Firmness Of Yoghurt Research Articles

Set yogurt incorporated with insoluble dietary fiber maintains non-sedimentation: Combined alkaline hydrogen peroxide modification and high-pressure homogenization process

Insoluble dietary fiber (IDF) settles in set yogurt due to its water insolubility. Making IDF non-settling in set yogurt without thickeners is the current objective. This study attempted to modify IDF with alkaline hydrogen peroxide (AHP) and combine it with a high-pressure homogenization (HPH) process to resolve the settling of IDF in set yogurt. The results showed that AHP-treated IDF (IDF-AHP) altered the structure of IDF, enhanced hydration properties, and had no hydrogen peroxide residue. Set yogurt incorporated with 1, 3, and 5% (w/w) IDF-AHP underwent a HPH process, resulting in non-settling IDF-AHP. The water retention, firmness, and cohesion of yogurt were improved, and the storage modulus (G′) increased during 28-day refrigeration. and the casein gel properties were improved. These results show that combining AHP with HPH treatment prevented the settling of IDF in yogurt and improved its texture. Further studies revealed that AHP and HPH were necessary to prevent IDF from settling in yogurt. This study confirms the applicability of the method and provides new ideas for the commercial production of IDF yogurt.

Effect of guar gum and fortification by haritaki (Terminalia chebula) extract and its encapsulates on physicochemical, textural, and rheological properties of yogurt

AbstractIn the present study functional yogurt was prepared by addition of guar gum (0.5% and 1.5%) and fortification by phytochemical extract of haritaki (Terminalia chebula) extracted using supercritical CO2 and freeze dried encapsulates of the extracts. The results indicated that the addition of guar gum led to a concentration‐dependent reduction in pH, with yogurt containing 1.5% guar gum exhibiting the highest acidity. During a 24‐day storage period at 4°C, all samples displayed a decrease in pH and an increase in acidity. Notably, all variations exhibited sporadic syneresis patterns, with higher syneresis observed on the 1st day, followed by a decline on the 12th day and a subsequent rise on the 24th day of storage. The color of haritaki encapsulated yogurt appeared greener and more yellowish compared to the control samples on the 1st day, with noticeable changes in L*, a*, and b* values during storage. Texture analysis revealed that encapsulation significantly affected textural characteristics, with reduced firmness but comparable adhesiveness in some cases. The firmness of plain yogurt ranged from 0.69 to 0.72 N, while its adhesiveness was between 6.14 × 10−2 and 8.51 × 10−2 N.s. The stiffness of the samples made with encapsulates (E1–E6) ranged from 0.38 to 0.70 N, while their adhesiveness was 5.74 × 10−2 to 8.78 × 10−2 N.s. The findings demonstrate that encapsulation significantly affected the textural characteristics. However, the samples' firmness (F1–F3) was less than the control, ranging from 0.36 to 0.54 N. Encapsulated haritaki extract outperformed nonencapsulated haritaki extract in terms of phenolic and antioxidant activities, making it a preferred option for yogurt fortification. Furthermore, yogurt enriched with up to 0.5% guar gum exhibited sensory qualities similar to or even better than the control sample.

The impact of animal protein partial substitution on the technological functionality of hybrid yoghurt

Following the new standard of using plant‐based ingredients, this study evaluated the effect of partially replacing milk proteins with plant proteins (almond and pumpkin seed) on yoghurt properties. Protein mixtures were prepared using rotational central composite design, investigating the percentage of animal protein replacement and the proportion between plant proteins. Milk protein substitution increased fermentation time, defined as the time needed to reach pH 4.6, and negatively impacted viscosity, firmness and syneresis of yoghurt. Nevertheless, replacing 25% of dairy proteins with an optimised plant protein blend (25% almond and 75% pumpkin seed) yielded yoghurt with typical composition and good sensory acceptance.

Impact of Storage Conditions of Yogurt Dry Ingredients on the Physicochemical Properties of the Final Product

This study investigated the impact of storage conditions of the ingredients for yogurt production on the rheological and physicochemical characteristics of the final fermented product. The novelty is the application of a special mix of milk protein concentrate and sodium caseinate for yogurt production. Separately exposing the protein mix powder and bacteria culture to 20 °C caused considerable changes in the obtained yogurt stiffness and the incubation times required to produce the gel due to a decrease in bacterial count. Minimal changes in bacteria viability were observed after storage at 5 °C. Lower temperature and shorter storage times increased yogurt firmness, viscosity, and storage modulus, resulting in a smoother and more viscous product. A linear correlation was found between yogurt firmness and water activity. Powders stored at lower temperatures and for shorter times produced yogurt with stronger texture and better water binding. Additionally, yogurt obtained from dry ingredients stored under these conditions required shorter incubation times. Storing the starter culture at 5 °C for at least 8 weeks had no significant effects on the physicochemical properties or incubation time requited to produce the final yogurt. This work highlights the importance of storage conditions of yogurt dry ingredients in maintaining the quality of the final product.

Improving the Quality of Set Yoghurt Using Milk Fat Globule Membrane Fragments

Lacprodan®PL20, a dairy ingredient that is rich in protein and polar lipids, was added into set yoghurts produced from nonhomogenized raw milk. The set yoghurts were prepared using concentrations of 2%, 4%, and 6% Lacprodan®PL20, while the control sample was only supplemented with skim milk powder. The effect of Lacprodan®PL20 concentrations on the physical and chemical properties, rheology, and microstructure of set yoghurt was thoroughly investigated to determine some likely improvement or changes in quality. Consequently, Lacprodan®PL20 showed a gradual improvement in the set yoghurt nutritive values, water holding capacity, and apparent viscosity. The results indicated that the firmness of set yoghurt was altered which steadily improved the gel strength, especially at 4% and 6% concentrations. The fermentation process was slightly delayed at 4% and 6% concentrations and pH values were raised as Lacprodan®PL20 concentration increased. The microstructures of the set yoghurts produced with Lacprodan®PL20, as examined by scanning electron microscopy, revealed compacted structures with fewer and smaller holes in the gel matrices. Also, a slight color change was observed in set yoghurt using a colorimeter. These results vividly showed that Lacprodan®PL20, an enriched milk fat globule membrane fragment, has the potential to improve set yoghurt quality by reducing some defects associated with set yoghurt, such as low gel strength, low dry solids, and the likes.

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.

Effect of rice bran on properties of yogurt: Comparison between addition of bran before fermentation and after fermentation

Recently, fortifying yogurt with dietary fiber has attracted considerable interest. Since fermentation by lactic acid bacteria might alter the fiber composition and structure, adding fiber into yogurt before and after fermentation might have different effects on properties of yogurt. Therefore, this work investigated effects of adding rice bran before and after fermentation on properties of yogurt to choose a better approach of fortifying yogurt with dietary fiber. Adding rice bran before fermentation significantly decreased syneresis of yogurt at the content of 2.0% and 3.0%, while adding rice bran after fermentation increased syneresis of yogurt. Scanning electron microscopy and confocal laser scanning microscopy analysis indicated that the yogurt gel with rice bran added before fermentation was more compact and porous than the yogurt gel with rice bran added after fermentation. Moreover, the autofluorescence from rice bran added after fermentation was significantly stronger than that in rice bran added before fermentation. Compared with yogurt added with rice bran after fermentation, yogurt added with rice bran before fermentation had higher free p-hydroxybenzoic acid, p-coumaric acid, ferulic acid and sinapic acid contents. These results suggested that fermentation converted bound phenolic acids of rice bran into free ones, which was beneficial to improve the yogurt stability. Thus, the pH, texture and rheological properties of yogurt added with rice bran before fermentation were investigated. It was found that rice bran increased the pH and decreased firmness, consistency, cohesiveness, viscosity and gel strength of yogurt.

Utilization of Fish Scales for Microbe-mediated Gelatin Extraction: A New Biotechnology and Microbiology Avenue

Waste materials are of major concern around the globe. This study aimed to utilize the scales of fish (Labeo rohita) in microbe-mediated gelatin extraction. Three bacterial isolates were isolated from the fish scales and one bacterial isolate FSW3 showing maximum gelatin yield (61.4 %) was subjected to further analysis. The bacterial culture FSW3 (identified as Staphylococcus spp.) with enhanced production of extracted gelatin was set for physiochemical testing, FTIR analysis, UV-Vis spectroscopy, and stereomicroscopic analysis. The extracted gelatin was successfully utilized in various applications including plant growth promotion under salt stress, anti-adhesion films, firmness of yogurt, biodegradable plastic, and anti-microbial food coatings. Results showed that 0.01 mM gelatin promoted plant growth promotion under salt stress. FSW3 extracted gelatin decreased the 2-fold biofilm-forming ability of E. coli, when exposed to the gelatin-based anti-adhesion films coated on a glass slide and polystyrene sheet. The gelatin showed promising findings as anti-microbial food coatings for tomatoes preservation after 21 days and helpful in the firmness of yogurt. Another advantage of gelatin was casting it into biodegradable plastic. The current study provides a promising approach for fish scales microbe-mediated gelatin extraction and uses it to explore new avenues in biotechnology and microbiology.

Yogurt production added ultrafiltered seed extract of Moringa oleifera Lam.

Currently, costumers seek foods that contain natural ingredients in their composition. Moringa oleifera is seen with potential for food use, making it an attractive alternative for healthy consumption. The main objective of this study was to evaluate the potentiality of the Moringa additive obtained from its ultrafiltered saline extract as a thickening agent in the production of yogurt. Physico-chemical analyses, syneresis, rheology , texture analyses, and scanning electron microscopy were performed on yogurts. The moisture content of yogurts ranged from 77.14 to 77.89%, and total solids from 22.86 to 22.11%. The other physicochemical characteristics showed no significant differences (p < 0.05) between the analyzed samples. For all concentrations of Moringa additives evaluated, G′ values were higher than G″ indicating that they presented a behavior viscoelastic. The concentrated additive (2 mg L −1 ) produced a yogurt with reduced susceptibility to syneresis as well as increased firmness, and confirmed with the microstructure that was more homogeneous and compact (C2). On the other hand, the increase in permeate additive concentration of Moringa seed increased the syneresis and decreased the firmness of yogurt. The results obtained show that the use of Moringa extract as an additive in the formulation of yogurt has the potential to be exploited in commercial use, improving the yogurt texture and with less syneresis. • Moringa additive obtained from its ultrafiltred saline extract. • The additives used did not change the fermentation time concerning the control. • Technological properties improvement yogurt with the moringa additive.

Non-Fat Yogurt Fortified with Whey Protein Isolate: Physicochemical, Rheological, and Microstructural Properties.

The demand for low- and non-fat products has recently increased due to the health problems, such as obesity, diabetes, and cardiovascular diseases, that have resulted from high-fat products. However, the reduction in fat can affect the quality of products adversely. The objective of this work was to explore the potential of whey protein isolate (WPI) in improving the quality of non-fat yogurt prepared using skim milk powder (SMP). Yogurt mixes (standardized at 14% total solids) were formulated using SMP as a milk base enriched with WPI. The SMP was replaced by WPI in the yogurt mixes at a rate of 3, 5, 7, and 9%. Full-fat and non-fat set-style yogurts were prepared from whole milk and skim milk, respectively, as controls. Yogurts were fermented at 43 °C to get a pH of 4.6 and stored at 4 °C for the next day. The texture, microstructure, rheological characteristics, and sensory properties of the yogurt samples were studied. The incorporation of WPI increased the water holding capacity to 50% as compared to the non-fat control. This improved the rheological properties while the yogurt viscosity increased in direct proportion with increasing the WPI. The firmness of yogurt was inversely proportional to the increase in WPI, which resulted in 180 g firmness when 9% WPI was added to the non-fat yogurt formulations. Yogurts’ microstructure improved by the addition of WPI. The non-fat yogurt incorporated with 3 and 7% WPI had comparable sensory and textural characteristics to the full-fat yogurt. WPI can be used as a fat replacer to develop low-fat yogurt with desired features. WPI may be a natural and economical ingredient for producing low- and non-fat fermented dairy food products.

Effects of seasonal variations on the quality of set yogurt, stirred yogurt, and Greek-style yogurt

We studied the effects of seasonal variations on the quality of stirred yogurt, set yogurt, and Greek-style yogurt over 2 milking seasons in New Zealand. Correlations between the properties of the yogurts, the characteristics of the milk, and the acid gelation properties induced by glucono-δ-lactone, reported in our previous works, were also explored. Set yogurt and Greek-style yogurt from the early season had the highest firmness over the seasons. The yogurt firmness correlated with the gel strength of glucono-δ-lactone-induced acid gels, indicating that the latter could, to some extent, predict the seasonal variations in the firmness of set yogurt. The correlation studies highlighted the potentially important role of the glycosylation of κ-casein in the seasonal variations in the yogurt structures. Yogurt made from mid-season milk had the lowest water-holding capacity, which may have played a part in lowering its firmness and viscosity. Late-season stirred yogurt displayed the strongest resistance to shear-induced thinning, which might arise from the unique viscoelastic properties of late-season yogurt gels.

Comparative studies on the effect of probiotic additions on the physicochemical and microbiological properties of yoghurt made from soymilk and cow's milk during refrigeration storage (R2)

Soymilk yoghurt is an option to consumers who are allergic to cow's milk yoghurt. Probiotics can provide gut health. The objective of this study was to investigate the physicochemical characteristics, including pH, colour, firmness and syneresis of yoghurt made from soymilk and cow's milk as affected by the addition of probiotics during storage at 4 °C for 28 days at 7-day intervals. Microstructure and bacterial populations were also determined. Two types of yoghurt were prepared. The first type was prepared with the additions of commercially available yogurt starter containing Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST). The second type was prepared with the same yogurt starters plus three probiotics, including Bifidobacterium animalis subsp. lactis BB-12 (BB), L. acidophilus La-5 (LA), and L. rhamnosus (LGG). Probiotics reduced syneresis and increased compact network of soymilk yoghurt significantly (p < 0.05) and shortened the time needed to reach pH 4.5 in both cow's milk and soymilk yogurts. During storage, the pH of cow's milk yoghurts slightly decreased (4.37–4.26 with probiotics and 4.54 to 4.33 without probiotics), however, the pH of soymilk yoghurts remained relatively constant. The firmness of yoghurt made from cow's milk was significantly decreased with the addition of probiotics, however, it remained stable in soy milk yoghurt during storage. Soymilk yoghurt (34–50 g force during compression) was generally firmer than cow's milk yoghurts (9.8–12.5 g force). The cow's milk yogurt had slightly higher counts of ST, LB and LA than soymilk yogurt, but the count of BB in soymilk yogurt is significantly higher than that in cow's milk yogurt.

Effect of Different Starches on the Rheological, Sensory and Storage Attributes of Non-fat Set Yogurt.

This study was conducted to investigate the effect of various native starches on the rheological and textural properties of non-fat set yogurt. The yogurt samples were prepared while using five types of starches (potato, sweet potato, corn, chickpea, and Turkish beans). The physical properties of the prepared yogurt were analyzed while using shear viscosity, viscoelasticity, and texture analysis. The tests were performed after 0, 7, and 15 days storage. The effect of these starches on the yogurt viscoelastic properties, texture, syneresis, and sensory evaluation were determined under optimum conditions. The results showed that adding 1% starch could significantly (p < 0.05) reduce syneresis and improve yogurt firmness. Starches exhibited different effect on the overall quality of the yogurt due to their origin and amylose content. Regardless of the number of storage period duration, all of the samples, including the control behaved as pseudoplastic materials (n < 1) with various levels of pseudoplasticity. Yogurts with corn and tuber starches had the highest consistency coefficient (k), which indicated higher viscosity. The yogurt sample with chickpea starch exhibited the highest G´, making the gel more solid like. Therefore, the influence of tuber starches (potato and sweet potato) on G´ was different when compared to corn or legume starches. The behavior of the starches changed with storage time, where some starches performed better only at the beginning of the storage period duration. Wheying-off was significantly reduced, regardless of starch type. The pH of the yogurt remained unchanged through storage. Sensory evaluation showed a preference for starch-containing samples as compared to the control, regardless of the starch type. The variation in yogurt quality as a function of starch type could be attributed to the starch granule structure, gelatinization mechanism, or amylose content.

Impact of Type and Enzymatic/High Pressure Treatment of Milk on the Quality and Bio-Functional Profile of Yoghurt.

The objective of the present study was to investigate the effect of the high pressure (HP) processing and transglutaminase (TGase) treatment of bovine (cow) or ovine (sheep) milk, when applied individually or sequentially, on the quality parameters and anti-hypertensive and immunomodulatory properties of yoghurt. Low-fat (2% w/w) bovine or ovine milk samples were used. Results showed that HP treatment of milk led to acid gels with equivalent quality attributes to thermal treatment, with the more representative attributes being whey separation and firmness, which ranged from 47.5% to 49.8% and 23.8% to 32.2% for bovine and ovine yoghurt, respectively, and 74.3–89.0 g and 219–220 g for bovine and ovine yoghurt, respectively. On the other hand, TGase treatment of milk, solely or more effectively following HP processing, resulted in the improvement of the textural attributes of yoghurt and reduced whey separation, regardless of milk type, exhibiting values of 32.9% and 8.7% for the whey separation of bovine and ovine yoghurt, respectively, and 333 g and 548 g for the firmness of bovine and ovine yoghurt, respectively. The HP processing and TGase treatment of milk led to the preservation or improvement of the anti-hypertensive activity of the samples, especially in the case in which ovine milk was used, with Inhibitory activity of Angiotensin Converting Enzyme (IACE) values of 76.9% and 88.5% for bovine and ovine yoghurt, respectively. The expression of pro-inflammatory genes decreased and that of anti-inflammatory genes increased in the case of samples from HP-processed and/or TGase-treated milk as compared to the corresponding expressions for samples from thermally treated milk. Thus, it can be stated that, apart from the quality improvement, HP processing and TGase treatment of milk may lead to the enhancement of the bio-functional properties of low-fat yoghurt made from either bovine or ovine milk.

Comportamento reológico e perfil de textura de iogurte integral com polpa de achachairu (Garcinia humilis)

&lt;p&gt;One of the parameters that most influence the sensorial acceptance of yogurt is the texture presented. By determining the rheological behavior, we enable the sizing of the equipment. The aim of the present study is to determine the rheological behavior and the texture of whole yoghurts with different concentrations of achachairu pulp submitted to different temperatures. In addition to that we aim to adjust the data to the rheological models studied and to evaluate the influence of pulp and temperature on the instrumental texture profile. The rheological study was performed and the rheological models were adjusted to the experimental data. The Herschel-Bulkley rheological model presented the best fit for all formulations and temperatures with determination coefficients (R2 ) greater than 0.99 and low chi-square values (X2 ). Yogurt firmness decreased due to the increase of pulp concentration, however when submitted to 9 °C temperature they presented more firmness. On the other hand, yogurt showed non-Newtonian fluid behavior, in the specific case of pseudoplastic and instrumental texture parameters, they tended to decrease with increasing temperature. &lt;/p&gt;

Physical, chemical, and microstructural properties of nonfat yogurts fortified with the addition of tara gum alone or in combination with buttermilk powder

Finding proper milk fat substitutes for manufacturing of nonfat dairy products is a major challenge for dairy industry in order to respond the consumer' demands. Three different concentrations of tara gum (TG) and three combinations of TG with buttermilk powder (BP) were used as fat replacers for manufacturing of nonfat yogurt. Use of TG (0.25 and 0.50/gl) and a combination of TG (0.25/gl) and BP (10/gl) decreased whey separation while improved the gel firmness and viscosity of nonfat yogurt (p < .05). Denser microstructure observed in nonfat yogurts fortified with TG (0.25 and 0.50/gl) and combination of TG and BP (0.25 + 10/gl). Significant changes were observed in pH and viscosity of yogurts (p < .05) during storage. In conclusion, fortification of nonfat yogurt with specific concentrations of TG or combination of TG and BP had positive effect on quality properties of the product. Practical applications Low-fat or nonfat yogurts have been preferred by consumers in recent years because of health concerns. However, nonfat products have quality defects due to the lack of milk fat. For this purpose, TG and BP as fat replacers at different rates for the production of nonfat yogurt were used in this research. Use of TG and BP changed yogurt's physicochemical characteristics and caused relatively denser microstructures. With this study, combined use of TG and BP provided the improvement of nonfat yogurt product.

Okra polysaccharide: Effect on the texture and microstructure of set yoghurt as a new natural stabilizer.

Four plant-derived polysaccharides including okra polysaccharide (OP), apple pectin (AP), sodium alginate (SA) and konjac glucomannan (KGM) were studied in yoghurt formulation to investigate their effect on gelling characteristics. The results indicated that OP, KGM and AP enhanced the water-holding capacity, firmness and elasticity of yoghurt while SA demonstrated the opposite effects. Gel structure was better improved with OP, the firmness of yoghurt increased from 9.01 g to 14.86 g when 0.08% OP was added. The yoghurt with OP achieved the closest transverse relaxation time (T2) to the control. The free water area (A23) decreased from 1592 for control to 1414 for yoghurt with 0.08% OP addition. All samples exhibited shear-thinning behavior, both apparent viscosity and elastic modulus (G', G″) increased with increasing concentrations of OP and KGM, with peak values at 0.06% OP and 0.015% KGM. Both G' and G'' reduced significantly as pectin concentration rose to 0.1%, while modules went up with the increasing concentration of SA. Microscopy results showed that addition of OP and AP reduced the porous structure of gel and promoted formation of larger protein clusters, which eventually led to more compact protein network. This study provided new insights for food application with plant-derived polysaccharides.

Effect of different hydrocolloids on texture, rheology, tribology and sensory perception of texture and mouthfeel of low-fat pot-set yoghurt

A systematic study on the effect of some commonly used hydrocolloids in yoghurt formulation, namely gelatin (0.5–1.5%), xanthan gum (0.005–0.015%), carrageenan (0.01–0.08%) and modified starch (0.5–1.5%) on the physical, tribology and sensory characteristics of skim pot-set yoghurt (0.1% fat) is presented. The results support to develop a tribology model for yoghurt, which can be directly correlated with the scores on texture and mouthfeel attributes from sensory panel by mean of statistical analysis. The tribological behavior, which signifies the lubrication property of the product, depended on the fat content, the type and dosage of hydrocolloid. Among the four hydrocolloids investigated, gelatin appeared to be the best hydrocolloid due to its ability to reduce syneresis, increase texture, viscosity, gel strength and lubrication properties of skim yoghurt. As a result, its sensory perception was significantly improved and attained the same sensory scores with full fat yoghurt for various desired sensory attributes, such as thickness, smoothness and creaminess. Both xanthan gum and carrageenan increased the firmness and viscosity of skim yoghurt, but also significantly increased the syneresis and undesired sensory mouthfeel characteristics, such as chalkiness and lumpiness. Modified starch slightly improved lubrication properties and thickness of skim yoghurt without significant changes in the product texture. From tribological analysis of investigated samples, a four-zone tribology model for yoghurt was proposed. Each zone corresponds to different mechanisms of fluid entrained between the two contact surfaces. The tribology behavior of the yoghurt fluid, therefore, can be represented by the position of each transition point and the slope of each friction zone, which were aligned with the sensory scores from trained panel.

Physical, rheological, and microstructural properties of whey protein enriched yogurt influenced by heating the milk at different pH values

Here, we investigate the effects of pH adjustment before heating milk on the textural properties of whey protein enriched yogurt. Whey protein enriched skim milk was adjusted to pH of 6.3, 6.7, and 7.1 followed by heating at 85 °C for 30 min. Yogurts prepared from milk heated at pH 6.7 showed remarkably higher G′ (storage modulus) values, water holding capacity and firmness compared to those prepared from unheated milk, or milk heated at pH 6.3 or 7.1. A relatively more compact protein network was observed in the yogurt made from milk heated at pH 6.7. Heating milk at pH 6.7 formed both whey protein-associated casein micelles (WPA-CM) and soluble whey protein/κ-casein complexes (SWP-CC), resulting in the presence of numerous aggregating particles, which was responsible for the firmer yogurt gel. Heating milk at pH 7.1 (mostly SWP-CC) resulted in higher yogurt firmness than heating at pH 6.3 (mostly WPA-CM). Practical applications Whey protein fortification and heating milk improve yogurt texture. However, different pH values of the milk before heating and whey protein fortification affect the properties of the yogurt. Variation of milk pH before heat treatment affects the degree of association between denatured whey proteins and casein micelles. As a result, inconsistencies occur in yogurt gel texture. This study showed that yogurt made from milk heated at pH 6.7 had increased firmness and water holding capacity compared with that when the milk was heated at pH 6.3 or 7.1. The pH of milk naturally changes slightly throughout the year, which in turn might affect yogurt firmness. Therefore, milk pH is an important parameter which needs to be adjusted to produce uniform quality yogurt to obtain a well-accepted commercial product.

Effect of Silkworm Pupae Peptide on the Fermentation and Quality of Yogurt

In the present study, the effect of silkworm pupae peptide on acidification, water-holding capacity (WHC), textural properties, sensory characteristics, angiotensin I-converting enzyme (ACE) inhibitory activity, and the amino acid composition of fermented milk products was studied. The addition of peptide enhanced acidification, thus reducing the fermentation time. Furthermore, addition of > 0.7% peptide significantly (P 0.3%. Therefore, further studies are necessary to optimize the flavor of yogurt containing silkworm pupae peptide. Practical Applications The demand for dairy products containing bioactive peptides is high because their intake can fulfill the nutritional requirement. In this study, the effect of silkworm pupae peptide on the qualities of dairy products was studied. Addition silkworm pupae peptide could enhance acidification and reduce the fermentation time. Addition of 0.5% silkworm pupae peptide could enhanced ACE inhibitory activity and amino acid content. Although addition of silkworm pupae peptide had beneficial effects on the firmness, consistency, and cohesiveness of yogurt, it reduced the overall flavor. The results are useful for the yogurt industry in improving production efficiency and product quality.