Optimization and Experimental Study of Drying Process Parameters for Rice in Hot-air Drying

doi:10.13304/j.nykjdb.2022.1109

Abstract

Abstract:

Rice is one of the important grain crops globally， with indica rice being the predominant variety cultivated in Southern China. The harvested fresh rice has high moisture content and is unsuitable for long-term storage. Aming at the challenges of grain quality deterioration， particularly the occurrence of rice grain fissures during hot air drying in southern China， this study took 2 typical indica rice varieties， Zhongzao 35 and Yuzhenxiang， to investigate the influence of drying temperature， tempering time ratio， and initial moisture content on the drying fissure formation rate and drying rate of rice grains through single-factor experiments and Box-Behnken Design trials. The results showed that drying temperature had the most significant impact on both drying rate and fissure formation rate， followed by the relaxation ratio and initial moisture content. Experimental trials were conducted to meet the national standard for fissure formation rate， and optimal drying temperature， relaxation ratio， and initial moisture content parameters were determined for the two rice varieties. The optimal parameters for Zhongzao 35 were found to be 49.48 ℃， 0.67 and 26%； while for Yuzhenxiang， they were 45.00 ℃， 0.698 and 26%， respectively. Subsequent drying experiments conducted under the optimal parameters yielded drying rates of 0.022 80%·min^-1 and 0.024 61%·min^-1 for Zhongzao 35 and Yuzhenxiang， respectively， with additional crack rateof 2.87% and 2.80%， both below the national standard of 3.00%. This study demonstrated that the optimized drying process parameters provided a theoretical foundation for practical production and in-depth exploration of rice grain quality changes.

Key words: rice, drying, drying speed, additional crack rate

摘要：

水稻是全球重要的粮食作物之一，籼稻是中国南方主要种植品种。收获的新鲜水稻含水率较高，不适合长期储存。针对南方籼稻在热风干燥过程中容易产生爆腰等问题，选择了中早35和玉针香2个典型品种，通过单因素试验和Box-Behnken Design试验，分析了热风干燥工艺条件下的影响因素（包括干燥温度、干燥缓苏比和初始含水率）与水稻的干燥爆腰增率和干燥速率之间的关系。结果显示，干燥温度对干燥速率和爆腰增率的影响最显著，其次是缓苏时间占比和初始含水率。在符合国家标准的爆腰增率要求下进行试验，得到了2个水稻品种的最佳干燥温度、缓苏时间占比和初始含水率参数组合：中早35的最佳参数为49.48 ℃、0.67、26%；玉针香的最佳参数为45.00 ℃、0.698、26%。在最佳参数下进行干燥试验，测得2种水稻品种的干燥速率分别为0.022 80%·min^-1和0.024 61%·min^-1，爆腰增率分别为2.87%和2.80%，均低于国家标准的3.00%。优化后的干燥工艺参数可为生产实践和稻谷品质变化机理的深入研究提供理论基础。

关键词: 水稻, 干燥, 干燥速率, 爆腰增率

CLC Number:

S226.6

Dawei LIU, Feng QIN, Qian LIAO, Xiushan WANG, Fangping XIE, Tiehui LI. Optimization and Experimental Study of Drying Process Parameters for Rice in Hot-air Drying[J]. Journal of Agricultural Science and Technology, 2024, 26(8): 93-102.

刘大为, 秦锋, 廖骞, 王修善, 谢方平, 李铁辉. 南方籼稻热风干燥特性及其工艺参数优化[J]. 中国农业科技导报, 2024, 26(8): 93-102.

Figures/Tables 7

References 23

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Test group	Factor			Evaluation index
Test group	Drying temperature /℃	Proportion of tempering time	Initial moisture content/%	Drying rate/（%·min^-1）	Explosive waist increase rate/%
1a	45	0.735	26	0.015 43	1.4
2a	45	0.735	22	0.014 01	1.8
3a	45	0.670	24	0.017 13	2.2
4a	45	0.800	24	0.013 83	1.8
5a	50	0.670	26	0.023 01	3.2
6a	50	0.800	22	0.013 96	2.0
7a	50	0.800	26	0.016 84	1.6
8a	50	0.735	24	0.017 60	3.0
9a	50	0.670	22	0.020 60	4.6
10a	50	0.735	24	0.017 47	2.8
11a	50	0.735	24	0.017 92	2.4
12a	50	0.735	24	0.017 85	2.6
13a	50	0.735	24	0.017 39	2.6
14a	55	0.735	22	0.025 37	5.6
15a	55	0.670	24	0.031 80	6.2
16a	55	0.735	26	0.026 53	5.2
17a	55	0.800	24	0.021 91	4.8

Test group	Factor			Evaluation index
Test group	Drying temperature /℃	Proportion of tempering time	Initial moisture content/%	Drying rate/（%·min^-1）	Explosive waist increase rate/%
1a	45	0.735	26	0.015 43	1.4
2a	45	0.735	22	0.014 01	1.8
3a	45	0.670	24	0.017 13	2.2
4a	45	0.800	24	0.013 83	1.8
5a	50	0.670	26	0.023 01	3.2
6a	50	0.800	22	0.013 96	2.0
7a	50	0.800	26	0.016 84	1.6
8a	50	0.735	24	0.017 60	3.0
9a	50	0.670	22	0.020 60	4.6
10a	50	0.735	24	0.017 47	2.8
11a	50	0.735	24	0.017 92	2.4
12a	50	0.735	24	0.017 85	2.6
13a	50	0.735	24	0.017 39	2.6
14a	55	0.735	22	0.025 37	5.6
15a	55	0.670	24	0.031 80	6.2
16a	55	0.735	26	0.026 53	5.2
17a	55	0.800	24	0.021 91	4.8

Test group	Factor			Evaluation index
Test group	Drying temperature /℃	Proportion of tempering time	Initial moisture content/%	Drying rate/（%·min^-1）	Additional crack percentage /%
1b	45	0.735	26	0.023 07	2.6
2b	45	0.735	22	0.021 23	3.2
3b	45	0.670	24	0.025 74	3.6
4b	45	0.800	24	0.019 61	2.2
5b	50	0.670	26	0.030 24	4.6
6b	50	0.800	22	0.020 88	3.2
7b	50	0.800	26	0.023 00	2.6
8b	50	0.735	24	0.026 93	4.2
9b	50	0.670	22	0.035 96	6.0
10b	50	0.735	24	0.026 60	4.4
11b	50	0.735	24	0.027 26	3.6
12b	50	0.735	24	0.025 71	4.0
13b	50	0.735	24	0.026 21	3.8
14b	55	0.735	22	0.044 76	6.8
15b	55	0.670	24	0.052 95	7.4
16b	55	0.735	26	0.037 37	6.4
17b	55	0.800	24	0.032 26	6.2

Test group	Factor			Evaluation index
Test group	Drying temperature /℃	Proportion of tempering time	Initial moisture content/%	Drying rate/（%·min^-1）	Additional crack percentage /%
1b	45	0.735	26	0.023 07	2.6
2b	45	0.735	22	0.021 23	3.2
3b	45	0.670	24	0.025 74	3.6
4b	45	0.800	24	0.019 61	2.2
5b	50	0.670	26	0.030 24	4.6
6b	50	0.800	22	0.020 88	3.2
7b	50	0.800	26	0.023 00	2.6
8b	50	0.735	24	0.026 93	4.2
9b	50	0.670	22	0.035 96	6.0
10b	50	0.735	24	0.026 60	4.4
11b	50	0.735	24	0.027 26	3.6
12b	50	0.735	24	0.025 71	4.0
13b	50	0.735	24	0.026 21	3.8
14b	55	0.735	22	0.044 76	6.8
15b	55	0.670	24	0.052 95	7.4
16b	55	0.735	26	0.037 37	6.4
17b	55	0.800	24	0.032 26	6.2

Variety	Index	Variation source	F value	P value
a： Zhongzao 35	Drying rate （Y_1a）	Model	259.47	<0.000 1^**
		Lack of fit	5.96	0.058 7
		Drying temperature （A）	1 518.35	<0.000 1^**
		Proportion of tempering time （B）	504.10	<0.000 1^**
		Initial moisture content （C）	46.36	0.000 3^**
	Additional crack percentage （Y_2a）	Model	40.28	<0.000 1^**
		Lack of fit	3.4	0.134 1
		Drying temperature （A）	273.93	<0.000 1^**
		Proportion of tempering time （B）	51.65	0.000 2^**
		Initial moisture content （C）	8.01	0.025 4^*
b： Yuzhenxiang	Drying rate （Y_1b）	Model	198.26	<0.000 1^**
		Lack of fit	3.19	0.145 9
		Drying temperature （A）	1 057.62	<0.000 1^**
		Proportion of tempering time （B）	423.12	<0.000 1^**
		Initial moisture content （C）	14.67	0.006 5^**
	Additional crack percentage （Y_2b）	Model	26.71	0.000 1^**
		Lack of fit	2.5	0.198 5
		Drying temperature（A）	175.79	<0.000 1^**
		Proportion of tempering time （B）	41.67	0.000 3^**
		Initial moisture content （C）	6.85	0.034 6^*