The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok,

Effect of Soaking Condition on Total Anthocyanin Content and Physical Properties of Brown cv. Cooked by Microwave Oven 1Piyaporn Suriya*, 2 Poonpat Poonnoy, 3Thanes Keokamnerd 1Graduate student, Food-Science and Technology Program, Faculty of Engineering and Agro-Industry, Maejo University, Chiang Mai, Thailand. 2Assist. Prof. Dr., Food Engineering Program, Faculty of Engineering and Agro-Industry, Maejo University, Chiang Mai, Thailand. 3Lecturer Dr., Food-Science and Technology Program, Faculty of Engineering and Agro-Industry, Maejo University, Chiang Mai,Thailand. * Corresponding author: [email protected]

Abstract cv. riceberry is dark purple rice contain considerably more anthocyanins than unpigmented rice in the aleurone layer of its grain. This study aimed to optimize soaking conditions of the brown rice cv. riceberry for cooking by microwave oven. Box-Behnken design (BBD) and response surface methodology (RSM) were applied to optimize soaking condition. With the different temperature of soaking water at 20, 35 and 50 oC in 20 min under 800 W microwave power. The Samples were analyzed total anthocyanin content, moisture content, hardness, swelling ratio and color (L* a* b*). The RSM indicated that the optimal soaking conditions of the brown rice cv. riceberry were as followed; a ratio of rice:water was 1:4.52 g/ml; soaking time was 49.88 min, soaking temperature was 29.46 oC, and the remaining of total anthocyanin content was 149.73 mg/100 g dry weight. The remaining of the total anthocyanin content was lower than that obtained from the untreated brown rice cv. riceberry by 47.66% and lower than that obtained from brown rice cv. riceberry cooking with rice cooker by 3.26%. Physical properties of rice cooked by microwave oven showed no difference from rice cooked by a rice cooker. This research implied the microwave oven could be used for cooking small quantity of rice to be consumed by the individual or a small group of people.

Keywords: Brown Rice cv. Riceberry, Total anthocyanin content, Microwave cooking

Introductionคลังความรู้ดิจิทัล มหาวิทยาลัยเกษตรศาสตร์

Rice is a staple food and an economic crop of Thailand.หมดอายุวันที่ It is not 28-10-2564only but also many special rice cultivars that contain color pigments, such as black (), Hom Nil rice (purple rice) and Sung Yod rice (red color) (Yossaporn and others 2013). Riceberry, a black purple rice variety ( L.), is a new breeding line developed by the Rice Research Center, Kasetsart University, Kamphaeng Saen, Nakhon Pathom, Thailand (Leardkamolkarn and others 2011). Riceberry is a dark purple rice contains considerably more anthocyanins than unpigmented rice in the aleurone layer of its grain. This rice cultivars possess potential capacity in

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand reducing LDL-cholesterol oxidation, other possible mechanisms involved in their ability to reduce the risk of heart diseases may include reduction of pro-inflammatory mediator synthesis, suppressing cyclooxygenase activity, and down-regulation of nitric oxide production (Kris-Etherton and others 2002). Microwave heating is gaining popularity over conventional heating owing to its inherent advantage of rapidity and convenience. It provides consistent better nutrition than any other method of cooking and reheating. Microwave oven is also used to cook rice. Cooking food with microwave oven might not convenient for mass cooking but it is convenience for cooking food in a small quantity, especially in the households (Decareau and Peterson 1986). Box-Behnken design (BBD) and response surface methodology (RSM) were used to optimize soaking condition of the brown rice cv. riceberry for cooking by microwave oven and compared the remaining anthocyanin content and physical properties of rice cooked in the rice cooker.

Materials and methods Sample preparation

Riceberry rice collecting from local farmers in Thailand was washed with tap water for elimination of debris. Soaking conditions were studied according to a ratio of rice:water, soaking time and soaking temperature. The variables were ratio of rice:water at 1:4, 1:5 and 1:6, soaking time at 0, 30 and 60 min and soaking temperature at 20, 35 and 50 oC. All samples used microwave (Panasonic, NN-S235 WF) power of 800 W and the heating time was 20 min. Samples were analyzed for obtaining moisture content, hardness, swelling ratio, color (L* a* b*) and total anthocyanin content.

Analyticalคลังความรู้ดิจิทัล methods มหาวิทยาลัยเกษตรศาสตร์

Moisture content was measured by using a moisture หมดอายุวันที่balance (Sartorius, 28-10-2564 MA30, U.S.A) (Jeya and others 2009). Hunter color meter readings (JUKI, 801, TOKYO, JAPAN) and hardness were determined as described by Lyon and others (2000). Swelling ratio were determined as described by Butt and others (2008).

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand

Extraction of anthocyanins

Selected samples were extracted at room temperature with 10 ml of 0.1 M HCl / methanol (85:15, (v/v)) for 30 min on a magnetic stirrer and then separated by centrifugation and the supernatants were collected and kept in dark and cold (+4 oC). The residues were twice re-extracted under the same conditions, and supernatants of all three extraction were combined. Supernatants were separated via centrifugation at 2500 g for 10 min. The solvent was removed at 40 oC using a rotary evaporator and the resulting anthocyanins concentrates were determined by a spectrophotometric method. (Hatch, DR/2000, U.S.A).

Determination of total anthocyanin content

Determination of the total amount of anthocyanins (TAC) was done using the reported spectrophotometric method (Abdel-Aal and Hucl 1999). Anthocyanins were extracted with acidified methanol (methanol and 1M HCL, 85:15, v/v) with a solvent to sample ratio of 1:10. Absorbance was measured after centrifugation at 525 nm against a reagent blank.

Experimental design and data analysis

The main and interaction effects of the factors: ratio of rice: water (X1), soaking time

(X2) and soaking temperature (X3) on the remaining of anthocyanin content (Y) were evaluated. The range and levels of the variables were given in Table 1, and the experimental designs with the observed responses and predicted values for the remaining of anthocyanin content were presented in Table 2. A second-order polynomial quadratic equation was fitted to evaluate the effect of each independent variable to the response.

Table 1คลังความรู้ดิจิทัล Independent มหาวิทยาลัยเกษตรศาสตร์ variable used in the BBD and actual factor levels corresponding to coded factor levels.

Independent variable Code Uncodeหมดอายุวันที่ Actual factor 28-10-2564 level at coded factor levels -1 0 +1 ratio of rice :water (g/ml) X1 X1 1:4 1:5 1:6 soaking time (min) X2 X2 0 30 60 o soaking temperature ( C) X3 X3 20 35 50

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand

Table 2 BBD with the observed and predicted values for the remaining of anthocyanin content

Run Coded variable level the remaining of anthocyanin content (mg/100 g dry weight) X1 X2 X3 Observed Predicted 1 1.000 1.000 -1.000 101.49 98.43 2 1.000 1.000 1.000 94.51 91.20 3 1.000 -1.000 1.000 88.82 89.33 4 1.000 -1.000 -1.000 93.48 92.10 5 1.000 0.000 0.000 97.25 104.49 6 -1.000 -1.000 1.000 106.73 106.59 7 -1.000 0.000 0.000 104.88 110.44 8 -1.000 1.000 1.000 112.57 110.75 9 -1.000 1.000 -1.000 96.77 93.06 10 -1.000 -1.000 -1.000 84.32 84.43 11 0.000 0.000 -1.000 127.58 135.62 12 0.000 1.000 0.000 129.49 141.38 13 0.000 0.000 1.000 138.31 143.08 14 0.000 -1.000 0.000 135.22 136.13 15 0.000 0.000 0.000 148.39 144.92 16 0.000 0.000 0.000 148.39 144.92 17 0.000 0.000 0.000 149.73 144.92

3 3 3 3 2 푌 = 훽0 + 훽푖 푋푖 + 훽푖푖 푋푖 + 훽푖푗 푋푖 푋푗 (1) 푖=1 푖=1 푖=1 푗 =푖+1

where xi, xj are the input variables, which influence the response variable , Y, β0 is the th intercept, βi is the ith linear coefficient, βii is the quadratic coefficient and βij is the ij interaction coefficient. The statistical software package Design-Expert (Version 7.0.0, Stat-Ease Inc., Silicon คลังความรู้ดิจิทัล มหาวิทยาลัยเกษตรศาสตร์ Valley, CA, USA) was used for the regression analysis of the experimental data and the response surface plots. Analysis of variance (ANOVA) was used to estimateหมดอายุวันที่ the statistical 28-10-2564 parameters.

Results and Discussions

Preliminary one-factorial experiments had identified the ranges for the three main factors. These ranges were 1:4–1:6 g/ml, 0–60 min and 20–50 oC for ratio of rice:water, soaking time and soaking temperature, respectively. Optimization of the pretreatment conditions was achieved by

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand employing BBD and the polynomial equation describing samples of the remaining of anthocyanin content as a simultaneous function of ratio of rice:water (X1), soaking time (X2) and soaking temperature (X3), is shown in Eq. (2) 2 2 2 Y=144.92-2.97X1+2.63X2+3.73X3-0.57X1X2-6.23X1X3-1.12X2X3-37.45X1 -6.16X2 -5.57X3 (2)

The statistical significance of the model equation was evaluated by the F-test for analysis of variance (ANOVA) in Table 3, which shows that the regression was statistically significant. The P- value for the model was 0.0006. The F-value (16.86) also suggests that the model was significant. The coefficient of determination (R2) of the model was 0.9559, which further indicates that the model was suitable for adequately representing the real relationships among the selected reaction variables. The high values of R2 and adjusted R2 of this model (Adj R2 = 0.9358) show a close agreement between the experimental results and the theoretical values predicted by the model. The similarity between predicted and observed results presented in Fig. 1 reflects the accuracy and applicability of the Box-Behnken model as a powerful method for process optimization. The

2 independent quadratic term of X1 and X1X3 had significant effects on the remaining of anthocyanin content, since the P-values less than 0.05 indicates the significant model terms. The 3D response surfaces and the 2D contour plots of the responses using Eq. (3) for the remaining of anthocyanin content are shown in Fig. 2. To depict the interactive effects of independent variables on responses, one variable was kept constant while the other two variables were varied. The shapes of response surfaces and contour plots indicate the nature and extent of the interaction between different factors (Prakash and others 2008). The results show that these variables (ratio of rice:water, soaking time and soaking temperature) substantially affected the remaining of anthocyanin content response. Additionally, two-way interactions between variables such as ratio of rice:water and soaking time, soaking temperature and soaking time, ratio of rice คลังความรู้ดิจิทัล มหาวิทยาลัยเกษตรศาสตร์ :water and soaking temperature, were important terms in the the remaining of anthocyanin content model. With P-values more than 0.05 (Table 3), the interactionsหมดอายุวันที่ between 28-10-2564 variables were ratio of rice:water and soaking temperature, affect the remaining of anthocyanin content significantly.

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand

Table 3 ANOVA of the quadratic model for prediction of total anthocyanin content Source of Degree of Sum of Means F-value P-value R2 variation freedom squares squares Model 9 7907.41 878.60 16.86 0.0006 0.9559 X1 1 88.33 88.33 1.70 0.2341 X2 1 68.96 68.96 1.32 0.2877 X3 1 139.13 139.13 2.67 0.1462 X1X2 1 2.63 2.63 0.051 0.8285 X1X3 1 310.63 310.63 5.96 0.0446 X2X3 1 9.97 9.97 0.19 0.6750 2 X1 1 3564.58 3564.58 68.42 < 0.0001 2 X2 1 72.04 72.04 1.38 0.2781 2 X3 1 56.57 56.57 1.09 0.3320 Residual 7 364.69 52.10 Lack of fit 5 363.49 72.70 121.46 0.0082

Fig 1 Predicted and actual anthocyanin contents Optimization and confirmation experiments

The optimal pretreatment conditions for the remaining of anthocyanin content were extracted by Design Expert software though a graphical optimization. Taking both cost and efficiencyคลังความรู้ดิจิทัล into consideration, มหาวิทยาลัยเกษตรศาสตร์ optimum operating parameters were: X1 = 1: 4.52 g/ml, X2 = o 49.88 min and X3 = 29.46 C. Under these optimal conditions,หมดอายุวันที่ confirmation 28-10-2564 experiments were conducted in five replicates. The microwave heating of brown rice cv. riceberry consisted of 50.95% moisture content, 139.46% swelling ratio, color (L* a* b*) = 12.75, 3.69 and 0.74 respectively, 154.60 N of hardness and the remaining of anthocyanin content 158.39 mg/100 g dry weight. The main composition of untreated brown rice cv. riceberry was determined to be 6.43% moisture content , L* a* b* = 7.49, 9.51 and 2.03 respectively, 772.33 N of hardness and the remaining of anthocyanin content was 302.62 mg/100 g dry weight. The main composition of

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The 16th FOOD INNOVATION ASIA CONFERENCE 2014 12 -13 June 2014, BITEC Bangna, Bangkok, Thailand brown rice cv. riceberry treated with rice cooker was determined to be 61.74% moisture content, 149.18% swelling ratio, L* a* b* = 13.94, 4.69 and 0.80 respectively, 142.30 N of hardness and the remaining of anthocyanin content was 168.27 mg/100 g dry weight. Compared with untreated brown rice cv. riceberry, increased moisture content, swelling ratio and color (L* a* b*) but decreased hardness and total anthocyanin content by 47.66 % . A B C

Fig 2 Response surface plots showing the interactions between the variables affecting the remaining of anthocyanin content: (A) interaction between ratio of rice:water and soaking temperature; (B) interaction between ratio of rice:water and soaking time; (C) interaction between soaking temperature and soaking time.

Conclusions The conditions for microwave heating treated of brown rice cv. riceberry were optimized by using BBD. The optimal conditions were found as follows: ratio of rice:water at 1: 4.52 g/ml, soaking time at 49.88 min and soaking temperature at 29.46 oC. The conditions allowed for the remaining of anthocyanin content of 149.73 mg/100 g dry weight. However microwave heating showed higher decrease of total anthocyanin content but shorter time with rice cooker.

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คลังความรู้ดิจิทัล มหาวิทยาลัยเกษตรศาสตร์

หมดอายุวันที่ 28-10-2564

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