2017 post harvest treatment on phytochemicals of thai rice norkaew

Phumon Sookwong , Sugunya Mahatheeranontand Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, ThailandResearch and Development, Phitsanulok 65130, ThailandabstractBecause black rice is rich in antioxidants, appropriate methods of post-harvest treatment are necessaryfor maintaining these bioactive phytochemicals. Drying methods, storage temperatures, storage duration,and packaging methods affected the contents of some bioactive compounds in the two varieties of Thaiblack rice used in this research. Sun drying reduces the loss of anthocyanins and c-oryzanols more thandoes hot air drying. Glutinous black rice stored as paddy at cool room temperature retains more antho-cyanins, c-oryzanols, and vitamin E than does paddy stored at room temperature. Nylon/LLDPE pouchescontaining N2are the most suitable packaging for preserving the key aroma compound 2-acetyl-1-chronic-disease-preventing properties (Chiang et al., 2006; Wanget al., 2007). The health benefits of black rice are attributed tothe bioactive pigments located in the bran layer of the rice. Apartfrom c-oryzanols and vitamin E, there are some water-soluble pig-ments responsible for bran color and anti-oxidative property ofblack rice are(Hou,are availablethe rice market: glutinous and non-glutinous. Black glutinousrice is a native variety widely grown in northern Thailandand is mostly consumed in a sweetened form or as a dessert.However, consumption of black glutinous rice cv. Luem Pua(LP) as a staple food is becoming increasingly popular becauseof its better nutritional, aroma, and textural properties. Like-wise, black non-glutinous rice, cv. Jao Hom Nin (JHN), whichmeans black gem jasmine rice, is a selected line of Khao DawkMali 105, the most popular non-glutinous Thai jasmine ricevariety.Corresponding author at: Department of Chemistry, Faculty of Science, ChiangMai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200, Thailand.E-mail addresses: sugunya.mcmu.ac.th, (S. Mahatheeranont).Food Chemistry 217 (2017) 98105Contents lists availableFood Chemi1. IntroductionBlack rice has gained increasing popularity today as a staplefood and is replacing white rice, due to its health-promoting andblack rice. Two major anthocyanins found incyanidin-3-O-glucoside and peonidin-3-O-glucosideZhang, Cui, Sompong, Siebenhandl-Ehn, Linsberger-Martin, Zhang, Zhang, Zhang, Kett, Tokyo, Japan) justbefore each analysis of phytochemical contents.2.2. Materials and chemicalsCyanidin-3-O-glucoside and naringin were obtained fromSigma-Aldrich Chemicals (St. Louis, MO). c-Oryzanols, Folin-Ciocalteau phenol reagent, gallic acid, and anhydrous sodium car-aromatic white rice varieties, such as Khao Dawk Mali 105 and Bas-mati, is conducive to their high favor and price.There is evidence that the stability of bioactive phytochemicalsin rice can be affected by some post-harvest treatments, includingdrying (Wongpornchai, Dumri, Jongkaewwattana, nylon/LLDPE pouches filled with N2; nylon/LLDPEpouches kept under vacuum at 0.8 bar; and aluminum poucheskept under vacuum at 0.8 bar. These black rice samples were thenkept at room temperature for 6 months.2.5. Analysis of anthocyanins, c-oryzanols, and vitamin E2.5.1. ExtractionRice samples were ground with a blender (Y46; Moulinex, Paris,France) before phytochemicals were extracted. One gram of each ofthe ground rice seed samples was used to determine anthocyaninsand c-oryzanols and two grams of the ground samples were usedto determine vitamin E. Acetic acid (0.5%) in methanol (10 mL),methanol (10 mL), and hexane (15 mL) were used for extractinganthocyanins (Castaeda-Ovando, Pacheco-Hernndez, Pez-Hernndez, Rodrguez, Agilent Technologies, PaloAlto, CA) set at an excitation wavelength of 295 nm and an emis-sion wavelength of 326 nm. Separations were achieved on a4.6C2250 mm VertiSepTMUPS silica column (Vertical Chromatogra-phy, Thailand) with a 5 lm particle size. The flow rate was 1 mL/min and the injection volume was 20 lL. The mobile phase usedwas hexane/isopropanol/ethyl acetate/acetic acid(97.6:0.8:0.8:0.8, v/v/v/v) (Huang loop temperature 130 C176C; transferline temperature 140 C176C; vial equilibration time 9 min with high-speed shaking; loop filling time 0.1 min; pressurizing time1.5 min; and injection time 0.4 min.The analysis column was HP-5MS capillary column with dimen-sions of 30 mC20.25 mm and 0.25 lm film thickness(Agilent Tech-nologies). The injection temperature was 230 C176C. The columntemperature program was started at 45 C176C and was increased to125 C176Cat3C176C/min. Purified helium, at a flow rate of 1.3 mL/min,was used as the GC carrier gas. The GC-MS transfer line tempera-ture was 280 C176C. The mass spectrometer was operated under elec-tron impact mode with electron energy of 70 eV, an ion sourcetemperature of 230 C176C, and a mass range of m/z 29350. Peak iden-tification of headspace volatiles was based on comparison of theobtained mass spectra with Wiley7n and Wiley275 mass spectrallibraries (Agilent Technologies).2.6.3. Quantification of 2AP and some off-flavor compounds in JHN riceAnalyses were done using an Agilent 6890 GC (Wilmington, DE)system coupled to an Agilent Technologies model G1888 head-space auto-sampler. A nitrogen-phosphorus detector (NPD) wasused to detect 2AP. Off-flavor compounds were detected using aflame ionization detector (FID). Headspace operating conditionswere the same as mentioned in Section 2.6.2.Separations were done on an HP-5 (30 mC20.53 mm i.d., 1.5 lmfilm thickness) column (J Sjvall, Virtalaine, Lapvetelinen, hexanal (A), nonanal (B),and vertical bars indicate standard deviations.off-flavor components of JHN black rice during 6 months of storage measured inoctanal (C), heptanal (D), and 2-pentylfuran (E). Data are presented as mean valuesin stored rice. 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