Spent Grain from Malt Whisky: Assessment of the Phenolic Compounds

Phenolic metabolites changes during baijiu fermentation through non-targeted metabonomic

To investigate the changes of phenolic metabolite during different grains fermentation stages of Chinse Baijiu, the ultra-performance liquid chromatography-quadrupole time of-flight mass spectrometry (UHPLC-QTOF-MS) was applied to identify and analyze the different phenolic metabolites, combined with principal component analysis and partial least squares discriminant analysis. Results indicated that significant differences in phenolic metabolites during different fermentation stages were found. Among the 231 phenolic metabolites detected, 36, 31, 19, 23, 14, and 50 differential phenolic metabolites were screened between different groups using partial least squares discriminant analysis. Twelve metabolic pathways with high correlation of differential phenolic metabolites and 23 main participating differential metabolites were identified through KEGG metabolic pathway enrichment analysis. The present study preliminarily revealed the differences of phenolic metabolites at different fermentation stages, and providing a theoretical basis for the further improving of the taste and quality of Chinese Baijiu.

Changes in Polyphenols and Antioxidant Activity in Fermentation Substrate during Maotai-Flavored Liquor Processing

To investigate the changes in phenols and antioxidant capacity in fermented grains during different stages of the fermentation process (Xiasha, Zaosha, and single-round stages) of Maotai-flavored liquor, the total phenolic contents of 61 samples, collected in different stages, were analyzed via the Folin-Ciocalteu method, and the phenolic compounds were then identified by high-performance liquid chromatography (HPLC). Subsequently, the antioxidant activities were determined using the DPPH free radical scavenging rate and ABTS and FRAP antioxidant capacities. The correlations among the total phenolic contents, individual phenolics, and three antioxidant activities of the samples were analyzed. The results show that the total phenolic contents of the fermented samples did not change significantly in the Xiasha and Zaosha stages but showed an upward trend in the single-round stage. A total of 12 phenol acids were identified in the fermented grains, including 5 phenolic acids (e.g., ferulic acid and caffeic acid), 4 flavonoids (e.g., luteolin and apigenin), and 3 proanthocyanidins (e.g., apigeninidin), for which the DPPH free radical scavenging rates and ABTS and FRAP antioxidant capacities of all of the fermented grain samples ranged from 78.91 ± 4.09 to 98.57 ± 1.52%, 3.23 ± 0.72 to 13.69 ± 1.40 mM Trolox, and 5.06 ± 0.36 to 14.10 ± 0.69 mM FeSO4, respectively. The total phenolic contents of the fermented grain samples were significantly and positively correlated with the ABTS and FRAP (p ≤ 0.05), while no significant correlations were found between total phenolic content and DPPH. In general, the total phenolic content, phenolic substances, and antioxidant capacity of the fermented grains exhibited changes during the fermentation process in liquor production, and the phenolic components contributed more to the antioxidant properties of the fermented grains. The present study provides a theoretical reference for analyzing the dynamic changes and antioxidant properties of functional phenolic components in fermented grains.

Chinese Baijiu and Whisky: Research Reservoirs for Flavor and Functional Food

Baijiu is a traditional spirit with high reputation in the Chinese community, and whisky, on the other hand, is a renowned spirit in Western culture, with both contributing a major proportion to the consumption and revenue in the global spirit market. Interestingly, starting with similar raw materials, such as grains, diverse production methods lead to different organoleptic profiles. In addition, such enormous attention they attract renders them as a crucial part in food and the related industry. Therefore, great efforts are made in improving product quality and optimizing production processes, such as flavor enhancement, facility development, and deep utilization of byproducts. Given the huge impacts and great involvements of these spirits in the general food industry, research focusing on either spirit is of referential significance for other relevant fields. With the aim of facilitating such collaboration, this review discusses the current research status, in a comparative manner, of both spirits in respect to key production processes-oriented sensory and flavor analysis, deep utilization of byproducts, and spirit-derived functional food investigations. Finally, the internal correlations based on the abovementioned criteria are identified, with research prospects proposed.

Spent Grain: A Functional Ingredient for Food Applications

Spent grain is the solid fraction remaining after wort removal. It is nutritionally rich, composed of fibers—mainly hemicellulose, cellulose, and lignin—proteins, lipids, vitamins, and minerals, and must be managed properly. Spent grain is a by-product with high moisture, high protein and high fiber content and is susceptible to microbial contamination; thus, a suitable, cost-effective, and environmentally friendly valorization method of processing it is required. This by-product is used as a raw material in the production of many other food products—bakery products, pasta, cookies, muffins, wafers, snacks, yogurt or plant-based yogurt alternatives, Frankfurter sausages or fruit beverages—due to its nutritional values. The circular economy is built on waste reduction and the reuse of by-products, which find opportunities in the regeneration and recycling of waste materials and energy that become inputs in other processes and food products. Waste disposal in the food industry has become a major issue in recent years when attempting to maintain hygiene standards and avoid soil, air and water contamination. Fortifying food products with spent grain follows the precepts of the circular bio-economy and industrial symbiosis of strengthening sustainable development. The purpose of this review is to update information on the addition of spent grain to various foods and the influence of spent grain on these foods.