International Food Research Journal 20(4): 1595-1600 (2013) Journal homepage: http://www.ifrj.upm.edu.my Effects of blanching and drying on fiber rich powder from pitaya (Hylocereus undatus) peel *Sengkhamparn, N., Chanshotikul, N., Assawajitpukdee, C. and Khamjae, T. Faculty of Applied Science and Engineering, Nongkhai Campus, Khon Kaen University, Chalermprakiet Road, Nong Khai 43000, Thailand Article history Abstract Received: 24 December 2012 The pitaya (Hylocereus undatus (Haw.)), a member of the Cactaceae, with white-flesh is a one of Received in revised form: the famous varieties in Thailand and shows antioxidant activity from its pigment. However, its 6 March 2013 peels was handled as a waste, therefore the applying these materials could be get more benefits Accepted:11 March 2013 in producing fiber rich powder. The effects of blanching in hot water and drying at various Keywords temperatures (60oC, 70oC and 80oC) were investigated. The result showed that the blanched pitaya peel showed lower amounts of anthocyanin and betacyanin contents. Moreover, thermal Pitaya peel degradation of anthocyanin and betacyanin could be occurred during drying process. However, betacyanin the higher drying temperature trends to increase the antiradical activity of dried sample. This antioxidant information provided that the pitaya peels is a valuable material for a manufacture of fiber-rich radical scavenging activity powder with high antiradical activity. blanching drying © All Rights Reserved Introduction are water-soluble pigments (Wybraniec et al., 2001). The betacyanins has been reported that it was found Pitaya (Hylocereus undatus (Haw.)) or Dragon in both flesh and peels of pitaya peel (Wuet al., 2006; fruit, member of the Cactaceae, is originally from Esquivel et al., 2007) which give deep red–purple Mexico, Central and South America (Haber, 1983; pigments and stable in a broad pH range, (Wybraniec Benzing, 1990) and has also been grown in Thailand. and Mizrahi, 2002). Moreover, betacyanins has been It has cladode stems and specific character, bracts or reported that it exhibited the highest antioxidant scales with a bright red color fruits (Wu et al., 2006). activities in both DPPH and FRAP assays and its The pitaya flesh contains small black seeds scattered activity were almost 10 times higher in peels than in in white-flesh (H. undatus) or red-flesh (H. polyrhizus) flesh of pitaya. (Tenore et al., 2012). These pigments or yellow-flesh (H. megalanthus) (Barbeau, 1990) may give a protection against certain oxidative stress- depending on the cultivar. In Thailand, the pitaya related disorders (Kanner et al., 2001). Morever, the with white-flesh was a one of the famous varieties. red pitaya (H. polyrhizus) peel showed effectively Pitaya is found to be rich in nutrients, such as beta- inhibit the growth of melanoma cells (Wu et al., carotene, lycopene and vitamin E in an edible portion, 2006). (Charoensiri et al., 2009) and contains essential Nowadays, a lot of works have an attention to use fatty acids, i.e., 48% linoleic acid (C18:2) and 1.5% the waste material from industry as a raw material linolenic acid (C18:3) in the black seed of pitaya fruit for produce a new food ingredients with a good (Ariffin et al., 2008). Moreover, oligosaccharides source of bioactive compounds. The pitaya peels are extracted form pitaya showed prebiotic properties, normally removed and handled as a waste, therefore which can stimulate the growth of lactobacilli and the processing these materials could get more bifidobacteria (Wichienchot et al., 2010) benefits such as for producing fiber rich powder. The pitaya is an interested agricultural product Dietary fiber (DF) is a food component and resistant since its antioxidative activity from its fruit pigments, to hydrolysis by human digestive enzymes. Some betalains group (Wybraniec et al., 2001; Wybraniec of by-products from the agricultural such as apples, and Mizrahi, 2002). The betalains also has been citrus fruits, lemon, and carrot have already been detected in Amaranthus (Cai et al., 2003) and beet reported in the production of dietary fiber (Grigelmo- roots (Escribano et al., 1998) which exhibited Miguel and Martín-Belloso, 1999; Figuerola et antiradical and antioxidant activity. Betalains al., 2005; Chantaro et al., 2008). The chemical consists of two important pigments, betacyanin (red- composition and functional properties of dietary violet color) and betaxanthins (yellow color) which fiber powder depends on raw material and processing *Corresponding author. Email: [email protected] 1596 Sengkhamparn et al./IFRJ 20(4):1595-1600 procedures. In order to inhibit unsuitable enzymatic dried samples were analyzed in triplicate using pH- reaction such as Lipoxygenases, Pectic enzymes, differential method (Guisti and Wrolstad, 2011). Polyphenoloxidases, Peroxidase, pretreatment is Briefly, the sample was dissolved in pH 1 buffer mostly done before drying process. However, the (0.25M potassium chloride and HCl) and pH 4.5 blanching steps may cause the loss of water soluble buffer (0.4M sodium acetate). The absorbance solid (vitamins, antioxidant compound etc.) and of solution in each pH buffer was measured at the some polymer or smaller fragment (Nilnakara et maximum absorbance wavelength and 700 nm. The al., 2009). Additionally, drying process, famous determination was performed in duplicates. Then, techniques to produce dietary fiber powder, also the concentration of anthocyanin was calculated as effected to antioxidants compounds and antioxidant follows; activity of plant powder products. Chantaro et al. (2008) reported that thermal degradation during both anthocyanin (mg/liter) = A (MW) (DF) x 1000 / ε L blanching and drying was reason of a decrease in β-carotene and phenolic compounds and the loss of when MW is molecular weight of anthocyanin which antioxidant activity of carrot peel powder. is 449.2 for cyanidin-3-glucoside, DF is dilution In this work, the effects of hot water blanching factor, L is path length, ε is molar absorptivity and hot air drying temperature on the production of (26,900) and A is absorbance of sample which was fiber-rich powder obtained from pitaya peel were calculated as follows; investigated. The obtained fiber rich powder were determined crude fiber content, anthocyanin content, A = (Aλvis-max - A700) pH 1.0 - (Aλvis-max - A700) pH 4.5 betacyanin content as well as antiradical activity of fiber-rich powder. Determination of betacyanin content The betacyanin content was determined according Materials and Methods to Wybraniec and Mizrahi (2002). Seven grams of fresh and dried sample were homogenized by 60% Raw materials ethanol and then centrifuge at 6,000 rpm for 15 min. Pitaya fruits with white-flesh were purchased The supernatant was concentrated by using rotary from local market. After removed the peels from its evaporator at 45oC, then sample were diluted by 60% fruits, the peels were cleaned with tap water and then ethanol. The absorbance of solution was measured at cut into 0.5 cm in width and 5 cm in length. 538 nm. The concentration of betacyanin content was calculated as follows; Preparation of fiber-rich powder For pretreatment, the peels were blanched in hot betacyanins (mg/g of dried extracts weight) o water at 95 + 2 C for 1 min and then cooled in cold = A538 (MW)V (DF) x 100/ ε LW water (2oC). One kilogram of pitaya peel pieces (with and without blanching) were expanded on aluminum Where A538 is the absorbance at 538 nm, MW = 550, tray and subjected to hot air oven and dried at 60, 70 L is path length, DF is the dilution factor, V is the and 80oC. The drying process was performed until solution volume (ml), W is the sample weight (g) the mass of sample reached at the equilibrium value. and ε is molar extinction coefficient (65,000). Each The moisture content of sample was determined sample was measured in triplicate and the results using Gravimetric method at 105oC (AOAC, 1995). were expressed as an average. The dried pitaya peel samples were ground using blender and then sieved and packed in the plastic bag DPPH radical-scavenging assay until analysis. The radical-scavenging capacities of fresh and dried sample were determined using DPPH Radical Determination of crude fiber content Scavenging Assay. Briefly, the sample was extracted After lipid extraction, the crude fiber content by 60% ethanol and then was mixed with a 0.2 mM in each sample was determined by acid and alkali 2,2-diphenyl-1-picryl-hydrazyl-hydrate(DPPH) digestion. Both fresh and dried samples were ethanol solution. After 10 min at room temperature, determined in triplicate in accordance with the AOAC the absorbance of solution was measured at 520 nm. method (1995). Radical scavenging capacity (%) is (1-Asample/Acontrol)× 100, when Asample is absorbance value of sample Determination of anthocyanin content solution and Acontrol absorbance value of control (60% The anthocyanin content in both fresh and ethanol). Sengkhamparn et al./IFRJ 20(4):1595-1600 1597 Color measurement Table 1. Drying time and equilibrium moisture content of Color of obtained fiber-rich powder was dried samples at various temperatures Equilibrium moisture content performed by measuring their reflectance using a Sample Drying Temperature (oC) Drying Time (hrs) colorimeter (JS 7555, China). Before each color (g/100 g dry basis) measurement, the colorimeter was calibrated using a 60 25 4.25 * * * standard white plate (L = 98.28, a = -0.11, b = -0.36). Unblanchedpitaya peel 70 22 3.90 Sample was filled in a glass cylinder and placed above the light source and covered with a black lid. 80 11 3.17 The color of sample was represented in 3 parameters; 60 18 4.08 L* (Lightness), a*(redness and greenness) and b* (yellowness and blueness). Moreover, the color of Blanched pitaya peel 70 17 3.31 sample also expressed as total color difference (ΔE) 80 10 3.06 which calculated from L*, a* and b* as follows; Table 2.