The Changes in GABA, GAD and DAO Activities, and Microbial Safety of Soaking- and High Voltage Electric Field-Treated Adzuki Bean Sprouts

Abstract

The level of γ-aminobutyric acid (GABA) in nongerminated adzuki bean seeds is low, but it increases substantially during germination and sprouting. In this study, three seed treatments, including soaking (S), high voltage electric field (HVEF), and soaking plus HVEF (SHVEF), were used to examine their effects on sprout growth, sprout GABA content, sprout glutamate decarboxylase (GAD), and diamine oxidase (DAO) activities and microbial loads on 6-day-old adzuki bean sprouts. All the treatments enhanced sprout growth, increased sprout’s GABA, and increased sprouts’ GAD and DAO activities. The examined seed treatments also significantly reduced the microbial loads of the produced 6-day-old adzuki bean sprouts. The most effective treatment that improved the morphological and biochemical traits and reduced microbial loads on produced sprouts was the SHVEF treatment. SHVEF treatment also achieved a 5-log reduction in the microbial loads of total aerobic bacterial counts, total coliform counts, and total mold counts on the produced adzuki bean sprouts. Therefore, SHVEF is effective for increasing adzuki bean sprout production. It can also be used to improve nutritional quality and provide an intervention technique against microbial contamination on produced sprouts.

Effect of selenium fortification during sprouting of peanut seeds receivingHVEFand selenium soaking combination on yield, selenium and resveratrol contents, anti‐oxidative properties, and microbial control

“…1). For HVEF and HVEF plus soaking combination treatments, seeds were initially loaded in a polyethylene tray and placed in a chamber equipped with electrodes and a high‐voltage power supply (20 kV, 50 Hz, You‐Shang Technical Corp., Kaoshiung, City, Taiwan) (Chiu, 2022). The seeds were exposed to an electric field under strength of 4 kV cm −1 for 10 min.…”

“…Additionally, a HVEF and H 2 O soaking combination was examined, and the result exhibited an increased germination percentage and accelerated germination speed in the treated peanut seeds in comparison with the seed receiving a single HVEF or H 2 O soaking treatment only (Table 1). Chiu (2022) reported that the HVEF treatment tended to intensify the degree of seed coat crack. These microstructural changes might further enhance the seed hydration, which were favourable for improving germination responses observed on the seeds receiving HVEF and H 2 O-soaking combination.…”

“…As shown in Table 4, sprouting substantially increased the microbial loads of 8-days-old sprouts produced from control seeds and the seeds subjected to all the seed treatments. The increased microbial loads on the produced peanut sprouts are possibly attributable to the microbes present on the seeds and the favourable environmental conditions (e.g., soaking water quality and sprouting temperature) in which they are grown (Chiu, 2022). Again, the HVEF and Se-soaking The data shown are mean values AE SD (n = 3); Mean value with different superscripts indicated a significant difference (P < 0.05).…”

“…High‐voltage electric field is a non‐thermal technology used in many food processes (Dalvi‐Isfahan et al., 2016). Chiu (2022) reported that the HVEF treatment intensified seed coat cracks in treated adzuki bean seed compared with that of non‐treated seeds. The increased seed coat cracks were favourable for seed hydration, and subsequently accelerated seed germination.…”

Proposing Signaling Molecules as Key Optimization Targets for Intensifying the Phytochemical Biosynthesis Induced by Emerging Nonthermal Stress Pretreatments of Plant-Based Foods: A Focus on γ-Aminobutyric Acid

“…There is rather limited information concerning PEF-derived electrochemical effects on the plant physiology and metabolic response occurring during the germination process, as pointed out by our previous review paper. 47 In a more recent research, 50 adzuki bean seeds with high voltage electric field pretreatments (2 kV/cm, 10 min) were subjected to a germination process, finding that the growth of mung bean sprouts was significantly promoted, with the length of six-day- old sprouts being 5.24 and 12.84 cm for the untreated and PEF-stressed samples, respectively. Simultaneously, PEFprestressed seeds prior to the soaking processes demonstrated significantly higher contents of GABA compared with the natural germination of seeds, but it was simply attributed to the improved activities of GAD and DAO.…”