Evolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field

Abstract

To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat (Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α-and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α-and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin.

Relationships between Falling Number, α‐amylase activity, milling, cookie, and sponge cake quality of soft white wheat

“…Other important factors to consider are that when grain experiences a rain event and preharvest sprouting takes place, other enzymes in addition to a-amylase are also activated in the wheat kernel, many of which can exert deleterious effects on soft wheat quality (Edwards, Ross, Mares, Ellison, & Tomlinson, 1989;Every, Simmons, Al-Hakkak, Hawkins, & Ross, 2002;Kruger, 1981;Mrva & Mares, 1996;Olaerts et al, 2016;Rani, Rao, Leelavathi, & Rao, 2001). Falling Number is currently the most widespread high-throughput method to predict how a wheat grain lot may perform in particular endproducts.…”

“…Therefore, it is important to understand the relationships among Falling Number, a-amylase activity, and end-use quality as assessed in this study by sugar-snap cookie diameter and cake volume and texture, and to bear in mind that the Falling Number test is an indirect measurement of the underlying physiological/biochemical processes occurring in a wheat kernel. Other important factors to consider are that when grain experiences a rain event and preharvest sprouting takes place, other enzymes in addition to a-amylase are also activated in the wheat kernel, many of which can exert deleterious effects on soft wheat quality (Edwards, Ross, Mares, Ellison, & Tomlinson, 1989;Every, Simmons, Al-Hakkak, Hawkins, & Ross, 2002;Kruger, 1981;Mrva & Mares, 1996;Olaerts et al, 2016;Rani, Rao, Leelavathi, & Rao, 2001). When late-maturity a-amylase occurs as a result of temperature fluctuations, it is primarily the a-Amy1 a-amylase genes that increase; no other deleterious enzymes are known to be involved that have a detrimental effect on wheat quality (b-glucanase may increase slightly) (Mrva & Mares, 1996).…”

Impact of Preharvest Sprouting on Endogenous Hydrolases and Technological Quality of Wheat and Bread: A Review

“…Upon controlled sprouting, the β‐amylase activity appears to increase ensuing the hydrolysis of the disulphide bonds of bound β‐amylases, which is already detected after 2 days of germination when studied under controlled conditions (Daussant & Corvazier, ; Kruger, , ). In contrast, during field sprouting of wheat, until a FN flour of 150 s, no release of bound β‐amylases into its free and active form was detected (Figure ), indicating that the enzymatic hydrolysis of bound β‐amylases probably takes some more time during sprouting in the field (Olaerts et al., ).…”

“…Olaerts et al. () studied the evolution of different hydrolytic enzymes during PHS of wheat with the use of representative wheat samples sprouted in the field (Figure ). To do so, wheat from 3 different wheat varieties, with a different susceptibility for PHS, was harvested regularly from prematurity until the moment that it was severely sprouted in the field.…”

“…Olaerts et al. () hypothesized that the removal of peptidase inhibitors are largely responsible for this increase in peptidase activity. These results assume that the regulation of α‐amylase and peptidase synthesis occurs differently or at different time points during germination (Olaerts et al., ).…”