Effects of ultraviolet on rice starch granules in functional drink processes

Transcription

1 P-STARCH-20 Effects of ultraviolet on rice starch granules in functional drink processes Suthaya Phimphilai 1, Somkiat Jaturonglumlert 1, Aphiwat Teerawutgulrag 2, Surat Nuglor 1 Jatupong Varith 1, Kajorndaj Phimphilai 3, Jantima Tongboon 1 and Suphannipa Kantima 1 1 Faculty of Engineering and Agro-industry, Maejo University, Thailand 2 Faculty of Science, Chiang Mai University, Thailand 3 Faculty of Engineering, Chiang Mai University, Thailand Abstract Broken red rice (Hom Sukhothai 1), a by-product from physically dehusking process, is approximately half price of the whole kernels and unlikely to be served for consumers on a menu list. The rice has comparable nutrients as well as active compounds to the whole kernels. To produce a functional drink with minimizing carbohydrate from the broken rice surface, a technique of ultraviolet (UV) was applied. The rice was firstly adjusted to two moisture content levels, and then treated under 254 nm - UV lamps for min prior to an ultrasonic (US) extraction procedure. The extracted samples had significant differences in color, solid contents, antioxidant properties and total phenolic compounds. Pictures from scanning electron microscopy (SEM) were clearly expressed changes on the starch granule resulting in lower solid content in the extract. UV doses subjected to raw materials with lower moisture content tended to decrease active compounds in the rice extract. However, it leaded to higher concentration of polyphenolic compounds when damped rice was used. The UV technique, therefore, could be used to facilitate the bran extraction process in a particular functional drink from broken red rice. Keywords: Rice kernels, gelatinization, brown rice, functional drink, production 1. Introduction Rice pericarp or bran is a source of oil and various phytochemicals beneficial to human health. The bran color could be brownish, reddish to dark purple depending on rice strain with alter active compounds. Hom Sukhothai 1, under an organic practice, has red pericarp (red rice) with phenolic compounds and antioxidant activities (Phimphilai and Nuglor, 2011). In ordinary dehusking process, about 25% broken red rice is obtained as a byproduct (Natural rice Co.,Ltd) and unlikely to be used in menu lists. As a consequence, its market price is only half of the full kernel. One option to value-add the broken red rice is focusing on phytochemical extraction for a functional drink with minimizing carbohydrate or starch. Functional drink markets have been grown up in recent year. Organic market is another add-on trend focusing on high-end consumers whose priorities are health and wellness. Limitation of general organic product is chemical usage. In order to make an organic rice-bran drink with low carbohydrate from broken red rice (Hom Sukhothai 1), physical extraction therefore is likely to be used. Ultrasonic is an option that could be applied during an extraction process. Positive results from the particular technique were revealed in many studies, i.e. blackberry juice (Tiwari et al., 2009), grape juice (Tiwari et al., 2010) and Angelica sinensis, a traditional Chinese medicine (Xie et al., 2009). However, a preliminary study stated that broken red rice extract processed under this technique was mixed with starch granules. They were likely from damaged areas on broken rice kernel. As a consequence, cloudiness product with sediment was found. Since this particular product is purposed as a 283

2 non-thermal sterilizing drink, existing starch granules possibly leads to grittiness mouth feel. Therefore, minimizing the kernel starch dispersion was expected. Ultraviolet at 254 nm has been used in germicidal lamp for years with its ability in microbial disinfection. Recent researchers also indicated the UV practicality especially in starch modifications. UV significantly had degradation effect on starch granules that promoted expansion in bakery products (Vatanasuchart et al., 2005). Hedin et al. (2010) used UV-light to initiate a free radical vinyl polymerization reaction that could make a crosslink gel. Kantima et al. (2011) used the same light during a casting process of tapioca starch gel resulting in higher strength film with lower oxygen permeability. In functional food application, there was no evidence of the light directly expose onto the rice kernels coating with functionally phytochemical bran. Optimization of UV dosage on minimizing starch with maximizing functional properties of final rice extract was a main objective in this study. 2. Materials and methods Broken organic red rice, Hom Sukhothai 1, was received from Natural rice Co.,Ltd (Sukhothai province, Thailand). The rice was adjusted to moisture contents of 13% and 23%, prior to 254 nm-uv exposures (15 watts, Phillip) at 0, 30, 60, 90 and 120 min. All treated samples were then transferred to an US extracting chamber (Honda, W-113) and processed in water under controlled temperature for 60 min with 28 khz frequency. The extracts were analyzed for their chemical and physical properties. Chemical or functional property determinations included total antioxidant activities; ABTS (2,2 -azinobis (3-ethybenzo thiazoline-6-sulfonic acid)) assay as modified from a method of Re et al. (1999), and FRAP (ferric reducing antioxidant power) assay as mentioned in a study of Benzie and Strain (1996). Total polyphenol contents (TPC) in the extracts were analyzed as described in a previous method of Pinsirodom and Changnoi (2001). The treated rice kernels were also investigated under a scanning electron microscope. Solid contents and color (L*, a*, b*; Tristimulus colorimeter, Japan) of the extracts were also monitored. A completely randomized design (CRD) was applied to each moisture content sample set. SPSS (v.17) software was used for ANOVA calculation and mean differentiation with 0.5 significant level. 3. Results and conclusion Broken red rice of Hom Sukhothai 1 has functional characteristics as can be seen in antioxidant properties; ABTS, FRAP as well as phenolic compounds of which 1 g of the rice strain is equivalent to approximately 15 mg gallic acid (Figure 1). UV pre-treatment to the different moisture contents rice (13% and 23%) showed significantly different in functional properties. Lower moisture content (13%) tended to have a downward effect on those properties with longer UV treatment. In contrast, it showed positive results on the damped rice. Moisture tended to facilitate UV efficacy in breaking down cell-walls of rice pericarb, resulting in more active or functional compounds in the extracted solution. This evident supported phenolic compound extraction in grapes after UV treatments (Tiwari et al., 2010). However, there was no significant different on ABTS properties of the rice extract subjected to min UV. Additionally, the longer UV doses had strong reduction effects on solid content in the extracted solution (p<0.05). 284

3 I II A A B B C C mg FeSO 4 equiv./ 50 ml extract a c b d e mg FeSO 4 equiv./ 50 ml extract mg Gallic acid equiv./ 50 ml extract Figure 1 Antioxidant properties (A=ABTS, B=FRAP) and total polyphenol contents (C) in red rice extracts after US extraction of 13% (I) and 23% (II) moisture content raw materials treated under different UV dosages. 285

4 Remarkable solid reduction was found during the first 30 min-uv exposure (Figure 2). The sample lightness (L*) were also dropped with longer UV exposure time which supported the lower starch or solid contents in the extract. To explain this evidence, all the rice samples were investigated under SEM especially at the broken surface of the rice kernel. It was found that the longer the UV exposed, the more starch morphologies changed (Figure 3). The rice starch granules tended to be aggregated to each other during higher UV exposure. As a result, lower starch granule was found in the sample extract even though strongly US extracting condition was confronted afterward. In conclusion, UV could be used to facilitate active compound extraction from damped broken red rice kernels during an US extracting step. The optimum UV exposure time was at 30 min resulting in 65% reduction of solid content in the final extract. This technique could be further applied to a manufacturing process for an organic drinking product from broken red rice, Hom Sukhothai 1. Solid content (%) Figure 2 Solid contents in red rice extracts after US extraction of 23% moisture content raw materials treated under different UV dosages. 0 min 30 min 60 min 90 min 120 min Figure 3 Starch morphologies at the broken area of red rice kernel (23% moisture content) after different UV treating time. 286

5 Acknowledgement We cordially give our thankfulness to Agricultural Research Development Agency (Thailand) for the research funding (2012), and great appreciation to our research team; Nitiporn Thong-ngam, Supika Kaewmuangma, Sasinutcharda Suwanagul, Pattawee Rochanapatya and Thongla Pukumvong for their assistants. References Benzie, I.F.F. and J.J. Strain The ferric reducing ability of plasma (FRAP) as a measure of antioxidant power the FRAP assay. Analytical Biochemistry. 239: Hedin, J., Östlund, Å. and Nydén, M UV induced cross-linking of starch modified with glycidyl methacrylate. Carbohydrate Polymers. 79(3): Kantima, S., Phimphilai, S., Rardniyom, C., Rattanaplome, T Influence of ultraviolet radiation on physical properties of tapioca-starch edible films. In Maejo University Annual Conference Chiang Mai, Thailand. Khan, M.A., Bhattacharia, S.K., Kader, M.A. and Bahari, K Preparation and characterization of ultra violet (UV) radiation cured bio-degradable films of sago starch/pva blend. Carbohydrate Polymers. 63(4): Phimphilai, S. and Nuglor, S Germinated color rice production. Final report. Faculty of Engineering and Agro-industry, Maejo University, Chiang Mai, Thailand. 42 pp. Pinsirodom, P., Changnoi, W Comparison of total polyphenol content and antioxidant potential of extracts obtained from seeds of different citrus cultivated in Thailand. Food Chem. 34(4): Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M. and Rice-Evans, C Antioxidation activity applying an improved ABTS radical cation decolorization assay. Free Radic. Biol. Med. 26(9-10): Tiwari, B.K., O Donnell, C.P. and Cullen, P.J Effect of sonication on retention of anthocyanins in blackberry juice. J. Food Eng. 93: Tiwari, B.K., Patras, A., Brunton, N., Cullen, P.J. and O Donnell, C.P Effect of ultrasound processing on anthocyanins and color of red grape juice. Ultrasonics Sonochemistry. 17: Vatanasuchart, N., Naivikul, O., Charoenrein, S. and Sriroth, K Molecular properties of cassava starch modified with different UV irradiations to enhance baking expansion. Carbohydrate Polymers. 61(1): Xie, J., Lu, J., Qian, Z., Yu, Y., Duan, J. and Li, S Optimization and comparison of five methods for extraction of coniferyl ferulate from Angelica sinensis. Molecules, 14: (doi: /molecules ). 287