Overcoming technical barriers to brewing with green (non-kilned) malt: a feasibility study

Abstract

Brewing using enzyme rich ‘green’ (germinated, but not kilned) malt has the potential to unlock considerable energy savings in the malting and brewing chain. This paper examines the major quality issues associated with green malt, by monitoring lipoxygenase (LOX) activity and S‐methyl methionine (SMM) levels through a micromalting cycle both with and without rootlets after 48 h of germination. The data suggest that rootlets are a major concern when brewing with green malt and that their influence on wort and beer quality needs to be further investigated. Lipoxygenase activity and nonenal potential were measured following treatment under varying conditions of pH, temperature and pre‐treatment. Results indicated that lipoxygenase activity can be controlled to a substantial degree by manipulating these limiting factors, while preserving diastatic enzyme activity. Green malt worts were then prepared from (i) whole green malt immediately post‐germination; (ii) heat treated green malt (65°C x 1 h); (iii) re‐steeped green malt and (iv) endosperm‐rich extracts of green malt after the husk and rootlets had been removed; using laboratory mashing with a ‘LOX‐hostile’ mash schedule. Data were compared with mashing of kilned pale malt made from the same green malt, as a reference point. Based on the present data, re‐steeping of green malt in combination with a LOX hostile mashing environment (63°C, pH 5.2) could help to control LOX activity and the trans‐2‐nonenal potential of green malt. The resultant brewing process would need to be optimised to deal with the elevated SMM levels in green malt worts. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling

Brewing with 100% green malt – process development and key quality indicators

“…Thus, future studies should be directed to the oxidation of unsaturated fatty acids to further elucidate why THFA increased when brewing with kilned malt, but contrary to expectations, not when using green malt. Previous research from our group ( 26 ) had indicated that re‐steeping of green malt in water for an hour was an effective means to reduce the LOX activity of green malt by around 50%. Accordingly, it was decided to assess the quality impact of this putative process at pilot scale, including the re‐use of re‐steep water as mashing liquor in the green malt brewing process in order to minimise overall water usage in the chain.…”

“…The malts used for the preparation of the beers were analysed for trihydroxy fatty acids (THFA) levels. Clearly, green malt has a higher lipoxygenase (LOX) activity compared to kilned malt ( 26 ) ; a major threat for beer flavour and stability. The determined contents of THFA in the malts used for this study were significantly lower in kilned malt (39.6 ± 9.9 mg/kg, dry basis) compared to green malt (68.3 ± 4.5 mg/kg, d.b.).…”

“…trans ‐2‐nonenal or hexanal, that are known beer staling compounds ( 8, 24, 25 ) . Recent laboratory scale trials ( 26 ) indicated that re‐steeping of green malt in combination with a LOX hostile mashing environment (63°C, pH 5.2 and oxygen free) could help to control LOX activity and the trans ‐2‐nonenal potential of green malt. Alternatively, LOX‐less ( 22, 27 ) or Null‐LOX barley ( 28 ) varieties are now available and might thus be suitable when brewing with green malt.…”

A Comprehensive Evaluation of Flavor Instability of Beer (Part 1): Influence of Release of Bound State Aldehydes

“…They found that along with ACA (K a = 485 × 10 3 ), Meth (K a = 50 × 10 3 ) and 3MB (K a = 29 × 10 3 ) showed higher affinity toward HSO 3 − compared to PA (K a = 17 × 10 3 ), 2MP (K a = 2.8 × 10 3 ), 2MB (K a = 2.6 × 10 3 ), or Fur (K a = 0.1 × 10 3 ). Higher values indicate an increased affinity toward nucleophiles [14,15].…”

“…For example, this can be done in the so-called nonenal potential. Hereby, the capacity of a wort to produce (E)-2-nonenal (T2N) and, since recently, also hexanal (Hex) is assessed [14,15]. Using 4-vinyl pyridine (4VP), Baert et al developed a method to release bound state aldehydes from these bound forms through a pH shift and trapping of cysteine [16,17].…”