Effect of pre‐treatment on the functional properties of germinated whole grains: A review

Background and objectives The pre‐treatments for germination of whole grains, including soaking, stress, non‐thermal processing treatments, and other methods, have been gained great attention for improving biological activity and functional properties of whole grains. The objective of this review was to summarize the effects of pre‐treatments on the γ‐aminobutyric acid (GABA), phenolics, dietary fiber, and mineral bioaccessibility in germinated whole grains for the development and utilization of them as functional food products or ingredients. Findings The GABA, phenolics, dietary fiber, and mineral bioaccessibility in germinated whole grains were increased by 10–55 mg /100 g, 0.1–1.5 mg/g, 0.39%‐4.92%, and 2%–12%, respectively, after pre‐treatment for germination compared with only soaking. The contents of GABA and total phenolic in germinated whole grains increased by 56.92% and 11.24%, respectively, by ultrasonic pre‐treatment. The contents of GABA and total phenolic in germinated whole grains increased by 38.89% and 70%, respectively, by high hydrostatic pressure pre‐treatment. After cold plasma pre‐treatment, the contents of GABA and total phenolic in germinated whole grains increased by 47.37% and 37%, respectively. Therefore, non‐thermal processing pre‐treatments have a significant promoting effect on GABA synthesis and phenolic accumulation for germinated whole grains, such as ultrasound, cold plasma, and high hydrostatic pressure. Conclusions Non‐thermal processing pre‐treatment has been a promising strategy for developing healthy and nutritious whole‐grain foods. According to the existing research results, high hydrostatic pressure and low‐temperature plasma can promote GABA and phenolic in germinated whole grains, while ultrasound can not only increase the content of GABA and phenolic in germinated whole grains, but also increase the bioaccessibility of calcium and iron. Therefore, ultrasound can promote nutrients in germinated whole grains better than other non‐thermal processing methods. It is very important for choosing pre‐treatment methods for germination to obtain whole grains with increased functional properties. Significance and novelty This review may provide a compilation of information that pre‐treatments can improve the biological activity and development of functional foods from the sources of germinated whole grains.