The effect of inulin as a fat replacer on the quality of set-type low-fat yogurt manufacture

The influence of different levels of inulin on the quality of fat-free yogurt production was investigated. Inulin was added to milk containing 0.1% of milk fat to give inulin levels of 1, 2 and 3%. The experimental yogurts were compared with control yogurt produced from whole milk. The total solids content of milk was standardized to 14% by adding skim milk powder to the experimental yogurt. The chemical composition, pH, titratable acidity, whey separation, consistency, acetaldehyde and volatile fatty acidity contents were determined in the experimental yogurts after 1, 7 and 15 days. Sensory properties of the yogurts were evaluated during storage. The addition of inulin at more than 1% increased whey separation and consistency. Acetaldehyde, pH and titratable acidity were not influenced by addition of inulin. Tyrosine and volatile fatty acidity levels were negatively affected by inulin addition. With respect to the organoleptic quality of yogurt, inulin addition caused a decrease in organoleptic scores: the control yogurt had the highest score, and the lowest score was obtained in yogurt samples containing 3% of inulin. Overall, the yogurt containing 1% of inulin was similar in quality characteristics to control yogurt made with whole milk.     

Production and Evaluation of Yogurt with Concentrated Grape Juice

Fruit yogurt was prepared by adding concentrated grape juice (pekmez) CGJ, to milk. Optimum CGJ concentration and its influence on quality and fermentation process of yogurt were evaluated. The pH, titratable acidity, protein content, viscosity, whey syneresis, starter bacteria, mold and yeast counts were determined weekly at 4°C for 1 month. Addition of 10% CGJ provided desired sweetness. After 4h incubation of 5–10–15% CGJ-added yogurts the pH was 4.44, 4.98 and 5.90, respectively, and the control was pH 4.26. CGJ addition increased fermentation time and decreased viscosity. During storage, acidity of 10% CGJ-added yogurt remained lower (P<0.05) than controls. CGJ did not affect (P>0.05) protein content and molds or yeasts were not detected.     

The development of a goat's milk yogurt

This study sought to establish conditions suitable for a small‐scale yogurt process using goat's milk and to examine the physicochemical properties (pH, titratable acidity, solids‐not‐fat (SNF), viscosity, texture) and organoleptic acceptability (preference by Filipino panellists) of the resultant product. Goat's milk was concentrated by heating (80 °C, 1 h), which resulted in an increase in SNF from 85 to 110 g kg^?1. To further improve the curd of goat's milk yogurt, two hydrocolloids were used: carrageenan (1.5 and 3 g l^?1) and pectin (50 g l^?1). The addition of dehydrated pineapple and banana cubes (50 and 100 g l^?1) in a sundae‐style formulation increased the SNF by an additional 2.5% and produced a curd that was firmer than the control, plain set yogurt. The use of carrageenan appeared to be a convenient way of controlling product viscosity. In terms of product preference and firmness the fruit‐flavoured sundae‐style yogurts were ranked higher by sensory panellists. Copyright © 2005 Society of Chemical Industry     

芦荟对嗜酸乳杆菌酸乳发酵性能的影响

选择嗜酸乳杆菌、嗜热链球菌为发酵菌种 ,研究芦荟全叶汁对酸乳发酵过程中的滴定酸度、pH值、黏度及感官性状等的影响。试验发现 ,芦荟的添加对嗜酸乳杆菌和嗜热链球菌的生长影响不大 ,但影响酸乳的凝固性、pH值、黏度 ,进而影响品质等。试验结果表明 ,当芦荟添加量为 10 %左右时 ,成熟后的酸乳中La可达 10 9,产品的品质最佳。     

酪蛋白磷酸肽-钙络合物对酸乳贮藏特性的影响

为探究酪蛋白磷酸肽-钙（CPP-Ca）络合物对酸乳贮藏特性的影响,研究CPP-Ca络合物不同添加量对酸乳21 d贮藏期内乳酸菌总数、pH值、滴定酸度、乳清析出率及黏度的影响。与对照组比较,当CPP-Ca络合物添加量为0.15 g/100 mL时,酸乳中乳酸菌存活率从32.92%提高至47.15%（P＜0.05）;滴定酸度增长率从9.96%降低至7.06%（P＜0.05）;乳清析出率降低了0.4%（P＜0.05）,黏度比提高了5 729 mPa·s （P＜0.05）。结果表明,CPP-Ca络合物的添加能增加酸乳贮藏期内的乳酸菌总数,延缓酸度积累,降低乳清析出率,增加黏度,改善酸乳贮藏期内的产品品质。     

An investigation of some properties of banana yogurts made with commercial ABT-2 starter culture during storage

Five yogurt batches were prepared with banana puree and sugar combinations and ABT-2 ( Streptococcus salivarius ssp. thermophilus, Lactobaccilus acidophilus and Bifidobacterium spp.) as starter culture. The addition of fruit influenced ( P <  0.05) the syneresis, titratable acidity and pH, whereas the viscosity value, and S. salivarius ssp. thermophilus, L. acidophilus and Bifidobacterium spp. counts were found to be insignificant. Storage time significantly ( P <  0.05) affected the syneresis, titratable acidity, pH value, and S. salivarius ssp. thermophilus counts, while the viscosity value and L. acidophilus and Bifidobacterium spp. counts were not affected. The sensory evaluations showed that the sample B was most preferred by panellists.     

Physicochemical and microbiological characteristics of camel milk yogurt as influenced by monk fruit sweetener

Camel milk, similar to cow milk, contains all of the essential nutrients as well as potentially health-beneficial compounds with anticarcinogenic, antihypertensive, and antioxidant properties. Camel milk has been used for the treatment of allergies to cow milk, diabetes, and autism. Camel milk helps decrease cholesterol levels in blood and improves metabolism. One of the most desirable food tastes is sweetness. However, the excessive ingestion of sugar negatively affects human health. Monk fruit sweetener is a natural, 0-calorie sweetener with many health-beneficial functions. Monk fruit sweetener helps decrease symptoms of asthma and diabetes, prevents oxidation and cancer, protects the liver, regulates immune function, and lowers glucose levels. Monk fruit sweetener is 100 to 250 times sweeter than sucrose. The objective of this study was to examine the influence of different concentrations of monk fruit sweetener on the physicochemical properties and microbiological counts of drinking yogurt made from camel milk. Camel milk drinking yogurt was produced with 0, 0.42, 1.27, and 2.54 g/L of monk fruit sweetener and stored for 42 d. The physicochemical characteristics and microbiological counts of yogurts were measured at d 1, 7, 14, 21, 28, 35, and 42. For the physicochemical characteristics, pH, titratable acidity, viscosity, and color [lightness-darkness (L*), red-green axis (a*), yellow-blue axis (b*), chroma (C*), and hue angle (h*)] values were evaluated. The counts of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, coliforms, and yeast and mold were determined. Three replications were conducted. The sweetener addition significantly influenced pH, viscosity, and color (a*, b*, C*, and h*) values. Control samples had significantly higher pH values, lower viscosity, lower b* and C* values, and higher h* values than the samples with 1.27 and 2.54 g/L of monk fruit sweetener. Growth of S. thermophilus, L. bulgaricus, and probiotic culture L. acidophilus was not affected by the incorporation of monk fruit sweetener. Monk fruit sweetener can be added in camel milk yogurts as a health-beneficial 0-calorie sweetener.     

Industrial yogurt manufacture: monitoring of fermentation process and improvement of final product quality

Lactic acid fermentation during the production of skim milk and whole fat set-style yogurt was continuously monitored by measuring pH. The modified Gompertz model was successfully applied to describe the pH decline and viscosity development during the fermentation process. The viscosity and incubation time data were also fitted to linear models against ln(pH). The investigation of the yogurt quality improvement practices included 2 different heat treatments (80°C for 30 min and 95°C for 10 min), 3 milk protein fortifying agents (skim milk powder, whey powder, and milk protein concentrate) added at 2.0%, and 4 hydrocolloids (κ-carrageenan, xanthan, guar gum, and pectin) added at 0.01% to whole fat and skim yogurts. Heat treatment significantly affected viscosity and acetaldehyde development without influencing incubation time and acidity. The addition of whey powder shortened the incubation time but had a detrimental effect on consistency, firmness, and overall acceptance of yogurts. On the other hand, addition of skim milk powder improved the textural quality and decreased the vulnerability of yogurts to syneresis. Anionic stabilizers (κ-carrageenan and pectin) had a poor effect on the texture and palatability of yogurts. However, neutral gums (xanthan and guar gum) improved texture and prevented the wheying-off defect. Skim milk yogurts exhibited longer incubation times and higher viscosities, whereas they were rated higher during sensory evaluation than whole fat yogurts.     

MODIFIED WHEAT STARCHES USED AS STABILIZERS IN SET-STYLE YOGURT

Yogurt was formulated with gelatin; native wheat starch (NWS); and modified wheat starches (MWS) (acetylated cross‐linked, hydroxypropylated, or hydroxypropylated cross‐linked). Yogurt samples were evaluated for chemical (fat, total solids, pH, titratable acidity); microbiological (yeasts/molds and lactic acid bacteria); and physical (rheological, textural, color, syneresis) properties during 60 days of refrigerated storage. Yogurt formulated with NWS exhibited a significantly greater storage modulus (G′) and firmness compared with yogurts prepared with MWS. Minimal syneresis was measured in all yogurt samples. The titratable acidity of yogurt samples increased and pH decreased during storage. Yeasts/molds were not detected while lactic acid bacteria counts decreased ～ 1 log CFU/g by day 60 in all yogurt samples. This study showed that the characteristics of yogurt formulated with NWS and gelatin were similar, so NWS may be used as an alternative stabilizer. The MWS stabilized yogurts were stable but had different consistencies than gelatin‐ and NWS‐stabilized yogurts.     

Effects of Extruded Sugar Bagasse Blend on Yogurt Quality

Extruded blends (EB) of whey protein concentrate 35 (WPC 35)–corn starch–sugarcane bagasse with 0%, 25%, and 50% substituted yogurt formulations were evaluated for some functional characteristics. Yogurts substituted with EB showed higher viscosity and lower syneresis index than that without EB. During storage for 48 h, the syneresis values of yogurt with and without EB decreased. The pH values and color differences (ΔE) decreased slightly in the yogurts formulated with EB. However, the color differences were not statistically significant (p > 0.05) and were also acceptable to the judges. In general, yogurts substituted with EB at different levels had sensory attributes of taste, acidity, texture, and viscosity scores similar to those observed for yogurt with no EB. Scores of yogurts were not affected significantly with substitution of EB at all the levels.     

QUALITY OF FLAVORED YOGURT CONTAINING ADDED COFFEE AND SUGAR

Yogurts flavored with instant coffee (0.5, 0.7 and 0.9%) and sweetened with sugar (4 or 5%) and a control yogurt (no coffee or sugar) were evaluated for chemical, physical, microbiological and sensory properties. The added ingredients generally had no effect on the chemical, physical and microbiological quality of yogurts at day 1 after preparation as compared to the control. During 15 days at 5–7C, pH and lactic acid bacteria counts decreased (P < 0.05) and titratable acidity increased (P < 0.05) in all samples. Yogurts with 0.5% coffee flavoring and 4 and 5% sugar met Turkish Institute Standards for yogurt sensory quality when evaluated by a trained 10‐member panel. Yogurt flavored with 0.5% coffee and containing 5% sugar had most attributes rated in the “like” category by 50% or more of 51 consumer panelists.     

Soybean hull polysaccharides affect the physicochemical properties and lactic acid bacteria proliferation in plant-based yogurt

As a by-product of soybean processing, soybean hulls contain soybean hull polysaccharides (SHPS). This study aims to develop a plant-based yogurt with SHPS addition and assess the consequences of SHPS on the physicochemical properties and growth of lactic acid bacteria (LAB) in yogurts. The study investigated the water holding capacity (WHC), microstructure, rheological properties, texture, pH, organoleptic attributes, volatile compounds, flavor profile, and LAB population. The findings reveal that the addition of SHPS significantly impacted these properties. SHPS improved the physicochemical properties, increased the level of flavor compounds, and improved the organoleptic properties of yogurt. Yogurt with 0.6% SHPS demonstrated superior WHC, texture, rheological properties, and the highest organoleptic evaluation scores. However, when SHPS additions exceeded 0.6%, WHC, texture, and rheological properties of the yogurts decreased. Furthermore, SHPS-added yogurts contained more LAB compared to yogurt without SHPS. LAB grew better in media with SHPS than in media without glucose. Streptococcus thermophilus grew best among the LAB strains. This study highlights the potential of SHPS in yogurt production and its promising applications in fermented food products.     

Effect of reduction of lactose in yogurts by addition of β‐galactosidase enzyme on volatile compound profile and quality parameters

A comparative study between reduced‐lactose yogurts made with added β‐galactosidase (E yogurts) and controls (C yogurts) was performed. The evolution of lactose content, pH, acidity and volatile compounds was measured during fermentation and storage at 5 °C. The hydrolysis percentages of lactose ranged from 75% to 78% in E yogurts and from 10% to 13% in C yogurts at the end of manufacture and stayed without changes throughout storage. There were no significant differences in pH and titratable acidity values among yogurts. A total of 22 volatile compounds were identified. The change in lactose level by the action of β‐galactosidase influenced the production of some volatile compounds derived from this sugar. At the end of fermentation, minor differences in volatile composition were recorded among yogurt samples. During storage, acetaldehyde and diketone levels were always higher in hydrolysed yogurts than their respective controls.     

Use of acid whey protein concentrate as an ingredient in nonfat cup set-style yogurt

Acid whey resulting from the production of soft cheeses is a disposal problem for the dairy industry. Few uses have been found for acid whey because of its high ash content, low pH, and high organic acid content. The objective of this study was to explore the potential of recovery of whey protein from cottage cheese acid whey for use in yogurt. Cottage cheese acid whey and Cheddar cheese whey were produced from standard cottage cheese and Cheddar cheese-making procedures, respectively. The whey was separated and pasteurized by high temperature, short time pasteurization and stored at 4°C. Food-grade ammonium hydroxide was used to neutralize the acid whey to a pH of 6.4. The whey was heated to 50°C and concentrated using ultrafiltration and diafiltration with 11 polyethersulfone cartridge membrane filters (10,000-kDa cutoff) to 25% total solids and 80% protein. Skim milk was concentrated to 6% total protein. Nonfat, unflavored set-style yogurts (6.0 ± 0.1% protein, 15 ± 1.0% solids) were made from skim milk with added acid whey protein concentrate, skim milk with added sweet whey protein concentrate, or skim milk concentrate. Yogurt mixes were standardized to lactose and fat of 6.50% and 0.10%, respectively. Yogurt was fermented at 43°C to pH 4.6 and stored at 4°C. The experiment was replicated in triplicate. Titratable acidity, pH, whey separation, color, and gel strength were measured weekly in yogurts through 8 wk. Trained panel profiling was conducted on 0, 14, 28, and 56 d. Fat-free yogurts produced with added neutralized fresh liquid acid whey protein concentrate had flavor attributes similar those with added fresh liquid sweet whey protein but had lower gel strength attributes, which translated to differences in trained panel texture attributes and lower consumer liking scores for fat-free yogurt made with added acid whey protein ingredient. Difference in pH was the main contributor to texture differences, as higher pH in acid whey protein yogurts changed gel structure formation and water-holding capacity of the yogurt gel. In a second part of the study, the yogurt mix was reformulated to address texture differences. The reformulated yogurt mix at 2% milkfat and using a lower level of sweet and acid whey ingredient performed at parity with control yogurts in consumer sensory trials. Fresh liquid acid whey protein concentrates from cottage cheese manufacture can be used as a liquid protein ingredient source for manufacture of yogurt in the same factory.     

Enrichment of yogurt with carrot soluble dietary fiber prepared by three physical modified treatments: Microstructure,rheology and storage stability

Three modified soluble dietary fibers including microwave (M-SDF), ultrasonic (U-SDF) and high-pressure cooking (H-SDF) and SDF without treatment (W-SDF) were prepared, then these SDF were supplemented in yogurt. U-SDF and M-SDF showed rougher structure than others. U-SDF and W-SDF possessed higher Mw (Molecular weight), water-holding, cholesterol absorption capacities, with more reddish and yellowish colour. Moreover, addition of SDF into yogurt resulted in stabilizing of structure, increasing of viscosity, consistency index, pH, and decreasing of flow index, titratable acidity, syneresis percent. U-SDF and W-SDF supplemented yogurts exhibited greater stability compared with others. Overall, our data demonstrated that U-SDF and W-SDF would be better choices to be incorporated in yogurt for improving its quality. This study could provide scientific evidence supporting SDF as potential reinforcing ingredients in production of fiber-supplemented yogurt and offer a new insight into design of novel dairy products with functional properties.     

Effect of Sweeteners on the Quality and Acceptability of Yogurt

Sweetened low fat plain and Swiss-style fruit-flavored yogurts were manufactured using cream and reconstituted nonfat dry milk. The Swiss-style yogurt was manufactured by adding commercial blueberry or strawberry fruit flavorings to the sweetened yogurt base. Sweeteners used in the study were sucrose, 36 dextrose equivalent corn syrup solids, and 42, 55, and 90% high fructose corn syrup. Varied combinations of sweeteners were used at 0, 2, 4, and 6%, by weight.Evaluations were conducted during incubation and after packaging. Analyses included rate of acid development (time required to reach pH 4.4), microbiological profile, and expert organoleptic evaluation. A consumer panel was used to compare yogurt made with sucrose with that utilizing 90% high fructose corn syrup.As amount of sweetener increased, the time required to get to breaking pH of 4.4 increased. There also appeared to be a preference for yogurt made with 90% high fructose corn syrup, especially in the strawberry yogurt. Most preferred was 4% added sweetener.     

Quality and acceptability of a set-type yogurt made from camel milk

Camel milk (CM) set yogurts were formulated with gelatin, alginate (ALG), and calcium (Ca). Titratable acidity, pH, sensory properties, and acceptability of CM yogurts were studied. Twelve treatments were prepared; 3 using gelatin at 0.5, 0.75, and 1% levels and 9 with combinations of ALG and Ca at different levels. Titratable acidity and pH of fresh yogurt were not affected by the addition of gelatin or the ALG and Ca combinations. Trained sensory panel results showed that CM yogurt containing 1% gelatin or 0.75% ALG + 0.075% Ca had the highest intensities for firmness and body. Consumer results indicated that the hedonic ratings of the sensory attributes and acceptability of CM yogurt containing 0.75% ALG + 0.075% Ca were similar to that of cow's milk yogurt. The CM yogurts containing ALG + Ca and flavored with 4 different fruit concentrates (15%) had similar hedonic ratings and acceptability. Addition of 0.75% ALG + 0.075% Ca could be used to produce acceptable plain or flavored CM yogurt.     

Physico-chemical,microbiological, and sensory characteristics of yogurt as affected by various ingredients

l-Glutamine, quercetin, slippery elm bark, marshmallow root, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate have been reported to help treat leaky gut. The purpose of this research was to explore the impact of these functional ingredients on the physico-chemical, microbiological, and sensory properties of yogurt. The milk from same source was equally divided into 9 pails and the 8 ingredients were randomly assigned to the 8 pails. The control had no ingredient. Milk was fermented to yogurt. The pH, titratable acidity, syneresis, viscosity, color (L*, a*, b*, C*, and h*), Streptococcus thermophilus counts, and Lactobacillus delbrueckii spp. bulgaricus counts of yogurts were determined on d 1, 7, 14, 21, 28, 35, and 42, whereas coliform counts, yeast and mold counts, and rheological characteristics were determined on d 1 and 42. The sensory study was performed on d 3 and particle size of the functional ingredients (powder form) was also determined. When compared with control, the incorporation of slippery elm bark into yogurts led to less syneresis. l-Glutamine increased pH and n′ values (relaxation exponent derived from G′) and lowered titratable acidity values. N-Acetyl-d-glucosamine incorporation resulted in higher n′ and lower titratable acidity values, whereas maitake mushroom led to lower n′ values. Incorporating quercetin increased the growth of L. bulgaricus. Adding maitake mushrooms increased the growth of S. thermophilus but lowered apparent viscosity values, whereas quercetin decreased its S. thermophilus counts. Quercetin decreased L* and a* values but increased b* values, and maitake mushroom increased a* values. Thixotropic behavior increased with the addition of licorice root and quercetin. Adding slippery elm bark, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate into yogurt did not affect the sensory properties, whereas yogurts with quercetin had the lowest sensory scores. Overall, most of these ingredients did not cause major changes to yogurt properties.     

The effects of carob juice concentrates on the properties of yoghurt

Plain and fruit-flavoured yoghurts were made by adding 2.5, 5.0, 7.5, 10.0 mL carob juice concentrate (CJC) portions to 100 mL milk. The titratable acidity, pH, viscosity, whey separation, yoghurt organisms and sensory properties were determined weekly over a period of 4 weeks. Addition of CJC caused an increase in the fermentation time and reduced viscosity and viable organisms, while increasing the pH and whey separation of the yoghurts ( P <  0.05). A lack of sweetness was the main criticism of the yoghurts with 2.5 and 5.0 mL CJC, while those with 7.5 or 10.0 mL were mostly preferred by sensory panellists.