Proteolysis of Hispanico cheese manufactured using lacticin 481-producing Lactococcus lactis ssp. lactis INIA 639

Hispánico cheese was manufactured using lacticin 481-producing Lactococcus lactis ssp. lactis INIA 639, bacteriocin-nonproducing L. lactis ssp. lactis INIA 437, or a combination of both strains, as starter cultures. Lactobacillus helveticus LH 92, a culture of high amino-peptidase activity sensitive to lacticin 481, was added to all vats. Milk inoculation with the bacteriocin producer promoted early lysis of Lb. helveticus cells in cheese. Cell-free aminopeptidase activity in cheese made with the 3 lactic cultures was 1.8 times the level reached in cheese made only with L. lactis strain INIA 437 and Lb. helveticus, after 15 d of ripening. Proteolysis (as estimated by the o-phthaldialdehyde method) in cheese made with the 3 lactic cultures was twice as high, and the level of total free amino acids 2.4 times the level found in cheese made only with L. lactis strain INIA 437 and Lb. helveticus, after 25 d of ripening. Hydrophobic and hydrophilic peptides and their ratio were at the lowest levels in cheese made with the 3 lactic cultures, which received the lowest scores for bitterness and the highest scores for taste quality.     

发酵剂对牦牛乳硬质干酪成熟过程中生物胺的影响

乳酸菌产生物胺的能力具有菌株特异性,因此,为了探究不同种类发酵剂对牦牛乳硬质干酪中生物胺形成的影响,该试验利用高效液相色谱对3种不同发酵剂制作的硬质干酪成熟过程中生物胺进行了测定和分析。结果表明,嗜热和嗜温发酵剂牦牛乳硬质干酪中检测出2-苯乙胺、腐胺、尸胺、组胺和酪胺,混合发酵剂干酪中检测出腐胺、2-苯乙胺、尸胺和酪胺。各生物胺之间呈现正相关性。3种不同发酵剂干酪在1～6个月成熟过程中,其各生物胺整体呈现增加趋势,嗜热、嗜温和混合发酵剂干酪中总生物胺最高含量分别为(448.3±9.6)、(456.8±58.4)、(293±24.5)mg/kg。组胺和酪胺是2种毒性相对高的生物胺,嗜热发酵剂干酪中组胺和嗜温发酵剂干酪中酪胺最高,其最高含量分别为(20.8±7.9)、(92.9±6.7)mg/kg,混合发酵干酪中未检测出组胺,酪胺含量次之,3种不同发酵剂干酪中组胺、酪胺含量均低于推荐安全剂量50 mg/kg和100 mg/kg。这为合理选择发酵剂和控制干酪中生物胺形成提供了依据。     

Effect of autochthonous starter cultures isolated from Siahmazgi cheese on physicochemical,microbiological and volatile compound profiles and sensorial attributes of sucuk,a Turkish dry-fermented sausage

The effect of adding autochthonous starter cultures isolated from Siahmazgi cheese, on the physicochemical parameters and microbial counts of sucuk was investigated during the ripening period. SPME–GC/MS was used in volatile compound analysis and a trained group of panelists carried out sensory analysis of the final product. After preliminary screening, three strains of Lactobacillus plantarum, which possess desirable technological properties, were used to prepare three starter cultures: LBP7, LBP10 and LBP14. The addition of LBP7 and LBP14 starter cultures had a significant effect (P < 0.05) on lightness, leading to higher L values compared to control sausages during the ripening period. Both LBP7 and LBP14 sausages showed higher counts of lactic acid bacteria, lower growth of Enterobacteriaceae and Gram-positive catalase-positive cocci and greatly lowered the pH value compared to control sausages throughout the ripening process. At the end of the ripening process, lactic acid bacteria counts were affected (P < 0.05) by the addition of starter culture since higher counts were observed in sausages prepared with LBP7 (9.14 log CFU/g) and LBP14 (8.96 log CFU/g) batches. The decrease of water activity during the ripening of sausages was not affected by the various starters. The texture profiles of all sausages were similar except for LBP10, which showed lower hardness and gumminess during ripening. Under the conditions of the study, volatile compounds were mainly from spices, and no marked differences were found among inoculated sausages. However, sensory evaluation revealed that most of the sensory attributes were scored higher for inoculated sausages than for the control ones. Therefore, LBP7 and LBP14 could be promising candidates for inclusion as starter cultures for the manufacture of sucuk.