Compositional factors associated with calcium lactate crystallization in smoked Cheddar cheese

Previous researchers have observed that surface crystals of calcium lactate sometimes develop on some Cheddar cheese samples but not on other samples produced from the same vat of milk. The causes of within-vat variation in crystallization behavior have not been identified. This study compared the compositions of naturally smoked Cheddar cheese samples that contained surface crystals with those of samples originating from the same vat that were crystal-free. Six pairs of retail samples (crystallized and noncrystallized) produced at the same cheese plant on different days were obtained from a commercial source. Cheese samples were 5 to 6 mo old at the time of collection. They were then stored for an additional 5 to 13 mo at 4°C to ensure that the noncrystallized samples remained crystal-free. Then, the crystalline material was removed and collected from the surfaces of crystallized samples, weighed, and analyzed for total lactic acid, l(+) and d(−) lactic acid, Ca, P, NaCl, moisture, and crude protein. Crystallized and noncrystallized samples were then sectioned into 3 concentric subsamples (0 to 5 mm, 6 to 10 mm, and greater than 10 mm depth from the surface) and analyzed for moisture, NaCl, titratable acidity, l(+) and d(−) lactic acid, pH, and total and water-soluble calcium. The data were analyzed by ANOVA according to a repeated measures design with 2 within-subjects variables. The crystalline material contained 52.1% lactate, 8.1% Ca, 0.17% P, 28.5% water, and 8.9% crude protein on average. Both crystallized and noncrystallized cheese samples contained significant gradients of decreasing moisture from center to surface. Compared with noncrystallized samples, crystallized samples possessed significantly higher moisture, titratable acidity, l(+) lactate, and water soluble calcium, and significantly lower pH and NaCl content. The data suggest that formation of calcium lactate crystals may have been influenced by within-vat variation in salting efficacy in the following manner. Lower salt uptake by some of the cheese curd during salting may have created pockets of higher moisture and thus higher lactose within the final cheese. When cut into retail-sized chunks, the lower salt, higher moisture samples contained more lactic acid and thus lower cheese pH, which shifted calcium from the insoluble to the soluble state. Lactate and soluble calcium contents in these samples became further elevated at the cheese surface because of dehydration during smoking, possibly triggering the formation of calcium lactate crystals.     

固态发酵白酒生产中芽孢杆菌属细菌产乳酸特性及降乳研究

本文对白酒生产现场分离纯化的芽孢杆菌属细菌产乳酸的状况及条件进行了研究，确认在白酒生产中，这些菌株是产生乳酸的重要菌类。菌株在以葡萄糖为碳源、蛋白胨为氮源、于３０～４０℃静置培养时可得到多量乳酸。发现有机物Ｃ－Ⅱ以０．０５％的加量添加到酒醅中时，白酒基酒中乳酸乙酯含量平均可降低２１．９％。     

鸡蛋壳制备乳酸钙工艺条件的研究

本试验对鸡蛋壳制备乳酸钙的工艺进行了研究。结果表明最佳条件为:鸡蛋壳在900℃下灰化110min,4g灰分加水50ml制成石灰乳,石灰乳中加入13mol/L乳酸14ml发生中和反应,经过滤、结晶、过滤后干燥制得白色粉末产品。产率为75.6%,乳酸钙含量为88.1%。     

Beef sausage structure affected by sodium chloride and potassium lactate

A histological and ultrastructural study was conducted to characterize changes in the muscle fibre structure of three fresh sausage preparations, depending on meat composition, sodium chloride (NaCl) and potassium lactate (K-lactate) contents. After addition of 0.8% and 1.6% NaCl, 65% and 51%, respectively, of the area observed showed well preserved fibres (histological data). The altered regions presented a large disorganization of the myofilaments and a solubilization of the sarcolemma and of the Z lines. K-lactate addition had no marked effects on meat structure. The preparation containing some sheep meat was more sensitive to salt than the others containing only bovine meat. The level of alteration was much lower than those obtained in pork meat in another study. Technological conditions used to modify the internal muscle fibre structure during sausage processing depend on the species used. Therefore, the classification of the sausage preparation to “meat preparation” or “meat product” under the EU regulation (EC) No. 853/2004 (which assign meat preparations to meat if the product has undergone a process insufficient to modify the internal muscle fibre structure of the meat) must be systematically controlled when changing the meat sausage composition.     

L-乳酸米根霉发酵体系LDH活力及代谢调控研究

乳酸脱氢酶(LDH)是米根霉代谢生产L-乳酸过程的关键酶，研究其在发酵过程中的活力变化，从酶水平分析发酵条件对L-乳酸发酵的影响，对米根霉发酵生产L-乳酸的人工代谢调节、菌种选育具有重要意义。本文研究了摇瓶条件下的米根霉AS3．1208发酵体系中乳酸脱氢酶的活力调控条件及与L-乳酸即时产率的关系，结果表明，发酵体系中L-乳酸产率与LDH活力在36～40h时最高。葡萄糖作为C源的L-乳酸产率与LDH活力比甘薯淀粉高。与牛肉膏和蛋白胨相比，硫酸铵是米根霉代谢的最佳N源，0．40％的硫酸铵具有较高的乳酸产率与LDH活力。发酵培养基中添加CaCO3与否，对乳酸产率与LDH活力有极大影响。以甘薯淀粉为碳源，在250ml三角瓶中的装液量为100ml，发酵36～40h时的L-乳酸即时产率最大，此时LDH活力也最高。     

乳酸脱氢酶高产菌株的选育及条件研究

以植物乳酸短杆菌RS2-2(Lactobacillus plantarum)为出发菌株,经紫外线、亚硝基胍单独处理和复合处理,获得1株乳酸脱氢酶高产菌株U-N-B14,通过优化实验对该菌株生产乳酸脱氢酶的营养要求和发酵条件进行了研究,优化后的发酵培养基组成为(g/L):酵母膏10,麦芽糖12,乙酸铵4,K2HPO44,NaCl 8,吐温80 2mL/L。发酵条件是:培养温度30℃,pH值6.5,培养时间24 h,接种量8%。在此条件下,1.5 m3罐中试生产的乳酸脱氢酶产量可达1 497 U/g。     

海藻糖、乳酸钠对冻藏鳙鱼鱼糜蛋白抗冻效果的影响

以凝胶强度、盐溶性蛋白含量、Ca~(2+)-ATPase活性、总巯基、表面疏水性为指标并结合DSC分析(差示扫描量热分析),研究了海藻糖、乳酸钠在8%(w/w)水平上对鳙鱼鱼糜蛋白在-18℃冻藏24周的抗冻效果,并将其抗冻效果与传统商业抗冻剂(4%蔗糖+4%山梨糖醇)进行了对比。结果表明,海藻糖、乳酸钠的加入能较好地抑制冻藏鳙鱼鱼糜蛋白的冷冻变性,表现在这2种物质加入后,冻藏鳙鱼鱼糜的凝胶能力得到较好的维持,盐溶性蛋白含量、Ca~(2+)-ATPase活性和巯基含量的下降及表面疏水性的增加也得到很好的抑制,2种物质的抗冻效果比传统商业抗冻剂具有明显的优势。DSC分析表明,抗冻剂的添加可能改变了鳙鱼鱼糜肌球蛋白的结构,使其变得更稳定,从而表现出较好的冻藏稳定性。海藻糖、乳酸钠都属于低甜度、低热值物质,因此在鱼糜加工业中有望成为传统商业抗冻剂的替代物。     

Sodium Lactate Affects Pathogens in Cooked Beef

Cooked, quartered beef top rounds containing either 1, 2, 3 or 4% sodium lactate were aseptically sampled and slice sections were inoculated with Listeria monocytogenes (ATCC 43256), Staphylococcus aureus (ATCC 27154), Salmonella typhimurium (ATCC 13311), Clostridium perfringens (ATCC 12924), or Escherichia coli O157:H7 (ATCC 43895). Inoculated slices were stored at 10°C for 0. 7. 14. 21 or 28 days.‘Three and 4% sodium lactate generally displayed lim-ited proliferation of S. typhimurium, L. monocytogenes and E. coli O157:H7 when compared with control roasts (0% sodium lactate) and roasts containing 2% sodium lactate.     

碳酸钙与外源蛋白复配物对含有MTGase的鱼糜凝胶特性的促进作用

目的研究钙盐、外源蛋白及其复配物对含微生物产转谷氨酰胺酶(MTG)的鲢鱼糜凝胶品质的影响。方法将碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白及其复配物添加到含MTG(2 U/gg_(鱼蛋白))的鲢鱼糜中并制成凝胶,测定鱼糜凝胶的持水性、质构特性(破断强度、凹陷深度、硬度、内聚性、咀嚼性)、白度和聚丙烯酰胺凝胶电泳图谱。结果添加碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白及其复配物均可不同程度地改善含MTG的鱼糜凝胶的凝胶特性,且添加其复配物优于单独添加碳酸钙、乳酸钙、卵清蛋白、大豆分离蛋白。经试验优化,将8μmol/U_(MTG)碳酸钙、4 mg/U_(MTG)卵清蛋白、4 mg/U_(MTG)大豆分离蛋白添加到含有2 U/g_(鱼蛋白)MTG的鲢鱼糜中可获得最佳凝胶品质,鱼糜凝胶的破断力、凹陷深度最高,硬度、咀嚼性、白度均显著高于单独添加MTG(P0.05),也明显高于添加2 U/g_(鱼蛋白)其他品牌商品MTG的(P0.05)。结论 CaCO_3与外源蛋白复配物对含有MTG的鱼糜凝胶特性具有显著促进作用,将碳酸钙、卵清蛋白、大豆分离蛋白与MTG按比例混合可制成鱼糜制品专用的复配酶制剂。     

乳酸及乳酸钠在鲜肉保鲜中的应用

本试验采用乳酸、乳酸钠及其二者的混合物按不同比例加入鲜猪肉中，在室温30℃湿度85～95％条件下贮存，定时进行内的鲜度检测，并与未添加任何深加剂的肉作比较，试验结果表明，单一使用与混合使用这二种添加剂均有不同程度的保鲜效果，以0．21％乳酸、2．79％乳酸钠添加量保鲜效果较好，可延长保鲜期1～3天。