模糊数学感官评价结合响应面法优化鲊辣椒混菌发酵工艺

以小米椒和玉米粉为原料,植物乳植杆菌XZ3和生香酵母菌Y50为菌种,制作一款混菌发酵鲊辣椒。以鲊辣椒的模糊感官评分为响应值,采用Box-Behnken中心组合设计试验对鲊辣椒混菌发酵工艺进行优化,并测定其产品的功能性成分。结果表明,混菌发酵鲊辣椒的最优发酵条件为:植物乳植杆菌XZ3与生香酵母菌Y50的比例为1∶1、混菌添加量为2.5%、食盐添加量为4%、发酵时间6 d。在此优化条件下,鲊辣椒的感官评分为8.45分。与不接种自然发酵鲊辣椒和利用植物乳植杆菌XZ3纯种发酵的鲊辣椒进行对比,发现优化后的混菌发酵鲊辣椒的香气更突出。进一步测定其功能性成分发现,混菌发酵鲊辣椒中多酚组分含量最高且种类检出最多,其总酸含量、辣椒碱含量和总黄酮含量都显著高于自然发酵鲊辣椒。除此之外,相比于其他两种,混菌发酵鲊辣椒中甜味氨基酸的含量上升,苦味氨基酸的比例降低。该研究为混菌发酵鲊辣椒的生产提供了有益参考。

鲊辣椒生香酵母的分离筛选鉴定及其应用研究

从自然发酵鲊辣椒中以嗅闻法结合总酯含量作为生香酵母的筛选依据分离筛选到1株生香酵母,经鉴定并分类命名为库德里阿兹威氏毕赤酵母菌(Pichia kudriavzevii)Y50,为探究该菌株混菌发酵生产鲊辣椒的品质提升作用,将Y50与植物乳杆菌混合发酵鲊辣椒(C),以自然发酵的鲊辣椒(A)以及接种植物乳杆菌发酵的鲊辣椒(B)为对比研究对象,对3种鲊辣椒的基本理化指标、辣椒碱、有机酸和挥发性成分进行比较分析。结果表明,3种鲊辣椒pH值、总酸、亚硝酸盐、胡萝卜素含量较为接近,但鲊辣椒C中有机酸含量达(25.46±0.32)g/kg,比鲊辣椒A和鲊辣椒B分别高出57.8%和32.2%。鲊辣椒A、B、C中分别检出挥发性风味物质90种、67种和72种,其中鲊辣椒C的挥发性物质含量最高,为(10101.11±99.04)μg/kg,酯类、醇类、醛类、酸类挥发性物质含量均有提高,相比A、B分别提升了75%、358%、106%、23%和102%、59%、68%、51%,赋予鲊辣椒更浓郁的酯香、花香和果香,说明添加生香酵母Y50能提升鲊辣椒整体的风味品质,通过气味活度值(odor activity value,OAV)的计算,共检出22种OAV>1的香气化合物,这些关键香味物质赋予了鲊辣椒特有的香气特征,其中β-紫罗兰酮、2-甲基丁酸乙酯、己酸己酯、正庚醇、(+)-柠檬烯、庚醛、愈创木酚是构成鲊辣椒C风味的关键物质。试验表明Y50具有进一步应用于鲊辣椒生产的潜力。

Improving the Antioxidant Properties of Fermented Camel Milk Using Some Strains of <i>Lactobacillus</i>

This study aimed at improving the antioxidant capacity of fermented camel milk using some single strains of Lactobacillus (Lb. helveticus B-734, Lb. casei subsp. casei B-1922, Lb. paracasei subsp. paracasei B-4560, Lb. rhamnosus B-1445 or Lb. rhamnosus B-442), as well as evaluating the acceptability of the final products. The acidity, proteolysis degree, antioxidant activity, viscosity and organoleptic properties of fermented milk were assessed during 14 days of storage at 4°C. Total phenolic content (TPC), DPPH radical scavenging activity, Ferrous ion chelating ability (FCA) and Ferric reducing antioxidant power (FRAP) assays were used to determine the antioxidant activity of fermented milks. The results indicated that fermented milks differed significantly (P < 0.05) in all studied parameters due to the type of starter culture used. During storage period, samples containing Lb. helveticus had the highest proteolysis degree, while samples with commercial starter culture (control) showed the lowest degree of proteolysis. Fermented milks containing Lactobacillus strains showed higher DPPH radical scavenging activity compared to those samples containing commercial starter culture. By the end of storage, there was a significant improvement (P < 0.05) in scavenging activity for all fermented milk samples. Regarding FCA, at the beginning of storage fermented milks containing Lb. paracasei, Lb. rhamnosus B-442 or commercial starter culture had the highest FCA values, while Lb. rhamnosus B-1445 samples recorded the highest value at the end of storage. Lb. helveticus samples had the highest TPC and FRAP values (P < 0.05) throughout the storage. There was a high significant correlation (P < 0.0001) between the proteolysis degree and the values of FRAP and TPC. Samples containing Lb. rhamnosus B-442, Lb. rhamnosus B-1445 or commercial starter culture received the highest taste and overall acceptability scores while Lb. helveticus samples were the lowest. It is recommended to use Lb. rhamnosus B-442 and Lb. rhamnosus B-1445 for producing fermented camel milk with high antioxidant activity and acceptability.

Validation of the Methods for Detection the Non-Milk Fat in a Mixture of Milk Fat and Palm Oil

Milk fat contains a variety of nutritive and health-promoting compounds that guard against some disease. In the current system of global competition, when the quality of milk and milk products is not an option but rather a requirement, therefore, determining the purity of milk fat is critical. This study aims to validate analytical methods for detecting palm oil in a mixture of milk fat and palm oil. Methods of this study was involved detection of non-milk fat in fat blinders by determining the saponification value, iodine number, refractive index, butyro refractometer reading, Gas chromatography, Reverse Phase High-performance liquid chromatography, and Fourier transforms Infrared. The results of this study revealed that the saponification value, Iodine number, refractive index, and Butyro Reading could be used to detect the addition of palm oil by a level of 10% - 20% or more to the milk. The level of some fatty acids in the milk as determined by GC, such as myristic acid (C14:0), palmitic acid (C16:0), and stearic acid (C18:0), is correlated well with the level of adding palm oil to milk fat. The determination of cholesterol and β-sito-sterol content by RP-HPLC could be used for the detection of the addition of palm oil to milk fat. The spectrum behavior produced by FTIR spectroscopy in this adulterated sample is almost the same, so this technique could not be used to detect the palm oil in milk fat.

The Impact of Microbial Transglutaminase on the Quality and Antioxidant Activity of Camel-Milk Soft Cheese

This study aimed at investigating the impact of adding microbial transglutaminase (MTGase) after rennet addition on some properties of fresh soft cheese made from camel milk. MTGase was added to milk at concentration of 80, 100 and 120 U/L after 20 and 30 min of renneting. The chemical composition, yield, hardness, antioxidant activity and sensory properties of cheese were estimated. Enzymatic protein crosslinking was analyzed by SDS-PAGE. Results revealed that MTGase-treated cheeses were higher in moisture and lower in protein content compared to control. In addition, the concentration of MTGase and time of addition significantly (P 0.05) impacted these parameters. Among treated cheeses, samples with 80 U of MTGase and addition time of 20 min were the highest in total solids and protein content. Adding MTGase significantly (P 0.05) increased the cheese yield, however, increased MTGase concentration at any time of addition did not improve it. The electrophoretic patterns of MTGase-cheese proteins showed a reduction in the intensity of caseins bands and the appearance of new protein fractions with high molecular weights. However, the changes in the intensity of the whey proteins bands were not sufficiently clear as caseins. The cheese hardness was significantly (P 0.05) affected by adding MTGase. Cheese containing 80 U of MTGase had the highest hardness value compared to control and other treated samples. The antioxidant activity of cheese was negatively influenced by adding the enzyme. The use of MTGase enhanced the mouthfeel, texture and overall acceptability of cheese. However, the effect of MTGase concentration and addition time was not significant (P > 0.05) on the sensory attributes. In conclusion, adding MTGase to milk at concentration of 80 U after 20 min of renneting is recommended to improve the yield, textural and some sensory properties of fresh soft cheese made from camel milk.

Application of Salt Whey from Egyptian Ras Cheese in Processed Cheese Making

The objective of this study was to evaluate characteristics of processed cheese made from salt Ras cheese whey and young Cheddar containing exopolysaccharide producing cultures (EPS) as compared with those in cheese made from EPS-negative cheeses. Processed cheeses were manufactured using young (1 day) or 1-month-old EPS-positive or EPSnegative Cheddar cheese and replacing the added water by Ras cheese whey or ultrafiltrated (UF) whey. Moisture and fat of processed cheese were standardized to 54% and 23%, respectively. Exopolysaccharide-positive processed cheese was softer, less chewy and gummy than the EPS-negative cheeses. The hardness and chewiness were lower in processed cheeses made from 1-month-old Cheddar than in the corresponding cheeses made from 1-day-old Cheddar cheese. Sensory scores for texture of EPS positive processed cheeses were higher than those of the EPS-negative cheeses. Generally, processed cheese made from replacing all added water with whey received higher scores in flavor and overall than did the corresponding cheeses made without whey. The obtained results are showing promise for application of salt whey in processed cheese making.

Antioxidant Properties of Fermented Camel Milk Prepared Using Different Microbial Cultures

This study investigated the effect of using different combinations of commercial starter culture and lactobacilli strains on the antioxidant properties of fermented camel milk for 14 days. The bacterial strains included Lb. casei subsp. casei B-1922, Lb. paracasei subsp. paracasei B-4560, Lb. rhamnosus B-442 and Lb. rhamnosus B-1445. The antioxidant activity of fermented milk was estimated using DPPH radical scavenging activity, ferrous ion chelating activity (FCA) and ferric reducing power assays. The total phenolic content (TPC), titratable acidity, proteolysis degree and sensory acceptability of samples were also evaluated. The results showed that all the studied parameters were affected by both the type of starter culture and storage. Samples containing the commercial starter and Lb. rhamnosus B-1445 had the highest DPPH radical scavenging activity and TPC throughout storage. Fermented milks prepared using the commercial starter and Lb. rhamnosus B-442 or Lb. paracasei retained their high FCA and reducing power throughout storage compared to the other samples. Fermented milk containing the commercial starter and Lb. casei showed the lowest antioxidant activity. The DPPH scavenging activity for all fermented milks decreased sharply during storage, while the change in FCA, reducing power and TPC differed among the samples during storage. The highest acidity was observed in the samples containing the commercial starter and Lb. paracasei, while fermented milk prepared using commercial starter and Lb. rhamnosus B-1445 had the lowest acidity. Samples containing the commercial starter and Lb. casei had the greatest proteolysis during the first week of storage, while samples containing the commercial starter and Lb. rhamnosus B-1445 had the highest proteolysis on day 14. Fermented milks with commercial starter and Lb. rhamnosus B-1445 or Lb. paracasei were the most acceptable products, while samples containing the commercial starter and Lb. casei were less acceptable.