Yogurt Texture Research Articles

Effect of roasting and high-pressure homogenization on texture, rheology, and microstructure of walnut yogurt

The effect of roasting and high-pressure homogenization on the quality of yogurt made from peeled walnut kernels was explored in this study. The G' and G'' values of yogurt made from walnuts roasted at high temperatures were reduced. The water-holding capacity and hardness of walnut yogurt were reduced to 47.73% and 24.22 g, respectively. Increasing the homogenization pressure reduced the particle size of the walnut yogurt to 20.50 μm. Homogenized walnut milk at 150 MPa increased the viscosity, hardness, and consistency of yogurt product from 11.71 to 16.74 Pa.s, from 30.01 to 71.63 g and from 283.17 to 455.24 g·s, respectively. The confocal laser scanning microscope observation demonstrated a reduction in the size of fat and protein micelles in the homogenized yogurt samples, resulting in a compact structure. This study will contribute valuable scientific insights to the advancement of plant-based yogurt quality.

Effects of mulberry pomace polysaccharide addition before fermentation on quality characteristics of yogurt

Mulberry pomace, a by-product of mulberry juice processing, is rich in natural bioactive substances including polysaccharides and polyphenols and is useful for the production of functional foods. As such the effects of mulberry pomace polysaccharide (MPP) on physicochemical, textural and microstructural features of yogurt during cold storage were investigated. MPP was incorporated into reconstituted skim milk at 0% (control), 0.5%, 1.0% and 1.5%, respectively and then fermented to yogurt and stored at 4 °C for 28 days. The color, pH, titratable acidity, syneresis, rheology, texture and microstructure of yogurt samples were analyzed. The addition of MPP before fermentation dose-dependently affected the pH value and titratable acidity of yogurt samples such that the addition of 0.5% MPP showed the most significant effect in reducing syneresis, increasing gel strength and viscosity, and improving texture and microstructure of yogurt. The results indicate that the appropriate amount of MPP can effectively improve the gel properties and physicochemical parameters of yogurt, and MPP played an important role in the yogurt quality improvement by mulberry pomace.

Effect of enzymatic modified pea peel dietary fibre on syneresis, texture, rheology and microstructural properties of yogurt

Effect of enzymatic modified pea peel dietary fibre on syneresis, texture, rheology and microstructural properties of yogurt

Quantitative image analysis of influence of polysaccharides on protein network formation in GDL-acidified milk gels

Exopolysaccharides (EPS) are commonly used to improve the texture of yogurt. These polysaccharides interact with casein micelles, the major protein in milk, via electrostatic and depletion mechanisms during fermentation by lactic acid bacteria (LAB). However, the relationship between the physicochemical properties and monosaccharide composition of EPS and their impact on yogurt texture is not yet fully understood. To address this knowledge gap, we studied the effects of polysaccharides commonly used as food additives on acid-induced milk protein networks. Confocal laser scanning microscopy (CLSM) was used to image the network microstructures. Image analysis, including Fourier transform, autocorrelation, and binarization-based techniques, was applied to quantify key structural features of the mixed milk protein/polysaccharide gels. These parameters were then related to the macroscopic properties of the model food matrices, such as elastic and viscous moduli and yield point. We found that the addition of neutral polysaccharides resulted in a concentration-dependent increase in structure factor, protein domain size, and pore fraction. In contrast, the presence of charged polysaccharides led to an increase in protein domain size, a decrease in pore fraction, and a decrease in elastic and viscous moduli. These results demonstrate the use of a quantitative image analysis method for selecting LAB with favorable EPS properties to improve yogurt texture.

Effects of different strains fermentation on the sensory and nutritional properties of soy-based yogurt.

Soy protein is the only full plant protein that is comparable to animal protein. Soy whey contains a variety of nutrients including isoflavones and oligosaccharides. Additionally, different strains have profound influence on functional metabolism. Most prospective studies used mixed strain fermented yogurt, but few studies on single strain fermented yogurt. The present study aimed to ferment nutritious and healthy soy-based yogurt using a single strain and to provide technical support for the reuse of soy whey. Streptococcus salivarius subsp. thermophilus HCS07-002, Bifidobacterium animalis subsp. lactis HCS04-001 and Lactiplantibacillus plantarum HCS03-084 had strong growth and metabolic activities. Bifidobacterium animalis subsp. lactis HCS04-001 fermentation raised the texture and rheological properties of yogurt and enriched the flavor substances in the yogurt, resulting in a good quality soy-based yogurt. The contents of arginine, glutamic and proline were greatly affected by the fermentation of different strains. The fermentation of B. animalis subsp. lactis HCS04-001 was beneficial to the enrichment of soy isoflavone and equol in yogurt, and enhanced antioxidant activity of yogurt. Our findings indicated that yogurt fermented with B. animalis subsp. lactis HCS04-001 had the best sensory and nutritional properties, which provides valuable insights into the selection of suitable strains to improve the quality and nutritional value of plant yogurt. © 2023 Society of Chemical Industry.

Structural elucidation and physicochemical properties of litchi polysaccharide with the promoting effect on exopolysaccharide production by Weissella confusa

Exopolysaccharide (EPS), as a secondary metabolite of microorganisms, has been commonly used in the dairy industry to replace the traditional stabilizers. However, the EPS production by microorganism is generally low, which limits its application. A litchi polysaccharide (Lzp2-2) with the promoting effect on EPS production by Weissella confusa was purified. The SEM and FT-IR analysis indicated that Lzp2-2 displayed a compact netlike structure and typical bands of carbohydrates. The structure of Lzp2-2 was further elucidated, which was comprised of a major backbone structure [→3)-β-D-Galp-(1→6)-β-D-Galp-(1 → 6)-β-D-Galp-(1 → 3)-β-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 3)-α-D-Glcp-(1→] linked with two side chains [α-L-Araf-(1 → 5)-α-L-Araf-(1→, and β-D-Glcp-(1 → or α-L-Araf-(1→] at the O-3 and O-6) of β-D-Galp-(1→, respectively. Finally, Lzp2-2 was applied as an additive to the medium of yoghurt fermented by W. confusa. The results indicated Lzp2-2 not only promoted the EPS production to improve the viscosity, texture and mouthfeel of yoghurt, but also facilitated the generation of other secondary metabolites (volatile organic compounds), thus elevating the flavor of yoghurt.

Influence of β-casein genotype on physicochemical properties and functionality of bovine milk

Several studies have been focused on the effect of milk protein genetic variants on milk physicochemical properties and functionality in recent years. β-casein, an important protein related to milk processibility, has been reported to have 2 main genetic variants A1 and A2, for which cows may be homozygous or heterozygous. In this study, several physicochemical properties of milk with β-casein variants A1A1, A1A2, and A2A2 from 3 collection occasions were analyzed. Higher manganese content and lower pH were found to be associated with the A1A1 variant compared with the other 2 genotypes. Better rennet and acid coagulation were found in A1A1 milk compared with A1A2 and A2A2 milk (although P > 0.05), whereas A2A2 milk was more stable to creaming compared with the other 2 genotypes, which may be linked to its smaller fat globule size. Thus, milk from cows with A1A1 genotype could be preferable for cheese making, while that with A2A2 variant can be used in formulations requiring good stability against creaming, and for example, yogurt making, where the softer yogurt texture may be easier to digest.

Physicochemical, sensory, and antioxidant characteristics of stirred-type yogurt enriched with Lentinula edodes stipe powder.

The Lentinula edodes stipe (LES), a by-product of L. edodes fruiting body processing, is rich in dietary fiber, protein, and polysaccharides, which can be served as the functional ingredient in dairy products. In this study, stirred yogurts fortified with 1%, 2%, and 3% LES were prepared, and the effects of LES on the changes in color, pH, titratable acidity (TA), viable lactic acid bacteria (LAB) cells, syneresis, viscosity, texture, and antioxidant activity of the flavored yogurt were monitored at the beginning and the end of storage. The LES decreased the lightness, increased the red-green color values and yellow-blue color values, decreased the pH values, and increased the contents of TA, the viable LAB cells, and the antioxidant activity of yogurt samples in a dose-dependent manner. The addition of LES showed double-edged effects on the texture of yogurt, which significantly reduced firmness and viscosity but decreased the syneresis. Compared with plain yogurt, the 2% LES-fortified yogurt exhibited similar index values of texture parameters and higher scores of the appearance, fermented odor, taste quality, and overall acceptance, suggesting that this might be the optimal dose for industrial production. After cold storage for 28 days, pH values of all yogurt samples further decreased with increasing of TA. Interestingly, syneresis of LES-fortified yogurt decreased and the viable LAB cells and antioxidant activity of 3% LES-fortified yogurt slightly decreased. Therefore, LES is beneficial to improve physicochemical, sensory, and antioxidant properties of yogurt, which has the potential to be used in functional dairy products.

Organoleptic Tests of The Addition of Telang Flower Extract (Clitoria ternatea) on Cow's Milk Yoghurt (Bos taurus) Production in Air Tawar Village, Langkat

Yogurt is the oldest dairy product and is quite popular almost all over the world. Yogurt comes from pure cow's milk. Butterfly pea (Clitoria ternatea ) often referred to as butterfly pea or blue bean is a distinctive flower with a single petal in purple, blue, pink and white. Researchers wanted to see the effect of adding butterfly pea flower extract (Clitoria ternatea) to cow's milk yogurt (Bos taurus). This study employs a quantitative approach as its method. A quantitative approach was used to understand what the research subjects experienced from the color, taste, aroma and texture of the yogurt. The results of the study found that the addition of butterfly pea flower extract (Clitoria ternatea) at different levels had an effect on the organoleptic characteristics and texture of yogurt. The best practice produces organoleptic characteristics of taste (slightly sour), color (light blue), texture (slightly thick) and aroma (typical of yogurt).

Exploring the textural dynamics of dairy and plant-based yoghurts: A comprehensive study

The mouthfeel and texture of dairy and non-dairy yoghurts play a critical role in food acceptance and liking. The present study aimed to understand the oral perception of commercially available dairy and non-dairy yoghurts. Four dairy and four non-dairy yoghurts with different levels of protein and fat were analyzed to understand the impact of particle size, textural properties and frictional coefficient on the dynamic sensory mouthfeel characteristics measured by the temporal dominance of sensations (TDS) method. Differences in friction coefficients of dairy and non-dairy yoghurts were observed. The friction factor was lower for high-fat dairy yoghurts than for non-dairy yoghurts. The particle size d90 in yoghurts was positively related to graininess perception (r=0.81) and negatively associated with mouthfeel liking (r=−0.87) and overall liking (r=−0.80). For the TDS results, “creaminess” and “thickness” were significantly dominant for dairy yoghurts, while “melty” and “easy to dissolve” were dominant attributes for non-dairy yoghurts. Creaminess perception improves the mouthfeel liking (r=0.72) and overall liking (r=0.59) of yoghurts and is the driver of liking. The findings of this study help understand the intrinsic mouthfeel properties of commercial dairy and non-dairy yoghurts, which will provide valuable insight to product developers during the new product formulation.

Microbiological, physico-chemical, and sensory quality of yoghurt supplemented with gelatinized pigeon pea (Cajanus cajan (L.) Millsp.) flour

Recent advances in functional food research fostered new food ingredients that can alleviate the properties already found in these foods. Among them, product diversification in fermented foods totally benefitted because of the array of raw materials that can be mixed with milk-based fermented milk products like yoghurt. Legumes were reported to have bioactive ingredients that can potentially increase the beneficial effects of yoghurt by increasing the viability of yoghurt starter cultures. In this study, the effect of supplementation with gelatinized pigeon pea flour on the microbiological, physicochemical, and sensory properties of yoghurt during 14 days of refrigerated storage was determined. Supplementation of yoghurt with gelatinized pigeon pea flour significantly increased the viability of Lactobacillus delbrueckii subsp. bulgaricus, fermentation rate and total titratable acidity, and significantly lowered the pH of the supplemented yoghurt. However, no significant effect on the viability of Streptococcus thermophilus was found. Results of sensory evaluation showed that the addition of gelatinized pigeon pea flour to yoghurt significantly affected the colour, texture and consistency of yoghurt, and imparted a perceivable aftertaste, but did not significantly affect the aroma, sourness, sweetness, and overall acceptability of the product. The findings suggested that pigeon pea flour can be considered a potential ingredient for yoghurt supplementation.

The texture of non-fat yogurt with proteins isolates and concentrates

Yogurt is one of the most common fermented milk products. It is consumed directly as food or used for the production of fermented milk desserts and ice cream. The urgent task for yogurt producers is improving product quality due to additionally introduced protein components. In this study, an effect of protein isolates and concentrates on the rheological parameters of yogurt was evaluated. The methods included the determination of dynamic viscosity and texture indices, such as hardness, gumminess, chewiness, springiness, cohesiveness and adhesiveness. The prepared yogurt samples were investigated immediately and after 30 days of storage at a temperature of 4±2°C. The water-holding capacity was evaluated. It has been established that introduction of whey proteins makes it possible to increase the water-holding capacity to 77% and 80%, respectively. The highest value of dynamic viscosity (19.3 and 26.1 Pa·s) was found in the samples with isolate and concentrate of native whey proteins after 5 hours of fermentation. A decrease in dynamic viscosity with the introduction of milk protein isolate, soy protein concentrate and native whey protein isolate was observed after 5 hours of fermentation. Addition of the protein components led to a significant increase in texture indices, except for cohesiveness. The highest cohesiveness value of 0.4 N·s was found in the sample without protein components and in the sample with whey protein concentrate. The indicators of hardness, gumminess, chewiness, springiness and adhesiveness were the highest in the sample with native whey protein isolate.

Effects of Oat β-Glucan on the Textural and Sensory Properties of Low-Fat Set Type Pea Protein Yogurt.

This study investigated the effect of oat β-glucan as a fat substitute on the structure formation, texture, and sensory properties of pea protein yogurt. The results showed that the incorporation of 0.5% β-glucan significantly accelerated the lactic acid bacteria-induced fermentation, with the time for reaching the target pH of 4.6 shortened from 3.5 h to 3 h (p < 0.05); increased the plastic module (G') from 693 Pa to 764 Pa when fermenting 3 h (p < 0.05); and enhanced the water-holding capacity from 77.29% to 82.15% (p < 0.05). The identification of volatile organic compounds (VOCs) in low-fat pea protein yogurt by GC-IMS revealed a significant decrease in aldehydes and a significant increase in alcohols, ketones and acids in the pea yogurt after fermentation (p < 0.05). Among them, the levels of acetic acid, acetone, 2,3-butanedione, 3-hydroxy-2-butanone, and ethyl acetate all significantly increased with the addition of oat β-glucan (p < 0.05), thereby providing prominent fruity, sweet, and creamy flavors, respectively. Combined with the results of sensory analysis, the quality characteristics of pea protein yogurt with 1% oil by adding 1% oat β-glucan were comparable to the control sample with 3% oil. Therefore, oat β-glucan has a good potential for fat replacement in pea protein yogurt.

Evaluation of milk source on physicochemical, texture, rheological and sensory properties of yogurts

Yogurt is one of the world's most widely consumed dairy products and can be produced from different types of milk. The present research aimed to compare the effects of utilizing whole raw milk from cattle viz. cows, buffaloes, sheep, and goats in four different milk-type yogurts, T1- cow’s milk (CM), T2- buffalo’s milk (BM), T3- sheep’s milk (SM), and T4- goat’s milk (GM) on their physicochemical, texture, rheological, and sensory qualities. The physiochemical testing included estimating pH, the percentages of moisture, fat, protein, ash, and total acidity, and the sensory assessment of the yogurt. The rheological tests also included the viscosity test, spontaneous whey separation, water-holding capacity, firmness, cohesiveness, and springiness. The results showed that T2- BM yogurt and T3- SM yogurt excelled in the percentage of fat, protein, lactose, and ash, where the ratio (4.35, 8.4, 4.70, 0.8) (5.55, 7.45, 4.80, 1.1) was for each of T2- BM yogurt and T3- SM yogurt respectively. The rheological properties were the spontaneous whey separation for each of T1-CM, T2-BM, T3-SM, T4-GM yogurt were 4.1, 2.2, 2.1 and 5.3, respectively, while the water holding capacity was 55, 60, 71 and 53 and the viscosity was 7000, 8900, 6700 and 1510 respectively. The results of the texture properties were 126.2, 199.5, 176.3, and 38.9 for firmness, while the cohesiveness values were 0.41, 0.63, 0.65, and 0.4, respectively. Finally, T2-BM and T3-SM yogurt excelled in the value obtained for sensory evaluation. The importance of the present study lies in the fact that milk with a high percentage of total solids gives good-quality yogurt.

Physicochemical properties, antigenicity and allergenicity of yoghurt fermented by Lactiplantibacillus plantarum AHQ‐14 combined with starter

SummaryCow milk proteins is one of the major food allergens, and some probiotics can abate allergenicity to some extent. Lactiplantibacillus plantarum AHQ‐14 isolated from the traditional dairy products in Xinjiang Province, China, has good ability to reduce the allergenicity of β‐lactoglobulin (LG) and good probiotic properties. In the presented study, L. plantarum AHQ‐14 was used to replace half of the commercial yoghurt starter to ferment yoghurt, and the effects of L. plantarum AHQ‐14 fortification on microstructure, textural and rheological attributes of yoghurt were investigated. In addition, milk protein hydrolysis, antigenicity and allergenicity of yoghurts during 28 days of cold storage were detected. The results indicated that AHQ‐14 and YC‐X11 fermentation could enhance the texture and rheological properties of yoghurt by reducing the syneresis (37%) and firmness (14%) and improving the cohesiveness by 50%. In addition, AHQ‐14 and YC‐X11 fermentation can shorten the fermentation time by about 30 min, SDS‐PAGE displayed that AHQ‐14 and YC‐X11 fermentation had stronger hydrolysis of whey protein compared with YC‐X11 yoghurt. Additionally, the fermentation by L. plantarum AHQ‐14 and YC‐X11 could significantly reduce the antigenicity and IgE‐binding ability of skim milk by 82% and 94%, respectively, thus reducing milk‐allergic reactions in patients significantly.

Shaping the Physicochemical, Functional, Microbiological and Sensory Properties of Yoghurts Using Plant Additives.

Nowadays, consumers pay particular attention to the quality of the products they buy. They also expect a high level of innovation. Hence, the offer from the dairy sector is increasingly focusing on the use of various additives with proven health benefits. Many scientific teams from various regions of the world are engaged in research, and their aim is to identify plant additives that have beneficial effects on the human body. The aim of this article was to summarize the latest literature pertaining to the effects of plant additives used in the production of yoghurts on their physicochemical, functional, microbiological and sensory properties. It was found that a wide range of additives in a variety of forms are used in the production of yoghurts. The most common include fruits, vegetables, cereals, nuts, seeds, oils, plant or herbal extracts, fruit or vegetable fibre, and waste from fruit processing. The additives very often significantly affected the physicochemical and microbiological characteristics as well as the texture and sensory properties of yoghurt. As follows from the analysed reports, yoghurts enriched with additives are more valuable, especially in terms of the content of health-promoting compounds, including fibre, phenolic compounds, vitamins, fatty acids and minerals. A properly selected, high quality plant supplement can contribute to the improvement in the generally health-promoting as well as antioxidant properties of the product. For sensory reasons, however, a new product may not always be tolerated, and its acceptance depends mainly on the amount of the additive used. In conclusion, "superfood" yoghurt is one of the products increasingly recommended both preventively and as a way of reducing existing dysfunctions caused by civilization diseases, i.e., diabetes, cancer and neurodegenerative diseases. The studies conducted in recent years have not shown any negative impact of fortified yoghurts on the human body.

Assessment of Quality Attributes of Yoghurt Fortified with Coriaandrum sativum and Mentha spicata

Diseases resulting from malnutrition are causing serious harm to human health not only among children but also among young ones equally. Now a days people are more aware of eating nutritious diet that enable them to enjoy a healthful life. The milk and yoghurt product variety has expanded by their enrichment with additives. In present study, effect of various herbs extract in yoghurt were explored. This study demonstrates that fermented food like yoghurt can be successfully fortified with plant extract in order to inculcate desirable changes in yoghurt. In present study effect of two different herbs was checked on yoghurt characteristics. Yoghurt fortified with Coriaandrum Sativum or Mentha Spicata has longer shelf-life, more nutritious and has more consumer acceptance. Herbs also have an influence on the texture and firmness of yoghurt. However more research and knowledge is needed in order to improve method employed for yoghurt fortification.

Influence of germinated black cumin (Nigella sativa L.) seeds extract on the physicochemical, antioxidant, antidiabetic, and sensory properties of yogurt

This study investigated the effect of adding germinated black cumin seed extract (GBSE) in the amounts of 0, 50, 75, and 100 mg/100 ml milk, which are mentioned in abbreviate as C, GBSE50, GBSE75, and GBSE100, respectively, on the physicochemical, antioxidant, antidiabetic and sensory properties of yogurt. In the present research, pH, titratable acidity (TA), syneresis, water-holding capacity (WHC), viscosity, total phenolic content (TPC), antioxidant activity (DPPH, ABTS radicals scavenging activity and FIC assay), α-amylase and α-glucosidase inhibitory effect and sensory attributes (taste, odor, texture, color, and overall acceptance) of fortified yogurts during 14 days of storage at 4 °C were determined. According to study results, fortification, even in the lowest amount (50 mg/100 ml milk), improved the qualitative and bioactive properties of yogurt significantly (p < 0.05). All samples that received acceptable sensory scores were appreciated. However, GBSE50 and 75 showed no significant difference (p > 0.05) after 14 days of storage compared to the control. Due to the results of all experiments, fortifying yogurt with the addition of 75 mg of GBSE in 100 ml milk is recommended to improve the qualitative and bioactive properties of the obtained functional yogurt.

Storage stability of texture, organoleptic, and biological properties of goat milk yogurt fermented with probiotic bacteria.

Goat milk is an attractive food due to its high nutritional values, easy digestibility and hypoallergenicity, but has an undesirable "goaty" flavor. In this study, goat yogurt was fermented with four probiotics, respectively, including Lactobacillus acidophilus (GYA), Bifidobacterium animalis (GYB), Lactobacillus casei (GYC) and Lactobacillus plantarum (GYP), and tested for texture, organoleptic, and biological properties during a 4-week storage period at the refrigerated temperature. All goat yogurt with probiotics showed an increase on titratable acidity and a corresponding downward trend on pH value. Viable counts of L. acidophilus and L. casei were above 6 log cfu/mL at the end of the storage, which met the minimum standards for viable probiotic bacteria in yogurt specified by the Food and Agriculture Organization of United Nation (FAO). The texture and organoleptic characteristics of fermented goat milk depended on the strain and the storage period. DPPH free radical scavenging rate and ferric reducing antioxidant power activity gradually increased in all goat yogurts during the storage and yogurt with probiotic bacteria showed higher values than those of GY0. Among all probiotic containing goat yogurts, GYC exhibited the desirable characteristics of hardness, adhesiveness, water holding capacity, antioxidant activity during the whole storage. Furthermore, the addition of L. casei effectively weakened the goaty flavor and enhanced the overall acceptability. Thus, fermented goat milk with L. casei is optional for the development of goat milk product with satisfactory texture properties, pleasant sensory quality and high bioactivity.

Microstructural evolution during acid induced gelation of cow, goat, and sheep milk probed by time-resolved (ultra)-small angle neutron scattering

Milks from small ruminant animals, such as goat and sheep, have gained increasing interest from the industry for the manufacture of various dairy products such as yoghurts. Heat treatment of milk is typically applied to improve the yoghurt texture. Here, time-resolved ultra-small angle neutron scattering (USANS) and small-angle neutron scattering (SANS) were employed to probe in situ the microstructural evolution of cow, goat, and sheep milks in D2O during acidification as affected by the heat treatment. Milk gelation can be envisaged as the progressive aggregation of the building blocks (casein micelles) in a fractal manner, which leads to the formation of micron scaled (∼3–10 μm) protein agglomerates. The heat treatment considerably enhanced the gelation of all milks, which is reflected by a faster increase in the fractal dimensions and aggregate sizes. For all three types of milks, similar final plateau fractal dimensions were observed for unheated (∼2.2–2.4) and heated milks (∼2.4–2.5), suggesting similar mass fractal microstructures in the size range probed by USANS. The final storage modulus after 10 h (G′final) follow the order of heated sheep milk ≈ sheep milk ≈ heated cow milk > cow milk > heated goat milk > goat milk. The colloidal calcium phosphate (CCP) dissolution kinetics tracked by SANS followed a similar trend as the evolution of the sample acidity (pD-value) and are not significantly affected by the types of milk or the heat treatment. This study shows a great potential of using time resolved USANS and SANS to investigate the microstructural evolution of protein aggregation and gelation.