Functional and nutritional properties of infrared and microwave heat moisture-treated sorghum meals

Proximate analysis: Sorghum meal samples were analyzed for moisture, ash, and crude fat using procedures 925.10, 923.03, and 920.39, respectively, from the Association of Official Analytical Chemists (AOAC, 2019). Protein (N × 6.25) was determined using the Dumas combustion method.
Total starch content: Total starch content of the sorghum types was determined using the megazyme method. Total phenolic content: The total phenolic content was determined using the Folin-Ciocalteu method by Waterman and Mole (1994) and reported as catechin equivalent.
Tannin content: Tannin content was determined according to Price et al., (1978). In brief, sorghum meal (1g) was weighed into a 25 ml beaker. Concentrated HCl in methanol (10 ml of 1% v/v) was used for the tannin extraction process by stirring on a magnetic stirrer for 2 h. Vanillin-HCl reagent was added to the extracted tannin and incubated in the dark for 20 min.
Nitrogen solubility: The nitrogen solubility index was determined according to Ogundele et al., (2017). Meals (1 g) were mixed for 1 hr at 30°C in 20 ml of 0.1 M NaCl solution. After centrifuging (9500 x g, 15 min), the supernatant was filtered using Whatman No.1 filter paper. Two more times, the residue from the suspension was washed in 10 ml of 0.1 M NaCl solution at pH 7. After being frozen at -10°C for the entire night, the filtrate was freeze-dried using a 13KL Instruvac Lyophilizer at Midrand, South Africa. 
Water absorption capacity and water solubility index: Sorghum meal solubility was determined using the method described by Mapengo & Emmambux, (2020). Samples of (1 g, dry basis) meal were cooked in 10 ml of distilled water at two different temperatures, 50 °C and 91 °C in a shaking water bath at 150 rpm for 30 min, with the mixture being vortexed every 5 min. The sample solution was centrifuged at 9154.3 x g for 15 min. 
Pasting properties: Sorghum meal samples were pasted according to Wokadala et al., (2012) with modification using the rheometer with a starch cell (Physica MCR 101, Anton Paar, Germany). The samples were then held at 91°C for 15 min, followed by cooling from 91°C to 50°C at a rate of 5.5 °C/min and allowed to stand for 2 min.
X-ray diffractions crystallinity: XRD was conducted using PANalytical X’pert PRO (Eindhoven, Netherlands) on native, HMT-treated, and pasted samples as described by Mapengo et al., (2019) with slight modification. 
In vitro starch digestibility: In vitro starch digestibility of the pasted sorghum meals was done using the method described by Goñi et al., (1997).

近缘分析：高粱粉样品分别采用美国官方分析化学家协会（AOAC，2019年）规定的925.10、923.03和920.39程序，对水分、灰分和粗脂肪进行了分析。蛋白质含量（N × 6.25）通过杜马燃烧法测定。总淀粉含量：使用megazyme方法测定高粱各类型总淀粉含量。总酚含量：采用Waterman和Mole（1994年）的Folin-Ciocalteu方法测定总酚含量，并以儿茶素当量表示。单宁含量：参照Price等人（1978年）的方法测定单宁含量。简言之，将1克高粱粉称入25毫升烧杯中。使用甲醇中的浓盐酸（10毫升1%体积比）在磁力搅拌器上搅拌2小时进行单宁提取。向提取的单宁中加入茴香-HCl试剂，在暗处孵育20分钟。氮溶解度：根据Ogundele等人（2017年）的方法测定氮溶解度指数。将1克粉料与20毫升0.1 M氯化钠溶液混合，在30°C下搅拌1小时。离心（9500 x g，15分钟）后，使用Whatman No.1滤纸过滤上清液。再用10毫升0.1 M氯化钠溶液在pH 7的条件下清洗悬浮物残留物两次。将溶液在-10°C下冷冻整个夜晚后，使用位于南非Midrand的13KL Instruvac冷冻干燥机进行冷冻干燥。吸水能力和溶解度指数：使用Mapengo与Emmambux（2020年）描述的方法测定高粱粉的溶解度。将（1克，干基）样品在10毫升蒸馏水中，在50°C和91°C两种不同温度下，在150 rpm的摇水浴中加热30分钟，每5分钟涡旋一次。样品溶液在9154.3 x g下离心15分钟。糊化特性：根据Wokadala等人（2012年）的方法，对高粱粉样品进行糊化，并使用配有淀粉细胞（Physica MCR 101，Anton Paar，德国）的流变仪进行改良。然后，样品在91°C下保持15分钟，随后以5.5°C/min的速率从91°C冷却至50°C，并静置2分钟。X射线衍射结晶度：使用PANalytical X’pert PRO（Eindhoven，荷兰）在原生、HMT处理和糊化样品上执行XRD分析，方法参照Mapengo等人（2019年）的描述，并略有修改。体外淀粉消化率：使用Goñi等人（1997年）描述的方法对糊化高粱粉的体外淀粉消化率进行测定。