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

Abstract

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.

Influence of sorghum grain type on wort physico-chemical and sensory quality in a whole-grain and commercial enzyme mashing process

“…The large increase in fermentable sugars is undoubtedly due to the combined activity of the malt amylase enzymes and the exogenous amylases. Similarly, the very large increase in FAN was due to the combination of malt and exogenous protease enzymes .…”

125thAnniversary Review: The science of the tropical cereals sorghum, maize and rice in relation to lager beer brewing

“…For example, sorghum lines with high protein digestibility have been developed where synthesis of certain kafirin sub‐classes, including specifically γ ‐kafirin, have been inhibited by chemical mutation or genetic modification . Research has shown that FAN in sorghum malt and FAN and extract in raw sorghum grain brewing can be substantially improved with the use of such sorghums.…”

Potential for improvement in yeast nutrition in raw whole grain sorghum and maize lager brewing and bioethanol production through grain genetic modification and phytase treatment

“…Nitric–perchloric acid digestion of the raw flour and spent grain samples was performed as described . The iron, zinc, magnesium, calcium and phosphorus contents of the digested flour, digested spent grain and wort were measured by inductively coupled plasma optical emission spectrometry (ICP‐OES; Optima 5300 DV, PerkinElmer, Johannesburg, South Africa).…”