Surveying the Effect of Oat Beta Glucan As a Fat Replacer on Rheological and Physicochemical Characteristics of Non Fat Set Yoghurt

Transcription

1 International Journal of Farming and Allied Sciences Available online at IJFAS Journal / ISSN IJFAS Surveying the Effect of Oat Beta Glucan As a Fat Replacer on Rheological and Physicochemical Characteristics of Non Fat Set Yoghurt Elham Nikoofar 1, Mohammad Hojjatoleslamy 1*, Amir Shakerian 1, Homan Molavi 1, Mohammad Ali Shariaty 2 1. Department of food science and technology, ShahreKord branch, Islamic Azad University, Shahrekord,Iran 2. Department of food science and technology, Science and Research Branch, Islamic Azad University,Tehran,Iran Corresponding author: Mohammad Hojjatoleslamy ABSTRACT: Increased awareness of people on fitness and healthy lifestyle has led to increased demand for low-calorie foods in particular for low fat or reduced fat foods. Oat beta glucan, a water soluble fiber is an indigestible polysaccharide that is made from β- D- glucopyranose units. In this study oat beta glucan fiber in amount of 0.5, 1, 1.5 and 2 %( w/w) was used in production of non fat yoghurts. Properties of manufactured samples to investigate the beta glucan s effect on yoghurt characteristics were compared with non fat and full fat yoghurts without beta glucan. Tests had been done were consist of measurement of acidity, syneresis, color, texture tests (compression test, stress- relaxation test, texture profile analysis (TPA) test). Results of these tests showed that the acidity of samples containing beta glucan were higher due to the ability of beta glucan to increase the activity of acid producing bacteria s in fermentation. The synereses of samples containing beta glucan were increasing due to the interaction of beta glucan polysaccharide with milk casein. Colors of samples containing beta glucan were darker than testifiers. Texture tests showed that samples containing beta glucan had firmer and stickier texture in comparison with samples without beta glucan. In general, samples containing beta glucan had a firm and creamy texture. Keywords: beta glucan, fiber, non fat, physicochemical properties, texture, yoghurt INTRODUCTION Dietary factors are implicated in the etiology of a number of chronic degenerative diseases. Healthconscious consumers continue to look for ways to improve nutritional habits without sacrificing psychological satisfaction. High fat intake is associated with increased risk for some types of cancer, and saturated fat intake is associated with high blood cholesterol and coronary heart disease. Also, consumption of a diet rich in fat has been identified as a risk factor for excess energy intake, positive energy balance, and the development of obesity (Ognean et al., 2006; Kahkonen, 2000). As a food component, fat contributes to key sensory and physiological benefits. Fat contributes to flavor, or the combined perception of mouth feel, taste, and aroma. Fat also contributes to the creaminess, appearance, palatability, texture, and lubricity of foods and increases the feeling of satiety during meals. Some lipids may be replaced in foods by reformulating with selected ingredients that

2 provide some fat-like attributes. These fat replacers can be lipid, protein or carbohydrate-based (Ognean et al., 2006). Cereal beta glucan is a water soluble fiber that typically found in the endosperm cell wall in oats, barley and wheat. Beta glucans derived from cereals are polymers of D- glucose with β (1 3) and β (1 4) linkage (fig1)( Bangari, 2011; Havrentova et al., 2011). Cereal beta glucan can be used as a fat replacer. It can add body and texture to low fat products (Ognean etal., 2011) Fig 1. basic structure of cereal beta glucan (Bangari, 2011) Beta glucan is also a dietary fiber that can be added to the foods because if it s proven health effects. Oat beta glucan actively lower blood LDL and total cholesterol (European Food Safety Authority, 2010; Pins and Kour, 2006). It also contributes to glycemic control and due to its viscosity and fermentibility; beta glucan plays a significant protective role against insulin resistance in various populations (El Khoury et al., 2012; Bays et al., 2011; Poppitt et al., 2007). Addition of hydrocolloids and gums in dairy products had been studied repeatedly. Addition of xantan and carrageenan in yoghurt led to decrease syneresis (Hematyar et al., 2012). Effects of inulin and partially hydrolyzed guar gum on the rheological, textural and sensory quality of low-fat yoghurt based products had been studied. The obtained results suggests that this dietary fibers caused to improve yield of yoghurt, decrease syneresis and overall improved acceptability in terms of sensory attributes (Brennan and Tudorica, 2008). In this study we survey the effect of oat beta glucan on the rheological and physicochemical characteristics of low fat yoghurt and compare them with non fat and full fat yoghurts without beta glucan. MATERIALS AND METHODS Non fat and full fat homogenized milk was prepared from PakPey dairy factory (Shahre Kord, Iran). Oat beta glucan (80% beta glucan) (MCRO Co, The Netherlands) was used. For inoculation of frozen starter culture No CY-220 consist of Streptococcus thermophillus and Lactobacillus delbrueckii subsp bulgaricus (DMC Co, Australia) was used. Homogenized milk with 2.5% fat and full fat, as testifier, combined with 2 %w/w skim milk powder and then heated. At C 0.5, 1, 1.5 and 2 % w/w oat beta glucan was added. Milk heated up to 80 C for 10 mins. Milk cooled up to 45 C and starter culture was added (0.02%v/v). After incubation in 45 C for 4 hours, samples move to refrigerator (4 C). A non fat sample without fiber and a full fat one were produced as a testifier as the way as above. Acidity measurment Acidity of samples was measured according to Dornic method. According to this method the acidity determined by end point titration of 10 ml yoghurt sample using 0.1 eq/l NaOH. The acidity of yoghurt samples calculate in this way: R= V (titr) * C (titr) * 90 * 10/ V (smp) V (titr): total volume titrant to reach end point in ml C (titr): titrant concentration in eq/l (currently 0.1) V (smp): sample volume in ml 90: molecular weight of lactic acid 10: factor for result expression in decigram/l Syneresis test To investigate susceptibility to syneresis, samples of 4-5 g were centrifuged at 2500 rpm for 10 min at room temperature. After centrifugation, the serum phase was poured off and remaining material weighed. The difference in the weight of the sample before and after centrifuge recorded as syneresis (%). 791

3 Texture Measurement Compression test, compression-relaxation test, and texture profile analysis (TPA) were performed on the intact yoghurt samples using a Brookfield texture analyzer-ct III (Middleboro, MA, USA). For these tests samples were taken out of refrigerator (4 C) just before test operation and sample s jar was about 2-fold longer than the probes diameter to minimize sidewall effects. Compression test to measurement the force for breaking the yoghurt gel was performed with probe number TA11/1000 at the distance target of 10mm, with speed of 1mm/s. Stress- relaxation test was done with probe number TA4/1000; distance target was 2mm, speed of 1mm/s and hold time of 120s. From this essay initial maximum force, the force in the contact area at time0; minimum residual force, the force that is not reversible by sample at the end of test; and relax able force, the force that is reversible by a sample at the end of test would be obtained. The quotient of minimum residual force to initial maximum force is equal to the percentage of structured that is broken down and is not recovered at the end of the test. Texture profile analysis (TPA) was performed by two sequential compression tests and a rest phase of 30s between them. The probe number TA25/1000 with the speed of 1mm/s was used. Target distance was 2 mm. From this test hardness, adhesiveness, cohesiveness, springiness, gumminess and chewiness values can be obtained. Color Measurement To measure the color parameters, pictures of the samples were taken in a controlled condition with a 16.2 mega pixels digital camera (Sony Cyber-shot, Japan). These pictures were analyzed with image pro plus program, version 6. Color parameters consist of L, A and B values evaluated to 10 times and their average investigated for each sample. Data Analysis Data obtained from tests were analyzed with SPSS statistical software No 19 and ANOVA test. RESULTS AND DISCUSSION Results of acidity test Results of acidity measurements of samples are shown in Figure 1. These results showed an increase in the acidity amount in samples containing beta glucan. Increasing the acidity of samples containing beta glucan as mentioned in previous studies (Havrelentova, 2011) can be due to beta glucan s effect on increasing the production of acetic and propionic acids during fermentation. Figure 1. results of acidity test in yogurt samples Results of syneresis test Measurements of syneresis in non fat and full fat samples are shown in Figure 2. According to these results, addition of oat beta glucan fiber led to increase in the syneresis of non fat yoghurts compared with non fat and full fat yoghurts without beta glucan. Unlike the results of studies that showed addition of cereal beta glucan to stirred yoghurt would decrease the syneresis in samples (Tudorica, 2004), in this study beta glucan fiber causes an increase in the syneresis in set yoghurts. It can be due to the thermo dynamical incompatibility between casein and beta glucan as a non-interacting polysaccharide. In such systems a weak protein network of acid milk gels with increased porosity will be produced.as mentioned in the previous study, (Corredig et al., 2011; W.de Bont et al., 2004) addition of a non-interacting 792

4 load(n) syneresis(%) Intl J Farm & Alli Sci. Vol., 2 (20): , 2013 polysaccharide to milk, causes depletion in the flocculation of the casein micelles. The incompatibility between the biopolymers causes the formation of a depleted layer around the casein micelles, which attracts casein micelles to each other. So, it results in the separation of the mixture in two liquid layers one rich in protein (casein) and the other rich in polysaccharide (beta glucan). day1 day7 day14 day nonfat0.5 nonfat1 nonfat1.5 nonfat2 nonfat blank full fat Figure 2. results of syneresis test in yoghurt samples Results of texture tests The Maximum force needed for breaking the yoghurt gel measured by the compression test is shown in Figure 3. These results showed that the non fat yoghurts containing beta glucan have lower maximum force than non fat and full fat samples without beta glucan. Results of stress- relaxation test are shown in table 1. These results showed an addition of beta glucan caused to decrease the elasticity of yoghurts compared to non fat and full fat blank samples. Yoghurts containing beta glucan also had weaker structure and more lost of structure against force. day1 day7 day14 day nonfat0.5 nonfat1 nonfat1.5 nonfat2 nonfat blank full fat Figure 3. results of compression test in yoghurt samples Results of texture profile analysis are shown in table 2. These results showed that full fat and non fat yoghurt without beta glucan was harder and more adhesive than non fat samples containing beta glucan fiber. In full fat and non fat samples without beta glucan, gumminess and chewiness also were more than non fat yoghurts containing beta glucan. The springiness in non fat yoghurts had no significant difference with non fat and full fat blank yoghurts. Cohesiveness in non fat yoghurts containing beta glucan increased compared to non fat and also full fat yoghurts without beta glucan fiber. Addition of beta glucan caused to increase the stringiness compared to non fat and full fat blank yoghurts. As mentioned above, in interaction between beta glucan (polysaccharide) and casein micelles, the particles and polymer have no specific interaction besides excluded volume. The polymers are therefore excluded from the surface of the sphere. This results in an effective excluded (depletion) layer where the osmotic pressure, generated by the polymer segments, is smaller than in the bulk (Kruif et al., 2001). So the casein gel in this situation is weak and with less flexibility accordingly. results of textural tests showed less hardness, less gumminess, less adhesiveness and destruction of gel structure in stress-relaxation test was more in yoghurts containing oat beta glucan but this yoghurt had a firm and creamy texture that was near to creamy mouth feel of full fat yoghurt. 793

5 Table 1. Results of stress-relaxation test in yoghurt samples test day Skim0.05%* Skim1% Skim1.5% Skim2% skimblank Full fat Maximuminitialforce(N) Table1- continue residualforce(n) Relaxable force(n) Lost structure (%) * Percentages show amount of oat beta glucan in yoghurt samples Table 2. results of TPA test in yoghurt samples Test Day Nonfat0.5%* Nonfat1% Nonfat1.5% Nonfat2% Nonfatblank Full fat Hardness b** b a a c d b a a b c d d c a b e f c b a a d e Adhesiveness ab 0.30 a 0.36 ab 0.34 ab 0.43 b 1.67 b bc 0.28 a 0.32 ab 0.29 a 0.55 c 1.17 d b 0.29 a 0.41 b 0.39 b 0.43 b 0.78 c a 0.30 a 0.34 a 0.34 a 0.45 a 1.02 b Cohesiveness d 0.86 d 0.79 d 0.71 c 0.47 a 0.59 b a 0.90 b 0.88 b 1.01 b 0.43 a 0.52 a bc 0.85 bc 0.90 c 0.86 bc 0.74 b 0.49 a c 0.86 c 0.90 c 0.71 b 0.46 a 0.49 a Gumminess c c a a b d b b a b b c c b a a c d c b a a b d Chewiness c 2.40 c 1.17 a 1.10 a 1.64 b 6.14 d b 1.94 b 1.08 a 1.47 ab 1.70 ab 4.82 c ab 1.91 ab 0.99 a 1.10 a 2.56 b 4.71 c c 2.40 c 1.03 a 1.10 a 1.82 b 4.99 d springiness abc 1.92 bc 1.78 abc 1.75 ab 1.87 a 1.88 c b 1.94 b 1.91 b 1.92 b 1.78 a 1.70 a 794

6 ab 1.88 b 1.90 b 1.85 b 1.41 a 1.65 ab b 1.92 b 1.78 b 1.75 b 1.46 a 1.72 b stringiness a 1.26 b 1.47 b 1.37 b 0.97 a 1.40 b Table2- continue ab 1.51 bc 1.68 c 1.74 c 1.10 a 1.36 ab b 1.35 b 1.66 c 1.68 c 1.00 a 1.35 b b 1.26 bc 1.58 d 1.37 cd 0.63 a 1.20 bc * Percentages show amount of oat beta glucan in yoghurt samples ** a,b, show the homogeneous groups after means comparing ( p 0.05) Color parameters are explained as L value from black (0) to white (100), A value from green (minus values) to red (plus values) and B value from blue (mines values) to yellow (plus values) that are showed in table 3. From these data it could be noticed that L value was decreased with increase in the amount of beta glucan. B value in yoghurts containing beta glucan increased and A values were decreased. From these results it can be concluded that the whiteness of samples containing beta glucan were slightly decreased while yellowish were slightly increased with increase of beta glucan percentage fortification. Table 3. Color properties of yoghurt samples treatment L A B Full fat Nonfat 0.5% Nonfat1% Nonfat1.5% Nonfat2% Nonfat blank CONCLUSION From the results of the present work, it can be concluded that the addition of oat beta glucan fiber to semi fat yoghurts has rheological and physicochemical influences on yoghurt. In non fat yoghurt fortified with oat beta glucan, the syneresis was more than full fat samples and these non fat samples had firmer and less elastic structure (low maximum force in compression test and less elastic properties obtained from stress- relaxation test, lower hardness, chewiness and gumminess in TPA test). Incorporation of high molecular weight beta glucan in milk results in weakening of the structure. This weakening of the gel structure could be reduced using higher concentration promotes an increase in viscosity of the consequent decrease in the rate of formation of the phase separated domains(corredig et al., 2010) use of surfactants and/or stabilizers can be studied too. REFERENCES Bangari S Effects of oat beta glucan on the stability and textural properties of beta glucan fortified milk beverage. Master of Science thesis. University of Wisconsin- Stout. USA. 795

7 Bays H, Frestedt J L, Bell M, Williams C, Kolberg L, Schmelzer W, Anderson J W Reduced viscosity barely beta glucan versus placebo: a randomized controlled trail of the effects on insulin sensitivity for individuals at risk for diabetes mellitus. Nutrition & Metabolism, 8: Brennan C, Tudorica C Carbohydrate-based fat replacer in the modification of the rheological, textural and sensory quality of yoghurt: comparative study of the utilization of barely beta-glucan, guar gum and inulin. International journal of food science and technology, 43: EFSA Panel on Diabetic Products, Nutrition and Allergies Scientific opinion on the substantiation of a health claim related to oat betaglucan and lowering blood cholesterol and reduced risk of (coronary) heart disease pursuant to article 14 of regulation (EC) No EFSA Journal 8(2): El Khairy D, Cuda C, Luhovyy B L, Anderson G H Beta glucan: health benefits in obesity and metabolic syndrome review article. Journal of Nutrition and Metabolism. Vol. 2012: 1-28 Havrlentova M, Petrulakova Z, Burgarova A, Gago F, Hlinkova A, Sturdik E Cereal β- glucans and their significance of the preparation of functional foods- review. Czech J. food SCI. Vol 29, No.1: 1-14 Hematyar N, Mohagheghi Samarin A, Poorazarang H, Elhamirad A H Effect of gums on yoghurt characteristics. World applied sciences journal, 20 (5): Kahkonen P Consumer acceptance of reduced- fat foods- the effects of product information. Academic dissertation. University of Helsinki, Department of food technology. Kruif C G, Tuinier R Polysaccharide protein interactions. Food Hydrocolloids 15: Ognean C F, Darie N, Ognean M Fat replacers- review. Journal of Agro alimentary Processes andtechnologies. Vol XII, No 2: Pins J J, Kour H A review of the effects of barely beta glucan on cardiovascular and diabetic risk. Cereal foods world, No 1: 8-11 Poppitt S D, Drunen J, McGill A T, Mulrey T B, Leahy F E Supplementation of a high carbohydrate breakfast with barely beta glucan improves postprandial glycamic response for meals but not beverages. Asia Pac J Clin Nutr, 16: