Yogurt Mix Research Articles

Effect of flaxseed lignan on the dynamics of Lactiplantibacillus plantarum and starter cultures in fermented milk

SummaryThe lignan from milled defatted flaxseed powder (DFP) and defatted hull powder (DHP) was extracted using direct alkaline hydrolysis and the quantity of lignan in the extract was estimated to be in the range of 11.74–14.30 mg g−1 flaxseed on a dry matter basis. Qualitative and quantitative analysis of different strains of Lactiplantibacillus plantarum (A1, Lp9, A5) along with yogurt mix culture (NCDC 146), Streptococcus salivarius ssp. thermophilus (NCDC 74) and Lactobacillus delbrueckii ssp. bulgaricus (NCDC 253) revealed that NCDC 74/A5 and NCDC 146/A5 co‐cultures are the most compatible. Buffalo milk containing different concentrations of lignan (100–400 mg of SDG/100 mL milk) was subjected to a fermentation dynamics study. The study revealed that the fermentation dynamics of Lactiplantibacillus plantarum in the milk did not get affected by starter cultures and flaxseed lignan. The results of this study could be useful in developing functional fermented probiotic milk products containing flaxseed lignan.

Fucoxanthin as a Biofunctional Compound in Goat Milk Yogurt: Stability and Physicochemical Effects

The food industry has increasingly added nutrients and other ingredients to products to enhance their health benefits. Fucoxanthin is recognized for its benefits in mitigating obesity, diabetes, hypertension, and inflammation. Therefore, addition of fucoxanthin into goat milk yogurt, its stability, and the physicochemical properties of yogurt during processing and storage was investigated. Yogurts with and without fucoxanthin were manufactured by mixing goat whole milk (82.85%, w/w), powdered goat milk (10.68%, w/w), and sugar (6.47%, w/w). Fucoxanthin (0.052 mg/g of yogurt mix) was added to the treatment. The mix was heated at 80 °C for 30 min, cooled, inoculated with a culture, and incubated at 43 °C for 5 h. Fucoxanthin in the yogurt mix and yogurt was quantified by an HPLC method. The recoveries of fucoxanthin from the mix before and after heating were 98.25% and 98.83%, respectively. However, less fucoxanthin (90.13%) was recovered from the freshly prepared yogurt than from the mix. Heating the yogurt mix did not affect the concentration of fucoxanthin but adding the inoculum to the mix reduced its concentration during fermentation. During the storage period, the concentration of fucoxanthin in yogurt remained the same. Fucoxanthin did not adversely affect the chemical composition and physicochemical properties of yogurt, but it influenced the color, decreasing lightness (81.47 ± 0.09), and increasing redness (7.67 ± 0.09) and yellowness (38.24 ± 0.09). Thus, goat milk yogurt can be an effective food matrix to deliver fucoxanthin to human diet.

Mix Root Beet And Red Guava's Yogurt Impact On Eligible Women's Haemoglobin Level

Nutritional problems in children are closely related to the health and nutrition preparation of a woman to become a mother-to-be, in this case, eligle woman (15-49 year) who do not yet have a legal partner. The results of the Nutrition International survey in 2018 found cases of anemia in eligible wowen’s in West Java of 41.93%, this is in line with the target of giving blood supplement tablets to eligible women’s, especially the adolescent group, which is still low (25.2%) and still below the target of West Java (52%). There is a need for intervention efforts to prevent anemia by optimizing the provision of iron-containing foods in addition to giving iron tablets. The purpose of this research was to determine the effect of a mix of beetroot and red guava yogurt on hemoglobin levels in eligible woman. The method used is a quasi-experiment with a one-group pre-post design approach. The sample in this study was 30 respondents using a purposive sampling technique with the inclusion criteria of mild and moderate anemia, not having allergies to yogurt ingredients, and not being on medication disease that can cause anemia. Determination of anemia by measuring hemoglobin levels with the POCT (Point of Care Testing) method. The analysis technique uses frequency distribution, normality test, and bivariate test using Wilcoxon test through SPSS version 20.0 computer software. The results showed that all respondents (100%) experienced mild anemia before being given the yogurt mix of beets and red guava. There is a significant change with a pvalue of 0.000 < alpha value (0.05). It can be concluded that giving beetroot and red guava yogurt if consumed regularly and appropriately can reduce the incidence of anemia, so it is hoped that this can be used as a policy for intervention in eligible women’s with anemia.

Value addition to frozen yoghurt through the use of orange peel solids as flavour adjunct

Frozen yoghurt rich in β‐carotene and dietary fibre was developed through incorporation of orange peel products. The suitability of two forms of peel viz., candied orange peel (COP) and orange peel powder (OPP), was studied as flavour adjunct in frozen yoghurt. The medium‐fat frozen yoghurt mix was prepared by blending yoghurt base with ice cream mix (25:75, w/w). COP and OPP were used as flavour adjuncts at levels of 8.0 and 2.5% by weight of mixes, respectively. The control (C) frozen yoghurt was devoid of the fruit peel. Incorporation of peel solids yielded frozen yoghurts which had markedly higher protein, carbohydrates, ash and total solids content. OPP used at 2.5% level was preferred over use of COP at 8.0% level as a valued ingredient in the preparation of ‘medium‐fat orange frozen yoghurt’. Such product had superior total sensory score when compared to the rest of the samples. The recommended frozen yoghurt was higher in terms of β‐carotene and dietary fibre by 37.20 and 240.0%, respectively, compared to control product.

Enumeration Of Bifidobacterium Spp., Lactobacillus Acidophilus and Starter Cultures from Commercial Probiotic Yogurts and Freeze-Dried Yogurt Starter Mixes

Probiotic yogurt is a popular functional food to deliver of probiotic cells for the health-enhancing effects worldwide. The viability of probiotics in yogurt before consumption is the most important factor to providing desired effects, however, probiotic microorganisms have occasionally inadequate viability in marketable food products. In this current study, Bifidobacterium spp., L. acidophilus and yoghurt starter bacteria enumerations were made in commercial probiotic yoghurt and freeze-dried yogurt mixes. RCA 5.3 and MRS 5.2 media were used for L. delbrueckii subsp. bulgaricus counting, ST Agar and M17 Agar were used for Stretococcus thermophilus counts. While using MRS-Bile Agar and RCA-Clindamycin Agar for L. acidophilus enumeration, Bifidobacterium spp. counts were performed using MRS-NNLP medium. 5 out of yoghurt samples (A, C, D, and E) did not reveal satisfactory recovery (< 5 log CFU/g) for L. delbrueckii subsp. bulgaricus colonies on MRS 5.2 Agar while L. delbrueckii subsp. bulgaricus colony counts on RCA 5.3 Agar below 5 log CFU/g for same tested 4 samples (A, C, D, and E). The recovery rates over 9 log CFU/g were obtained in the enumerations made for all yogurt samples on both ST and M17 media. The problem of insufficient recovery rates that occurred for L. delbrueckii subsp. bulgaricus in some yogurt samples was not valid for S. thermophilus. This work indicated that high amounts of L. acidophilus were detected on both media in both of the two yoghurt samples declared as L. acidophilus on the label (F and G). On the other hand, bifidobacteria was determined above 5 log CFU/g in only 1 yoghurt sample (B) out of 7 probiotic yoghurts claimed to be Bifidobacterium spp. This study reveals relevant information on probiotic and starter counts of commercial probiotic yogurts in Turkey and discusses in detail the possible reasons for the results obtained.

A new method for producing superior set yogurt, focusing on heat treatment and homogenization

Extended shelf life (ESL) processing (i.e., heat treatment at 130°C for 2 s) is usually not used for producing set yogurt because of the fragility of the curd structure. We investigated the effects of homogenization conducted at higher pressure than the conventional conditions (10 MPa for the first stage and 5 MPa for the second stage) on the curd structure of set yogurt, with a focus on the fat globule size. Each yogurt mix was adjusted at the range of fat globule sizes from 0.45 μm to 1.1 μm by a homogenizer and then heated at 95°C for 5 min (conventional heat treatment), 120°C for 2 s, ESL processing, or 140°C for 2 s. The yogurt mixes were fermented by a common yogurt starter, and the curd texture of the obtained yogurts was evaluated. We observed that the curd hardness and curd firmness of the yogurt were each negatively correlated with the fat globule size regardless of the heat-treatment temperature. Compared with the curd obtained with conventional heat treatment, the ESL-processed curd was extremely fragile, but significantly smooth. With ESL processing, a curd hardness >40 g, which is a sufficient strength for commercial transport systems, was obtained by making the fat particle size <0.6 µm, using 2-stage homogenization pressure: 35 MPa for the first stage and 5 MPa for the second stage. A microscopy analysis indicated that the smaller fat globules reinforce the network structure. The yogurt made by ESL processing and that created with 35 + 5 MPa homogenization had significant sensory evaluation scores. Our results indicate that the combination of ESL processing and 35 + 5 MPa homogenization is a novel and useful method for manufacturing set yogurt.

Properties of Low Fat Bio-frozen Yoghurt Fortified with Extract and Powder of Pomegranate Peel (Punicaganatum L.)

The present study aimed at using Pomegranate peel powder and extract (PPPE) (Punica ganatum L.) as a source of dietary fiber, natural colorant, prebiotic, polyphenols, and antioxidant activity in developing low fat frozen yoghurt. Pomegranate peel has been added in form of powder (added to yoghurt at at a rate of 1.5%) and extract (added at a rate of 0, 25, 50, 75, and 100% as a substitute of water used in preparing the frozen yoghurts that given codes of T1, T2, T3, and T4).Also, control frozen yoghurt sample was prepared without fat replacer (simplesse) as compared to other treatments. The results of frozen yoghurt revealed that the conversion of yoghurt into frozen mix caused an increments in acidity, viscosity, total phenolic content, total flavonoids content, and antioxidant activity values. Moreover, the viable count of lactic acid bacteria strains increased in frozen yoghurt mix. While the pH value, specific gravity (sp.gr.) and freezing point have been decreased by adding PPPE. Also, adding PPPE along with the fat replacer (simplesse) led to calorie reduction. Additionally, adding PPPE into traditional frozen yoghurt or bio-frozen yoghurt increased mineral content (Fe, Zn, P, and K). The freezing and hardening processes decreased the viable counts of LAB strains keeping its therabeutic level (106/g). Thus, T5 sample had the highest viable counts over storage time. The final frozen yoghurt was characterized with higher overrun, stronger melting resistance and the highest value of hardness as the PPPE were replaced and when it was made using ordinary yoghurt versus the bio-yoghurt. The quality of all sensory criteria of body and texture, flavour as well as overall quality of the PPPE-replaced frozen yoghurt was evidently better than that of the control, which was made with fat replacement. Scores ofsensory attributes increased with adding PPPE up to 100%.

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.

Comprehensive Evaluations of Physicochemical Characteristics and Sensory Acceptance of Selected Fruits, Almond and Dark Chocolate Incorporated Yogurt

The research aimed to formulate a yogurt mix by combining with natural flavored selected fruits (papaya, apple, banana and mango), almond and dark chocolate for enriched nutritional value and taste. For quality assessment of the yogurt mixture, physicochemical, phytochemical, nutritional and sensory properties were considered. The experimental data of yogurt mix were fitted to 14 models where plain yogurt was used as a control and concomitant 10% and 20% yogurt supplements were considered with the mentioned ingredients. The comparative results of all the formulations revealed notable enrichment in yogurt samples compared to the control. Moreover, a significant reduction in lipid content and pH of the enriched yogurts were observed. In contrast, the fortified yogurt exhibited higher carbohydrate, protein, phenolic and flavonoid contents than the control. Furthermore, the Ash content of all yogurt formulations excluding the yogurt-banana mix was found to be lower than the control and total soluble solids (TSS) were observed to be increased ranging from 10.81 to 15.30g per 100g of fortified yogurt. Nevertheless, the yogurt fusions conclude that almond-yogurt (AlY20) and mixed-fruits yogurt (MxY20) are the best suitable mix in terms of their acceptability, phytochemical and physicochemical composition.

Formulation and development of composite fruit peel powder incorporated fat and sugar-free probiotic set yogurt

Reduction of milk fat and added sugar makes the yogurt even healthier, yet texture deformations and less consumer acceptability will be attributed. Fiber incorporation may be counteracting these problems, which is tested in the present study by incorporating underutilize and cheap fiber sources. Composite fruit peel powder (FPP) formulated from industrial waste was incorporated into fat and added sugar-free set yogurts in three different proportions as 0.5%, 0.7% and 1% (w/v). Yogurt without added FPP was considered as the control. Alteration of titrable acidity, pH and lactic acid bacteria viability were evaluated over a period of a month. Total soluble solids content (TSS), color values, texture profile, and consumer acceptability also were tested. Results showed that FPP incorporation reduces the initial pH of the yogurt mix while increasing the TSS and impart color changes. The elevated amount of FPP mixture (0.7% and 1%) adversely affect texture parameters, microbial count and sensory acceptability. Firmness increased, syneresis decreased, and comparatively high lactic acid bacteria counts observed in fat and sugar-free yogurt with 0.5% FPP incorporation. No significant difference (p

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.

Short communication: Influence of an aqueous myrrh suspension on yogurt culture bacteria over yogurt shelf life

Myrrh is an essential oil and natural flavoring approved by the US Food and Drug Administration, and it has antibacterial and antifungal activity against pathogens. Our objective was to determine the effect of an aqueous myrrh suspension on Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus counts in peptone solution and yogurt, as well as pH and titratable acidity of yogurt during 5 wk of storage at 1 to 4°C. The myrrh suspension (10% wt/vol) was prepared and incorporated into a pure culture dilution in peptone and into yogurt mix at a 1% (vol/vol) level. A control with no myrrh was also prepared, and 3 replications were conducted. Streptococcus thermophilus were enumerated using Streptococcus thermophilus agar with aerobic incubation at 37°C for 24 h, and Lactobacillus delbrueckii ssp. bulgaricus were enumerated using de Man, Rogosa, and Sharpe agar adjusted to pH 5.2, with anaerobic incubation at 43°C for 72 h. During the 8-h period after inoculation, S. thermophilus and L. delbrueckii ssp. bulgaricus counts in peptone solution at 37°C and 43°C, respectively, were not significantly different in the presence or absence of the aqueous myrrh suspension. Counts of S. thermophilus in yogurt containing myrrh (mean ± SD; 4.96 ± 0.58 log cfu/mL) were not significantly different from those in the control yogurt (4.87 ± 0.39 log cfu/mL). The log counts for L. delbrueckii ssp. bulgaricus in yogurt containing myrrh (5.04 ± 1.44 log cfu/mL) and those of the control (5.52 ± 1.81 log cfu/mL) did not differ, and the counts remained within 1 log of each other throughout 5 wk of storage. The pH of the yogurts containing the aqueous myrrh suspension was not significantly different from that of the control yogurts, and their pH values were within 0.1 pH unit of each other in any given week. Titratable acidity values remained steady around 1.1 to 1.2% lactic acid for both yogurt types throughout the storage period, with no significant differences between them. Yogurt culture bacteria can survive in the presence of a myrrh suspension in yogurt with no significant change in pH or titratable acidity. Therefore, it may be beneficial to add an aqueous myrrh suspension to yogurt.

Yogurt Fortification with Chickpea (Cicer arietinum) Flour: Physicochemical and Sensory Effects

AbstractYogurt, a popular dairy product made by bacterial fermentation of milk, is a nutritious food that contains probiotics beneficial for digestive health. Protein fortification is an effective way to design foods with increased satiety. Chickpea is rich in protein, fiber, and prebiotics and can be a source for enhancing the nutritional quality of food products while providing functional attributes of macromolecules and promoting probiotic growth. The present study evaluated the effects of the addition of chickpea flour (1%, 2%, 3%, or 5%, w/v, level) on selected quality parameters of yogurt of 2% fat‐containing milk that was inoculated with a yogurt culture, fermented, and stored at 4 °C up to 21 days. The results demonstrated that addition of chickpea flour to the yogurt mix promoted the growth of bacteria during yogurt making, and decreased the incubation time. Fortification of yogurt with 1% and 2% chickpea flour provided a significant improvement in the viscosity of stored yogurt. Chickpea flour stimulated the growth of probiotic bacteria and maintained higher counts over the 21‐day refrigerated storage. Sensory evaluation revealed no significant influence on the acceptance scores of yogurt with addition of 1% or 2% of chickpea flour. The results suggest that addition of chickpea flour up to 2% level can be an option to enhance the protein level of yogurt without adverse effects on product qualities and sensorial properties.

Use of β-glucan from spent brewer's yeast as a thickener in skimmed yogurt: Physicochemical, textural, and structural properties related to sensory perception

Powdered β-glucan extracted from brewer's yeast (Yestimun, Leiber GmbH, Bramsche, Germany) was incorporated into skimmed-milk yogurt at varying concentrations (0.2-0.8% wt/wt) to investigate its potential application as a thickener. The effect of β-glucan fortification on the nutritional profile, microstructure, physicochemical properties, and texture of freshly prepared yogurts was investigated. Sensory evaluation was also conducted and was correlated with instrumental analysis. The addition of Yestimun significantly reduced the fermentation time of the yogurt mix from 4 h to 3 h. Scanning electron microscopy revealed that β-glucan particles formed small spherical clusters within the yogurt matrix. The majority of the physicochemical properties (syneresis, viscosity, color, and titratable acidity) remained unaffected by the incorporation of Yestimun in the recipe. Textural properties showed a gradual increment with increasing β-glucan concentration. Hardness, total work done, adhesive force, and adhesiveness increased by 19.27, 23.3, 21.53, and 20.76%, respectively, when using the highest amount of Yestimun powder. Sensory analysis (n = 40) indicated that fortifying yogurt with Yestimun at 0.8% (wt/wt) concentration may affect overall acceptance ratings, which was attributed to adverse flavor and aftertaste effects. However, the overall liking score of the yogurt (5.0/9.0) shows potential for commercialization of the product.

PROXIMATE COMPOSITION, ACCEPTABILITY AND STABILITY OF PROBIOTIC DAIRY YOGHURT CONTAINING COOKING BANANA/MATOOKE PUREE AND Lactobacillus rhamnosus yoba

Cooking bananas/matooke are eaten in the unripe state but quickly ripen leading to postharvest losses. The purpose of this study was to develop fruit-based probiotic dairy yoghurt using ripe matooke and Lactobacillus rhamnosus yoba. Yoghurt mixtures containing varying proportions of matooke (0%, 5%, 7.5% and 10%) were fermented at room temperature for 32 hours. Acidity, pH and counts of Lactobacillus rhamnosus were determined during fermentation and storage (4°C for three weeks). Consumer acceptability was determined at weekly intervals. Lactobacillus rhamnosus counts increased from 7 – 9 log cfu.g-1 after 24 hours of fermentation. Banana accelerated the acidification rate with banana yoghurts attaining pH = 4.4 – 4.5 and acidity of 0.60 – 0.67% in 24 hours. The control took 32 hours to attain a pH = 4.5. Ripe cooking banana introduced a slight banana aroma but did not significantly (p &gt; 0.05) affect consumer acceptability. Yoghurt containing 7.5% banana was most acceptable and contained: 148 kcal 100 g-1, 76.81% moisture, 12.37% carbohydrates, 6.18% protein, 3.35% fat, 0.77% ash and 1.04% calcium. Yoghurt with 7.5% banana was stable at 4°C for 21 days and maintained viable counts above the target of log 6 cfu.g-1 . This study showed that an acceptable fruit based probiotic yoghurt can be produced by adding ripe banana to the yoghurt mix.

Evaluating Moringa (Moringa oleifera) as a valued ingredient in frozen yoghurt

This study was aimed to develop a functional frozen yoghurt with incorporation of the Moringa pod powder (MPP). Frozen yoghurt was prepared using indirect acidification method. Optimization of the product formulation was done by Response Surface Methodology (RSM) with central composite rotatable design (CCRD) at different levels of MPP, stabilizers and mango pulp. The composition of yoghurt mix was 2% milk fat, 12.5% MSNF, 14.0% sucrose and 4.0% corn syrup solids. Based on the results obtained in RSM, it was found that 1.49% MPP, 0.86% stabilizer blend and 14% mango pulp gave the most acceptable product with respect to sensory analysis. With respect to proximate chemical composition, frozen yoghurt with Moringa contained 33% total solids, 1.8% fat, 3.9% protein, and 0.8% ash. This product can be labeled as “excellent source of Vitamin C” having 21% daily value (DV) and “good source of calcium” having 13.96% DV of these nutrients. It also contained appreciable amounts of potassium, about 246.39 mg/100g moringa frozen yoghurt mix. Results of the study reveals that an, acceptable quality of frozen yoghurt with enhanced nutritive value can be prepared with Moringa.

Steady and dynamic rheological behaviour of frozen soy yogurt mix affected by resistant starch and β-glucan

ABSTRACTThe present study investigated the effect of resistant starch (0, 1%, 2%) and β-glucan (0, 1%, 2%) on the steady and dynamic rheological properties of frozen soy yogurt mixes. The results showed that addition of fibres to the mix caused an enhancement of pseudoplasticity. The power law model was the best model to fit with data. The lowest and the highest of hysteresis loop area belonged to sample containing 1% β-glucan and 2% resistant starch, respectively. Dynamic rheology results showed that storage modulus (G’) and loss modulus (G”) increased within the frequency range of 0.01–100 Hz. The loss tangent (tan δ) of all samples was above 1, indicating liquid viscoelastic behaviour. Resistant starch at concentration of 2% as compared to β-glucan was a better choice to modify the rheological properties of frozen soy yogurt mixes.

QUALITY OF LOW FAT PREBIOTIC FROZEN YOGHURT

Frozen yoghurt is a complex fermented frozen dairy desert that combines the physical characteristics of ice cream with sensory and nutritional properties of fermented milk products.Six batches of frozen yoghurt were made to study the effect of replacing milk fat with inulin (Frutafit HD®) on the quality of frozen yoghurt. Control vanilla frozen yoghurt mix containing 4% fat, 13% milk solid not fat, 15% sucrose and 0.5% stabilizer was prepared. The other 5 batches were made by replacing 20, 40, 60, 80 and 100% of milk fat with inulin. The obtained results indicated that replacement of milk fat with inulin increased the acidity, the specific gravity, weight per gallon and viscosity of all mixes and specific gravity, weight per gallon, melting resistance and carbohydrate content of frozen yoghurt and this increase was proportional to the rate of replacement, and decreased pH values of frozen yoghurt mixes, fat and caloric value of frozen yoghurt, while replacement of milk fat inulin did not affect the ash, total protein and total solids content of frozen yoghurt. Increasing the rate of replacing milk fat with Frutafit HD® up to 60% increased the overrun and improved the acceptability of the resultant frozen yoghurt, while increasing the rate of the replacement above that decreased the overrun and the scores of organoleptic properties of frozen yoghurt.

Plant extract enhances the viability of Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus acidophilus in probiotic nonfat yogurt.

A commercial plant extract (prepared from olive, garlic, onion and citrus extracts with sodium acetate (SA) as a carrier) was evaluated to extend the viability of yogurt starter and probiotic bacteria as a means to enhance the shelf life of live and active culture, probiotic nonfat yogurt. Yogurts prepared from three different formulas (0.5* plant extract, 0.25* SA, or no supplement) and cultures (yogurt starter plus Bifidobacterium animalis,Lactobacillus acidophilus, or both probiotics) were assessed weekly during 29 days of storage at 5°C. Supplemented yogurt mixes had greater buffering capacities than non-supplemented yogurt mixes. At the end of storage, Lactobacillus bulgaricus and L. acidophilus counts in supplemented yogurts were greater compared with non-supplemented yogurts. Supplementation did not affect Streptococcus thermophilus and B. animalis counts. Hence the greater buffering capacity of yogurt containing plant extract could enhance the longevity of the probiotics, L. bulgaricus and L. acidophilus, during storage.

Effect of incubation and storage temperatures on Quality of set Yoghurt

This study aimed to investigate the effect of incubation and storage temperatures on quality of set yoghurt made from cow milk during storage life of 10 days. The yoghurt mix was prepared by adding 100 Kg skim milk powder to 341 liters of distilled water and then mixed for 20 minutes and adding 60 liters fresh cow milk. The yoghurt mix was pasteurized at 90oC for 20 minutes and then cooled to 45oC. A 2% of mixed starter culture type (CH-1, B-3) was added. Then it was incubated at different incubation temperatures (41oC, 43oC, 45oC) for 4 hours. Physiochemical characteristics such as acidity, viscosity, wheying-off and sensory quality were carried out at zero time and after one day in order to select optimum incubation temperature. Then optimum sample was stored at two temperatures (6oC and 10oC) to study the effect on quality. The results showed that the incubation temperature of 45oC gave the best quality yoghurt compared with incubation temperatures of 41oC and 43oC as measured with the parameters of acidity, wheying-off, viscosity and sensory quality. Storage temperature of 6oC gave the better quality yoghurt compared with storage temperature of 10oC which resulted in large amount of whey separated, low viscosity and low acidity.