Quality Of Yogurt Research Articles

Grainy properties of post–heating fermented milk with different particle sizes

Post–heating operation is crucial to produce ambient yogurt, which is also a direct cause of sensory defects, especially graininess. Consumers’ perception of graininess varies based on individual sensitivities. Accurate evaluation of graininess is a prerequisite for improving the sensory quality of ambient yogurts. The purpose of this study was to propose a method to discriminate consumers' sensitivity to grainy perception of post–heating (55 °C–85 °C, 25 s) fermented milk, and to further determine the volume proportion threshold required to produce different graininess intensities by blending fermented milk with different particle sizes. The results suggested that increasing the post–heating temperature induced various graininess by promoting different microgel aggregation. Fermented milks with microgel aggregate sizes of ∼14–∼20 μm, ∼27 μm, and ∼46–∼65 μm were classified as “weak”, “moderate”, and “strong” graininess, respectively. This result was obtained by approximately 81% of the panelists with moderate and high sensitivity on the perception of graininess. Furthermore, the graininess can be modulated by regulating the fermented milks with larger microgels and with smaller microgels; however, the blending volume of the latter must exceed 50% to reduce the graininess of the former by 1–2 sensory intensity ranks.

Effects of lactic acid bacteria exposed to extreme conditions on yoghurt quality

In this study, two bacterial strains used in the production of yoghurt were subjected to three distinct stress conditions (low pressure, infrared light, and low pressure + infrared light) and then used as starter cultures for yoghurt production. The obtained results revealed that the bacterial stress response mechanisms, especially those of bacteria exposed to low pressure, positively affected the physicochemical, textural, and microbiological quality during storage of yoghurts produced with these bacteria. In addition, it was found that prolonging the exposure time to stress conditions increased this effect even more. The samples subjected to low pressure for 2 hours had the shortest fermentation time among all samples, while the samples subjected to infrared light for 2 hours had the longest fermentation time. Yoghurts produced with bacteria subjected to low pressure conditions had more organic acids and aroma components and less syneresis during storage compared to other samples. Furthermore, it was determined that yoghurt samples produced with bacteria exposed to stress conditions had higher L* and a* values, lower b* values, improved textural values, and higher bacterial counts during the 7-day storage period compared to control samples.

Assessment of plain yoghurt quality parameters affected by milk adulteration: Implications for culture kinetics, physicochemical properties, and sensory perception

In developing nations, the widespread practice of adulterating milk with water, driven by economic motives, poses a significant threat to milk derivatives like yoghurt. Despite the absence of mandatory water detection tests for plain yoghurt, our study investigated the repercussions of adding 0–15% water to milk on plain yoghurt quality parameters over 28 days of refrigerated storage. Starter culture kinetics were notably affected, influencing colour and texture. Yet, sensory analysis indicated minimal impact on consumer perception. These results underscore the potential risk of unknowingly consuming adulterated yoghurt, emphasising the necessity for stringent regulatory measures to counteract such practices.

Lactiplantibacillus plantarum ZFM55 improves texture and flavor of yogurt, increases beneficial metabolites, and the co-fermented yogurt promotes human gut microbiota health

Yogurt offers potential health benefits, particularly for the intestines. The choice of starter culture is key to the production of functional yogurt. In this study, Lactiplantibacillus plantarum ZFM55 was incorporated into a commercial starter and its effects on the quality of yogurt was evaluated. Changes in texture, flavor, composition, and metabolites were assessed, along with its impact on the gut microbiota. We found adding ZFM55 improved the water holding capacity, cohesiveness, viscosity, and hardness of the yogurt. Analysis using gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) and liquid chromatography-mass spectrometry (LC-MS) demonstrated that ZFM55 contributed to a desirable flavor profile and increased the levels of non-volatile metabolites, such as amino acids and carbohydrates. Stool samples from volunteers who consumed fermented milk were collected and analyzed using 16 S rDNA sequencing and GC-MS. The results showed that fermenting yogurt with ZFM55 significantly altered the beta diversity of the gut microbiota. Notably, probiotics such as Bifidobacterium, Blautia, and Lactobacillus exhibited substantial increases, along with a notable rise in the production of short-chain fatty acids, particularly acetic acid and butyric acid. These findings highlight the potential of ZFM55 for developing high-quality functional yogurt products.

THE INFLUENCE OF STARCH PRODUCTS ON THE RHEOLOGI-CAL, PHYSICAL AND CHEMICAL PROPERTIES OF YOGURT

Expanding the assortment of low-fat yogurt with natural structuring sweeteners and regulated quality indicators is an actual direction of scientific research. The purpose of the study is to study the patterns of influence of the products of enzymatic hydrolysis of corn starch with different dextrose equivalents on the rheological, physical and chemical characteristics of yogurt. Тhe functional and technological properties of starch products of different chemical composition were studied – maltodextrin MD-10, glucose syrup IG-42 and glucose-fructose syrup GFS-42. The possibility of completely replacing dry skimmed milk and sugar in the composition of yogurt with a fat content of 1% drinkable with an equivalent content of dry substances of maltodextrin MD-10 and glucose syrup IG-42, which ensure the formation of rheological characteristics inherent high-quality yogurt. Yogurt with sucrose, which inhibits the organization of macromolecular chains of milk proteins, has the lowest thixotropic ability, and yogurt with maltodextrin MD-10 and glucose syrup IG-42 has the highest. The predominance of higher sugars in the composition of MD-10 maltodextrin lengthens, and the increased content of monosaccharides in GFS-42 accelerates the duration of fermentation of milk mixtures in the technological process of production of yogurt with a fat content of 1.0%. Monosaccharides in the composition of GFS-42 significantly affect the activity of water and at the same time reduce the moisture-retaining capacity of the sour-milk yogurt curd. The degree of influence on the rheological characteristics and moisture-binding capacity of yogurt increases with a decrease in the dextrose equivalent of starch products in the following sequence: GFS-42 → IG-42 → MD-10. So, it is the dextrose equivalent of starch products that is an objective criterion of their technological activity as part of yogurt. The results of the study will allow purposeful management of the process of forming low-fat yogurt quality indicators.

Comparative transcriptomic analysis of the flavor production mechanism in yogurt by traditional starter strains

The synergistic fermentation of milk by Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus is one of the key factors that determines the quality of yogurt. In this study, the mechanism whereby yogurt flavor compounds are produced by a mixture of S. thermophilus SIT-20.S and L. delbrueckii ssp. bulgaricus SIT-17.B were investigated by examining the flavor production, growth, and gene transcription of these strains. The results showed that yogurt produced by a 10:1 mixture of the aforementioned strains had the highest abundance of acetoin, whereas yogurt produced by a 1:1 mixture had the highest abundance of diacetyl and acetaldehyde. In addition, the growth of S. thermophilus SIT-20.S was enhanced in the 10:1 mixture. Transcriptomic analysis revealed differentially expressed genes in the flavor-compound-related pathways of S. thermophilus SIT-20.S and L. delbrueckii ssp. bulgaricus SIT-17.B in yogurts produced by 10:1 and 1:1 mixtures compared with those produced by either strain alone. Mixed fermentations regulated the expression of genes related to glycolysis, resulting in an increase of pyruvate, which is an important precursor for diacetyl and acetoin synthesis. The gene encoding the acetoin reductase (SIT-20S_orf01454) was decreased in S. thermophilus SIT-20.S, which ensured the accumulation of acetoin. In addition, the gene encoding the acetaldehyde dehydrogenase (SIT-20S_orf00949) was upregulated in S. thermophilus SIT-20.S, and the expression of alcohol dehydrogenase (SIT-20S_orf01479; SIT-17B_orf00943) was downregulated in both strains, maintaining the abundance of acetaldehyde. In addition, the gene encoding the NADH oxidase (SIT-17B_orf00860) in L. delbrueckii ssp. bulgaricus SIT-17.B were upregulated, which promoted the accumulation of diacetyl and acetoin. Overall, we characterized the mechanism by which S. thermophilus and L. delbrueckii ssp. bulgaricus synergistically generated yogurt flavor compounds during their production of yogurt and highlighted the importance of appropriate proportions of fermentation starters for improving the flavor of yogurts.

Effects of Semen Ziziphi Spinosae extract and binary probiotics co-fermentation on the quality of yogurt and their underlying molecular mechanisms

The study aimed to investigate the impact of water-soluble extract from Semen Ziziphi Spinosae (SZSE) on yogurt quality and understand the underlying mechanism. The results demonstrated that adding 0.5% (w/v) SZSE had a significant effect on reducing yogurt syneresis and resulted in a more compact and uniform casein gel. Notably, the co-fermented yogurt with binary probiotics (Lacticaseibacillus casei CGMCC1.5956 and Levilactobacillus brevis CGMCC1.5954) along with SZSE led to increased viable probiotics and a higher odor score (23.23). This effect might be attributed to the increased amino acid utilization by binary probiotics through biosynthesis of valine, leucine and isoleucine, metabolic pathways, and amino acid biosynthesis to produce amino acid derivatives such as N5-(l-1-carboxyethyl)-l-ornithine and diaminopyrimidine acid. The yogurt contained 79 volatile flavor compounds, with hexanoic acid, 2-heptanone, and 2-nonanone potentially contributing to the high odor scores. These findings have strategic implications for developing yogurt with high gel characteristics and distinctive flavor.

Effects of Panax notoginseng Saponins Encapsulated by Polymerized Whey Protein on the Rheological, Textural and Bitterness Characteristics of Yogurt

Panax notoginseng saponins (PNSs) have been used as a nutritional supplement for many years, but their bitter taste limits their application in food formulations. The effects of PNS (groups B, C, and D contained 0.8, 1.0 and 1.2 mg/mL of free PNS, respectively) or Panax notoginseng saponin-polymerized whey protein (PNS-PWP) nanoparticles (groups E, F, and G contained 26.68, 33.35 and 40.03 mg/mL of PNS-PWP nanoparticles, respectively) on the rheological, textural properties and bitterness of yogurt were investigated. Group G yogurt showed a shorter gelation time (23.53 min), the highest elastic modulus (7135 Pa), higher hardness (506 g), higher apparent viscosity, and the lowest syneresis (6.93%) than other groups, which indicated that the yogurt formed a stronger gel structure. The results of the electronic tongue indicated that the bitterness values of group E (−6.12), F (−6.56), and G (−6.27) yogurts were lower than those of group B (−5.12), C (−4.31), and D (−3.79), respectively, which might be attributed to PNS being encapsulated by PWP. The results indicated that PWP-encapsulated PNS could cover the bitterness of PNS and improve the quality of yogurt containing PNS.

Physical quality of goat milk yogurt with the addition of pineapple and purple sweet potato

It is necessary to eliminate the rancid smell of goat milk by fermentation technology through yogurt-making plus pineapple juice and purple sweet potato juice stabilizer. Adding pineapple juice and purple sweet potato is a food diversification by utilizing agricultural production and maintaining environmental sustainability. The study sought to enhance consumer enthusiasm for ingesting goat milk yoghurt by incorporating pineapple juice and purple sweet potato. This study used a factorial experiment in RAL 3 x 3 with 3 replications. Factor I pineapple juice dose consists of N1 = 5%, N2 = 10%, and N3 =15%. Factor II dose of purple sweet potato juice consisted T1: 0.2% (T1), T2: 0.4% and T3: 0.6%. Control goat milk yogurt without adding pineapple and purple sweet potato juice. The parameters studied consisted of. swell ability and solubility, syneresis, viscosity and WHC (Water Holding Capacity). The results of the study the addition of 15% pineapple juice (N3) and 0.6% purple sweet potato (T3) produced the best physical quality of goat milk yogurt increasing the swelling power, solubility, water holding capacity, viscosity with respective values of 10.73%, 3.08%, 90%, and 352.93% and decreasing syneresis with a value of 15.73%.

Olive oil and coconut oil improved the quality and digestibility of set soybean yoghurt

Abstract The results of GC-MS analysis showed that the set soybean yoghurt without oil contained only two esters and one alcohol: delta-dodecalactone, 5-decanolide, and R-(−)-2-butanol. The set soybean yoghurt with olive oil was characterized by five volatile flavors: hexanoic acid, 2-nonanol, phenylacetaldehyde, 3-heptylacrolein, and acetylpyrazine. The set soybean yoghurt with coconut oil was characterized by nine volatile flavors: 5-hydroxyoctanoic acid lactone, ethyl caprylate, ethyl caprate, ethyl laurate, 2-tridecanone, dihydro-2-methyl-3(2H)-thiophenone, lauric acid, 1-octanol, and 2-decanol. Gas chromatographic analysis showed that free fatty acid species increased in set soybean yoghurt after oil addition, which were positively correlated with volatile flavor substances. By confocal laser microscopy observation, the oil droplets in the three groups of set soybean yoghurt were reduced after digestion. Research has proved that adding an appropriate amount of olive oil or coconut oil to set soybean yoghurt can improve the flavor and does not increase the digestive burden.

Effect of Whole Egg Liquid on Physicochemical, Quality, Fermentation and Sensory Characteristics of Yogurt.

With the purpose of developing an alternative set yogurt with high consumer acceptability, liquid whole egg (LWE), at levels that varied from 0 to 30%, was incorporated into set yogurt, and the effects on the physicochemical, quality, fermentation, and sensory characteristics of yogurt were evaluated. The fat content was lower in egg yogurt than in control yogurt. All color variables were significantly affected by LWE amount. The amount of bacteria in the egg yogurt was greater than in the control yogurt. Sensory analysis data suggested that color, odor, and texture consistently impacted the overall acceptability of the egg yogurt. The addition of 5% whole egg, which resulted in an increase of 6.28-fold in hardness, increase of 6.1-fold in viscosity, decrease in pH values, and a 5.6% decline in water-holding capacity (WHC). The aroma and flavor of the set yogurt was improved as well. LWE addition significantly increased the protein content and dynamic rheology. More importantly, the addition of LWE increased the protein content of the set yogurt. This investigation demonstrated the feasibility of fabricating LWE-enriched set yogurt and its superior quality compared with the corresponding normal product. It also emphasized the reconstruction of LWE with enhanced properties.

Green efficient preparation and on-line monitoring: Hybrid effect of okra pectin and controlled-temperature ultrasound on physicochemical properties of low-fat yogurt

Pectin replaces fat as a stabilizer in making green low-fat yogurt. Controlled-temperature ultrasonic-assisted fermentation (CTUAF) was used, and its acoustic field was monitored in time-frequency domains during the fermentation. Meanwhile, the effect of the addition of okra pectin (OP) on the acoustic field intensity in the yogurt was discussed. Furthermore, the synergistic effect of ultrasound and OP on the physicochemical and structural properties of yogurt was studied, including post processing operations and storage of yogurt. Results showed that adding OP increased the intensity of acoustic field and improved the efficiency of yogurt fermentation. 0.1% OP, ultrasound and hybrid of both shortened the fermentation time of yogurt by 0.75 h, 0.5 h and 1.0 h, respectively. Ultrasound and OP reduced syneresis and optimized hardness, rheological properties and processing quality of yogurt. The cross-linking of OP with casein increased and filled casein cavities, and ultrasound enhanced this interaction. The hybrid of OP and CTUAF also improved the survival rate of probiotics.

Physicochemical, microbiological and metabolomics changes in yogurt supplemented with lactosucrose

Lactosucrose (LS) is a known prebiotic that has gained recognition for its low caloric content and various health benefits. However, its potential in food applications remains largely unexplored. In this study the effects of adding LS to milk at concentrations (0 %, 2 %, 5 % and 8 % w/v) for yogurt production, and the relevant changes in yogurt texture, microbial composition and metabolomics were investigated. Our findings revealed that LS played a role in promoting the formation of a structured gel during fermentation, resulting in increased elasticity and viscosity while reducing fluidity. Additionally incorporating high doses of LS into yogurt led to reduced post-acidification, enhanced survival of starter bacteria, improved water retention capacity and overall texture throughout a refrigerated storage period of 21 days. Notably higher concentrations of LS (8 % w/v) exhibited effects on enhancing yogurt quality. Furthermore, untargeted metabolomics analysis using UPLC Q TOF MS/MS revealed 45 differentially expressed metabolites, including up-regulated L-arginine, L-proline and L-glutamic acid along with the down-regulated glutathione, L-tyrosine, L-phenylalanyl and L-proline. These differential metabolites were primarily associated with amino acid metabolism such as thiamine metabolism, nicotinic acid salt and nicotinamide metabolism, and pyrimidine metabolism. As a result, the inclusion of LS in yogurt had an impact on the production of various beneficial metabolites in yogurt, highlighting the importance of combining prebiotic LS with probiotics to obtain desired physiological benefits of yogurt.

Influence of milk fat and skimmed milk powder on quality of goat milk yoghurt

Influence of milk fat and skimmed milk powder on quality of goat milk yoghurt

Quality of yogurt produced from various types of milk as raw materials

Different types of milk are used to make yogurt, which gives it different qualities. Fresh milk, powdered milk, low-fat milk, non-fat milk, and Ultra High Temperature (UHT) milk all have different qualities. The goal of the study was to look at the chemical, physical, and sensory properties of yogurt made from different ingredients. The treatment’s base materials were P1: yogurt made with fresh milk, P2: yogurt made with milk powder, P3: yogurt made with ultra-high-temperature milk, P4: yogurt made with low-fat milk, and P5: yogurt made with non-fat milk. Commercial yogurt starters were used to make yogurt, and each treatment was done four times. Other tests were done with Duncan. The factors for the study are the amount of moisture, total solids, pH, total titratable acidity, and how it tastes. The results showed that the moisture content, total solids, pH, and total titratable acidity were all significantly different (P<0.05), as were the taste and preferences. The results of the study show that yogurt with different ingredients has different qualities.

Yogurt Production.

Yogurt is a widely consumed dairy product that is obtained through the fermentation of lactic acid bacteria. During fermentation, these bacteria produce lactic acid, which lowers the pH and causes the coagulation of milk proteins. Metabolites of lactic acid bacteria, such as carbonyl compounds, nonvolatile or volatile acids, and exopolysaccharides, significantly affect the quality of yogurt. The production method also greatly influences yogurt characteristics. Yogurt can be produced in various forms, including solid, fluid, and soft-drinking types, depending on the manufacturing method employed. In addition, the raw materials, sterilization, homogenization, fermentation, and other conditions in each manufacturing method greatly affect yogurt's physical properties and flavor. This chapter summarizes common and modern methods of yogurt production.

The Physicochemical, Textural, Microbiological and Sensory Properties of Skimmed Buffalo Milk Yoghurt with Tragacanth Gum During Storage.

In the food industry, research interest in the functional effects of natural polysaccharides from plants has increased in recent years. Tragacanth gum is used in dairy products because of its stabilising, thickening, fat-replacing and prebiotic properties. However, skimmed milk is considered a significant commercial loss in the production of buffalo clotted cream. Therefore, the aim of the present study is to investigate the potential of tragacanth gum in the production of yoghurt from buffalo milk residues with different concentrations of tragacanth gum (0.5, 1 and 1.5 g/L). Skimmed buffalo milk with different concentrations of tragacanth gum was pasteurised and, after cooling at 45 °C, a starter culture was added to each sample. All samples were fermented to a pH=4.80±0.2. The gross composition, acidity, water activity, water-holding capacity, whey separation, mass fractions of organic acids and volatile aroma compounds, counts of total aerobic mesophilic bacteria, yeasts and moulds, Lactococcus spp. and Lactobacillus spp. as well as sensory and textural properties were analysed during 15 days storage. The results showed that the use of tragacanth gum increased the dry matter mass fraction, water-holding capacity and mass fraction of proteins in the samples, while whey separation decreased as the concentration of gum increased. The addition of gum improved textural properties and hardness of the yoghurt. In terms of consistency, the sample with 1 g/L tragacanth gum was the most reliable. In the control group, the total aerobic mesophilic bacteria count was highest on the first and last day of storage. According to the results of the sensory evaluation, the sample with 0.5 g/L tragacanth gum was the most favourable. Research has shown that the use of stabilisers in varying ratios improves the quality of yoghurt made from fat-free buffalo milk, which is a by-product of industrial production. So instead of ending up as industrial waste, it is recycled and its value is increased.

Dextrose Equivalent (DE) Variation and Maltodextrin Concentration Effects in Yoghurt Powder Characteristics Using Foam-mat Drying

Lactic Acid Bacteria (LAB) in yoghurt is a probiotic bacteria which potentially improves intestinal health. Yoghurt has a high moisture content. Thus, storing it at low temperatures can maintain the stability of microbes in the yoghurt. Yoghurt stored in the refrigerator has a maximum shelf life of 10 days. Yoghurt powder is one of the alternative solutions to prolong the shelf life. This study used a randomized design of factorial groups with variations of dextrose equivalent (DE) values of 10-12 and 18-20, as well as variations of maltodextrin concentrations of 10, 15, and 20%. The study aimed to determine the DE value and maltodextrin concentration which can produce the best quality synbiotic yoghurt powder. The quality of this synbiotic yoghurt was assessed by the highest yield, lowest water content, highest solubility, highest water absorption, highest acidic titrated total, highest total of lactic acid bacteria, and highest organoleptic. The study obtained that the DE value of maltodextrin affected the total LAB. Meanwhile, the concentration of maltodextrin affected the yield, moisture content, solubility, acidic titrated total, and total of LAB. The interaction between the DE value and the concentration of maltodextrin did not affect all the parameters of this study.

Fortification of set yoghurts with lemon peel powders: An approach to improve physicochemical, microbiological, textural and sensory properties

Lemon peel powder (LPP) is an excellent source of pectin and has been used as prebiotic polysaccharide. This study was conducted to assess the possibility of fortifying yoghurt with LPP (0.25 %, 0.5 % and 0.75 %) to improve the functionality of yoghurt. Physico-chemical properties of LPP as well as pH, acidity, color, total solids, viscosity, water holding capacity, syneresis, microbial, textural and sensory properties of LPP fortified yoghurt during 14 days of storage were evaluated. The results showed that bulk density, swelling, water absorption, emulsifying, and foaming capacity of LPP were 0.548, 8.61, 5.23 ml/g, 14.22 % and 11.33 % respectively. Addition of LPP enhanced the viscosity from 480 mPas to 610 mPas, total solid from 22.73 % to 25.93 %, acidity from 815 mg/100 ml to 1006 mg/100 ml and decreased pH values from 4.83 to 4.52. LPP fortification also improved the water holding capacity, microbial viability, and microstructure. The sensory test revealed that yoghurt with 0.5 % LPP had higher sensory scores and overall acceptability. Based on the data obtained from the current study, the addition of 0.5 % LPP in yoghurt had been suggested to enhance the nutritional quality of yoghurt by providing better physicochemical and organoleptic qualities.

A comparison of the quality of plain yogurt and its analog made from coconut flesh extract

The aim of this study was to compare the quality of plain yogurt made from cow milk (n = 10) and its plant-based analog made from coconut flesh extract (n = 14). Coconut yogurt alternatives were divided into 2 experimental groups based on differences in their color, which were noted after the packages had been opened. The first group included products with a typical white color (n = 8), and the second group comprised products with a grayish pink color (n = 6) that developed as a result of oxidative processes. In comparison with its plant-based analog, plain yogurt was characterized by higher values of lightness (L*), yellowness (b*) and chroma (C*), higher titratable acidity, a higher content of retinol and α-tocopherol, higher nutritional value of fat, and lower values of water-holding capacity (WHC) and redness (a*). Plain yogurt had lower volatile acidity than its plant-based analog with a grayish pink color. A comparison of yogurt analogs with different colors revealed that the product with a grayish pink color was characterized by a lower value of L*, and higher values of a*, b*, C*, and pH. An analysis of its fatty acid profile demonstrated that it also had a higher proportion of C14:0 and C18:1 cis-9; higher total monounsaturated fatty acids content; a lower proportion of C10:0, C12:0, and C18:2; a lower total content of polyunsaturated fatty acids (PUFA) and essential fatty acids; and a lower ratio of PUFA to saturated fatty acids. The yogurt analog with a grayish pink color had a lower total content of tocopherol isoforms than the remaining products. The yogurt analog with a white color had the highest WHC and γ-tocopherol content. Consumers should be aware of the fact that coconut yogurt alternatives may have nonstandard quality attributes. The differences between such products and yogurt made from cow milk should be explicitly communicated to consumers so that they could make informed purchasing decisions.