Low pH Enhances the Glucosinolate-Mediated Yellowing of Takuan-zuke under Low Salt Conditions

Abstract

This study was performed to clarify the enhancement of the 4-methylthio-3-butenyl isothiocyanate induced yellowing of salted radish root (takuan-zuke) by low pH during short-term salt-aging at low temperature and low salinity. We used two different methods to prepare the dehydrated daikon prior to salt-aging: air-drying outdoors (hoshi takuan-zuke) or salting with a stone press (shio-oshi takuan-zuke). Low salt-aging at low temperature was carried out under pH control with citrate-phosphate buffer. The yellowing of both types of takuan-zuke was accelerated below pH 5, and the color of air-dried takuan-zuke was deeper than that of salt-pressed takuan-zuke. To elucidate this phenomenon, several previously reported yellowing-related compounds were analyzed by high-performance liquid chromatography. The result showed that the production of the primary pigment, 2-[3-(2-thioxopyrrolidin-3-ylidene)methyl]-tryptophan, was low compared with that in previous reports. Therefore, we suggest that an unknown pigment was generated through a previously unreported pathway.

Branched‐chain amino acid synthesis and glucosinolate–myrosinase system during takuan‐zuke processing of radish root

“…It breaks down to form methanthiol (a characteristic sulfur‐containing flavored compound) and 2‐[3‐(2‐thioxopyrrolidin‐3‐ylidene)methyl]‐tryptophan (TPMT; a natural yellow pigment) (Matsuoka et al., 2002, 2008; Takahashi et al., 2015; Uda et al., 1990) (Figure 1). 2‐thioxo‐3‐pyrrolydinecarbaldehyde (TPC) is a metabolic intermediate of TPMT, and its antibacterial and antimutagenic activities have been linked to the important health benefits of takuan‐zuke (Kobayashi et al., 2020; Uda et al., 1993, 2000). Specifically, a prospective cohort study published by the National Cancer Center reported that the higher intake of various cruciferous vegetables and pickles was associated with a lower risk of all‐cause mortality in males and females.…”

Nutritional Content Dynamics and Correlation of Bacterial Communities and Metabolites in Fermented Pickled Radishes Supplemented With Wheat Bran

“…4-MTBI, which is released from 4-methylthio-3-butenyl glucosinolate by endogenous myrosinase hydrolysis, is mainly considered as the principal isothiocyanate generating pungency in radish roots and contributed to the yellow coloring observed during fermentation. Numerous studies have shown that isothiocyanates can act as cancer chemopreventive agents (45)(46)(47). However, volatile sulfur compounds have an extremely low odor threshold, and high concentrations of sulfides may cause off-flavors (48).…”

Effect of neutralizers and silicone softeners on phenolic yellowing phenomenon of OBA treated cotton knitted fabric

“…This generally occurs with high-liking OBAs for cotton that are not stable in less than p H 5.0. Along with these lines in the ensuing balance after OBA treatment and/or during finishing, if pH is highly acidic, the whiteness index is reduce [19,20].…”