Olamiti G, Takalani T K, Beswa D, Jideani A I O
Department of Food Science and Technology, School of Agriculture, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa.
Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, Johannesburg, South Africa.
Heliyon. 2020 Dec 7;6(12):e05467. doi: 10.1016/j.heliyon.2020.e05467. eCollection 2020 Dec.
The effect of malting and fermentation on colour, thermal properties, level of crystallinity and functional groups of , pearl millet cultivars and sorghum flours were studied using response surface methodology. The central composite rotatable design was performed on two independent variables in terms of malting and fermentation time at intervals of 24, 48 and 72 h, respectively using design expert software. One-way analysis of variance at p < 0.05, regression analysis, response surface plots for interactions between malting and fermentation processing times with response variables were recorded. The results indicated that malting and fermentation times have significant effects on the thermal and colour properties as well as the level of crystallinity and functional groups of pearl millet cultivars and sorghum flours. In terms of colour, sorghum exhibited high content in L∗ at 72.02-73.72, a∗ ranged from 2.50-3.30 and chrome at 13.10-14.82, while flour was high in b∗ and hue at 12.15-14.27 and 73.00-84.80, respectively. In terms of thermal properties, sorghum was noticed to be high in melting peak at 87.57-104.83 °C, 102.66-111.14 °C for end completion and gelatinisation range at 10.70-25.79 °C, whereas, recorded high values in onset and enthalpy at 93.20-100.11 and 5.72-21.62 J/g, respectively. The Fourier transform infrared (FTIR) spectroscopy showed that malted and fermented and sorghum flour showed peaks in OH, carbonyl, amide and C-O bonding. The optimal processing time for the colour of was 50.69 h (malting) and 39.38 h (fermentation), was 54.40 h (malting) and 65.30 h (fermentation); and sorghum was 49.90 h (malting) and 54.61 h (fermentation). While the optimal malting and fermentation time for thermal properties for was 45.78 h and 42.60 h; was 40.94 h and 29.07 h and sorghum was 34.83 h and 36.33 h, respectively with product quality at the desirability of 1.00. X-ray diffractogram results of the optimum processing points of the thermal properties showed that malted and fermented , and sorghum flour showed high peak intensities, while the unprocessed flour exhibited diffused peaks. The obtained results would assist food processing companies to improve the colour and thermal properties and also the behaviour of the crystallinity and functional groups in food during processing.
采用响应面法研究了发芽和发酵对珍珠粟品种和高粱面粉的颜色、热性能、结晶度水平及官能团的影响。使用Design Expert软件，分别以24、48和72小时为间隔，对发芽和发酵时间这两个自变量进行中心复合旋转设计。记录了p < 0.05时的单因素方差分析、回归分析以及发芽和发酵处理时间与响应变量之间相互作用的响应面图。结果表明，发芽和发酵时间对珍珠粟品种和高粱面粉的热性能、颜色特性、结晶度水平及官能团有显著影响。在颜色方面，高粱的L∗含量较高，为72.02 - 73.72，a∗范围为2.50 - 3.30，色度为13.10 - 14.82，而面粉的b∗和色调较高，分别为12.15 - 14.27和73.00 - 84.80。在热性能方面，高粱的熔点峰值较高，为87.57 - 104.83℃，终了温度为102.66 - 111.14℃，糊化范围为10.70 - 25.79℃，而[珍珠粟品种]的起始温度和焓值较高，分别为93.20 - 100.11和5.72 - 21.62 J/g。傅里叶变换红外光谱（FTIR）显示，发芽和发酵后的[珍珠粟品种]和高粱面粉在OH、羰基、酰胺和C - O键处有峰值。[珍珠粟品种]颜色的最佳加工时间为50.69小时（发芽）和39.38小时（发酵），[另一种珍珠粟品种]为54.40小时（发芽）和65.30小时（发酵）；高粱为49.90小时（发芽）和54.61小时（发酵）。而[珍珠粟品种]热性能的最佳发芽和发酵时间分别为45.78小时和42.60小时；[另一种珍珠粟品种]为40.94小时和29.07小时，高粱分别为34.83小时和36.33小时，产品质量期望度均为1.00。热性能最佳加工点的X射线衍射图谱结果表明，发芽和发酵后的[珍珠粟品种]、[另一种珍珠粟品种]和高粱面粉显示出较高的峰值强度，而未加工的面粉显示出弥散的峰值。所得结果将有助于食品加工公司改善食品的颜色和热性能，以及加工过程中食品结晶度和官能团的行为。
