EFFECTS OF FUNCTIONAL DAIRY BASED PROTEINS ON NONFAT YOGURT QUALITY

Production of nonfat yogurt demands a careful control of quality parameters. It is common to use skim milk powder (SMP) to increase the total solid content of nonfat yogurt, but some functional dairy-based proteins, such as casein/caseinates and whey proteins, may improve the quality of nonfat yogurt.
The objectives of this study were to use whey protein isolate (WPI), sodium caseinate (NaCn) and yogurt texture improver (TI) in nonfat yogurt manufacture as an alternative for SMP, and to compare their potential influences on the physical, chemical and microbial properties of nonfat yogurts over a 12-day storage. All dry ingredients were added at 1% (w/v) concentration to yogurt milk. Yogurts differed from each other with different hardness values. Acetaldehyde contents of yogurts were in the range of 35–43 ppm. The acetaldehyde content of all yogurt types decreased during storage. The control yogurt had the most tyrosine content, and the WPI-fortified yogurt had the least. Using different dry dairy ingredients did not affect the numbers of starter cultures. In addition, no significant differences were observed among yogurt types regarding their mineral composition.

PRACTICAL APPLICATIONS

Functional dry dairy ingredients can be used to increase the total solid content of nonfat yogurt instead of using skim milk powder (SMP) or evaporation. Their high protein content, water-binding capacity, texture improvement properties and health benefits make these proteins suited for use in nonfat yogurts. This study compares the possible effects of using whey protein isolate (WPI), sodium caseinate (NaCn) and yogurt texture improver (TI) as an alternative for SMP on the physical, chemical and microbial properties of nonfat yogurts. It was found that substitution of SMP for WPI, NaCn and TI at the level of 1% affected the physical, chemical and microbial properties of nonfat yogurt.     

Quality characteristics and consumer acceptance of yogurt fortified with date fiber

Yogurt is considered a healthy food and incorporating dietary fiber will make it even healthier. Date fiber (DF), a by-product of date syrup production, is a good source of dietary fiber. The effect of fortification with DF on fresh yogurt quality was investigated. Acidity, pH, color [L* (lightness), a* (redness), and b* (yellowness) values], texture profile, sensory properties, and consumer acceptance were studied. Control yogurt (without fiber), yogurt fortified with 1.5, 3.0, and 4.5% DF, and yogurt with 1.5% wheat bran (WB) were prepared. Fortification with DF did not cause significant changes in yogurt acidity, although pH was increased. Yogurts fortified with DF had firmer texture (higher hardness values) and darker color (lower L* and higher a*) compared with control or WB yogurts. Consumer test results indicated that the appearance, color, and flavor ratings were significantly affected by fiber fortification. Yogurt fortified with up to 3% DF had similar sourness, sweetness, firmness, smoothness, and overall acceptance ratings as the control yogurt. Sensory ratings and acceptability of yogurt decreased significantly when increasing DF to 4.5% or using 1.5% WB. Flavoring yogurt fortified with 4.5% DF with vanilla did not improve flavor or overall acceptance ratings. Thus, fortifying yogurt with 3% DF produced acceptable yogurt with beneficial health effects.     

Fat-free plain yogurt manufactured with inulins of various chain lengths and Lactobacillus acidophilus

ABSTRACT:  Inulin is a prebiotic food ingredient that increases the activity of Lactobacillus acidophilus , increases calcium absorption, and is a good source of dietary fiber. The objective was to determine the effect of short, medium, and long chain inulins on the physicochemical, sensory, and microbiological characteristics of fat-free plain yogurt containing L. acidophilus . Inulins of short (P95), medium (GR), and long (HP) chain lengths were incorporated at 1.5% w/w of the yogurt mix. Viscosity, pH, syneresis, sensory properties (flavor, body and texture, and appearance and color), L. acidophilus counts, and color ( L *, a *, and b *) of yogurts were determined at 1, 11, and 22 d after yogurt manufacture. The P95 containing yogurt had a significantly lower pH than the remaining yogurts, higher flavor scores than the yogurt containing HP, and comparable flavor scores with the control. The yogurts containing HP had less syneresis than the control and a better body and texture than the remaining yogurts. Yogurts containing prebiotics of different chain lengths had comparable L. acidophilus counts with each other but higher counts than the control. However, inulins of various chain lengths did not affect viscosity, color, and product appearance. Chain length of prebiotics affected some quality attributes of probiotic yogurts.     

Consumer perception,health information,and instrumental parameters of cupuassu (Theobroma grandiflorum) goat milk yogurts

Although the demand for goat milk products has been growing, they have lower consumer acceptability than products derived from cow milk. However, the addition of cupuassu pulp can be used to improve the formulation of these products. For this reason, the aim of this study was to investigate the influence of new goat milk yogurt manufactured with cupuassu pulp on physicochemical properties, consumers’ perceptions, and overall consumer acceptance. In addition, the effect of antioxidant health information on consumer acceptance and purchase intention of cupuassu goat milk yogurts was evaluated. The results demonstrated a positive expectation regarding linking and familiarity to goat milk products and products with cupuassu pulp. The pH, total phenolic content, lightness, redness, yellowness, and apparent viscosity were potentially affected by the addition of cupuassu, with the highest concentration of cupuassu (10%) exhibiting the greatest changes in parameters. Based on principal component analysis, partial least squares regression, and just-about-right and penalty analysis, the addition of cupuassu pulp improved some sensory attributes of goat milk yogurt, such as cupuassu aroma, cupuassu flavor, yellow color, consistency, and viscosity, which positively influenced product acceptance. In addition, antioxidant health information increased the acceptance and purchase intention of cupuassu goat milk yogurts. Taking into account the parameters investigated in this study, the best scoring formulation was goat milk yogurt with 10% cupuassu pulp. Our results suggest that cupuassu pulp can be considered a potential ingredient to improve the sensory and texture properties of goat milk yogurt. Furthermore, the antioxidant health information could be a sensory strategy to increase the acceptance of cupuassu goat milk yogurts.     

PARAFAC: Adjustment for modeling consumer study covering probiotic and conventional yogurt

The feasibility of the parallel factors model (PARAFAC) as a modeling tool for consumer sensory acceptance data of complex food matrices was investigated. The attributes of aroma, flavor, taste, texture, and overall liking of probiotic and conventional yogurts were evaluated by 120 consumers using a 9-point hedonic hybrid scale. Six yogurt samples were used: three were prototypes supplemented with a glucose oxidase/glucose system, which is a potential oxygen scavenging system, and the other three were commercial yogurts. The yogurts supplemented with the glucose oxidase/glucose system presented similar sensory acceptance towards commercial probiotic and conventional yogurts (p > 0.05), besides having garnered lower mean scores for the sensory attributes. Appearance and overall liking were the most significant attributes for the first two components of the PARAFAC model. Finally, the advantage of using this method to explore the intrinsic nature of consumer sensory data is discussed and compared to principal component analysis (PCA).     

Consumer-perception,nutritional, and functional studies of a yogurt with restructured elderberry juice

We investigated the effects of supplementation of yogurt with elderberry juice (Sambucus nigra L.), in both natural and restructured forms, on certain technological, physicochemical, sensory, and health-promoting properties of yogurt, including antioxidant activity and inhibition of angiotensin-converting enzyme (ACE), α-amylase, and α-glucosidase activity. Consumer acceptance of the yogurt-juice products was assessed. Gel-strength restructured elderberry juice retained a spherical shape and most of the juice, despite decreasing in mass from 57.2 to 50.9 g during storage. As a result, yogurt supplemented with 10 and 25% restructured elderberry juice appeared to be more desirable from a sensory and technological perspective than yogurt with natural juice. Yogurt supplemented with restructured elderberry juice had a high water-holding capacity (94.4–96.4%), exhibited no spontaneous whey syneresis, and maintained a dense consistency (up to 5,626 g). Consumer penalty analysis of the just-about-right diagnostic attributes indicated that the flavor of these yogurts may not be sufficiently refreshing. High correlation was demonstrated between ACE inhibition, ABTS, α-amylase, and α-glucosidase in yogurt supplemented with restructured juice. An in vitro gastrointestinal simulation estimated bioaccessibility of antioxidants to be in the range of 62 to 66%. This model fermented yogurt supplemented with restructured elderberry juice is a novel dairy-juice beverage that represents a new approach for the development of functional fruit yogurt beverages.     

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.     

Fat free plain set yogurts fortified with various minerals

Seven different minerals (iron, magnesium, zinc, manganese, molybdenum, chromium and selenium) were incorporated separately into the yogurt mixes at 25% of their recommended dietary allowances of 15 mg, 420 mg, 15 mg, 5 mg, 200 μg, 200 μg, 70 μg, respectively. The various attributes studied on the yogurts were viscosity, syneresis, color/lightness (L*), body and texture, appearance and flavor. No significant (P>0.05) difference was observed for viscosity of the yogurts fortified with minerals when compared to the control. Yogurts fortified with iron, selenium and magnesium had better water-holding capacities compared to the control. No significant (P>0.05) differences were observed for flavor and appearance scores of the yogurts fortified with the minerals compared to the control. Fortification of yogurts with these minerals can be accomplished without adversely affecting product characteristics.     

Fortification of sweetened plain yogurt with insoluble dietary fiber

 Seven types of insoluble dietary fiber from five different sources (soy, rice, oat, corn and sugar beet) were used to fortify sweetened plain yogurt. Fiber addition caused an acceleration in the acidification rate of the experimental group yogurts, and most of the fortified yogurts also showed increases in their apparent viscosity. Soy I and sugar beet fibers caused a significant decrease in viscosity due to partial syneresis. In general, fiber addition led to lower overall flavor and texture scores. A grainy flavor and a gritty texture were intense in all fiber-fortified yogurts, except in those made with oat fiber. Oat II fiber gave the best results; differences with controls in terms of flavor quality scores not being statistically significant. The evolution of organic acids during the fermentation and cold storage of control and oat-II-fiber-fortified yogurts showed a similar pattern; only acetic and propionic acids were found in significantly higher amounts in the fiber- fortified product. Received: 27 June 1996/Revised version: 2 September 1996     

Fortification of sweetened plain yogurt with insoluble dietary fiber

 Seven types of insoluble dietary fiber from five different sources (soy, rice, oat, corn and sugar beet) were used to fortify sweetened plain yogurt. Fiber addition caused an acceleration in the acidification rate of the experimental group yogurts, and most of the fortified yogurts also showed increases in their apparent viscosity. Soy I and sugar beet fibers caused a significant decrease in viscosity due to partial syneresis. In general, fiber addition led to lower overall flavor and texture scores. A grainy flavor and a gritty texture were intense in all fiber-fortified yogurts, except in those made with oat fiber. Oat II fiber gave the best results; differences with controls in terms of flavor quality scores not being statistically significant. The evolution of organic acids during the fermentation and cold storage of control and oat-II-fiber-fortified yogurts showed a similar pattern; only acetic and propionic acids were found in significantly higher amounts in the fiber- fortified product. Received: 27 June 1996/Revised version: 2 September 1996     

EFFECT OF SOLID CONTENT AND SUGAR COMBINATIONS ON THE QUALITY OF SOYMILK-BASED YOGURT

A research to evaluate the effect of two levels of solids and two sugar combinations in the quality of a soymilk yogurt-type food was carried out. Yogurts were elaborated by inoculating lactic cultures ( Lactobacillus dellbruckii spp. bulgaricus and Streptococcus salivarius spp. thermophilus ) into soymilk with 8% and 11% solid levels and glucose/sucrose and glucose/fructose mixtures. Also, a control treatment with cow milk was prepared. Yogurts were analyzed after two days of preparation for their chemical (protein, lipids, titrable acidity and pH), physical (syneresis and viscosity) and sensory characteristics (quality and acceptability). Protein content of soymilk based yogurts ranged between 3.56 and 4.45 g/100 g. The higher titrable acidities (0.66% and 0.63% lactic acid) were shown by treatments with higher solids level, which also shown the lowest syneresis. All soymilk yogurts were yellowier than the control. The highest sensory acceptability was for the 8% solids treatment enriched with glucose and sucrose.

PRACTICAL APPLICATIONS

There are an increasing number of people suffering of lactose intolerance, which need an alternative product to milk. Besides, some people have adopted a strictly vegetarian way of life. Soymilk has been used for a long time by this part of the population; however, it usually has a beany flavor, which can cause some rejection among occidental consumers. A fermented product from soymilk, such as soymilk yogurt, may offer a good alternative for those people. In soymilk production it is necessary to carefully adjust the amount of solids and the sugar used in fermentation in order to obtain a well accepted commercial product. Soy yogurt could be used to formulate a number of different new products like desserts, high fiber yogurt, fruit-added yogurt and so on.     

Effects of partially replacing skimmed milk powder with dairy ingredients on rheology, sensory profiling, and microstructure of probiotic stirred-type yogurt during cold storage

This study aimed to evaluate the quality of stirred-type skim milk probiotic yogurt fortified by partially replacing skim milk powder (SMP) with whey protein concentrate (WPC) and sodium caseinate (Na-CN) during cold storage for 28 d compared with nonfortified yogurt. The rheological properties (as measured using dynamic oscillation) and sensory profiles of probiotic yogurts were greatly enhanced when SMP (i.e., 45%) was replaced with WPC and Na-CN. Higher values of mechanical parameters related to storage and loss modulus and consistent microstructure were found in the fortified yogurts. The acidification profile was not affected by supplementation of the solids in the milk base, and the viable counts of probiotic microbiota were high and satisfactory. These positive characteristics of probiotic yogurts were maintained until the end of the storage period. The microstructure of the fortified yogurt showed some differences compared with the nonfortified product, which were due to changes in chemical composition of the milk base in addition to the colloidal characteristics of the product.     

Lutein Is Stable in Strawberry Yogurt and Does Not Affect its Characteristics

ABSTRACT:  The impact of various levels of lutein on the physicochemical, microbiological, and sensory characteristics of yogurt over its shelf life was determined. Nonfat strawberry yogurts were prepared with 0, 0.5, 1.5, and 3.0 mg lutein per 170 g serving (20% overages were included to account for processing losses). The lutein was incorporated prior to homogenization of the yogurt mix. Stability of lutein, viscosity, pH, syneresis, standard plate counts, coliform counts, color (L*, a*, b*), and sensory evaluation (flavor, body and texture, and appearance and color) were measured at weeks 0, 1, 3, and 5 after product manufacture. The interaction effect between levels of lutein and storage time was significant for a* (redness-greenness) values. Lutein levels remained above target throughout the 5-wk storage study. Lutein did not affect viscosity, pH, syneresis, L* (lightness) and b* (yellowness-blueness) values, standard plate counts, coliform counts, flavor, body, texture, appearance, and color scores. These results suggested that lutein was suitable for inclusion in functional yogurts. The skin and eye health benefits provided by lutein can easily be incorporated into yogurt to complement inherent nutritional properties.     

消费者感官评价对酸奶品质提升的导向研究

消费者感官评价为产品开发和工艺改良提供实际依据。本文以酸奶为例,结合消费者感官测试完成其品质提升。分别收集消费者的基本信息,以及他们对酸奶整体喜好度、香气喜好度；香气、甜味、酸味、稠度接受度；和酸奶所需要提升的感官属性的主观建议等。结合喜好度分析、惩罚分析、词云频率等数据分析方法,得到消费者对酸奶的品评结果。实验结果表明四种酸奶的整体喜好度与香气喜好度平均值都在5分以下,说明消费者的认可度不高；且酸奶的香气与整体喜好度之间有正相关性。酸奶661和467的产品更受消费者的欢迎。由于这两者目前的喜好度分值仍较低(<5.0),需要进一步优化其配方,以期获得更好的市场价值。消费者关注的酸奶品质主要包括酸度、甜度、香气和稠度。喜好度分析和接受度惩罚分析的结果发现酸奶467是目前消费者喜好度较高的产品,后期通过降低其酸度,可以更好地提高它的接受度,从而获得更多消费者的青睐。以消费者为导向探究乳制品的风味感官品质,为产品的优化升级提供指导意义。未来通过调试酸奶的风味性质可生产出深受消费者喜爱的产品。