糖基化凝胶增强剂对鱼糜制品凝胶特性的影响

以新鲜蛋清、刺槐豆胶和瓜尔豆胶为原料,采用湿法糖基化法制备凝胶增强剂,并加入到冷冻鱼糜中,研究糖基化凝胶增强剂对红娘鱼鱼糜制品的凝胶强度、质构、白度、持水性和化学作用力等的影响。结果表明,凝胶增强剂经湿法糖基化改性后可显著提高鱼糜制品的凝胶强度（P＜0.05）。最佳改性条件为反应温度55?℃、加热时间12?h。在此条件下,凝胶增强剂接枝度为（23.37±1.62）%,十二烷基硫酸钠-聚丙烯酰氨凝胶电泳显示蛋白聚集体的形成,表明蛋清蛋白与刺槐豆胶和瓜尔豆胶复配胶显著发生糖基化反应,添加到冷冻鱼糜中可明显改善鱼糜制品的凝胶强度、白度和持水力等。与未添加凝胶增强剂的鱼糜制品相比,凝胶强度提高64%;与添加同等含量的新鲜蛋清的鱼糜制品相比,凝胶强度提高26.9%;与添加未发生糖基化反应的凝胶增强剂的鱼糜制品相比,凝胶强度提高4.7%。实验表明,糖基化改性后的凝胶增强剂具有显著提高鱼糜制品凝胶特性的作用,在鱼糜产业中具有广阔的应用前景。     

木质素/PAM黏附水凝胶传感材料的制备与性能研究

本研究以木质素和丙烯酰胺为原料,制备了具有一定机械性能及黏附性的木质素/聚丙烯酰胺复合水凝胶.结果表明,添加木质素有利于提高复合水凝胶的力学性能及黏附性能.在木质素含量1％时,复合水凝胶的拉伸应变525％,拉伸应力50kPa,韧性11.2MJ/m3,压缩应变88.7％,压缩应力97kPa,且木质素的加入使复合水凝胶的黏...     

葡聚糖及其糖基化修饰对白鲢鱼糜凝胶特性的影响

以鲢鱼为对象,研究糖基化反应时间和比例（蛋白与葡聚糖质量比）对鲢鱼鱼糜凝胶特性及微观结构的影响。结果显示：未添加葡聚糖的鱼糜凝胶的pH以及420 nm和294 nm处的吸光值随着加热时间的延长没有显著变化（P>0.05）,而添加了葡聚糖的鱼糜凝胶的pH值显著降低（P<0.05）,420 nm和294 nm处的吸光值也逐渐增加,说明在40 ℃加热过程中,添加葡聚糖的鱼糜凝胶发生了糖基化反应,且随着葡聚糖的增多,糖基化反应程度逐渐增大。未经过糖基化反应的鱼糜凝胶（CK组）的凝胶强度和网络致密度在加热的前4 h内显著高于经糖基化反应的鱼糜凝胶。CK组的凝胶强度和微观网络致密度随着加热时间的延长而显著降低（P<0.05）,而经糖基化反应的鱼糜凝胶的强度及微观结构变化不显著（P>0.05）。当葡聚糖添加量越多,鱼糜凝胶的特性越弱。葡聚糖在白鲢鱼糜加热过程中与蛋白发生糖基化反应,添加葡聚糖虽降低了鱼糜凝胶的特性,但增强了凝胶在加热过程中的稳定性。     

糖基化反应改善蛋清粉凝胶性的影响因素研究

试验研究葡聚糖添加量,以及在一定量葡聚糖添加的条件下,反应温度、相对湿度、反应时间、pH对蛋清蛋白凝胶性的影响。结果表明,增加葡聚糖的添加量,提高反应温度、相对湿度、反应时间、pH,蛋清蛋白凝胶强度和持水性均先增加后减小。当葡聚糖添加量为7%,温度为70℃,反应相对湿度为70%,反应时间为3 d,反应初始p H为8时,凝胶强度与持水性较高。研究证实糖基化反应可显著改善蛋清蛋白的凝胶性。     

响应面法优化纳米SiOx/鸡蛋清蛋白可食性膜的琥珀酰化改性工艺

目的：以鸡蛋清蛋白为原料,制备纳米SiOx/鸡蛋清蛋白可食性膜,研究琥珀酰化改性工艺对膜性能的影响。方法：以琥珀酸酐添加量、反应时间、反应温度及反应pH值为影响因素,以拉伸强度、断裂伸长率、水蒸气透过系数及透油系数为响应值,采用单因素试验和响应面分析法,优化可食性膜的琥珀酰化改性工艺。结果：建立了回归模型,优化琥珀酰化改性工艺为琥珀酸酐添加量0.70 g、反应时间40.35 min、反应温度34.87 ℃、反应pH 8.30,在此条件下可食性膜拉伸强度、断裂伸长率、水蒸气透过系数及透油系数的预测值分别为4.935 MPa、75.446%、3.499 g·mm/（m2·d·kPa）、0.874 g·mm/（m2·d）,验证值为：（4.891±0.126）MPa、（73.560±4.329）%、（3.651±0.097）g·mm/（m2·d·kPa）、（0.914±0.008）g·mm/（m2·d）,与之接近,优化结果可靠。结论：琥珀酸酐添加量和反应pH值是影响膜性能的主要因素。     

添加罗望子果肉及真空处理对鱼糜凝胶特性的影响

为研究真空处理条件下罗望子果肉添加量对鱼糜凝胶特性的影响，利用质构仪、低场核磁共振等对鱼糜凝胶强度、水分状态及蛋白质分子间作用力变化进行测定。结果表明：在真空度0.09 MPa、罗望子果肉添加量3%时，真空油浴组鱼糜凝胶强度最大，为（861.36±15.32）g·mm，该组鱼糜凝胶白度及pH值也呈现下降趋势；低场核磁共振结果显示，该组自由水峰值也出现下降，二硫键含量降低，疏水相互作用力增加，有利于鱼糜凝胶结构的形成。     

增强纤维对用于燃料电池碳纸性能的影响研究

本研究分别采用亚麻纤维、黏胶纤维、ES纤维作为增强纤维与碳纤维复合制得碳纸前驱体(CPP),经树脂浸渍、热压(温度140℃,压力10 MPa)、热处理(氮气保护下,温度980℃)制备了可应用于燃料电池气体扩散层的高性能碳纸,研究了3种增强纤维及其用量对CPP强度以及对碳纸电阻率、孔隙率、拉伸强度的影响。结果表明,增强纤维显著提高了碳纸的拉伸强度,并使碳化后的树脂产生固定作用,降低了碳纸电阻率及孔隙率。亚麻纤维用量20%时,增强效果最优。相比未添加增强纤维碳纸,碳纸的拉伸强度由18. 5 MPa提升至20. 4 MPa,提高了10%;电阻率由36. 7 mΩ·cm降低至34. 2 mΩ·cm,降低了7%;孔隙率由63%下降至56. 4%,降低了10%。     

百里香酚纳米复合诱导大豆蛋白自组装凝胶及机制

为了揭示百里香酚纳米复合诱导大豆蛋白自组装凝胶的途径及机制,该文研究了蛋白浓度、百里香酚添加量、反应初始pH值和反应终止pH值对大豆蛋白与百里香酚相互作用及其凝胶形成的影响。结果表明：四者协同调控大豆蛋白-百里香酚纳米复合物凝胶的形成,百里香酚荷载量的提高可降低大豆蛋白凝胶的临界蛋白浓度（75 mg/mL）,反应结束后调节pH值至中性是凝胶形成的必要条件。在pH值为7.0条件下,百里香酚复合诱导大豆蛋白产生了明显的纤维化聚集,其颗粒平均粒径增加27.60%、光散射强度提高154.67%、Th T荧光强度提高93.78%,因此推测百里香酚复合主要通过诱导大豆蛋白纤维化聚集的产生继而诱导凝胶的形成。大豆蛋白-百里香酚纳米复合物凝胶在尿素和DTT溶液中的溶解度提高,因而推测维持凝胶网络的分子间相互作用力主要为氢键、疏水相互作用力和二硫键。研究结果为大豆蛋白冷致凝胶提供了新的技术解决方案,并为百里香酚的开发利用提供理论支撑。     

花椒水提物对鳜鱼鱼糜凝胶特性的影响

为探索花椒水提物（Zanthoxylum bungeanum aqueous extract,ZBAE）对鳜鱼鱼糜凝胶特性的影响,研究ZBAE添加量为0、0.125%、0.25%、0.5%和1.0%时,该鱼糜凝胶持水性、凝胶强度、质构、白度、二级结构和微观结构的变化。结果表明,随着ZBAE添加量增加,持水性、凝胶强度、硬度和胶着性指标均呈现先增强再减弱的趋势,并且在0.25%时均达到最大值;傅里叶红外光谱检测表明,ZBAE的添加使α-螺旋、β-折叠和无规则卷曲的相对含量值呈现先上升后下降的趋势,其中,添加量为0.125%和0.25%时,分别对应β-折叠和α-螺旋的最高值;扫描电子显微镜结果显示,ZBAE添加量为0.25%时,该凝胶网络结构更致密,分形维数、孔隙率和孔数量均显著优于未添加组（P<0.05）;此外,低添加量（<0.25%）的花椒水提物能够提高鱼糜凝胶的感官品质。因此,ZBAE具有改善鱼蛋白凝胶特性的潜力。     

超高压耦合热处理对鳙鱼鱼糜凝胶特性和水分迁移的影响

研究不同压力（100~500 MPa）耦合热处理（40 ℃/30 min,90 ℃/20 min）对鳙鱼（Aristichthys nobilis）鱼糜凝胶特性及水分迁移的影响,考察了不同处理条件下鳙鱼鱼糜的凝胶强度、持水性（WHC）、白度、质构、微观结构、SDS-PAGE电泳及水分迁移的变化,并进行相关性分析。研究发现,超高压耦合热处理能显著改善鳙鱼鱼糜的凝胶特性。超高压条件为300 MPa/15 min的压力耦合热处理（记为300PH）样品的凝胶强度和不易流动水单位质量峰面积（A22）显著性高于其他处理组（p<0.05）。与传统二段热处理样品相比,300PH样品的凝胶强度和WHC分别提高了88.40%、4.75%。与鱼糜凝胶的凝胶强度具有高度相关性的指标分别是破断强度、凹陷深度、硬度、弹性、胶着性、咀嚼性和A22。结合水单位质量峰面积（A21）与鱼糜凝胶强度具有中度相关性,这些表明300PH样品形成致密的凝胶网络结构,锁住更多结合水,限制不易流动水向自由水迁移,从而改善鱼糜凝胶的凝胶特性。该研究旨在为超高压技术鱼糜凝胶制品加工中的产业化应用、优质淡水鱼鱼糜制品的加工提供数据参考。     

Effect of high pressure and salt on pork meat quality and microstructure

The interaction of salt (0%, 1.5%, and 3% in the final product) and a high-pressure treatment (500 MPa, 20 °C, 6 min) was investigated using pork biceps femoris muscle. The Warner-Bratzler shear force and the water holding capacity (WHC) were assessed and linked to the microstructure evaluation by environmental scanning electronic microscopy (ESEM). Pressure-treated and cooked samples showed a high Warner-Bratzler shear force with a low WHC compared to control cooked samples. These negative effects could be linked to the general shrinkage of the structure as observed by ESEM. The addition of 1.5% salt was sufficient to improve the technological properties of the high-pressure-treated samples and to counteract the negative effect of high pressure on texture and WHC. This phenomenon could be linked to the breakdown in structure observed by ESEM. This study states that it is possible to produce pressurized pork products of good eating quality by adding limited salt levels.     

Comparative study on the stability of fish actomyosin and pork actomyosin

Effects of temperature, pH and ionic strength on the stability of actomyosin (AM) from fish and pork were studied using UV spectra, solubility, turbidity, and sulfhydryl group content measurement for comparison. Pork AM exhibited higher stability to cold storage and heating than fish AM. The unfolding rate of AM increased with increasing temperature. Intense aggregation occurred over 30 °C for fish AM and 40 °C for pork AM. New disulfide bonds mainly formed over 40 °C for fish AM and 60 °C for pork AM. Pork AM exhibited the higher turbidity than fish AM in the range of 50-90 °C, suggesting the higher extent of aggregation of pork AM. Ionic strength mainly influenced solubility of AM, but there was no effect on cleavage and formation of disulfide bond. The lowest solubility of both AM was at pH 5.42. Additionally, fish AM was more sensitive to pH changes than pork AM.     

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).     

Tenderisation of lamb meat: Effect of rapid postmortem temperature drop on muscle conditioning and aging

Lamb Longissimus dorsi muscles were excised from carcasses of 9-12 kg and 16-20 kg weight and brought to internal temperatures of either 0°C, 4°C, 10°C, 15°C, 20°C or 36°C within 3-4h post mortem. After rigor completion they were allowed to age at 4°C for 7 days. Sensory panel scores obtained on the first day of post-rigor aging showed that meat from heavier animals was tougher than that of lighter ones at any temperature. In all cases aging for 7 days had a marked tenderising effect which was similar at all studied temperatures, and greater in heavier animals. Tenderness was also dependent on the temperature at conditioning, as shortening caused by either high or low temperature resulted in meat toughening. The sole and surprising exception to this fact was, however, the high sensory scores obtained in 0°C experiments, even though shortening occurred as expected. In fact, a more intense proteolysis was evident in this case, which was already apparent on the first day of aging. The effect of a rapid drop of muscle temperature to 0°C on the fast and intense proteolysis, capable of even overcoming toughness due to cold shortening, was explained by the higher pH and the dramatic increase of the sarcoplasmic Ca(++) level induced early post mortem by chilling and which might result in the activation of calpain.     

The properties of connective tissue membrane and pig skin as raw materials for cooked sausage

Pig skin and epimysial membrane from young bulls were comminuted in a colloid grinder and mixed with water and additives. The resultant mixture was heated in a water bath to give an internal temperature of 72°C, and centrifuged while still hot. Such variations in the amount of water added, the salt content, the phosphate content and the pH value as are possible in cooked sausage heated to over 65°C during processing did not cause marked changes in the amount of water bound by the connective tissues, the amount of dissolved protein or the gel strength of the liquid released from the connective tissues. As the temperature rose the amount of bound water dropped, but the amount of dissolved protein and the gel strength increased. The liquid released from the connective tissue membranes formed a gel at 32°C and re-melted at 49°C. For pig skin, the corresponding temperatures were 23°C and 47°C. On the basis of this study it appears that connective tissue may be important for the water-binding capacity and firmness of cold sausage. The connective tissue membranes obtained from young bulls and pig skin are of roughly equal value in this respect, although the gel formed from connective tissue membrane is tougher.     

Effects of postmortem temperature and time on the water-holding capacity of hot-boned turkey breast and thigh muscle

Turkey breast and thigh muscles were excised immediately after slaughter and held from 0.25 to 4 h postmortem at 0, 12 or 30 °C to determine postmortem time and temperature effect on muscle pH, drip loss, sarcomere length, homogenate supernatant weight, salt-soluble protein and cooking yields. Higher temperature and longer storage time induced greater drip losses in breast. Longer storage time induced greater drip losses but the least drip loss occurred at 12 °C in thigh muscle. High temperature increased the supernatant weight in breast but decreased that in thigh. Storage time increased supernatant weight and supernatant salt soluble protein levels in both muscles. Homogenate cooking yields of breast containing water, salt and phosphate (HWSP) were higher for 0 and 12 °C compared with 30 °C, and increased with storage. The low postmortem temperature (0 °C) decreased homogenate cooking yields in thigh. These findings indicate that lower postmortem temperatures (0 and 12 °C) and shorter storage time (24 h) produced the greatest water-holding capacity in turkey breast muscle, whereas high and low postmortem temperatures (30 and 0 °C) and longer storage (168 h) produced the least water-holding capacity in raw turkey thigh muscle.     

The effect of cooking temperature on the functional properties of beef proteins: The role of ionic strength, pH, and pyrophosphate

This study examined the effect of ionic strength (0·12 to 0·52), pH (5·50 and 6·00), pyrophosphate (PP) concentration (0 and 0·31%) and cooking temperature (52 to 87°C) on the cook yield (CY) and tensile strength (TS) of beef homogenates. Increasing the ionic strength, pH and pyrophosphate concentration increased the temperature at which cooking loss first occurred and decreased the temperature required for maximum TS. For most treatments, ionic strengths between 0·32 and 0·42 prevented cooking loss at all temperatures; the lower ionic strengths were required at the higher pH and PP concentration. Maximum TS occurred at 66°C for treatments that had no cooking loss between 60° and 75°C. For treatments that had cooking loss in this temperature range, TS increased linearly with increasing temperature; however, the TS values of these treatments were much lower than those in the former category. CY and TS were optimized by heating to 66°C. PP had a positive effect on both functional properties at ionic strengths >0·25 but a negative effect at ionic strengths <0·25.     

纸浆物理强度与纤维表面木素含量关系的探讨

通过酸析木素的方法在漂白硫酸盐浆纤维表面沉积木素,探讨了纸浆纤维表面木素含量对纸浆强度性能的影响.研究结果表明,随着硫酸盐木素溶液pH值的降低,木素在纸浆纤维表面的沉积吸附量增加;经过打浆作用的纸浆纤维暴露出更多的表面,能够吸附更多的木素;纸浆纤维表面木素含量与纸浆的抗张指数、耐破指数呈负的线性相关性,相关方程式分别为y=-1.23x +56.9(R=0.99)和y=-0.104x +4.62(R=0.96);增加纤维表面木素含量会降低纸浆纤维间的结合强度.     

Listeria monocytogenes inhibition by defatted mustard meal-based edible films

An antimicrobial edible film was developed from defatted mustard meal (Sinapis alba) (DMM), a byproduct from the bio-fuel industry, without incorporating external antimicrobials and its antimicrobial activity against Listeria monocytogenes and physical properties were investigated. The DMM colloidal solution consisting of 184 g water, 14 g DMM, and 2g glycerol was homogenized and incubated at 37°C for 0.2, 0.5, 24 or 48 h to prepare a film-forming solution. The pH of a portion of the film-forming solution (pH 5.5) was adjusted to 2.0 or 4.0. Films were formed by drying the film-forming solutions at 23°C for 48 h. The film-forming solution incubated for 48 h inhibited L. monocytogenes in broth and on agar media. Antimicrobial effects of the film prepared from the 48 h-incubated solution increased with decrease in pH of the solution from 5.5 to 2.0. The film from the film forming solution incubated for 48 h (pH 2.0) initially inhibited more than 4.0 log CFU/g of L. monocytogenes inoculated on film-coated salmon. The film-coating retarded the growth of L. monocytogenes in smoked salmon at 5, 10, and 15°C and the antimicrobial effect during storage was more noticeable when the coating was applied before inoculation than when it was applied after inoculation. The tensile strength, percentage elongation, solubility in watercxu, and water vapor permeability of the anti microbial film were 2.44 ± 0.19 MPa, 6.40 ± 1.13%, 3.19 ± 0.90%, and 3.18 ± 0.63 gmm/kPa hm(2), respectively. The antimicrobial DMM films have demonstrated a potential to be applied to foods as wraps or coatings to control the growth of L. monocytogenes.     

Influence of growth conditions on pressure resistance of Vibrio parahaemolyticus in oysters and the optimization of postpressure treatment recovery conditions

Vibrio parahaemolyticus ATCC 43996 was grown at 15°C for 53 h, 20°C for 24 h, 25°C for 12 h, 30°C for 9 h, 35°C for 9 h, or 40°C for 6 h to early stationary phase. Oyster meats were blended, autoclaved at 121°C for 15 min, inoculated with V. parahaemolyticus, and pressure treated at 250 MPa for 2 and 3 min and at 300 MPa for 1 and 2 min at 21°C. Overall, growth temperatures of 20 and 40°C yielded the greatest pressure resistance in V. parahaemolyticus. The effects of salt concentration and H(2)O(2)-degrading compounds on the recovery of V. parahaemolyticus also were investigated. Sterile oyster meats were inoculated with V. parahaemolyticus and treated at 250 MPa for 1, 2, or 3 min at 21°C. These meats were then blended with 0.1% peptone water supplemented with 0.5 to 1.5% NaCl and plated on tryptic soy agar (TSA) supplemented with 0 to 3.5% NaCl. For recovery of pressure-injured cells, peptone water with 1% NaCl and TSA with 0.5% NaCl were the best diluent and plating medium, respectively. Addition of sodium pyruvate (0.05 to 0.2%) or catalase (8 to 32 U/ml) did not increase the recovery of V. parahaemolyticus after pressure treatment. The effect of incubation temperature and gas atmosphere on the recovery of V. parahaemolyticus after pressure treatment also was determined. Aerobic incubation at 30°C resulted in the highest recovery of V. parahaemolyticus in sterile oyster meats. The 30°C incubation temperature was also the optimum temperature for recovery of V. parahaemolyticus in pressure-treated live oysters. The results of this study indicate that the growth conditions for V. parahaemolyticus before and after high hydrostatic pressure treatment should be taken into consideration when assessing the efficacy of pressure inactivation.