ORGANIC RICE BRAN MILK: PRODUCTION AND ITS NATURAL QUALITY ATTRIBUTES

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1 ORGANIC RICE BRAN MILK: PRODUCTION AND ITS NATURAL QUALITY ATTRIBUTES Utthapon Issara and SAROAT RAWDKUEN* Food Technology Program, School of Agro Industry, Mae Fah Luang University, Thailand *Corresponding author, Abstract: Rice bran is an underutilized milling by-product of rough rice and has high nutritional value. However, using the whole rice bran (without isolating into a single component) has not been reported. Therefore, this study was aimed to utilize the whole organic rice bran for Rice Bran Milk (RBM) production. Quality attributes in terms of physico-chemical, stability, biological and sensory properties of RBM were compared with the commercial soy milk. Three different ratios of rice bran to water (1:5, 1:10 and 1:15 w/v) were prepared and their properties were determined. Proximate analysis showed reduction of content for each component, which depend on the dilution. Significant differences in protein, fat, and carbohydrate content in the sample ratio of 1:15 were observed when compared with the soy milk (p<0.05), while this was not found for moisture, ash, and fiber content (p>0.05). Rice bran milk (ratio of 1:15) also showed significantly lower in TSS (3.7 o Brix), viscosity (3.05cP), and total sugar content (0.38%) when compared with the soy milk (11.7 o Brix, 9.85cP, and 5.80%, respectively) (p<0.05). The highest whiteness and L* value was observed in soy milk. However, the highest stability was found in RBM with the ratio of 1:5. Total polyphenol content as well as the DPPH radical scavenging activity was also directly affected by the dilution. High amount of water added to produce RBM lowered the phenolic content and biological activity. However, the values obtained were higher than those presented in the commercial soy milk. Sensory profile evaluation found that only color attribute was close to the commercial soy milk, whereas vast differences were observed in the attributes of appearance, taste, flavor, sweetness, and overall liking. These findings could be use as preliminary results for development of organic RBM that meet consumer quality requirements. Keyword: Rice bran, Milk, Organic, Soybean, Functional drink Introduction: Bran is an industrial residue of cereal from milling process. It consists of pericarp, aleurone and subaleurone fractions [1]. Generally, the bran is known that it have more importance nutrients including: soluble and non-soluble fibers, vitamins, minerals, lipids and proteins [2-4]. Rice bran is a good source of bioactive phytochemicals such as γ-oryzanol, tocopherols, and tocotrienols; which have health beneficial properties and antioxidant activity [5-6]. In the last decades until present, the amounts of rice bran is more than 60 million tons, which it is a production of the five largest rice producers worldwide such as Thailand, China, India, Indonesia and Bangladesh [3]. The previous studies reported about chemical composition of full-fat and defatted rice bran (percent dry basis) that was composed of carbohydrate ( %), protein ( %), fat ( %), ash ( %), and fiber ( %) [7]. The interesting nutritional qualities in oil, fiber, carbohydrate and proteins of rice bran have made it a valuable food material. Nonetheless, rice bran has been used for animal feed, rice bran oil extraction, wax production, and some used as a food ingredients [6]. In rice bran oil industry, the extraction offers the oil recovery around 13-20%, thus, the rest residues still contain other active components e.g. protein, fiber, carbohydrate, and minerals [8]. Moreover, by-product resulting from stabilized rice bran extraction is utilisable for human food; especially it is currently being used in baked products, energy bars, and protein fortification of powdered drink formulations [9]. Only a few papers associated with rice bran milk production and its properties have been reported. Furthermore, high nutrition in rice bran and the demand for functional food products drive the researchers try to develope whole rice bran related products. The beverage production from rice bran, rice bran milk, to be functional drinks is one of the alternative interesting aspects to added-value of rice bran. Apart from increasing the value, rice bran milk related products have not been launched in the market. As a consequence, the objective of this study is not only to produce the rice bran milk product, simultaneously to investigate its physical, chemical and biological properties but the comparison of those properties with commercial soy milk was also performed. Materials and Methods: 1. Organic rice bran preparation Stabilized organic rice bran (full fat) was obtained from Urmatt Co. Ltd., Chiang Rai province, Thailand. The rice bran was dried in the oven at 60 o C for 8 h, ground and then passed by sieving 82

2 machine (Retsch, AS200 Digit) with 35 mesh (500 µm) and stored in vacuum condition at -18 o C. This sample was used as the starting material for rice bran milk production. Soy milk (Japanese rice germ flavour and low sugar) bran DNA GABA of Daily plus Ltd., was purchased from the local supermarket (Tesco) in Chiang Rai, Thailand and use as a commercial control sample for comparison. This product was selescted according to its quality attributes, especially appreance is high similarity to rice bran milk. 2. Organic rice bran milk production Organic rice bran milk was prepared according to the method of Faccin et al. [3] with some modification. The ratio of rice bran to water was varied (1:5, 1:10, and 1:15 w/v). Then, the mixtures were blended using colloids mill machine at the speed of 3000 rpm for 15 min (ASAKO, YJTM85D-2P, China). The obtained suspension was filtered by sheet cloth for 3 times. After that, the filtrate was pasteurized at 72 o C, for 15 Sec and referred to as Rice Bran Milk: RBM. After thermal processing, the RBM was cooled. The obtained RBM was packed in 150 ml polypropylene (PP) plastic bottle under aseptic techniques and covered with Parafilm M Laboratory Film. 3. Proximate analysis Organic rice bran and RBM were determined for moisture, total ash and total lipid content according to the methods of the Association of Official Analytical Chemists [10]. Crude fiber was digested with acid and alkaline in crude fiber analyzer (Foss Tecator 10.1, Sithiphorn Associates Co.,Ltd.) according to AOAC [11]. For total nitrogen content was determined by using Kjeldahl method (conversion factor 5.95 to protein content. Total carbohydrate content was calculated by difference. 4. Physico-chemical properties determinations 4.1 Color measurement Color of RBM and soy milk was measured by using Color Quest XE (Hunter Lab, Virginia). Color of the sample was presented as L*, a*, b*, and E. Whiteness and E of RBM and soy milk were calculated as following: ( ) ( ) ( ) ( ) ( ) ( ) Where: L, a, b are the value of the commercial soy milk sample. 4.2 ph determination ph of RBM and soy milk was determined using ph meter according to method of Sadler [12]. Sample volume of ml was poured into 50 ml beaker, and then ph of sample was recorded. 4.3 Total sugar determination Total sugar of RBM was determined according to the method of Jame [13]. In brief, sample (50g) was weighed and put into 250 ml Volumetric flask and 5 ml of Carrez I and II solution was added. Then sample was diluted to the volume and filled with filter paper. Filtrated was transfered into 100 ml Volumetric flask and concentrate HCl was added. After that the sample was incubated in water bath at 70 o C, cool, and neutralized with NaOH (40% w/v). The Lane and Eynon Volumetric method was used to determine the total sugar content. 4.4 Total acidity determination Total acidity was determined according to the method of Sadler [12]. Sample (2g) was weighed and put into 250 ml Erlenmeyer flask and 90 ml of distilled water was added. Then 2-3 drops of phenolphthalein was added, and titrated with NaOH until reach end point (pink color). 4.5 Viscosity determination RBM and soy milk were evaluated the viscosity according to the method of Faccin et al. [3] with some modification. A Brookfield viscometer (Brookfield engineering labs Inc. Middleboro, Ma 02346, U.S.A) and UL Adapter spindle (UL-0) No.00 probe was used. 83

3 5. Stability of organic rice bran milk The stability of organic RBM was measured by pouring the RBM into 10 ml cylinder. Then the sample was kept at 4 o C for stability monitoring. The sample was observed for the precipitate during the 0, 3, 5, 7 day and recorded. 6. Biological activity determinations 6.1 Determination of total polyphenol content The total polyphenol content was determined according to the method described by the ISO [14], using gallic acid as a standard. Sample 0.5 ml was transferred into tubes containing 2.5 ml of 10% v/v Folin-Ciocalteu s reagent. Then, 2.0 ml of 7.5% w/v sodium carbonate solution was added. The mixture was left at room temperature for 1 h and then measured the absorbance at 765 nm using UV-visible spectroscropy. The total polyphenol was expressed as gallic acid equivalents (GAE) in g/100 g extract. 6.2 Determination of radical scavenging activity (DPPH) The DPPH assay was determined according to the method of Molyneux [15]. Sample 50 µl was mixed with 1950 µl of 60 µm of DPPH solutions. Then, the mixtures were left in the dark place for 30 min and measured the absorbance at 517 nm. The radical scavenging activity was expressed as µmol Trolox/100g dry basis. 7. Sensory evaluation RBM (ratio 1:15) at zero day of storage (immediately after pasteurization) and commercial soy milk were tested for sensory preference using nine-point hedonic scale with 50 untrained panalists (evaluated color, flavor, sweet, taste, appearance, and overall liking), where 0 was used disliked very much and 9 used for like very much, according to Stone and Sidel [16]. 8. Statistical analysis All determinations were performed in triplicate. Statistical analysis of the results was conducted by using the analysis of variance (ANOVA) and the Duncan s multiple range test at 95% confidence level by using SPSS software (SPSS 16.0 for window, SPSS Inc, Chicago, IL). Results and Discussion: Proximate composition The composition of organic rice bran, RBM and commercial soy milk is shown in Table 1. The proximate composition, except moisture content of RBM was shown significantly higher than those of rice bran (p<0.05). These results showed that all composition in the rice bran still remained in RBM after passed through the colloid mill process. The organic rice bran compositions were found different content when compared with other studied. According to Prakash [7] reported that the full-fat rice bran and defatted rice bran composed of carbohydrate ( %), protein ( %), fat ( %), ash ( %), and fiber ( %). Silva et al. [17] summarized that the different contents of rice bran composition possible caused from different sources and cultivars. In addition, when the ratio between rice bran and water increased, all composition decreased except moisture content. This caused by the dilution effect as well as the extractability of those compounds contain in rice bran. Table 1. Proximate composition of organic rice bran, RBM and commercial soy milk * Samples Compositions (g/100g) Moisture Ash Protein Fat Fiber Carbohydrate Rice bran 4.21±0.02d 9.18±0.02a 12.75±0.02a 21.48±0.02a 8.14±0.03a 48.44±0.44a RBM 1: ±1.86c 1.41±0.00b 1.82±0.03c 1.79±0.09c 2.92±0.13b 8.89±0.50b RBM 1: ±1.59b 0.68±0.15c 0.57±0.05d 1.60±0.37c 0.95±0.21c 8.13±0.54c RBM 1: ±2.11b 0.44±0.04d 0.19±0.06e 1.08±0.09d 0.62±0.14d 6.82±0.10d Soy milk 94.49±1.40a 0.48±0.10d 2.15±0.06b 2.14±0.07b 0.58±0.10d 0.74±0.08e * Mean ± SD of triplicate determination Mean with different letter in the same column are significant different at (p<0.05). However, when compared to commercial soy milk compositions, RBM (1:15) showed significantly different in moisture, protein, fat, and carbohydrate content (p<0.05). In addition, the extraction medium and condition play an important role for protein extraction and influence the 84

4 recovery of protein [18]. When compared between RBM to other beverages such as plain milk, soy extracted, and commercial soy milk, found that the carbohydrate content was higher than those samples. The similar result was found in previous study that rice bran beverage with flavor (cocoa and strawberry) showed recovery composition, especially carbohydrate were 43.2 and 41.3%, respectively [3]. Physico-chemical properties Color characteristic of RBM and soy milk are exhibited in Table 2. Color characteristic is one of the important parameters for food products that directly affected to the consumer acceptance. The highest whiteness and lightness (L*) value were observed in commercial soy milk as 70.59%, 72.22, respectively. The results showed significantly lowered on L*, redness (a*), yellowness (b*) value of RBM sample when water ratio increased (p<0.05). The whiteness of all RBM was significantly lowered when compared to the commercial soy milk (p<0.05). These properties could be used as fundamental criterion and concern for furhter developing organic rice bran milk. Table 2. Color characteristics of RBM and commercial soy milk * Samples Color Parameters L* a* b* E Whiteness (%) RBM 1: ±0.03c 1.55±0.01a 13.12±0.03a 7.58±0.03b 64.04±0.02c RBM 1: ±0.06b 0.69±0.04b 11.41±0.04b 5.26±0.07c 66.10±0.05b RBM 1: ±0.04d -0.31±0.02c 7.91±0.04d 9.93±0.02a 61.71±0.04d Soy milk 72.22±0.01a -1.91±0.02d 9.44±0.03c - ** 70.59±0.00a * The values are expressed as Mean ± SD (n=3). Mean with different letter in the same column are significant different at (p<0.05). ** Soy milk was used for comparision with others. Physico-chemical properties of developed rice bran milk and soy milk are also presented in Table 3. ph and total acidity was determined since they were used to identify the shelf-life of the products. For chemical properties, ph of all RBM ranged from whereas ph of commercial soy milk was RBM 1:5 provided the highest total soluble solid (TSS) (12.7) compared to commercial soy bean milk (11.7) followed by RBM 1:10 (6.0) and RBM 1:15 (3.7). The results of TSS coincided with total sugar that decreased when the amount of water increased ( %). High in TSS value may obtain from particle of rice bran rather than sugar content. For total sugar content, even though RBM was no sugar added (natural flavor) meanwhile its presented some sugar content value. It is possible deliverated from starch content (48.44%) in rice bran [7]. Table 3. Physico-chemical properties of RBM and commercial soy milk * Parameters Samples RBM 1:5 RBM 1:10 RBM 1:15 Soy milk ph 6.77±0.01c 6.89±0.01b 6.97±0.02a 6.99±0.01a TSS ( o Brix) 12.7±0.58a 6.0±0.00b 3.7±0.58c 11.7±0.58a Viscosity (cp) ±0.74a 6.63±0.29c 3.05±0.06d 9.85±0.07b Total sugar (%) 0.61±0.02b 0.54±0.00b 0.38±0.01c 5.80±0.08a Total acidity (%) 0.07±0.02c 0.11±0.02bc 0.19±0.02a 0.14±0.02ab * Mean ± SD of triplicate measurement Mean with different letter in the same row are significant different at (p<0.05). Total acidity of RBM ranged from 0.07 to 0.19% and increased with the ratio of water in RBM increased.the viscosity of each ratio directly depended on the dilution effect. The maximum viscosity was found in RBM 1:5 (142cP), followed by RBM 1:10 (6.63cP) and RBM 1:15 (3.05cP). For rice bran milk (1:15) showed significant lower in TSS (3.7 Brix), total sugar content (0.38%) and viscosity (3.05cP) when compared to the commercial soy milk (11.7 Brix, 9.85cP, and 5.80%, respectively) (p<0.05). Hence, these properties could be used to further new plant-based milk development. Stability of RBM The stability of RBM by using coagulation technique was monitored and depicted in Figure 1. The highest stability of RBM was found in the sample with the ratio of rice bran to water of 1:5 (w/v). The precipitate increased with the storage time, especially at day 7. Although, rice bran was passed the colloid mill process, the RBM still contained with large particles suspended in the final product. Therefore, the phase separation between soluble fraction and insoluble fraction was clearly observed in RBM since the first day of analyzed, especially the treatment that contained more extractant. 85

5 Day 0 Day 3 Day 5 Day 7 Figure 1. The stability of rice bran milk at 4 o C for 7 days. Bar (---) indicated the level of the precipitate. To increase stability of milk products, generally emulsifier or stabilizer needs to be applied. According to Yadav et al. [19] and Lal et al. [20] studied for application of emulsifiers/stabilizers in dairy products and they noted that the combination of emulsifiers and stabilizers has provent to be effective in formulating functionalized liquid product. Furthermore, other stabilizers such as carboxymethylcellulose (CMC) can use for product stabilization and the stability of colloidal systems [21]. However, RBM is not animal based milk, so different techniques to increase its stability should be investigated. Biological activity The total polyphenol content and radical scavenging activity (DPPH) were determined for antioxidant activity of RBM compared to commercial soy milk and depicted in Figure 2. Total polyphenol content in RBM (1:5, 1:10 and 1:15 (w/v)) ranged from 41.33±0.08 to ±0.01 ggae/100g dry basis, while the DPPH ranged from ±0.10 to ±0.14 µmol Trolox/100g dry basis. Total polyphenol content as well as the DPPH radical scavenging activity was directly a b Figure 2. Total polyphenol content (a) and DPPH radical scavenging activity (b) of rice bran milk and commercial soy milk. depends on dilution effect. High amount of water added to produce RBM lowered the phenolic content and biological activity was obtained. Extractant concentrations including ratio of medium to solid play 86

6 important role in phenolic extraction and influence the phenolic content recovery [22]. Besides, a significant decreased of the antioxidant activity of the RBM possibly caused by dilution effect as well. Therefore, the high of phenolic content in RBM, especially low dilution level could be used as a potential source of antioxidative activity. High antioxidant foods can help preventing disease such as cancer, heart disease and cardiovascular disease (CVD) [23]. Interestingly, the antioxidant activity of RBM was higher than those found in the commercial soy milk ( µmol Trolox/100g dry basis). Normally rice bran and soybean contains more bioactive compounds which act an antioxidant [6, 24-25]. Generally, antioxidant compounds are sensitive and can easily destroyed by thermal processing, especially high temperature during pasteurization process [26-28]. Sensory profile The organic rice bran milk (ratio 1:15 (w/v)) was chosen to evaluat the sensory profile since its physical, chemical and biological properties were comparable to the commercial soy milk. The correlated sensory profile evaluation of organic RBM compared to commercial soy milk is demonstrated in Figure 3. Color attributes of RBM was closed to the commercial soy milk, while big differences were observed in the attributes of appearance, taste, flavor, sweetness, and overall liking. These results also conformed to the physico-chemical of the samples, especially the TSS, total sugar as well as viscosity between RBM 1:15 and soy milk (p<0.05). These attributes resulted in low score in sweetness, taste, and overall liking of RBM. The obtained data suggested that the taste and flavor aspects should be improved for organic RBM development. Due to specific aroma compounds, rice bran showed the unique flavor, which affects the overall liking and consumer acceptance as well. Furthermore, this rice bran beverage (natural flavor) can be alternative functional drinks with low sugar and high antioxidant properties. Besides, it could be certified that was made from organic raw materials. Figure 3. Sensory profile of organic rice bran milk compare with commercial soy milk. Conclusion: The obtained RBM provided an acceptable physical and chemical properties, besides, good antioxidant properties. Rice bran milk can be a new alternative plant-based beverage for health concern consumer. The ratio of rice bran to water (1:15) is suitable for using as a starting condition for further product development. However, RBM need further experimemt to improve it quality attributes, especially taste and flavor by using these preliminary results. References: 1. Friedman, M., Rice Brans, Rice Bran Oils, and Rice Hulls: Composition, Food and Industrial Uses, and Bioactivities in Humans, Animals, and Cells. J. Agric. Food Chem. 2013, 61, Chronakis, I. S.; Öste Triantafyllou, A.; Öste, R., Solid-state characteristics and redispersible properties of powders formed by spray-drying and freeze-drying cereal dispersions of varying (1 3,1 4)-β-glucan content. J. Cereal Sci. 2004, 40, Faccin, G. L.; Miotto, L. A.; Vieira, L. d. N.; Barreto, P. L. M.; Amante, E. R., Chemical, Sensorial and Rheological Properties of a New Organic Rice Bran Beverage. Rice Sci. 2009, 16, Murtaugh, M. A.; Jacobs, D. R., Jr.; Jacob, B.; Steffen, L. M.; Marquart, L., Epidemiological support for the protection of whole grains against diabetes. proceedings of the 7th International Vahouny 87

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