Species of lactic acid bacteria (LAB) represent as potential microorganisms and have been widely applied in food fermentation worldwide. Milk fermentation process has been relied on the activity of LAB, where trans- formation of milk to good quality of fermented milk products made possible. The presence of LAB in milk fermentation can be either as spontaneous or inoculated starter cultures. Both of them are promising cultures to be explored in fermented milk manufacture. LAB have a role in milk fermentation to produce acid which is important as preservative agents and generating flavour of the products. They also produce exopolysaccharides which are essential as texture formation. Considering the existing reports on several health-promoting properties as well as their generally recognized as safe (GRAS) status of LAB, they can be widely used in the developing of new fermented milk products.
The characterization of kivuguto milk and milks fermented by two strains of kivuguto starter in monoculture was studied regarding four technological properties: acidification, rheology, proteolysis and flavor compounds. The results of this study allowed for the evaluation of the acidification level and counts of bacteria in milk made by selected kivuguto starters, as well as the viscoelastic properties. These properties showed how far the kivuguto rheology can be compared with other fermented milks, like yogurt, filmjölk and leben. Assessment of the static headspace by GC coupled to mass spectrometry is a suitable method for the extraction and analysis of volatile compounds in fermented milks and revealed the kivuguto aroma profile. The discrimination test by a sensory panel also detected differences in kivuguto milk compared to other milks. Our findings show that the selection procedure satisfactorily provided a starter culture for manufacturing kivuguto milk.
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In the selected formulation added kefir fermented from each type of milk. After gel was formed, the gel stability evaluation included organoleptic observation, homogeneity observation, pH measurement, viscosity measurement, spreading energy measurement, and freeze thaw test conducted over 28 days i.e. 1 st , 3 rd , 5 th , 7 th , 14, 21, and 28. The product of gel kefir has also been made by panelist test and antibacterial activity test. The gel evaluation data from the research results were analyzed by Analysis of Variation (ANOVA) method using SPSS program.
confirmed that L. helveticus strains, in particular, were able to form antihypertensive peptides from milk proteins, including Val-Pro-Pro (VPP) and Ile-Pro-Pro (IPP) with demonstrated in vivo antihypertensive activity in a rat model and human studies (Masuda et al., 1996, Seppo et al., 2003, Hirota et al., 2007). Also yoghurt starter cultures and commercial probiotic bacteria have been verified to form different bioactive peptides in milk during fermentation (Donkor et al., 2007b). Virtanen et al (2007) also showed that a single industrial dairy culture generated antioxidant activity in the whey protein fractions during milk fermentation. The activity was positively correlated with the degree of proteolysis suggesting that peptides were responsible for the antioxidative property. Similarly Chen et al (2007) observed that a commercial starter culture mixture consisting of five LAB strains released peptides that increased Angiotensine Converting Enzyme inhibitory (ACE-I) activity of the final hydrolyzate. A body of literature on this topic is extensive and covered into a greater detail in Chapter 2. For example, Donkor et al (2007b) studied growth, proteolytic and in vitro ACE inhibitory activities in milk fermented by several dairy LAB cultures and probiotic strains (L. acidophilus, Bifidobacterium. lactis, L. casei). Again they found that Lactobacillus strains showed the greatest ACE-inhibitory activity. Pihlanto-Leppala et al (1998) studied the potential of in vitro ACE-inhibitory peptides released from cheese whey and caseins during fermentation by the action of various commercial dairy starters used in the manufacture of yoghurt, ropy milk and sour milk. While there was no ACE-inhibitory activity detected initially, after adding pepsin and trypsin, as digestive enzymes, to the hydrolysates, several strong ACE-inhibitory peptides were produced and identified.
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Matar and colleagues  have reported different roles and functions of biologically active peptides released from fer- mented milks. Peptides and free fatty acids released during fermentation were shown to increase the immune response. In this way, peptidic fractions liberated during milk fermentation with Lactobacillus helveticus R389 stimulated the immune system and inhibited the growth of an immunodependent fib- rosarcoma in a mouse model . The peptidic profiles of milk proteins were significantly different after fermentation by LAB, suggesting that microbial proteolysis could be a potential source of bioactive peptides . Milk fermented with L. hel- veticus R389, a bacterium with high protease and peptidase activity, exerted an antimutagenic effect, while a mutant strain (L. helveticus L89) deficient in proteolytic activity did not . In a similar way, milk fermented with the proteolytic strain increased the number of IgA-positive cells in the small intes- tine as well as in the bronchus of mice, but fermented milk obtained with the proteolytic-deficient mutant strain did not show the same in vivo results .
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Experimental design and results of Box-Behnken In order to optimize fermentation conditions of skimmed goat milk fermentation temperature (A), the strain ratio (B), and inoculum size (C), response surface methodology (RSM) which has been demonstrated to allow evaluation of the effects of multiple parameters on response variables (Pinho et al., 2011)was used. Among them, the strain ratio is about (BB: LC:(LB: ST)), L.bulgaricus and S.thermophilus are used as basic culture medium. The corresponding Box-Behnken design and the results are listed in Table 3. The viable counts of B.bifidum and L.casei were represented by Y 1 (×10 6 cfu/mL), Y
supplementation in younger dairy cows (up to 2 lacta- tions). A similar finding on milk production was re- ported in dairy cows fed a total mixed ration supplemented with Propionibacterium strain P169 , in which the positive effect of the DFM was more marked in multiparous than in primiparous cows. The studies cited above suggest that parity may have an in- fluence on the response to DFM, with primiparous cows, like the ones used in our study, being less reactive. More in vivo studies needed to confirm this suggestion. Not- withstanding, strain particularities and other factors might also be involved.
The ruminal pH and temperature were similar among treatments (P > 0.05) and were in normal ranges (Table 3), which have been reported as optimal for microbial digestion of fiber (39˚C to 41˚C and 6.5 to 7.0, respect- tively) as mentioned by Wanapat . Moreover, it may confirm that cow obtained an appropriate level of rough- age to concentrate ratio for optimum of rumen fermenta- tion. Results from many studies have shown that rumen fermentation is generally change when animal fed with difference of forage to concentrate ratio [26,27]. Fur- thermore, diets higher in non-structural carbohydrate such as starch normally cause of a decrease in microbial growth efficiency due to a decrease in ruminal pH and a slower ruminal passage rate . Concentrations of ammonia nitrogen (NH 3 -N), blood urea nitrogen, milk
goat milk could possibly have a stronger inhibitory effect on the growth of Salmonella enteritidis D than fermented cow milk. Consequently, one of the primary objectives of this research was to compare the inhibition degree of fermented cow milk on the growth of S. enteritidis D with that of fermented goat milk. There is no clear scientific evidence of the antagonistic effect of goat milk fermented with the use of bifidobacteria against pathogenic bacteria, especially against Salmonella species. In order to establish the possible diffe- rences, in vitro microbiological experiments were conducted. Furthermore, the correlation between the inhibition degree and some fermentation pa- rameters was determined in this study. Following up some earlier studies (Bernet-Camard et al. 1997; Holzapfel et al. 1998; Slačanac et al. 2005), the inhibition degree was connected to CFU of Bifidobacterium longum Bb-46 and pH value of fermented milk. Correlations were determined during the whole fermentation process. The results entirely confirm the hypothesis that goat milk fermented using Bifidobacterium longum Bb-46 has a higher inhibitory potential than is that of cow milk. Furthermore, high correlation between the inhibition degree and the measured fermen- tation parameters of cow and goat milk (CFU of Bifidobacterium longum Bb-46 and pH value of fermented milk) was also determined.
Food flavour (taste plus odour) is a characteristic not only related with the acceptance of the product but also associated with the feeling of consumer sat- isfaction (Routray & Mishra 2011). Consumers usually chose food according to the whole acceptance, not accentuating different characteristics. However, we can accentuate the milk-G sample, treated with L. sakei and SmF, which showed not only the highest overall acceptability but also the separate character- istics (overall taste acceptability, taste pleasure, low external taste and smooth consistence) were the most acceptable to the panellists.
diseases (Dirar, 1993; Abdelgadir et al., 1998; Suleiman et al., 2007). In the Horn of Africa, 10% of produced milk is derived from camels (Faye and Konuspayeva, 2012). However, most camel milk is produced in traditional farming or pastoral systems by hand milking that cannot provide consistent quantity and quality of raw milk for urban markets (Abeiderrahmane, 2005). The camel dairy industry, including machine milking, processing, and distribution, has been established in the last decade but it is still in an early stage of development (Nagy et al., 2013). Seifu et al. (2012) isolated and characterized lactic acid bacteria from Ethiopian traditional fermented camel milk, and they concluded that the isolated lactic acid bacteria species could be considered as potential candidates for development of starter cultures that can be used for the production of fermented camel milk products under controlled condition. Enterococcus species are known by their production of enterocins which exert different specific inhibition activity against pathogenic bacteria (Sabia et al., 2002).
Increasing folate concentration in fermented milk products using folate producing LAB can be an alternative in producing natural folate-rich products as an effort to prevent folate deficiency without prompting the side effects. Milk is considered as the best medium for folate production because of its complex nutritional content and the presence of folate binding proteins that can increase the stability of folate. Increasing folate content in fermented milk depends on the LAB used as a starter culture to produce extracellular folate which secreted to the media. The ability to synthesize folate is a special characteristic of the strains of LAB, hence the selection of folate-producing strains is critical to obtain LAB that are able to synthesize folate. Folate production by LAB is affected by temperature, incubation time, medium composition and the availability of folate precursors such as PABA and glutamate. Therefore, the technological approach to improve the nutritional value of fermented milk has to include optimizing conditions along with a substrate for fermentation.
Milk clotting enzyme is known as Rennet which is composed of rennin and pepsin. Rennin with high milk clotting activity and low proteolytic activity is the potent enzyme source which is commercially acceptable for cheese making in the food processing Industries. The calf rennet used for cheese making is the oldest method and it is extracted from the fourth stomach of young calves. Due to the legal problems against the animal sacrifice for the research purpose leads to the new search for alternate rennet production from plant and microbial sources.The present study deals with the Production of Milk clotting enzyme by Streptococcus lactis using whey water as a medium for the submerged fermentation. The Streptococcus lactis is the bacterial culture which is widely used in dairy industries.
In this study, cheeses with LD-type cultures acidified to 4.88-4.94 had higher proteolysis during ripening than samples with O-type cultures acidified to 4.63-4.89. In view of the preceding discussion, lower degree of proteolysis in cheeses with O-type cultures was not expected. The cheeses were expected to retain more coagulating enzymes because of their lower pH at cheese-draining stage, which meant that the rate of proteolysis would be higher than in the LD-type cheeses (Grappin et al., 1985; Guinee and Wilkinson, 1992). This however did not agree with our observations because there was higher proteolysis in LD-type cheese with higher (curd) pH. In the present study, Mucor (M.) miehei aspartic proteinase was used as substitute for chymosin as milk coagulant (Section 3.2.2). The results may be explained by the fact that M. miehei is not pH-sensitive, thus the amount of microbial proteases retained in curd is not influenced by pH at curd-cutting or whey-draining (Guinee and Wilkinson, 1992; Holmes et al., 1997; Ward et al., 2009). The amount of rennet retained at whey-drainage increases with moisture content of cheese (Guinee and Wilkinson, 1992). Increased proteolysis in cheeses with LD-cultures was probably associated with higher pH level of cheese curd at draining, which can lead to higher syneresis (Schlesser et al., 1992). High whey content of cheese curd may retain higher concentration of coagulating enzyme in the curd (Guinee and Wilkinson, 1992), thus probably allowing primary proteolysis to occur more readily (Grappin et al., 1985; Guinee and Wilkinson, 1992). The increased moisture level in cheese samples may also enhance the growth of P. camemberti and its proteolytic system, resulting in higher final pH by end of ripening, thereby contributing to a greater degree of proteolysis (Spinnler and Gripon, 2004).
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Abstract- Microbial rennet-like milk-clotting enzymes are aspartic proteinases that catalyze milk coagulation, substituting calf rennet. Crude enzymatic extract produced by the Aspergillus oryzae NCIM 1032, on solid state fermentation (SSF) using mixture of wheat bran and rice bran (7:3), exhibited high milk- clotting activity (MCA) and low proteolytic activity (PA) after 120 h of fermentation. Highest milk-clotting activity was at pH 7.5, at 30 ºC. Glycerol (5%) was found to be best solvent for leaching out milk clotting enzyme. The yield of enzyme was improved with the supplementation of glucose and beef extract as a carbon and nitrogen source respectively. Metabolic heat generated due to fermentation was equally distributed throughout the substrate bed by agitation in rotating drum bioreactor and enzyme production increased at speed of 25 rpm and at intermittent agitation (1 min/day). High ratio of milk clotting to proteolytic activity strengthens the potential usefulness of milk- clotting enzyme of Aspergillus oryzae NCIM 1032 as a substitute for calf rennet in cheese manufacturing.
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by flavouring with the selected fruit component, the increase of the natural folate content can be reached. The folate content in the fermented milk product prepared by inoculation of pasteurised milk by the butter starter and Streptococcus ther- mophilus No. 144 in combination with Propioni- bacterium freudenreichii subsp. shermanii No. 160, fermented at 37°C for 12 h and flavoured with the strawberry component, was in this way increased by 4.8 µg/100 g, with 69% originating from fermenta- tion and 31% from the fruit component addition. The folate losses after 15 days of storage in the refrigerator did not exceed 8%.
(Bayat et al., 2018). Modifying the FA content of animal products such as milk and meat to improve product quality, by increasing the content of PUFA is of great interest, especially for the consumer due to the health benefits of PUFA (Marventano et al., 2015). Omega-3 FA also have a positive influence on the reproductive and immune systems of dairy cows (Santos et al., 2008). Calcium salts are high in palmitic acid (C16:0), and are made from palm oil or soyabean. Higher levels of C16:0 are delivered to the cow in order to increase milk fat yield, as C16:0 is found in high concentrations in milk (Lock et al., 2013; Vyas et al., 2012). A diet enriched in LC-FA can result in a higher production of propionate and a lower production of acetate and butyrate, decreasing milk fat (Weisbjerg et al., 2008). It has also been reported that diets rich in PUFA such as rapeseed oil may inhibit the formation of precursors for milk fat in the rumen, and also inhibit de novo synthesis, referred to as milk fat depression in dairy cows (see section 1.6.6; Bauman and Griinari, 2001). Increasing the dietary supplementation of a specific FA does not mean that this FA will be increased in the milk or meat. This is due to biohydrogenation in the rumen, which is discussed in section 1.6.4. Protected fats and oils have been developed that are less susceptible to rumen biohydrogenation, with the FA of these rumen protected fats passing through the rumen to be digested and absorbed post-ruminal, and possibly be
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sorted out according to the presence of the specific enzyme (Jin et al. 2009). The bacteria of the genus Lactococcus produce only l(+)-lactic acid, those of genus Leuconostoc produced only d(–)-lactic acid, some lactobacilli produce only l(+)-lactic acid (e.g. Lb. casei subsp. casei), some produce both isomers of lactic acid (e.g. Lb. brevis), and some lactobacilli produce only d(–)-lactic acid (e.g. Lb. delbrueckii subsp. lactis). A few species (Lb. curvatus, Lb. sakei) produce an enzyme racemase. This enzyme converts l(+)-lactic acid to d(–)-lactic acid (Axcelsson 2004). The starter bacteria and their production of lactic acid isomer can be seen in Table 1 (Krieg et al. 2010). Lactic acid is normally present in the blood of mam- mals due to the activity of gastrointestinal (GIT) mi- croflora (Ewaschuk et al. 2005) or due to glycogen cleavage (Gleeson & Dalessio 1990). Increased amount of d(–)-lactic acid in blood serum, ≥ 3 mmol/l, can cause d-lactic acidosis. This metabolic disease occurs more often in humans suffering from short- bowel syndrome (Bongaerts et al. 1997; Uribarri et al. 1998; Ewaschuk et al. 2005). The patients with d(–)-lactic acid acidosis can exhibit neurological dysfunctions characterised by ataxia, slurred speech, and confusion. Hallucination, sleepiness, clumsiness, lethargy, and dizziness can occur as well (Ewaschuk et al. 2005). The main aim of this work was to evaluate the parameters influencing the formation of organic acids and the ratio of optical isomers of lactic acid during the fermentation of milk, and to design milk beverage fermented with ABT culture (Lactobacillus acidophilus, Bifidobacterium sp., Streptococcus ther- mophilus) with a lowered content of d(–)-lactic acid.
Abstract- Yogurt or yoghurt is one of the most popular fermented dairy products worldwide which has great consumer acceptability due to its health benefits other than its basic nutrition. In general, yogurt is considered as a nutrition-dense food due to its nutrient profile and is a rich source of calcium that provides significant amounts of calcium in bio-available form. In addition, it provides milk proteins with a higher biological value and provides almost all the essential amino acids necessary to maintain good health.Yogurt is considered as a probiotic carrier food that can deliver significant amounts of probiotic bacteria into the body which can claim specific health benefits once ingested. These are usually marketed as bio-yogurts. Moreover, yogurt is reported to claim improved lactose tolerance, immune enhancement and prevention of gastrointestinal disorders. Because of these known health benefits of yogurt,consumer demand for yogurt and yogurt related products has been increased and became the fastest growing dairy category in the global market. Yogurts are now being manufactured in a numerous styles and varieties with different fat contents, flavors and textures suitable for different meal occasions and plates as a snack, dessert, sweet or savory food.
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The present study deals the production of Milk-Clotting Enzyme using synthetic, whey and distillers sludge medium as substrates in submerged fermentation by Streptococcus lactis the production of enzyme was improved with the addition of lactose and casein along with the basal medium. Distillers yeast sludge containing casein by Streptococcus lactis under the shaking condition produced the highest Milk clotting activity of 0.608 units/mg and the Proteolytic Activity of 0.488 units/ mg. The high milk clotting activity with low proteolytic activity is the best condition for rennet strength in cheese making. The kinetics of Logistic model for cell growth and Leudeking- Piret model for product formation were evaluated on the milk clotting enzyme production by Streptococcus lactis.