Danou Pao1, Seiha Lim1*, Limhong Chhom1 and Chancherdchai Sangketkit2
1Department of Food Processing, Faculty of Agriculture and Food Processing, University of Battambang, Cambodia
2Department of Agro-Industry, Faculty of Agriculture and Technology, Rajamangala University of Technology Isan, Surin Campus, Thailand
* Corresponding author: limseiha.ubb@gmail.com
Abstract
The objective of this study was to investigate the effect of various ratios of cow milk (CM) and soymilk (SM) on physicochemical, nutritional value and sensory of jamun drinkable yogurt.
Jamun drinkable yogurt was prepared using 35% (w/v) yogurt mixed with 65% (v/v) jamun juice, 0.2% pectin and 2% sugar. Nutritional value was analyzed by total solid, crude protein, fat, ash, vitamin C, calcium and total phenolic content (TPC). Physicochemical was investigated by pH, lactic acid, phase separation, moisture, total soluble solid (TSS), reducing sugar, total sugar and non-reducing sugar. Sensory was evaluated by 5-point hedonic scales. pH of drinkable yogurt increased with increasing SM with pH 4.62 at 100% SM. 100% CM resulted in the maximum lactic acid content of drinkable yogurt. Adding SM alone was greatly increased phase separation by68.89%. 75% CM : 25% SM had the highest TPC with 22.07mg GAE/100g. Addition of SM alone had decreased TSS content, reducing sugar, total sugar and non-reducing sugar with 8.97
°Brix, 4.81%, 16.96 and 12.15%, respectively. Total solid was raised by an increase in SM. Using CM alone produced a high protein content with 8.16%. Combination of 50% CM and 50% SM obtained the highest fat content with 0.62%; while CM or SM alone contained low amount.
Vitamin C was higher in drinkable yogurt used 75% CM and 25% SM, with 7.32mg/100g. Ash content was not affected. 75% CM and 25% SM exhibited maximum calcium content with 0.12%.
The sensory evaluation of CM alone or 75% CM : 25% SM got the highest score at overall acceptability with 3.50. Therefore, combined 75% CM and 25% SM was comparable with CM alone for both proximate values, physicochemical properties and sensory evaluation; and these results suggested that SM characteristic wasn’t good enough for making drinkable yogurt.
Keywords: Cow milk, soy milk, yogurt, physicochemical, drinkable yogurt.
Introduction
Drinkable yogurt is a healthy dairy beverage being offered today and is consumed worldwide. Drinkable yogurt ranges in consistency from dilute, low-viscosity to thick, viscous products [1].These products were produced by dilution of yogurt with water or fruit juice [2]. It is a nutritiously balanced food, containing the nutrients present in milk and added fruits [3]. As the main ingredient, yogurt is a source of highly protein, milk fat, energy from added sugar and vitamins [4]. Yogurt is a fermented milk product resulting in lactic acid, which produced by Streptococcus thermophilus and Lactobacillus bulgaricus. The aqueous phase of milk becomes a three-dimensional network of aggregated casein, which characteristics textural attributes of yogurt [5]. An emulsion system of this product is thermodynamically unstable that tend to breakdown during storage through a variety of physicochemical mechanisms, including creams, flocculation, coalescence and Ostwald ripening [6], [7]. Emulsifiers or stabilizers are needed for stabilizing emulsions to decrease the interfacial tension between oil and water phase and form a protective coating around the droplets which prevents them from coalescing [5].
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A human requires macronutrients such as protein, carbohydrate, fat/lipid; and micronutrients such as vitamins, minerals, water and fiber[8]. Cow milk naturally contains a readily absorbable form of calcium and higher protein [9]. Soybean is a low-cost source of protein (essential amino acids) that has been consumed in Asian nations including Cambodia for many centuries. The rapidly growing population of Cambodian is facing acute shortage of protein, soybean is rich protein and fiber, lipid, vitamins and minerals[10].Some people who cannot drink cow milk or consume dairy products because of allergy. Thus, soy products are healthy and important for those people[9]. Soy milk should be chosen to object healthy drink. Soymilk is produced a yoghurt, cheese and ice cream [11], [12]. One of the major limiting factors that is hindering and objectionable the use of soymilk is flavor. The flavors are very important in food appreciation [13].The addition of ingredients such as banana, strawberry, pineapple, vanilla, and ginger improved soy yogurt flavor [14]. Jamun fruit is one of plant sources which contain a variety of important nutritional compositions[15].
The main objective of this research is to investigate the effect of yogurt from different ratios of cow milk and soymilk on physicochemical, nutritional value and sensory evaluation of jamun drinkable yogurt.
Materials and Methods
Raw materials: Pasteurized cow milk, soybeans, starter culture (a yogurt product from the market), jamun fruits, sugar, corn starch, pectin were used in this study.
Yogurt preparation: Yogurts were prepared using different ratios of cow milk (CM) and soymilk (SM) as following 100% CM as control, 75% CM : 25% SM, 50% CM : 50% SM, 25%
CM : 75% SM, and 100% SM. SM was prepared by soaking soybeans in hot water (1:8 ratio), milled, filtered by cloth filter, and cooked at 85 °C for 10 min; then filtered twice, stored in refrigerator until used. Milk was pre-heat at 35 °C, and added 0.2% pectin, 2% corn starch and 12% sugar. Milk was heated at 85 °C for 30 min and rapidly cooled to 45 °C. 3% (w/v) starter culture was added. The mixture was fermented at 45 ºC for 6 h. Yoghurts were stored in a refrigerator at 4ºC.
Jamun juice: Jamun fruits were cooked by adding water (1:3 ratio) at 60 ºC for 15 min and filtered twice by cloth filter.
Drinkable yogurt: 35% (w/v) yogurt mixed with 65% (v/v) jamun juice, and 0.2% pectin and 2% sugar were added. Drinkable yogurts were packed into glass bottles and pasteurized at 90 ºC for 5 min in a water bath. Drinkable yogurts were stored in arefrigerator at 4 ºC.
Physicochemical analysis
pH measurement: pH was determined at room temperature (25 ºC ± 2) using a digital pH meter (Metrohm 827 pH Lab)[3].
Total lactic acid: The titratable acidity was used to measure total lactic acid [16]. Sample (15 ml) was titrated with 0.1 M NaOH until the substance reached a pH value 8.2, which corresponding to the end of the phenolphthalein. NaOH volume was recorded and total acid was calculated as follows:
% total lactic acid =VNaOH× M × 90 × 100 Vsample × 1000 Where: M = Molar concentration of NaOH.
Phase separation: Syneresis separation was measured using gravity separation. Sample (100 ml) was poured into a beaker and placed in a cooler at 2.8 ± 0.2 °C. Separation of the serum fluid from the gel matrix was visually measured after storingfor 5 days. All samples were evaluated in triplicates [17].
Determination of sugars: Determination of sugars (total sugar, reducing sugar and non-reducing sugar) were carried out though Lane and Eynon Method as described by [18].
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Total soluble solid (TSS): TSS was determined by using a refractometer(Digital Hand-held, Pocket, PAL-1). Sample (0.3 ml or several drops) on prism surface and determined about 2 min [19].
Reducing sugar: Sample (10 g) was weighed in a beaker and added 200 ml warm water.
Stirred and left solution cooled at room temperature. Sample solution was placed into a 250 ml volumetric flask with 4ml carrez 1 and 4ml carrez 2 and made the solution up to 250 ml using distilled (DI) water. Sample solution was filtered through Whatman No. 1 paper in an Erlenmeyer flask. 10 ml Fehling’s solution, 2-5 chips of boiling chip and a few drops of methylene blue were prepared. This solution was used for titration sample. Sample solution was titrated on a hot plate and purple color is the end of the reaction. Reducing sugar was calculated by following:
% Reducing sugar =F × 100 × Dilution T × W × 1000
Where: F = 64.6 mg (lactose), Dilution = 250 ml, T = volume of titrated, W = weight of sample.
Total sugar: 100 ml sample solution (residue from reducing sugar determination) pipetted in a 250 ml Erlenmeyer flask. 10 ml HCl was added and boiled for 5 min. After cooling, neutralized (pH 7.0) the solution to the phenolphthalein with 10% NaOH and made up to volume in a 250 ml volumetric flask. Sample solution was used for titration against Fehling’s solution and calculated as follows:
% Total sugar =F × Dilution × 2.5 T × W × 10
Where: F = 64.6 mg (lactose), Dilution = 250 ml, T = volume of titrated, W = weight of sample.
Non-reducing sugar: was estimated as the difference between the total sugar content and reducing sugar content.
% Non − reducing sugar = % Total sugar − % Reducing sugar Proximate analysis
Moisture content determination: The moisture content (MC) was measured according to a method of Association of Official Analytical Chemists [21]. Sample (10 g) was weighed in a beaker and heat at 100 °C in a water bath for 30 min. Residue sample was dried at 105 °C overnight in a hot air oven. MC was calculated as follows:
% MC =(W2− W3)
(W2− W1)× 100
Where: W1 = weight of the container, W2 = weight of the container + sample, W3 = weight of the container + dried sample.
𝐓𝐨𝐭𝐚𝐥 𝐬𝐨𝐥𝐢𝐝𝐬 (%) = 100 − % MC
Protein content: Protein content was estimated by the Formol titration [20]. 10 ml sample was pipetted into a conical flask and added 1 ml of 2.5% phenolphthalein and 0.4 ml saturated potassium oxalate. The mixture was left for 2 min. Neutralization sample to a faint color with 0.1 M NaOH from a burette. 2 ml of 40% formaldehyde (previously neutralized to phenolphthalein with 0.1 M NaOH) was added. Continue the titration with the same pink color as previously and record the amount of 0.1 M NaOH required for the second titration only. Blank was prepared by 2 ml of 40% formaldehyde mixed with 10 ml DI water and 1 ml of 2.5% phenolphthalein. Protein content was calculated as follows:
% protein content = (V2− V1) × 1.7
Where: V1 = volume of NaOH titrated with blank, V2 = volume of NaOH titrated with sample.
Fat determination: Fat content was determined by the modified Mojonnier ether extraction method [20], [21]. Fatcontent was determined gravimetrically after extraction with diethyl ether (ethoxyethane) and petroleum ether from an ammonia alcoholic solution of the sample. Sample (5 g) was taken into a separatory funnel. 1.5 ml of ammonia and a few drops of phenolphthalein were added. The mixture was mixed with 10 ml ethanol. Added 25 ml diethyl ether, shacked vigorously and added 25 ml petroleum ether, and stood for 30 min. The extraction
in the distillation flask for 30 min. Extracted sample was removed to a flask. 5 ml DI water was added and boiled at 80-90 ⁰C. Extracted fat was dried in a hot air oven at 105 ⁰C for 15 min. The extracted fat is expressed as percent fat per weight.
% Fat =(W2− W1) − (WB− W1)
W × 100
Where: W = weight of sample, W1 = weight of flask, W2 = weight of flask + fat, WB = weight of blank.
Vitamin C: Vitamin C was determined by a method of Titromateric which modified by [20], [22]. Drinkable yogurt (10 ml) pipetted into 250 ml Erlenmeyer flask and 2 ml MPA (metaphosphoric acetic acid) was added. The mixture was titrated by DCP standard (2,6-dichlorophemolindophenol). Vitamin C content was expressed as mg/100ml and calculated as follows:
Vitamin C =
1 A× B
10 × 100
Where: A = volume of DCP titrated with vitamin C standard, B = volume of DCP titrated with sample.
Ash content determination: Ash content of each of the samples was determined at 550 ⁰C according to [21]. The Nabertherm GmbH furnace was used. Drinkableyogurt (10g) was heated on a hot plate at 550 ⁰C for 30 min prior to burning in a furnace [23]. Ash content is expressed as a percentage of the total weight of sample incinerated.
% Ash =(W3− W1) × 100 (W2− W1)
Where: W1 = weight of crucible, W2 = weight of crucible + sample, W3 = weight of crucible + ash.
Calcium content: Calcium content was determined by permanganate titration [20].
Residue ash sample from ash analysis was used. Ash sample was mixed with 5 ml of 3 M HCl, heat on a hot plate and another 5 ml of 3 M HCl was added. Ash solution was placed in a beaker and made volume up to 40 ml ofDI water, then heat for 10 min. The solution was cooled down at room temperature. The sample was filtered through Whatman No. 1 paper in 100 Erlenmeyer flask and made volume up to 100 ml using DI water. 50 ml of the solution was placed in a 250 ml beaker with dilute NH4OH until blue color, then added acetic acid to made red color. The solution was boiled, added an excess of ammonium oxalate (about 0.8g), boil vigorously for 1 min and gentled for 30 min. The supernatant was poured through a Whatman No. 1 paper in a funnel and washed the precipitate twice with hot water in a beaker. The precipitate was heated with 60 ml of 2 M H2SO4 at 60 ⁰C. Warmed to 70 ⁰C and titrated with 0.01 M KMnO4 solution to a persistent pink color. Calcium content was expressed as a percent and calculated as follows:
% Calcium =T × 0.1 W Where: T = volume of KMnO4 titrated, W = weight of ash.
Measurement of total phenolic content (TPC): TPC was estimated using Folin–Ciocalteu assay [24], with slight modifications. TPC was determined by using spectrophotometry, and gallic acid was used as a standard [25]. Concentration of gallic acid was prepared with ethanol at 0, 0.05, 0.1, 0,2, 0.4, 0.6, 0.8 and 1.0. Sample (5 g) added 20 ml of 70% ethanol for the extraction phenolic compound. Extracted sample (0.1 ml) mixed with 0.4 ml DI water,2.5 ml of Folin–
Ciocalteu reagent (1:9; Folin–Ciocalteu reagent: DI water) and 2.5 ml of 7.5% (w/v) Na2CO3, stirred 10 sec. Then the mixture was heated at 45 °C for 15 min in a water bath. The mixture could stand at room temperature for 30 min. TPC was determined at 765 nm. TPC was expressed as gallic acid equivalents mg/g (GAE)[26].
Sensory analysis
Sensory evaluation: was carried out using a 5-point hedonic scale[27],[28]. The scale and categories are as follows: 1 = Disliked much, 2 = Disliked, 3 = Neither liked nor disliked, 4 =
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Liked and = 5 = Liked much. All samples were evaluated for appearance, flavor, taste, consistency and general acceptability were evaluated by 24 students who were trained.
Statistical analysis
All experiments were run in the statistical analysis. Data obtained were subjected to analysis of variance (ANOVA) using Statistix (version 8.0) in completely randomized design according to the methods of [29]. When results were found significant, means were separated using least significant difference (LSD) at a level of 0.05. Correlation analyzes were applied where necessary to establish the extent of relations between variables.
Results
Physicochemical properties of jamun drinkable yogurt
pH: pH of jamun drinkable yogurt samples is summarized in Figure 1A.100% SM showed the highest average pH of 4.62 with a standard deviation of 0.03 while 100% CM showed the lowest average pH of 4.41standard deviation of 0.05 (P < 0.05).
Total lactic acid: Lactic acid was expressed by titratable acidity, showed in Figure 1B.
Drinkable yogurt from 100% of CM had the highest lactic acid of 0.46%, whereas 100% SM had the lowest lactic acid of 0.26% (P < 0.05).
Phase separation: The average percent of phase separation of these samples after stored 5 days were exhibited in Figure 1C. Drinkable yogurt samples made with 100% SM had the greatest phase separation about 68.89%, although made with 100% CM had the lowest phase separation about 27.04% (P < 0.05).
Moisture content: As shown in Figure 2A, MC of these products was ranged from 54.00%
to 65.80%. 100% CM and 75% CM : 25% SM made drinkable yogurt samples had the highest MC, while 100% SM exhibited the lowest. But all samples were not significantly different (P >
0.05).
Figure 1: Chemical analysis of jamun drinkable yogurt, A: pH, B: total lactic acid, and C: phase separation.
Sugar determination
Total soluble solid (TSS): The percent of TSS for samples were displayed in Table 1.
Drinkable yogurt made with 100% CM had the largest TSS with 14.07°Brix, although made with 100% SM had the smallest TSS with 8.97°Brix (P < 0.05).
Total sugar: The total sugar content of the drinkable yogurt samples was abridged in Table 1. 100% CM presented the highest average total sugar with 24.48%, while 100% SM showed the lowest average total sugar with 16.96% (P < 0.05).
b b
a b b
4.0 4.2 4.4 4.6 4.8
100:0 75:25 50:50 25:75 0:100
pH
CM:SM ratio (%)
a ab
b b
c
0.0 0.2 0.4 0.6
100:0 75:25 50:50 25:75 0:100
Total Lactic acid (%)
CM:SM ratio (%)
c bc ab ab
a
0 20 40 60 80
100:0 75:25 50:50 25:75 0:100
Phase separation (%)
CM:SM ratio (%)
A B C
Table 1: Total soluble solids (TSS) and sugar of jamun drinkable yogurt.
CM:SM ratio TSS (°Brix) Reducing sugar (%) Total sugar (%) Non-reducing sugar (%)
100:0 14.07±0.42a 9.33±0.40a 24.48±0.86a 15.16±1.27ns
75:25 13.87±0.81a 8.19±0.06ab 23.21±0.66ab 15.03±0.60ns
50:50 13.47±0.47a 7.27±0.42ab 21.70±0.54b 14.43±0.96ns
25:75 10.57±0.50b 5.29±0.54bc 18.30±0.72c 14.86±0.18ns
0:100 8.97±0.35c 4.81±0.57c 16.96±0.11c 12.15±0.67ns
Reducing sugar: An appropriate amount of reducing sugar in jamun drinkable yogurt products was observed as shown in Table 1. The average range of reducing sugar was from 4.81%
to 9.33%, which 100% CM provided the highest reducing sugar and 100% SM was the lowest amount (P < 0.05).
Non-reducing sugar: Table 1 showed the non-reducing sugar mean of samples ranged from 12% to 15%, with was not significantly different (P > 0.05).
Nutritional value of jamun drinkable yogurt
Total solid content: Total solid content of each sample was revealed in Figure 2B. 100%
SM had the highest total solid of 46.00%, whereas 100% CM and 75% CM : 25% SM contained less total solid about 34%. All samples were not significantly different (P > 0.05).
Figure 2: A: moisture content, and B: total solid of jamun drinkable yogurt.
Fat content: Fat content of jamun drinkable yogurt was exposed in Table 2. There was not significantly different from percentage of fat content in these samples (P > 0.05). The highest percentage of fat content was about 0.6 (75% CM : 25% SM and 50% CM : 50% SM), while the lowest percentage of fat content was 0.27 (100% SM).
Ash content: Drinkable yogurts obtained ash content between 0.40% to 0.45% (Table 2). There was not significantly different (P > 0.05). The Ash value of the 100 % CM was the highest and 100% SM provided the lowest value.
Calcium content: Calcium content of the samples was shown in Table 2. Drinkable yogurt made from 100% CM had the greatest calcium content with 0.11% and from 100% SM had the lowest amount to 0.02% (P < 0.05).
Vitamin C: This water-soluble vitamin was not significantly different (P > 0.05). Vitamin C of 100% SM was the highest with 7.06 mg/100g, whereas 100% CM contained the lowest vitamin C with 6.67% (Table 2).
Protein content: Table 3 showed mean of protein content. Protein content was higher when drinkable yogurt made with 100% CM (8.16%) than made by combined 75% CM : 25% SM, 50% CM : 50% SM, and 100% SM (8.08, 7.76, 7.79 and 6.40, respectively).
20 30 40 50 60 70
100:0 75:25 50:50 25:75 0:100
Moisture content (%)
CM:SM ratio (%)
10 20 30 40 50 60
100:0 75:25 50:50 25:75 0:100
Total solid (%)
CM:SM ratio (%)
A B
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Table 2: Proximate analysis of jamun drinkable yogurt CM:SM
ratio Fat (%) Ash (%) Calcium (%) Vitamin C
(mg/100g) Protein (%) 100:0 0.38±0.07ns 0.45±0.09ns 0.11±0.02a 6.67±0.79ns 8.16±0.74a 75:25 0.61±0.68ns 0.43±0.04ns 0.12±0.03a 7.32±0.99ns 8.08±0.47a 50:50 0.62±0.40ns 0.43±0.08ns 0.08±0.04ab 7.19±1.13ns 7.76±0.57a 25:75 0.40±0.12ns 0.41±0.06ns 0.04±0.01bc 6.80±0.99ns 7.79±0.40a 0:100 0.27±0.18ns 0.40±0.02ns 0.02±0.01c 7.06±1.18ns 6.40±0.50b
Total phenolic content (TPC): The results exhibited that not significantly different in the TPC of drinkable yogurt (P > 0.05). The TPC of jamun drinkable yogurt products were ranged from 20 to 22 GAE/100g (Figure 3B).
Figure 3: A: Standard curve of gallic acid, and B: total phenolic content of jamun drinkable yogurt.
Sensory evaluation
Figure 4 displays the observed of sensory evaluation of jamun drinkable yogurts. 100% CM had a white pink color while increasing SM was an off-white color; mean color scores were 4.17, 3.42, 2.92, 2.71 and 2.38, respectively (P < 0.05). Average scores of appearances had a range from 2.63 to 3.58 (P < 0.05), which 100% CM and 75% CM : 25% SM exhibited a good appearance. The smell of drinkable yogurt made from 100% CM got the highest score with 3.42, while samples of 75% CM: 25% SM, 50% CM: 50% SM and 100% SM were not significantly different. Samples of 100% CM and 75% CM : 25% SM were smoothness enough to drink, which mean scores for smooth were 3.54 and 3.38, respectively. Average mean scores of sweet and sour tastes was not significantly different (P > 0.05). Most assessors accepted the jamun drinkable yogurt made from 100% CM and 75% CM : 25% SM, which led the highest score with 3.50, whereas other samples got 3.04, 2.71 and 2.38, respectively.
Figure 4: The sensory characteristics of jamun drinkable yogurts.
y = 1.869x - 0.0113 R² = 0.9958
0 0.5 1 1.5 2
0 0.2 0.4 0.6 0.8 1
Absorbance at 765 nm
Concentration (mg GAE/ml)
5 10 15 20 25
100:0 75:25 50:50 25:75 0:100
Total phenolic conten (mg GAE/100g)
CM:SM ratio (%)
0 1 2 3 4 5
Color
Appearance
Smell
Smooth Sweet
Sour Overall
Acceptance 100:0
75:25 50:50 25:75 0:100 CM:SM ratio (%) A
B
Discussion
Effect of CM and SM composition on physicochemical properties of jamun drinkable yogurt Changes in pH and lactic acid content indicates the activity of the starter culture during milk fermentation. pH increased and lactic acid of jamun drinkable yogurt products decreased with increasing SM, suggesting lower content of probiotics in SM. The main prebiotic for this product is lactose and [30] reported that CM is a main source of lactose while SM contains sucrose and fructose. Lactic acid fermentation of milk depended on the action of the starter culture bacteria, including Streptococcus thermophilus and Lactobacillus bulgaricus [34] which used lactose and fructose, and converted it to lactic acid through the Embden-Meyerhof-Parnas (EMP). However, Lactobacillus bulgaricus cannot convert sucrose to lactic acid, because this bacterium could not produce the invertase enzyme needed for breaking down sucrose [30]. [35]
reported that pH of soy yogurt ranged between 4.7-4.26. Drinkable yogurt should have contained pH between 4-4.5 [36].
Phase separation in this study increases with increasing amounts of SM. [37] explained that phase separation or whey separation was greatly augmented when adding SM in yogurt making.
Casein is a major protein in CM which contain 80% of total protein, whichplays an important role in holding water [38]. [39] reported that SM did not have casein. Previous study showed that phase of drinkable yogurt was separated immediately after thermal treatment, including pasteurization or sterilization [40]. [41] exhibited that proteins were denatured (unfolded) and precipitated by high thermal treatment. [42]-[44]suggested that addition of stabilizer such as CMC (carboxymethylcellulose) and HMP (high methoxy pectin) should be extended phase separation of drinkable yogurt.
MC decreases with increasing SM, which is like research of [45]. [3]explained that theMC of yogurt is indicated the thickness and it increased by adding SM.
Ratio of SM and CM effect on sugar content of jamun drinkable yogurt
Results from Table 1 show that addition of SM significantly decreased level of TSS, reducing sugar, total sugar and non-reducing sugar of jamun drinkable yogurt. Reducing sugar is a reducing agent because it has a free ketone group.Glucose, galactose, maltose, lactose and fructose are reducing sugar. Sucrose and trehalose are non-reducing sugar. Brown color was produced by reducing sugar as non-enzymic browning reaction under some conditions upon heating and it is undesirable for long-term storage of food products[31]-[33]. Drinkable yogurt makes from CM alone contained high reducing and non-reducing sugar, whereas made from SM contained lower amounts.
Ratio of SM and CM effect on nutritional value of jamun drinkable yogurt
Addition of SM increased total solids of jamun drinkable yogurt, which similar results [37].
[47] reported that soy yogurt had higher total solid from 34.2% to 44.4%. SM was selected for making yogurt caused it contained high total solid [48].
Based on Table 2, fat content of drinkable yogurt using CM alone was higher than that made from SM alone, and the combination of CM and SM were increased fat content. According to [46] yogurt made from CM contained higher fat content than soy yogurt. [37] reported that fat content of soy yogurt from a combined of SM:CM (1:2) was higher than sample of 100% SM.
Ash content was not also improved by increasing SM. These results were similar [30],[46],[42]. [47] reported that the ash content of CM yogurt and soy yogurt was different amount and ash result expressed the mineral content which used to grow human bond, teeth and body.
Calcium content was decreased with increasing SM, which SM alone was low calcium content and indicated that the viscosity of the product decreased. [11] reported that CM is a good source of calcium (290.36 mg/cup) while SM contains only 9.8 mg/cup. [51] explained that casein exists in fresh milk in the form of a “micelle” structure, which is a complex protein aggregate by calcium and responsible form water holding. Thus, smooth of drinkable yogurt from SM was lower than CM [42].
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Vitamin C was not affected by various ratios of CM and SM. The main source of vitamin C was from jamun juice [53]. According to [54] and [55] reported that CM was source of fat soluble vitamin such as vitamin A, D, E and K. Soybeans contained low vitamin C about 6.0 mg [56], vitamin C of soy products was disappeared by heating [57].
Protein content measures by Formol method expressed that protein content decreased with increasing SM. [45] informed that yogurt made from CM contained higher protein content than soy yogurt. [11] reported that the protein content of CM was 0.033 g/ml greater than SM (0.028 g/ml).
Total phenolic content was not affected by increasing SM because most of phenolic compound was provided by adding jamun juice. The main source of phenolic compound was from plants, including fruits [58]. A phenolic compound of jamun juice after cooking was approximately 129 mg GAE/100g [59] and SM contained 2.5 mg GAE/100g [60] whereas CM contained 0.7 µg GAE/100g [61]. [59] total phenolic content was reduced by heating.
Effect of SM and CM on sensory quality of jamun drinkable yogurt
According to sensory value (Figure 4) showed that all sensory factors decreased with increasing SM. The average scores of color from 100% CM and 75% CM : 25% SM were not different, supported by studying of [45]. [47] suggested that soy yogurt normally was a yellowish color. Flavor of SM products wasa major limiting factor which hinders the use of SM [14], therefore increasing SM for jamun drinkable yogurt get the lowest score of flavor. [37] suggested that using SM was decreased smoothness and appearance. Sour taste decreased with increasing SM caused acid of these samples was lower [62]. Overall acceptability of jamun drinkable yogurt was suggested that sample of 100% CM and 75% CM : 25% SM were accepted by most assessors.
Conclusions
The results of this research suggest that jamun drinkable yogurt produced from cow milk alone or soymilk alone or their combination produces different physicochemical and sensory properties.Increasing soymilk from 50% or higherreduces physicochemical properties of drinkable yogurt such as pH, total acid, phase separation and moisture content. Nutritional values, including total solid, fat, ash, vitamin C are not affected; whereas calcium and protein content is decreased with increasing soymilk. Sensory evaluation indicates that assessors preferred drinkable yogurt made using cow milk alone or combined 75% cow milk and 25% soymilk. Smell and color are a problem which maintains when increasing soymilk.Further work will be conducted to investigate the changes of the protein structure of milk by thermal treatment and application of emulsion stability by emulsifier or stabilizer to extend shelf-life of drinkable yogurt.
Acknowledgements
This research was supported by University of Battambang, Cambodia and University of Technology Isan, Surin Campus, Thailand.
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