Wet vacuum impregnation assisted in malting; its implication on steeping degree, germination energy and malt properties

Abstract

Summary The wet vacuum impregnation (WVI) was used in malting process to reduce soaking period. To implement WVI during steeping, vacuum pressure of 500 mmHg for 300 s, was applied twice on five Thai barley cultivars. The effect of WVI on germination energy, moisture content, phenolic acids, antioxidant activity (AOA) and malt quality were examined relative to Central European Commission for Brewing Analysis (MEBAK) malting condition. Moisture content in barley soaked by WVI and MEBAK steeping method were in the range of 36.1–39.9% and 39.9–47.8%, respectively with germination energy of 96–97%. The physicochemical properties of malt from steeping via WVI and MEBAK showed the malts were protein‐rich cultivars, adequate β enzyme and low α amylase activities, hence, low‐malt extract. Total fermentable sugars were relative higher in MEBAK malts than WVI malts. Nevertheless, steeping by WVI had higher free and bound phenolic acids, which led to higher AOA via ABSTS and DPPH assays in some barley cultivars than MEBAK. This research highlights the WVI did not limit barley gemination and the potential of this technology in malting process by limiting steeping time. Further study is required to reduce air‐rest period and optimise condition to achieve moisture content of 40–45% in soaked barley.

Modification of the Malting Process of Barley Grains of Different Varieties by Vacuum Impregnation and Its Effect on Selected Wort Parameters

“…However, steeping by WVI gave a higher content of free and bound phenolic acids, leading to a higher AOA. Studies have also shown that WVI does not limit barley germination and indicates the high potential of this technology in the malting process, as it reduces steeping time [12].…”

“…According to Gonu et al [12], wet vacuum impregnation (WVI) can be used in the malting process to reduce the soaking period. Grains of five Thai barley varieties were soaked at 500 mmHg for 300 s. The effects of WVI on germination energy, moisture content, phenolic acid content and antioxidant activity (AOA) were studied.…”

“…In malt production technology, there is a steeping process, the purpose of which is to initiate life processes in the grain and which is based on the exchange of mass in the water-grain system. This is a lengthy process (lasting up to 72 h) [12] and is carried out until the water content of the grain is between 40% and 46% [13].…”

“…For example, high intensity and short-time VI before rice germination caused a negative effect through the destruction of cellular structures and the rupture of cell membranes, causing lower germination ability and reduced metabolite production [15]. There are many questions, especially regarding the quality of malt produced using VI [12]. Among the important quality characteristics of malt is the level of extractability and the level of viscosity of the wort obtained; hence, the aim of this study is to compare these quality characteristics of malt made from barley grains treated with VI at the steeping stage, with barley malt made under the same conditions without the application of VI.…”