Changes in enzymatic activity and in vitro protein digestibility of four millet varieties upon germination and quality evaluation of cookies prepared from germinated millet composite flours

Abstract

The millet kernels of four millet varieties (foxtail, finger, and red and white proso millets) were germinated for 24, 48, and 72 h at 30 and 35°C. Changes in proximate composition, activity of α-amylase, cellulase, and protease, and in vitro protein digestibility, were determined in whole flours obtained from the germinated seeds. Germination increased protein content while decreasing ash and moisture contents in most millet varieties. Enzyme activities in all the millets were influenced by germination time and temperature (p < 0.05). α-Amylase activity in foxtail and red proso millet significantly increased during the germination (from 1774.05 to 2643.18 U/g, and from 1608.19 to 1816.84 U/g, respectively at 30°C). Protein digestibility increased after germination and correlated with protein content, α-amylase, and protease activities. Cookies made from the germinated foxtail composite flour presented a comparable sensory acceptance to the reference cookies made from wheat flour. Practical applications Germination increased protein content while decreasing ash and moisture contents in most studied millet varieties. Enzyme activities (α-amylase, cellulase) in all the millets, and especially in foxtail millet, were influenced by germination time and temperature. Protein digestibility increased after germination and correlated with protein content, α-amylase, and protease activities but was reduced in the formulated cookies.