Lactic Acid Bacteria In Yogurt Research Articles

High performance poly(L-lactic acid)-based film by one-step synthesis of poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) for efficient preservation of yogurt storage

Biodegradable poly(L-lactic acid) (PLLA) has seldom used for dairy packaging due to medium permeability and brittleness. Novel PLLA copolymers, poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) (PLBIGA), were developed by integrating glycolic acid (GA) and poly(butylene itaconate) (PBI) into PLLA's structure using low molecular weight PLLA as a key initiator. Then, packaging materials with better barrier and mechanical properties were obtained by blended PLBIGA with PLLA. Both PLLA/PLBIGA films and polyethylene nylon composite film (PE/NY) were used for stirred yogurt packaging and storage at 4 °C for 25 days. Results revealed that yogurt packed by PLLA/PLBIGA films maintained stabler water-holding capacity, color, and viscosity over the storage period. Moreover, the integrity of the gel structure and the total viable count of lactic acid bacteria in yogurt packaged in PLLA/40-PLBIGA8 were also found to be superior to those in PE/NY packages, highlighting its eco-friendly advantages in dairy packaging.

Influence of lysozyme utilization with lactic acid bacteria in yoghurt on some foodborne pathogens

Despite the existence of many different food preservation methods, foodborne pathogens are still the most common related problems to dairy products. Developing naturally alternative techniques to control such problems is necessary. This research was planned to assess the bacteriological quality of yoghurt samples commercially available in Kafr El-Sheikh city, Egypt. Also to study the impact of natural antibacterial agents on the inhibition of selected foodborne pathogens artificially inoculated in yoghurt samples. The obtained results revealed poor bacteriological quality of the examined yoghurt samples, as total staphylococci and coliforms were detected in 80% and 90% yoghurt samples, with mean values of 2.4 ×103±0.13× 103cfu/gm and 3.6×105± 2.4×105 MPN/gm, respectively. S. aureus was noticed in 4% of examined samples, polymerase chain reaction (PCR) confirmed the pres­ence of virulence adhesion gene (clfA) in one isolate. E. coli was detected in 14% of yoghurt samples, then serologically identified as O146:H5 (2), O111:H2 (2), O125:H11 (1), O26:H10 (1) and O158:H7 (1). Artificially inoculated yoghurt with S. aureus (7.39 log cfu/gm) and E. coli (8.3 log cfu/gm), were used to investigate the ability of hen egg-white lysozyme either with LAB classic or with ABT-5 (L. acidophilus LA5+ S. thermophiles + Bifidobacterium Bb12) starter cultures to inhibit the growth of these pathogens. During refrigerated storage, all yoghurt batches showed a reduction in pH value. It was observed that both pathogens couldn't be detected in the yoghurt batch containing LAB classic starter + heated lysozyme. Furthermore, S. aureus was completely inhibited in that containing ABT-5 cultures alone, while E. coli decreased by 6.23 log. Conversely, there was not complete inhibition in other batches containing (LAB classic starter, LAB classic starter+ native lysozyme, ABT-5 culture+ native lysozyme and ABT-5 culture+ heated lysozyme) as the reduction rate during all storage periods for S. aureus count was 1.66, 2.63, 4.47 and 4.19 log, While for E. coli count was 3.3, 3.81, 5.53 and 4.89 log, respectively. This study highlighted the importance of adding natural antibacterial agents like lysozyme with LAB culture to yoghurt as a bio-control strategy to overcome foodborne pathogens that cause a public health hazard.

The Improvement of Sensory and Bioactive Properties of Yogurt with the Introduction of Tartary Buckwheat

The incorporation of cereals in yogurt has recently gained increasing consumer approval, for its high nutritional value and health benefits, all over the world. Following this emerging trend, Tartary buckwheat (TB) was supplemented into yogurt as a natural functional ingredient in order to develop a yogurt with enhanced product characteristics and consumer acceptability. The impact of TB addition on physicochemical properties (pH, acidity, apparent viscosity, etc.) and the viability of lactic acid bacteria in yogurt was investigated. It is found that the TB introduction can reduce the pH, increase the acidity and apparent viscosity, and also greatly boost the bioactivities of yogurt. Response surface analysis demonstrated that yogurt with 8 g of TB, 10 g of sugar, and a fermentation duration of 5 h had the highest overall acceptability, and these cultural conditions were chosen as the best. Furthermore, the TB-added yogurt had not only a better sensory and aroma profile, but also good prospective health advantages when compared to regular yogurt. Our research shows that adding TB to yogurt has a significant positive impact on both overall quality and sensory characteristics, making a compelling case for using TB yogurt and developing new fermented dairy products.

Preservation of Squid (LOLIGO SP.) Using Yogurt in Low Temperature Storage on Organoleptic Characteristics

This research aims to determine the shelf life of squid (Loligo sp.) using Lactic Acid Bacteria in yogurt and its organoleptic characteristics. This research was carried out at the Fishery Product Processing Laboratory, Faculty of Fisheries and Marine Sciences, Padjadjaran University in November 2020. This research was carried out using yogurt as a preservative for squid (Loligo sp.) in the treatment of LAB concentrations used 0%, 1, 5%, 3%, 4.5%, and 6%. Observations were made for 11 days and stored at a temperature of 5-10oC, and organoleptic testing (discoloration, brilliance, aroma, and texture) was carried out on days 1, 3, 5, 7, 8, 9, 10, 11 for the treatment 1.5%, 3%, 4.5% and 6% and organoleptic testing on days 1, 3, 5, 7, 8 for control samples. The observed data were analyzed for pH and organoleptic with Friedman test and Chi-Square test. The results showed that 1,5% Lactic Acid Bacteria into yogurt as a preservative in squid has the best effect on the shelf life and organoleptic characteristics of squid during storage at low temperatures with an acceptable limit of up to 10 days.

Visualization of Gene Reciprocity among Lactic Acid Bacteria in Yogurt by RNase H-Assisted Rolling Circle Amplification-Fluorescence In Situ Hybridization.

Recently, we developed an in situ mRNA detection method termed RNase H-assisted rolling circle amplification-fluorescence in situ hybridization (RHa-RCA-FISH), which can detect even short mRNA in a bacterial cell. However, because this FISH method is sensitive to the sample condition, it is necessary to find a suitable cell permeabilization and collection protocol. Here, we demonstrate its further applicability for detecting intrinsic mRNA expression using lactic acid bacteria (LAB) as a model consortium. Our results show that this method can visualize functional gene expression in LAB cells and can be used for monitoring the temporal transition of gene expression. In addition, we also confirmed that data obtained from bulk analyses such as RNA-seq or microarray do not always correspond to gene expression in individual cells. RHa-RCA-FISH will be a powerful tool to compensate for insufficient data from metatranscriptome analyses while clarifying the carriers of function in microbial consortia. By extending this technique to capture spatiotemporal microbial gene expression at the single-cell level, it will be able to characterize microbial interactions in phytoplankton–bacteria interactions.

EFFECT OF Pleurotus ostreatus AQUEOUS EXTRACT ON PHYSICOCHEMICAL PROPERTIES, PROTEIN PROFILE AND TOTAL LACTIC ACID BACTERIA OF YOGURT FORTIFIED WITH Lactobacillus acidophilus

Syneresis and low viscosity are two major quality defects found in yogurt. The addition of food stabilizer is necessary to overcome the issue. Oyster mushroom (Pleurotus ostreatus) could be utilized as a source of natural food stabilizer because it contains β-glucan. The objective of this study was to evaluate the effect of Pleurotus ostreatus aqueous extract (POAE) on physicochemical properties, protein profile and total lactic acid bacteria of yogurt fortified with Lactobacillus acidophilus. Yogurt was processed with the addition of POAE at 1%, 2%, and 3% (v/v) before fermentation and compared with control. Yogurt added with 3% POAE had the highest viscosity (P<0.05), protein content (P<0.05), and total acid content (P<0.05), but had the lowest syneresis (P<0.05) among others. The addition of POAE up to 3% (v/v), however, did not affect reducing sugar content and total lactic acid bacteria in yogurt. A 12.49 kDa protein was present in yogurt added with 3% POAE. Therefore, POAE could be used as natural stabilizer for yogurt fortified with Lactobacillus acidophilus with recommended addition level of 3% (v/v).

Pengaruh Variasi Suhu dan Lama Penyimpanan terhadap Viabilitas Bakteri Asam Laktat (BAL) dan Nilai pH Yoghurt

Consuming yogurt indicates the increasing public awareness of healthy lifestyles has led many people to consume yogurt. Yogurt is a fermented milk product by adding pasteurized skim milk concentrate and adding lactic acid bacteria culture. L. casei is the bacterial culture commonly used in the production of yogurt, which has a role in breaking down lactose into lactic acid. To maintain its quality, yogurt is generally stored at a low temperature. However, there are still many business actors who only store it in a cool box or even at room temperature. The purpose of this study was to describe the viability of LAB and the effect of variations in temperature and storage time on the viability of LAB and pH value of yogurt. This study used an experimental method with a completely randomized design (CRD) with 3 treatments in the form of variations in storage temperature, namely 5°C, 15°C, and 25°C, each treatment temperature was stored for 1 week, 2 weeks, 3 weeks, and 4 weeks. This study was conducted in December 2020. The results showed that the highest viability value (289x106 CFU/mL) of lactic acid bacteria in yogurt was obtained at 5°C with two weeks of storage. Yogurt's pH value is influenced by temperature and storage time; the higher the temperature and storage time, the causes the yogurt's pH value decreases. The conclusion that can be drawn from this study is that the highest viability of LAB was obtained at 5°C with a shelf life of two weeks, while the best pH value of yogurt was achieved at 5°C for one week.

Physicochemical and microbiological properties of yogurt made with microencapsulation probiotic starter during cold storage

Abstract. Rossi E, Restuhadi F, Efendi R, Dewi YK. 2021. Physicochemical and microbiological properties of yogurt made with microencapsulation probiotic starter during cold storage. Biodiversitas 22: 2012-2018. This study's purposes were to characterize probiotic properties, identify strains of K12.1, produce a microencapsulated starter (MS) for yogurt, and evaluate yogurt's microbiological quality during storage refrigerated temperatures. This research was conducted experimentally using isolate was further identified based on 16S rRNA gene sequence analysis. The identified strain and Streptococcus thermophilus were microencapsulated using sago starch and whey isolate protein (1:1 w/w) for yogurt starter. The starter was added as much as 1, 3, 5, or 7% (v / v), then incubated for 18 hours at 37°C. The best yogurt was evaluated for its microbiological quality at refrigerated temperature for 0, 7, 14, 21, and 28 days. The results showed that K12.1 isolate with probiotic characteristics was Lactobacillus plantarum VP3.3. The microencapsulation starter concentration affected acidity, total acid, total lactic acid bacteria (LAB), viscosity, and total solids. The use of 7% microencapsulation starter of Lactobacillus plantarum VP-3.3 and Streptococcus thermophilus gave the best yogurt, with a pH value 4.36, total lactic acid 0.99%, total LAB 10.00 log CFU mL-1, viscosity 546.37 cP, and total solids 10.40%. The total amount of LAB in yogurt stored during cold temperature for 28 days still meets the probiotics standards (9.98 log CFU/mL).

In vitro digestibility and stability of encapsulated yerba mate extract and its impact on yogurt properties

The development of ready-to-eat foods containing bioactive extracts represents an important step to improve food consumption. This study aimed to develop a yogurt containing an encapsulated bioactive yerba mate extract. For this, the lyophilized extract was protected through encapsulation in solid lipid particles (SLPs) of beeswax. An encapsulation efficiency (EE) greater than 90% was achieved with an extract content higher than 20%. The FTIR spectrum of the capsules’ wall material, indicated that beeswax efficiently encapsulated the yerba mate extract. The extract antioxidant potential was protected for 45 days under cold storage, and the encapsulation maintained the viability of the yogurt lactic acid bacteria. The increase in free fatty acids from seven to 33% during in vitro digestion indicated the capsule rupture during the digestion process. Moreover, the extract encapsulation maintained viable lactic acid bacteria in yogurt. The addition of SLPs did not affect the acceptability of the yogurt or the consumers’ intention to buy the product. However, the score attributed to the product evaluators was surprisingly low and portrayed the consumer's preference for foods with added sugar. This work introduced a natural, ready-to-eat and health-promoting food product containing SLP-protected antioxidant compounds. The addition of compounds encapsulated in foods is promising and can benefit consumers.

Incorporation of Microencapsulated Probiotic Lactic Acid Bacteria in Yoghurt

Background: Probiotics are live microorganisms known for the many health benefits they confer on their host. Lactobacillus acidophilus is a lactose fermenting bacterium that is found naturally in the human body and is also found to exhibit probiotic properties. The gastrointestinal tract of humans is however, a harsh environment for microorganisms to survive and render the intended health benefits. Microencapsulation is a technique by which a substance is enveloped by another, forming a capsule that may range up to several hundred microns in size. In this study the probiotic organism L. acidophilus was microencapsulated in a hydrocolloid bead (alginate) and then incorporated in yoghurt. Methods: Probiotic properties of Lactobacillus acidophilus was evaluated. It was then micro encapuslated in 50 per cent carrot juice and then incorporated in yoghurt. Nutrient composition of this value added yoghurt was studied and its sensory parameters compared with control yoghurt. Result: In the present experiment the viability of L. acidophilus at 90 mins was 10.750± 0.553log10cfu/ml and the tolerance of L. acidophilus to 0.4 per cent of bile was significant. Microencapuslation of L. acidophilus was attempted by mixing carrot juice at 50 per cent to the alginate beads, thus imparting an appealing orange colour to the beads. The yoghurt thus prepared using microencapuslated L. acidophilus had an acidity of 0.7 ± 0.and total solid of 21.35 per cent on dry matter basis. Sensory analysis revealed maximum overall acceptability for carrot juice admixed microencapsulated probiotic-enriched yoghurt.

Evaluation of the bioprotectivity of Lactobacillus binary/ternary cultures in yogurt.

The attempts toward addition of biocontrol agents in dairy products have gained popularity. Here, we worked on analysing the antifungal activity of binary and ternary combinations of three Lactic Acid Bacteria (LAB) against five spoilage yeasts in yogurt. The yogurt samples were characterized in terms of pH, acidity, WHC, textural parameters, viscosity, survivability and antifungal activity of LAB and sensorial properties during cold storage. The results showed that the inoculation of LAB in yogurt gave rise in significant reduction of pH throughout cold storage while titrable acidity and WHC decreased (p < .05). Inoculation of LAB resulted in significant increase in hardness and adhesiveness while springiness remained constant. On the other hand, apparent viscosity of all samples experienced a profound increase up to the 10th day of storage followed by a reduction trend for the rest of storage period. Analysis of inhibitory activity of LAB showed an efficient barrier against all five yeasts, in which the most activity was recorded for Lactobacillus reuteri followed by Lactobacillus acidophilus. On the other hand, the most resistance yeast was Kluyveromyces marxianus followed by Rhodotorula mucilaginosa. Sensorial analysis revealed that addition of LAB in yogurt brought about a profound improvement in textural quality of samples. Inoculation of LAB cultures in yogurt at 5% (v/v) not only could improve the physicochemical and sensorial properties of yogurt, but also could introduce a strategy toward substituting of chemical preservatives with biocontrol agents.

Optimizing ectoine biosynthesis using response surface methodology and osmoprotectant applications.

Numerous applications of compatible salts (osmolytes) as ectoine in food and pharmaceutical industries have been intensively increased nowadays. Decreasing the cost of industrial production of ectoine using low-cost cultivation media and improving the yield through modeling procedures are the main scopes of the present study. Three statistical design experiments have been successfully applied for screening the parameters affecting the production process, studying the relations among parameters and optimizing the production using response surface methodology. A novel semi-synthetic medium based on hydrolyzed corn gluten meal has been developed to cultivate moderate halophilic bacterial strains; Vibrio sp. CS1 and Salinivibrio costicola SH3, and support ectoine synthesis under salinity stress. Two regression equations describe the production process in the new medium have been formulated for each bacterial strain. Response surface optimizer of the central composite model predicts the maximum ectoine production is achieved at incubation time; 63.7h, pH; 7.47 and salinity; 7.27% for Vibrio sp. CS1 whereas these variables should be adjusted at 56.95h, 7.089 and 10.34%; on the same order regarding Salinivibrio costicola SH3. In application studies, 50µg ectoine decreases RBCs hemolysis due to streptolysin O toxin by 21.7% within ten minutes. In addition, 2% ectoine succeeds to increase the viability of lactic acid bacteria in Yogurt as a classic example of functional food during the storage period (7days). The present study emphasizes on modeling the process of ectoine production by halophilic bacteria as well as its activity as a cryoprotectant agent.

Survival of Lactobacillus bulgaricus and Bifidobacterium animalis in yoghurts made from commercial starter cultures during refrigerated storage

All over the world, fermented dairy products have been consumed for nutrition and maintenance of good health for a very long time. This study evaluated the survival of Lactobacillus delbrueckii ssp. bulgaricus and Bifidobacterium animalis ssp. lactis BB-12 in yoghurts after the manufacturing during the shelf-life up to 21 days at 4 °C, which is mostly accepted by the consumers. The titratable acidity and pH showed the same patterns of increase or decline after manufacturing and storage of yoghurts. There was a significant difference (p &lt;0.05) in acidity between yoghurts in glass bottle and plastic cup. The increase in numbers of lactobacilli and bifidobacteria and their survival during storage time were dependent on the species and strain of associative yoghurt bacteria (control-only yoghurt lactic acid bacteria and experimental containing except yoghurt culture also Bifidobacterium animalis ssp. lactis BB-12) and on the packaging material (glass bottle versus plastic cup). It was observed, that counts of bifidobacteria were lower than counts of Lactobacillus delbrueckii ssp. bulgaricus (190 to 434 x 107 at 1d) and slowly increased (p &lt;0.001) at maximum level on day 7 (294.3 - 754 x 107) and then slowly declined to 6.33 x 107 in glass bottle and 2.33 x 107 in plastic cups, respectively. Lactobacillus delbrueckii ssp. bulgaricus multiplied better in glass bottles than in plastic cups, as observed during experimental period in-group with Bifidobacterium animalis ssp. lactis BB-12. At the end of the storage period at 4 ºC, viable counts of lactobacilli were higher (p &lt;0.001) in glass bottles. Al the yoghurts, contained the recommended levels of lactobacilli and bifidobacteria (107 cfu.g-1) at the end of storage period (21 d).

Rapid quantification of live/dead lactic acid bacteria in probiotic products using high-sensitivity flow cytometry

A laboratory-built high-sensitivity flow cytometer (HSFCM) was employed for the rapid and accurate detection of lactic acid bacteria (LAB) and their viability in probiotic products. LAB were stained with both the cell membrane-permeable SYTO 9 green-fluorescent nucleic acid stain and the red-fluorescent nucleic acid stain, propidium iodide, which penetrates only bacteria with compromised membranes. The side scatter and dual-color fluorescence signals of single bacteria were detected simultaneously by the HSFCM. Ultra-high temperature processing milk and skim milk spiked with Lactobacillus casei were used as the model systems for the optimization of sample pretreatment and staining. The viable LAB counts measured by the HSFCM were in good agreement with those of the plate count method, and the measured ratios between the live and dead LAB matched well with the theoretical ratios. The established method was successfully applied to the rapid quantification of live/dead LAB in yogurts and fermented milk beverages of different brands. Moreover, the concentration and viability status of LAB in ambient yogurt, a relatively new yet popular milk product in China, are also reported.

Effect of conjugated linoleic acid supplementation on the microbial, physical, chemical and sensory properties of yoghurt

The aim of this study was to determine the effect of synthetic conjugated linoleic acid (CLA) supplementation on the quality of yoghurt. Yoghurt was prepared by adding CLA to create yoghurt with 0%, 25%, 50% and 100% w/w of the recommended dietary allowance for CLA. CLA inclusion had no effect on the viability of the yoghurt lactic acid bacteria. Physical properties such as viscosity and pH increased with increased CLA levels. CLA inclusion had a significant effect on the fatty acid composition of the yoghurt. Yoghurts from all four treatments were found acceptable by a consumer panel.

Efficacy of Alginate-Taro (Colocasia esculenta L. Schott) Starch for Yoghurt Starter Culture Encapsulation

Yoghurt is a probiotic product due to the presence of beneficial microorganisms so-called lactic acid bacteria (LAB). However, the viability of LAB in the product must reach the optimum microflora balance of 106 to 108 cfu.ml-1 to be considered as probiotic and for consumers to enjoy its health benefits. One of the alternatives in maintaining the viability of LAB in yoghurt is to encapsulate the LAB cells which would protect the cells from the environment. In this study, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, the yoghurt starter cultures, were encapsulated in different levels of alginate-taro starch matrix. Physico-chemical properties of the reconstituted skim milk medium and the sensory qualities of resulting yoghurt were determined. The developed alginate-taro starch encapsulated, non-encapsulated and pure alginate encapsulated starter cultures were compared in terms of their effectivity in yoghurt production. The highest percentage of taro starch (1.5%) was found to retain a high viable cell count of 3.4 x1010 cfu.ml-1 after 12-day storage at 4oC. No significant effect of encapsulated starter cultures was observed on the physico-chemical properties (i.e. pH, TSS, and % lactic acid) of reconstituted skim milk. Incubation and storage periods significantly affected the physico-chemical properties of the reconstituted skim milk (p &lt;0.05). No significant differences among the treatments were found for sensory qualities. However, the yoghurt produced from 4% alginate-1.5% taro starch-encapsulated LAB, which was stored for 2 weeks, was found to be acceptable due to its right degree of sweetness and acidity and similarity with the control treatment. It can be concluded that taro starch is, indeed, a potential wall material that can be used with alginate to encapsulate yoghurt starter cultures and can retain or increase the lactic acid bacteria cell viability without affecting the activity of the cultures.

Effect of Colored Barley Flours on Quality Characteristics of Fermented Yogurt by Lactobacillus spp.

Quality characteristics of yogurt with added colored barely flour was investigated during fermentation by lactic acid bacteria. Chemical properties such as moisture, crude protein, starch, ash and β-glucan contents was measured. pH, acidity, brix, Hunter color value and growth of lactic acid bacteria in yogurt was investigated during fermentation by L. acidophilus, L. bulgaricus, and S. thermophilus mixed culture. Crude protein contents of Daeanchal and Boseokchal was 16.16 and 12.17%, respectively. Starch contents of daeanchal were shown lower score. The pH of yogurt by addition of barley flour (Daeanchal) addition 0 and 20% were 6.66 and 6.40, respectively. The pH of yogurt supplemented with barley flour tended to be lower than before control which was not added barely flours and oligosaccharide in yogurt. Titratable acidity of yogurt added barley flour was higher compared with that of control. Brix of yogurt was decreased during fermentation by lactic acid bacteria. Lightness of yogurt added barley flour (Daeanchal) addition 0 and 20% were 83.25 and 69.83, respectively. The original microbial population of the yogurt during 0, 5, 8, and 15 hr fermentation were 7.48, 7.79, 8.15, and 8.71 Log CFU/g, respectively. Moreover, the addition of colored barley flour was to promote the proliferation of lactic acid bacteria in yogurt. In our research, addition of colored barley flours added into the yogurt may also have contributed to growth of lactic acid bacteria.

Suppression of Helicobacter Pylori in Mice Intestine by Ingestion of Lactic Acid Bacteria in Yoghurt

Helicobacter pylori (H. pylori) is a major cause of chronic gastritis and peptic ulcer. Antibiotics- based H. pylori eradication treatment is 90% effective, but it is expensive and can have side effects and antibiotic resistance. Probiotics costs less and are easily available. These studies were conducted to investigate the role of probiotics in the treatment of H. pylori infection. H. pylori were recovered from stool culture of peptic ulcer patients. Twenty albino wister mice weighing (25g -29g) were kept in 5cages, A to E (4 mice per cage). Faecal occult blood (FOB) test and viable bacterial count (VBC) were done on all the mice at different stages of the experiment. Animals in cages A to D were fed orally with different concentrations of H. pylori for 1week. Animals in cage E were fed with water as control. Finally the test mice were fed for another one week with yogurt which contains lactic acid bacteria then a retest was done. The results generated showed that the H.pylori can induce stomach ulcer and the Lactic acid bacteria in the yogurt suppressed the ulcer disease. Conclusively, this study has proven that Lactic acid bacteria in yoghurt can suppress Helicobacter pylori

Analisa Keasaman dan Total Bakteri Asam Laktat Yogurt Akibat Bahan Baku dan Persentase Lactobacillus casei yang Berbeda

Analyze of acidity and amount of lactic acid bacteria of yogurt made from different milk types and lactobacillus casei percentageABSTRACT. The objective of this experiment is to determine the effect of milk types and percentages of Lactobacillus casei as a starter to the amount of Lactic Acid Bacteria in yogurt and its pH value and Lactic Acid value. Factorial Completely Randomized Design with two factors and three replications was applied. The A factor was the milk types that were a1 = Powder Milk, a2 = Fresh Milk and a3 = UHT milk. The B factor was the percentages of Lactobacillus casei (b1 = 5% and b2 = 10%). Parameters observed were the level of lactic acid, the pH value of yogurt and the amount of lactic acid bacteria. The result showed significantly difference (P0.01) from the use of milk types and Lactobacillus casei percentages on the lactic acid level, and there are no interaction between factors. There was also significant different (P0.01) showed from pH value and an interaction between both factors was presented. In addition there was significant difference (P0.05) showed by the amount of lactic acid bacteria, and an interaction between both factors was also existed. The research concluded that the higher the percentage of starter, the higher the level of lactic acid and the amount of lactic acid bacteria of yogurt that made from all milk types. On the contrary, the higher the percentage of starter, the lower the pH value of yogurt.

장내 세균의 생육과 요구르트의 발효특성에 대한 D-Tagatose의 영향

To investigate the effect of tagatose on the growth of intestinal bacteria, various species were cultivated individually on m-PYF medium containing tagatose as a carbon source. The tagatose inhibited the growth of intestinal harmful microorganisms such as Staphylococcus aureus subsp. aureus, Listeria monocytogenes, Vibrio parahaemolyticus, Salmonella Typhimurium, and Pseudomonas fluorescens. In the case of beneficial microorganisms found in the intestine, Lactobacillus casei grew effectively on m-PYF medium containing tagatose, while Lactobacillus plantarum, Lactobacillus brevis, Leuconostoc citreum, and Lactobacillus acidophilus did not. To examine the effect of tagatose on fermentation by Lactobacillus casei, yogurt was prepared with tagatose as a carbon source. The resulting acid production stimulated a remarkable growth of lactic acid bacteria in the yogurt. After fermentation for 24 hours, the viable cell count and viscosity of yogurt were above 8.49 log CFU/mL and 1,266 cps, respectively. Moreover, sensory evaluations showed that the yogurt supplemented with tagatose was as acceptable as control yogurt prepared with glucose as a carbon source. The changes in pH, titratable acidity and lactic acid bacteria in yogurt prepared with tagatose did not show any significant changes during storage for 15 days at 4℃.