Characteristic changes in malt, wort, and beer produced from different Nigerian rice varieties as influenced by varying malting conditions

Chigozie E Ofoedu; Chibugo Q Akosim; Jude O Iwouno; Chioma D Obi; Ivan Shorstkii; Charles Odilichukwu R Okpala

doi:10.7717/peerj.10968

Characteristic changes in malt, wort, and beer produced from different Nigerian rice varieties as influenced by varying malting conditions

PeerJ. 2021 Mar 19:9:e10968. doi: 10.7717/peerj.10968. eCollection 2021.

Authors

Chigozie E Ofoedu¹, Chibugo Q Akosim¹, Jude O Iwouno¹, Chioma D Obi², Ivan Shorstkii³, Charles Odilichukwu R Okpala⁴

Affiliations

¹ Department of Food Science and Technology, School of Engineering and Engineering Technology, Federal University of Technology, Owerri, Owerri, Imo, Nigeria.
² Department of Food Science and Technology, Nnamdi Azikiwe University, Awka, Anambra, Nigeria.
³ Department of Technological Equipment and Life-Support Systems, Kuban State Technological University, Krasnodar, Russian Federation.
⁴ Department of Functional Food Products Development, Faculty of Biotechnology and Food Science, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland.

Abstract

Gluten-free beer could be produced with rice, although the latter would primarily serve as adjunct in combination with barley malt in today's brewing. However, the recent growing realisation of the potential and applications of rice malt for brewing an all-rice malt beer through varying malting conditions cannot be overlooked. In this study, therefore, the characteristic changes in malt, wort, and beer from different Nigerian rice varieties (FARO 44, FARO 57, NERICA 7) as influenced by varying malting conditions (steeping duration (18, 24 and 30 h), germination periods (2, 3 and 4 days) and kilning temperatures (50 and 55 °C)), were investigated. Rice (grain) samples were examined by thousand kernel weight (TKW), germinative energy (GE), germinative capacity (GC), and degree of steeping (DoS). To ensure that rice wort/beer with unique beer style and enhanced attributes, comparable to barley wort/beer is produced, malting conditions that produced rice malts with peak diastatic power (DP), cold water extract (CWE), and hot water extract (HWE) were selected. Peak DP, CWE and HWE were obtained at FARO 44 (18 h steeping, 3 days germination, 55 °C kilning (S₁₈G₃K_55°)), FARO 57 (30 h steeping, 2 days germination, 50 °C kilning (S₃₀G₂K_50°)) and NERICA 7 (24 h steeping, 3 days germination, 55 °C kilning (S₂₄G₃K_55°)). Selected malts were further tested for moisture content, total nitrogen, malt yield and malting loss and subsequently progressed to wort and beer production. Wort's pH, total soluble nitrogen (TSN), brix, kolbach index (KI), free amino nitrogen (FAN), dextrose equivalent (DE), original extract (OE) and sugar profile were determined, as well as beer's pH, colour, apparent extract (AE), alcohol by volume (%ABV), turbidity and sensory attributes. Rice grain varied significantly (p < 0.05) in TKW, GE, GC and DoS across varieties. Despite wort's pH, TSN, DE, OE as well as beer pH, colour, AE and turbidity resembling (p > 0.05) across varieties, wort's brix, KI, FAN, sugar profile as well as beer's %ABV, differed significantly (p < 0.05). Sensory attributes of appearance, colour, mouthfeel, and overall acceptability in beer differed noticeably (p < 0.05), except for aroma and taste (p > 0.05). Overall, the rice beer, though very slightly hazy, represented a pale yellow light lager, which is indicative of its peculiar beer style. Besides increased DP and enhanced hydrolysis, varying malting conditions of current study could serve as a pathway of reducing the cost of exogenous (commercial) enzymes or barley malt imports, together with decreasing barley's dependency for brewing in the tropics.

Keywords: Malting conditions; Mashing process; Rice beer; Rice malt; Rice wort.

Grants and funding

Publication was financed by the project UPWR 2.0: international and interdisciplinary programme of development of Wrocław University of Environmental and Life Sciences, co-financed by the European Social Fund under the Operational Program Knowledge Education Development, under contract No. POWR.03.05.00-00-Z062/18 of 4 June 2019. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.