As. J. Food Ag-Ind. 2010, 3(04), 368-372 Asin Journl of Food nd Agro-Industry ISSN 1906-3040 Aville online t www.jofi.info Reserch Article Effect of drying nd frying time on texturl nd sensory chrcteristics of popped rice Smtch Phnitchroen, Anon Mliket nd Prsong Siriwongwilicht* Deprtment of Food Technology, Fculty of Engineering nd Industril Technology, Silpkorn University, Nkhon Pthom 73000 Thilnd. *Author to whom correspondence should e ddressed, emil: siriwong@su.c.th Astrct The ojective of this study ws to investigte the effect of drying time nd frying time on the texturl nd sensory chrcteristics of popped rice to e used s n ingredient se for snck rs. The roken sticky rice ws stem-cooked efore drying t 65 o C for 2, 3 nd 4 hours. The popped rice ws prepred y deep ft frying dried rice t 210 o C for 5, 10 nd 15 seconds. The product qulity ws evluted for moisture content, wter ctivity, colour, texture nd sensory perceptions. It ws found tht the drying time significntly ffected the product colour (p<0.05). However, the effect of frying time on finl product qulity ws not significnt t ny given drying time (p>0.05). The colour of the fried product otined from cooked roken sticky rice dried for 2 hours ws significntly lighter thn tht dried for 3 nd 4 hours. The hrdness of product mesured s pek compression force incresed with incresing drying time. Sensory evlution indicted tht the product otined from drying cooked sticky rice for 3 hours, followed y deep ft frying for 10 seconds ws the most cceptle. Keywords: sncks, moisture content, wter ctivity, colour, Thilnd Introduction Sticky or glutinous rice is produced nd widely consumed in Thilnd. Its lck of mylse provides good properties for producing vrious porous textured products, such s popped, fried or ked sncks [1]. Nevertheless, the roken sticky rice hs not een fully developed to vlue dded products. Popped rice is one of the most well known puffed sncks in Thilnd. It could e lso used s n ingredient se for vrious snck rs, thus considered for this study. The min process of popped rice preprtion includes steming, drying nd frying [2]. Initil moisture content of rice efore frying is mjor fctor influencing finl product qulity. With lower initil moisture content, lower oil content is sored inside the fried product [3]. Thus, pre-fry drying is significnt process determining the finl product [4]. Frying time nd temperture lso influence
As. J. Food Ag-Ind. 2010, 3(04), 368-372 369 the product chrcteristics, especilly texture nd colour [5, 6, 7]. It hs lso een reported tht incresing frying time nd temperture cused deep fried rice crckers to ecome hrder [1]. The ojective of this study ws to investigte the effect of drying nd frying times on the texturl nd sensory chrcteristics of popped rice to e used s n ingredient se for snck rs. Mterils nd Methods Mterils Broken sticky rice, plm oil, sucrose, slt, wter. Equipment Thermometer, deep ft fryer, try dryer, texture nlyzer (TA-XT2i, New York, USA), colourview spectrophotometer, wter ctivity meter (thermoconstnter), hot ir oven. Methods For ech tretment, sticky rice of 200 g ws wshed nd soked in wter for 1 h, then drined efore steming t 100 o C for 30 min. The stemed rice ws dried in try dryer t 65 o C, followed y frying t 210 o C. Two vriles, drying time nd frying time, were included in this study. Drying time ws vried t 2, 3 nd 4 h. Frying time ws vried t 5, 10 nd 15 s, respectively using 3 2 fctoril design. Two replictions were performed for ech experiment. The fried popped rice ws evluted for moisture content, wter ctivity, colour, texture (proe p/100, compression plte, loding speed of 1.5 mm/s, with 25 kg lod cell) nd sensory perceptions. For sensory evlution, popped rice r ws prepred using inding syrup comprising 2 g of slt, 175 g of sucrose nd 175 g of glucose syrup with 650 g of popped rice. Out of six tretments, the top three smples were selected using rnking test with 40 untrined pnelists s tsters. Hedonic scle (from 1-extremely dislike to 9-extremely like) ws lso pplied with 40 untrined pnelists s tsters for product cceptnce evlution. The product colour, iting hrdness, crispiness nd overll liking were evluted. Results nd Discussion Rice steming nd drying preprtion Stemed rice ws prepred nd dried efore frying to otin popped rice. During drying, smples were collected t 2, 3 nd 4 hours for moisture content determintion. The results re presented in Tle 1. Rice moisture content decresed with incresing drying time. The smples with vried levels of moisture content were then used for frying experiments. Tle 1. Moisture content of dried rice. Drying time t 65 o Moisture content (% dry sis) C (h) (men±s.d.) 2 9.85±0.02 3 5.45±0.01 4 3.47±0.01 Rice frying Rice frying experiments were conducted to exmine the effect of initil moisture content of rice efore frying nd frying time on popped-rice chrcteristics. After frying, the product s wter ctivity ws vried etween 0.3-0.4. It ws found tht the colour of popped-rice s indicted y L*, *, nd * (Tle 2) ecme drker yellow when initil moisture content of rice ws lower
As. J. Food Ag-Ind. 2010, 3(04), 368-372 370 (longer drying time). However, only popped rice dried for 2 hours with the highest initil moisture content gve significntly different colour from tht of rice dried for 3 nd 4 hours (p<0.05). Tle 2. The effect of drying nd frying time on popped rice colour. Drying time (h) Frying time (S) Colour 1 (men±s.d.) L* * * 2 5 74.12 4.21 2.49 1.61 20.33 2.10 c 10 72.96 2.00 2.96 1.63 22.86 2.58 c 15 72.73 3.52 3.94 1.84 22.57 2.02 c 3 5 65.16 0.26 8.51 0.91 26.97 0.22 10 64.94 1.59 7.29 0.58 24.57 0.61 15 64.44 0.45 8.05 0.87 26.79 1.01 4 5 62.69 0.56 8.47 0.85 26.92 0.98 10 62.38 0.04 7.96 0.44 27.33 0.69 15 61.234 0.58 8.04 0.68 27.025 1.02 Note: 1 Letters,, nd c indicte the significnt different men vlues in the sme column. Texture of popped rice ws mesured s pek compression force s shown in Figure 1. The results indicted tht t given drying time, the pek compression force of fried product tended to rech mximum t 10 minutes of frying. However, the pek compression force incresed with incresing drying time or when the initil rice moisture content ws lower. It ws in n greement with the results reported y Denth et l. [4] tht the hrdness of fried chickpe flour-sed snck incresed t the lower moisture content of the pre-fried product. Three product tretments including drying 2 hours, frying 10 seconds, drying 2 hours, frying 15 seconds nd drying 3 hours, frying 10 seconds were chosen y rnking preference test. To evlute the consumer s liking of the popped rice, plin rice snck rs were prepred. Hedonic score ws employed. The results shown in Figure 2 indicte tht the product prepred from 3 hours of drying followed y 10 seconds of frying received the highest overll liking score (p<0.05). It ws noticed tht the most cceptle product lso provided the highest colour nd texture liking scores. Nevertheless, the crispiness liking scores of ll smples were not significntly different (p>0.05)
As. J. Food Ag-Ind. 2010, 3(04), 368-372 371 Averge Pek Compression Force (g) 10,000 8,000 6,000 4,000 2,000 Drying 2 hours Drying 3 hours Drying 4 hours 0 0 5 10 15 20 Frying Time (seconds) Note: Letters nd indicte the significnt difference of men vlues of the sme line. Figure 1. Effect of rice drying nd frying time on popped rice hrdness. 9 8 Liking score 7 6 5 4 3 2 1 0 Color Biking hrdness Crispiness Overll liking Drying 2 h, frying 10 s Drying 2 h, frying 15 s Drying 3 h, frying 10 s Figure 3. Preference score of popped rice snck r. Conclusions The experimentl results showed tht popped rice chrcteristics were ssocited with the initil moisture content prior to frying nd frying time. According to this study, drying cooked rice for 3 hours (moisture content of out 3.47%d..) followed y 10 seconds of deep-ft frying ws the est condition for popped rice preprtion.
As. J. Food Ag-Ind. 2010, 3(04), 368-372 372 Acknowledgements This reserch ws sponsored y the Reserch nd Development Institute, Silpkorn University, Thilnd. References 1. Mneerote, J. Noomhorm, A. nd Tkhr, P.S. (2009). Optimiztion of processing conditions to reduce oil uptke nd enhnce physico-chemicl properties of deep fried rice crckers. LWT-Food Technology, 42, 805-812. 2. Niyomwit, N. (1989). Rice processing. (Lecture). Seminr on Food Processing nd Consulting Clinic; 27-28 June, 1989; Industril Development Centre, Deprtment of Industril Promotion, Bngkok, Thilnd, pp. 1-13. 3. Shrm, S.K., Mulvncy, S.J. nd Rizvi, S.S.H. (2000). Food Processing Engineering Theory nd Lortory Experiment. John Wiley & Sons, Cnd, p. 259-265. 4. Denth, S., Bht, K.K. nd Rstogi, N.K. (2003). Effect of pre-drying on kinetics of moisture loss nd oil uptke during deep ft frying of chickpe flour-sed snck food. LWT-Food Technology, 36, 91-98. 5. Vrel, G. W. (1998). Current Fcts out the Frying of Food. In Frying Of Food: Principles, Chnges, New Approch, Edited y Vrel, G., Bender, A.E. nd Morton, I.D., Chichester, Ellis Horwood, pp. 9-25. 6. Mth, R.G. Velu, V., Ngender, A. nd Ro, D.G. (2004). Effect of frying conditions on moisture, ft, nd density of pdpd. Journl of Food Engineering, 64, 429-434. 7. Kit, A., Linsinsk, G. nd Goluowsk, G. (2007). The effects of oils nd frying tempertures on the texture nd ft content of potto crisps. Food Chemistry, 102, 1-5.