Effect of malting time,mashing temperature and added commercial enzymes on extract recovery from a Nigerian malted yellow sorghum variety

Preliminary microbiological studies carried out on sorghum grains showed that the major microorganisms found were mainly bacteria and that aflatoxin‐producing fungi were not found. The effect of added commercial enzyme preparations and different infusion mashing temperatures on extract yield, from sorghum malted at 30 °C, was studied. The infusion mashing method (65 °C) developed for mashing well‐modified barley malt produces poor extract yields with sorghum malt. The extract yield from the sorghum malt in this study was very low with infusion mashing at 65 °C, without the addition of commercial enzyme preparations. A higher extract yield was obtained from the sorghum malt, without the commercial enzyme addition, when using infusion mashing at 85 °C. Both infusion mashing temperatures (65 and 85 °C) showed an improved extract yield over the control malt when commercial enzyme preparations were used during mashing of the sorghum malt. The added enzyme preparations resulted in a higher extract yield from the germinated sorghum when infusion mashing was performed at 65 °C over mashing at 85 °C. The use of individual commercial enzymes (α‐amylase, β‐glucanase, protease, xylanase, saccharifying enzyme and combinations of some hydrolytic enzyme) increased extract yields, when complemented with the enzymes that had developed in the sorghum malt. Copyright © 2016 The Institute of Brewing & Distilling     

DEVELOPMENT OF A MASHING PROFILE FOR THE USE OF MICROBIAL ENZYMES IN BREWING WITH RAW SORGHUM (80%) AND MALTED BARLEY OR SORGHUM MALT (20%)

Different time and temperature programmes were used to evaluate the production of hot water extract (HWE) and free amino nitrogen (FAN) from mashes containing raw sorghum and either malted sorghum or malted barley in the presence of microbial enzymes. Two malted varieties of sorghum (SK 5912 and Zaria) were used. The former gave higher HWE but lower FAN than the latter. Sorghum malts were unable to provide enzyme activity for starch extraction and exogenous enzymes were always needed. Seventeen commercially available enzyme preparations were assessed. A double-mash process was developed. Inclusion of calcium ions (200 ppm) was beneficial but adjustment of mash pH had little effect. Raw sorghum was gelatinised at 100°C for 30–40 min in the presence of a heat-stable α-amylase followed by mixing with a malt mash (started at B0°C) to give a temperature of 65°C with a total mash time of 167 min (127 min from mixing the mashes). The inclusion of a single commercial enzyme preparation (containing both proteolytic and amylolytic activities) was sufficient to achieve satisfactory HWE and FAN. Addition of different activities or combinations of activities gave no significant advantages. To obtain levels of FAN of 100–140 mg/l however excessive amounts of enzymes were required.     

THE PROPERTIES,COMPOSITION AND FERMENTABILITIES OF WORTS MADE FROM 100% RAW SORGHUM AND COMMERCIAL ENZYMES

A mashing regime was developed using 100% raw sorghum which enabled commercially acceptable hot water extracts to be obtained in 85 minutes with minimal use of a heat stable α-amylase and proteolytic enzymes. This gave worts of HWE 295 1°/kg, with FAN levels of about 40 mg/l and ammonium ion concentration of about 60 mg/l. Higher, but commercially unacceptable, levels of proteolytic enzymes gave worts with FAN from 84.5 to 95 (mg/l). Addition of an amyloglucosidase as the commercial preparation Amylo300L, was required to convert the HWE to fermentable extract. The addition of Amylo300L, increased the DP1, DP2 and DP3 carbohydrate fractions of the worts from 22% to more than 90% of the total, compared to about 80% for a wort made from malted barley without the use of enzymes. Two different proteolytic enzymes gave different extracts and FAN contents presumably reflecting either differences in susceptibilities of the sorghum to the two enzymes or the presence of different additional enzyme activities in the different preparations. The level of ammonium ions in malted barley worts was 86 mg/l and up to 88 mg/l in worts produced from sorghum and enzymes. Enzyme addition produced increased levels of ammonia. The content of Group A (the most readily assimilated) amino acids was proportionally higher in sorghum worts compared to malted barley wort. Worts made from raw sorghum and enzymes, containing as little as 40 mg/l FAN, were fully attenuated. The yeast consumed about 35 mg/l FAN and 45 mg/l ammonium ions. Under identical fermentation conditions, the same yeast, fermenting a malted barley wort of comparable extract consumed 104 mg/l FAN and 37 mg/l ammonium ions.     

Proteolysis of Sorghum Endosperm Proteins when Mashing with Raw Grain Plus Exogenous Protease and Potassium Metabisulphite

With the aim of improving free amino nitrogen (FAN) production when mashing with raw sorghum grain and exogenous enzymes, the effect of mashing with the addition of the reducing agent potassium metabisulphite (KMS) on the sorghum endosperm proteins was studied. When mashing was conducted at low temperature (40°C) over an extended period (7 h) with 0.1% KMS (sorghum basis) in addition to exogenous protease, FAN increased by approx. 6 fold to approx. 91 mg/100 g sorghum, as opposed to 5 fold to approx. 75 mg/100 g sorghum with the exogenous enzyme only. Confocal laser scanning microscopy revealed that the exogenous protease caused the endosperm protein matrix that surrounds the starch granules to break up on cooking. Transmission electron microscopy showed that the exogenous protease predominantly hydrolysed the glutelin matrix protein surrounding the kafirin protein bodies. In the presence of KMS there was also substantial breakdown of the protein bodies. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis indicated that KMS had the effect of reducing kafirin polymers and oligomers into monomers. It appears that the addition of KMS in a sorghum grain mashing system significantly improves the rate of sorghum protein hydrolysis because of the reduction of intermolecular disulphide bonds in the kafirin protein, which allows better access of the protease, resulting in improved FAN production.     

Evaluation of the potentials of millet,sorghum and barley with similar nitrogen contents malted at their optimum germination temperatures for use in brewing

Studies on the malting physiology of barley have led to similar studies on millet and sorghum. This study compares the outcomes of the malting physiology of millet, sorghum and barley. Results show that optimal development of diastatic power, soluble nitrogen, hot water extract and the wide range of amino acids of these three cereals is related to optimal malting conditions and appropriate mashing procedures. Transfer of the nitrogen/extract/soluble nitrogen/diastatic concepts of barley malt do not apply to millet and sorghum. However, all the cereals studied produced the range of amino acids required by yeast for fermentation. Sorghum malt released the highest amounts of group 1 amino acids, usually taken up faster by yeast. It also produced and released the highest amounts of amino acids, classified as group 2, which are assimilated more slowly than group 1 amino acids. It also produced and released more of the amino acids that are slowest to be assimilated during fermentation, as well as very high levels of proline. Optic barley malt produced and released the least amount of proline. The fate of proline during yeast fermentation is not clear, but it is believed that proline is not utilized during fermentation. Copyright © 2013 The Institute of Brewing & Distilling     

Influence of High Protein Digestibility Sorghums on Free Amino Nitrogen (FAN) Production during Malting and Mashing

In sorghum brewing, obtaining sufficient Free Amino Nitrogen (FAN) for rapid and complete fermentation remains a problem due to the high proportions of unmalted sorghum used and the poor digestibility of wet‐heat treated sorghum protein. Sorghum mutant lines with high protein digestibility have been developed through breeding. These high protein digestibility sorghums (HPDS) have protein bodies with villi‐like borders that apparently facilitate protease access. This work investigated FAN production from HPDS when malted and mashed, to assess their potential for use in sorghum brewing to improve wort FAN levels. When malted, HPDS contained substantially higher levels of FAN than normal protein digestibility sorghums (NPDS), 32 mg/100 g malt more. However, when the HPDS were mashed either as malt, or as grain or malt plus exogenous proteases, FAN production during mashing was not substantially higher than with NPDS subjected to the same treatments, only 6, 6–18 and 9–13 mg/100 g grain or malt, respectively. This is probably due to wet‐heat induced cross‐linking of the kafirin proteins reducing their susceptibility to proteolysis. Notwithstanding this, HPDS could be very useful for improving FAN levels in sorghum brewing if they are malted.     

热处理对‘塔罗科’血橙物流变温环境下的保鲜效果

以‘塔罗科’血橙为试材,采用48、52、56℃的热水分别短时处理1 min和2 min,研究其在贮藏期(3℃、相对湿度(relative humidity,RH)90%~95%条件下21 d)、模拟运输期(10℃、RH 60%~70%条件下7 d)和货架期(20℃、RH 60%~70%条件下7 d)3个物流变温阶段的保鲜效果。结果表明,适宜的热水处理能明显减缓物流过程温度变化引起的不利影响,提高血橙果皮中多酚氧化酶、过氧化物酶、超氧化物歧化酶、过氧化氢酶的活性,使其维持在较高水平;同时,也能够保持很好的色泽(柑橘色泽指数、色相)、硬度和营养品质(花色苷含量、总酸含量、可溶性固形物含量)。然而处理温度超过56℃造成血橙产生不可逆的热损伤,物流过程中的温度变化促进了其腐烂。综合分析,52℃、2 min条件下血橙的保鲜效果最佳。