What question did this study set out to answer?

This study aims to examine how the form and level of intermediate wheatgrass influence the chemical composition and aroma development in sake brewing.

June 3, 2026Open Access

Impact of Intermediate Wheatgrass an Adjunct Ingredient on the Chemical Composition and Development of Aroma Compounds in Sake Brewing

Key Points

This study aims to examine how the form and level of intermediate wheatgrass influence the chemical composition and aroma development in sake brewing.
Sake was brewed with 70% polished Calrose rice and two forms of IWG (whole and refined) at levels of 7.5% and 15% w/w.
Chemical analyses included evaluating starch, protein, free amino acids, glucose, pH, alcohol, and organic acids after fermentation.
Volatile profiling used HS-SPME-GC-TOFMS with PCA for characterizing differences among sake samples.
Refining IWG resulted in lower starch (44.14 g/100 g) and higher protein (15.25 g/100 g) content compared to whole IWG (starch 69.46 g/100 g, protein 18.20 g/100 g).
Free amino acids were highest in whole IWG (W15 ≈ 309 mg/100 mL), compared to RICE (~245 mg/100 mL) and refined IWG (R15 at 231 mg/100 mL).
Higher ABV was achieved with whole IWG (up to 17.81%), while refined IWG led to reduced free amino acids and volatile light esters.

Abstract

ABSTRACT Background Replacing a portion of polished rice with intermediate wheatgrass (IWG) could diversify raw materials for sake, but its effects on composition and fermentation outcomes are not well characterized. The objective of this study was to quantify how adjunct form (whole vs. refined IWG) and level (7.5% or 15% w/w) influence starch and protein supply, free amino acids, sugars, pH, alcohol, organic acids, and volatiles in sake, using two commercial products as benchmarks. Methods Sake was brewed with 70%‑polished Calrose rice, yellow koji ( Aspergillus oryzae ), lactic‑acid–adjusted shubo , and static fermentation at 15°C following sandan‑jikomi. Whole IWG was hammer‑milled ( RIWG > rice (16.40, 13.85, 3.37 g/100 g). In finished sakes, free amino acids were highest with whole‑grain adjuncts (W15 ≈ 309; W7.5 ≈ 299 mg/100 mL), intermediate for RICE and R7.5 (each ≈245), and lowest for R15 (231). Across sakes, aspartate was the highest free amino acids (mean ≈ 95.5 mg/100 mL). Glucose declined over 15 days (e.g., Rice 4.75 → 3.71 g/100 mL), pH was stable (3.47–3.82), and ABV rose to 11.44–17.81% (Rice highest at moromi ). In‑house brews had high citric acid (~2528–4472 ppm) versus commercial references (~97–150 ppm); lactic and malic acids were also higher. Volatile profiling (29 compounds) showed lower isoamyl acetate in all IWG sakes (73–429 ppb) and very high ethyl hexanoate in Taka (2577 ppb). PCA (PC1 = 41.0%, PC2 = 34.7%) separated samples by heavier aldehydes/lactones versus light esters/higher alcohols and highlighted medium‑chain ester features. Conclusions Adjunct form and level are key factors in producing IWG sake. Use of whole‑grain IWG increased free amino acids, favored medium‑chain ester formation, and achieved higher ABV than refined IWG at matched inclusion, whereas higher refinement of IWG reduced the free‑amino‑acid pool and light esters. These data provide a compositional baseline for optimizing IWG‑adjunct sake through ingredient selection and process control; however, under the conditions tested, IWG did not yield a compositional profile clearly advantageous for sake quality.

Impact of Intermediate Wheatgrass an Adjunct Ingredient on the Chemical Composition and Development of Aroma Compounds in Sake Brewing

Key Points

Abstract

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