Interest in phlorotannins has increased in recent years largely due to antioxidant capacity, however, the redox mechanism of phlorotannins is still obscure. In the present study, the electrochemical oxidation mechanisms of eckol (EL) and phlorofucofuroeckol‐A (PFF‐A), two representative phlorotannin compounds, were comparatively analyzed in a wide pH range using cyclic and differential pulse voltammetry as well as spectroscopic assay. The voltammetric study revealed that EL and PFF‐A were successively oxidized in three pH‐dependent steps. Moreover, it was found that the PFF‐A presented a stronger proton and electron transferring activity as compared to EL since PFF‐A exhibited lower acid–base dissociation constant (pKa) value and higher heterogeneous rate constant (kbh) value in the first oxidation step. These property were further evidenced by comparison of direct antioxidant activity (i.e., superoxide anion and peroxide radicals) as well as indirect antioxidant activity (i.e., mRNA expression of two phase II enzymes) between EL and PFF‐A. Practical applications Phlorotannins from edible algae have been regarded as novel antioxidants those presented high application potential in food industry. Even though antioxidant activity of phlorotannin compounds have been widely investigated in both in vitro and in vivo studies, very few reports focused on electron transferring functionality which is chemical basis for antioxidant process. Herein, the oxidative mechanisms of two representative phlorotannins were comparatively analyzed using multiple electrochemical methods. This is hopefully to give information on the chemical meaning behind the antioxidant activity of dietary phlorotannins.

Millet Huangjiu is a national alcoholic beverage in China. The quality of Chinese millet Huangjiu is significantly influenced by the protein components in the raw materials of millet. Therefore, in this study, the impact of different protein components on the quality of millet Huangjiu was investigated by adding exogenous proteins glutelin and albumin either individually or in combination. The study commenced with the determination of the oenological parameters of different millet Huangjiu samples, followed by the assessment of free amino acids and organic acids. In addition, the volatile profiles of millet Huangjiu were characterized by employing HS-SPME-GC/MS. Finally, a sensory evaluation was conducted to evaluate the overall aroma profiles of millet Huangjiu. The results showed that adding glutelin significantly increased the contents of total soluble solids, amino acid nitrogen, and ethanol in millet Huangjiu by 32.2%, 41.5%, and 17.7%, respectively. Furthermore, the fortification of the fermentation substrate with glutelin protein was found to significantly enhance the umami (aspartic and glutamic acids) and sweet-tasting (alanine and proline) amino acids in the final product. Gas chromatography-quadrupole mass spectrometry coupled with multivariate statistical analysis revealed distinct impacts of protein composition on the volatile organic compound (VOC) profiles of millet Huangjiu. Excessive glutelin led to an over-accumulation of alcohol aroma, while the addition of albumin protein proved to be a viable approach for enhancing the ester and fruity fragrances. Sensory analysis suggested that the proper amount of protein fortification using a Glu + Alb combination could enhance the sensory attributes of millet Huangjiu while maintaining its unique flavor characteristics. These findings suggest that reasonable adjustment of the glutelin and albumin contents in millet could effectively regulate the chemical composition and improve the sensory quality of millet Huangjiu.

Succinic acid is valuable due to its historical use in food industry. In this paper, Corynebacterium crenatum was engineered to enhance succinic acid production and the fermentation properties of engineered strains were investigated. The lactate dehydrogenase gene (ldhA) inactivation mutant was first constructed, and then the pyruvate carboxylase gene (pyc) or phosphoenolpyruvate carboxylase gene (ppc) was expressed in the ldhA mutant. The ldhA inactivation resulted in a 52% decrease on glucose consumption, and the succinic acid yield produced by the ldhA mutant was 0.62 g/g, representing a 2‐fold increase compared with the yield obtained from the original strain. Overexpression of pyc gene could improve the glucose consumption rate, resulting in a 37% increase compared with the ldhA mutant strain. Meanwhile, the final succinic acid concentration represented a 50% increase than the ldhA mutant strain, and a 106% increase than the original strain. Overexpression of ppc gene had no significant effect. Practical applications The biobased succinic acid and the derivative can be used as food additives. C. crenatum is used for producing amino acid for many years, and it was found that succinic acid and lactic acid are the major products when fermented under anaerobic conditions. This study suggests that C. crenatum can be utilized as a potential cell factory for producing succinic acid after genetic modification. The results obtained in this paper could contribute to the depth development of C. crenatum for producing succinic acid or other products in food industry, not only for amino acid production.

In the present study, germinated brown rice (GBR) from three Japonica and three Indica rice cultivars were subjected to metabolomics analysis and volatile profiling. The statistical assessment and pathway analysis of the metabolomics data demonstrated that in spite of significant metabolic changes in response to the germination treatment, the Japonica rice cultivars consistently expressed higher levels of several health-promoting compounds, such as essential amino acids and γ-aminobutyric acid (GABA), than the Indica cultivars. No clear discriminations of the volatile profiles were observed in light of the subspecies, and the concentrations of the volatile organic compounds (VOCs), including alkenes, aldehydes, furans, ketones, and alcohols, all exhibited significant reductions ranging from 26.8% to 64.1% after the germination. The results suggest that the Japonica cultivars might be desirable as the raw materials for generating and selecting GBR food products for health-conscious consumers.

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