Investigating the malting suitability and brewing quality of different rice varieties

Authors: GUIMARAES, BERNARDO - University Of Arkansas; SCHRICKEL, FLORIAN - Research And Training Institute For Brewing In Berlin (VLB); RETTBERG, NILS - Research And Training Institute For Brewing In Berlin (VLB); Pinson, Shannon; ATUNGULU, GRIFFITHS - University Of Arkansas; MCCLUNG, ANNA - Retired ARS Employee; SHA, XUEYAN - University Of Arkansas; DE GUZMAN, CHRISTIAN - University Of Arkansas; LAFONTAINE, SCOTT - University Of Arkansas

Submitted to: Beverages
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2024
Publication Date: 2/1/2024
Citation: Guimaraes, B.P., Schrickel, F., Rettberg, N., Pinson, S.R., Atungulu, G.G., Mcclung, A., Sha, X., De Guzman, C., Lafontaine, S. 2024. Investigating the malting suitability and brewing quality of different rice varieties. Beverages. 10(16). https://doi.org/10.3390/beverages10010016.
DOI: https://doi.org/10.3390/beverages10010016

Interpretive Summary: Beer is traditionally brewed using four ingredients: hops, malted barley, water, and yeast. During the fermentation process, enzymes breakdown the barley starch into sugars to feed the yeast which produce alcohol. These starch-degrading enzymes come primarily from the barley, which also provides the yeast with proteins and nutritional elements. Various other grains can be used as adjunct starches, and to impart characteristic flavors to the beer. Rice, being relatively flavorless itself, results in a lighter bodied beer with a light, crisp flavor. Rice used as adjunct starch is not malted but is milled and cooked before being mixed into the malted barley mash. In this study, we evaluated the possibility of producing beer using malted rice, as needed for rice to replace all or a portion of the barley. Brewing beer from rice alone would yield a gluten-free beer, and consumer demand for gluten-free food products has grown rapidly in the last decade. Rice is a less costly starch source than barley in many parts of the world, including the USA. In this study, we obtained grain of 19 genetically diverse rice varieties all grown in the USA, malted them in a small-sample pilot malting process, and collected their worts, which is the liquid extracted from the post-malting mashing process. These worts were analyzed chemically to compare the malting qualities of the rice varieties with each other, and with barley. All 19 rice varieties germinated sufficiently well, and provided enough amylase enzymes for their starches to be well saccharified (converted to sugars) during malting. Rice is known for containing less protein than wheat or barley grains, causing the widespread belief in the brewing community that rice beer cannot be produced without adding exogenous proteins. Contrary to this belief, our data identified some rice varieties with sufficiently high wort protein contents to indicate the brewing of beer without nutrient supplementation. Further study would be required to determine the flavor and quality of the resultant rice beers. We also discovered that rice varieties with purple pigmented brans imparted a unique and desirable color to the wort; further research would be required to confirm that this reddish color carries through to the final brewed beer. This study of worts from malted rice provides direction and motivation for further study on the use of malted rice for beer production, as well as direction for the breeding of rice varieties containing the trait combinations that can provide cost savings and price premiums for malted-rice beers.

Technical Abstract: Historically, rice has been treated as a neutral flavor starch adjunct in brewing and not utilized as malted grain and, thus, the malt quality of rice varieties has been minimally evaluated. Nineteen globally diverse rice varieties were procured following production in the USA for a pilot scale, pale ale malting test. The rice was analyzed for various chemical parameters important to malting including, amylose content, protein, germination energy, and enzymatic activity. These results show that the rice varieties were able to germinate well, with some varieties being notably uninhibited by anoxic germination conditions due to excess water. All rice varieties provided sufficient diastatic power and enzymatic activity for full saccharification without exogenous enzymes. Furthermore, this data disproved that malted rice does not have adequate protein for healthy fermentation by identifying multiple varieties with worts containing sufficient protein for fermentation without further nutrient supplementation. This data highlights that certain U.S. rice varieties can be utilized to make acceptable rice malt. Additionally, rice varieties with purple pigmented bran were found to contain moderately high levels of ß-amylase and could serve as novel natural colorants for future malt recipes.