.72 micromol/10 g meat. Infusion of chicken meat with selected plant extracts is an effective method to minimize lipid oxidation and volatiles developments caused by irradiation.     

Effect of different vitamin D supplementations in poultry feed on vitamin D content of eggs and chicken meat

According to a new European Union regulation, vitamin D(3) can be partially or totally substituted with 25-hydroxyvitamin D(3) (25-OH-D(3)) in hens' feed. The purpose of this study was to clarify how this regulation has affected the vitamin D content of commercial eggs and chicken meat. Another aim was to investigate how effectively 25-OH-D(3) is transferred from the hens' diet to egg yolk by analyzing eggs from farms using known commercial feeds and by conducting an animal study. Vitamin D determinations were made by HPLC methods. The vitamin D(3) contents of two commercial egg yolk pools were 4.9 ± 0.14 and 4.0 ± 0.10 μg/100 g, and the 25-OH-D(3) contents were 1.3 ± 0.19 and 1.0 ± 0.07 μg/100 g. The chicken meat pools contained 0.2-0.3 μg of vitamin D(3)/100 g, whereas the content of 25-OH-D(3) was ≤0.2 μg/100 g. These results are comparable to earlier data. The animal and farm studies showed that 25-OH-D(3) was effectively transferred from the hens' diet to yolk. However, because the relative activity between 25-OH-D(3) and vitamin D(3) is unknown, it remains questionable whether the use of 25-OH-D(3) in hens' feed is beneficial to human vitamin D intake from eggs.