Relative Effects of Alcohol and pH on Betacyanin Stability in Aqueous Djulis Extracts and Their Color Qualities after Organic Acid Addition

Abstract

Djulis is a Taiwanese cereal plant containing betacyanin pigment. The aim of this study was to elucidate the relative effect of ethanol (10–80%) and pH (3.5 and 5.5) on pigment stability in aqueous extracts of Djulis. Organic acids were further used to investigate their effects on color protection. All samples were thermally processed (60C, 30 min) and stored (25C, 21 days) after pigment regeneration (4C, 24 h). Results showed that ethanol promoted the pigment degradation in Djulis extract. The hypsochromic shift (decrease of λmax) and isomerization of the pigment were more pronounced in the systems with higher ethanol concentrations. At a fixed concentration of ethanol, betacyanin was more stable at pH 5.5 than that at pH 3.5. A stronger dependence of the discoloration on the ethanol concentration was found and explained by the competing result between ethanol–water mixing and ethanol–betacyanin interaction. This effect was lowest in pH 5.5 samples at 20% ethanol concentration. Statistical analysis indicated that pigment degradation was affected more by ethanol concentrations than by pH. Addition of 1% ascorbic acid exhibited the best pigment protection and explained by its best interaction with ethanol in the system. Practical Applications Djulis, high in nutrient and physiochemical attributes, is a traditional food for aboriginals in Taiwan. They are used as a wine starter due to their high amylase activity. Their beautiful color, mainly comes from betacyanin, in the hull was not stable and was discarded as wastes. Due to high demand by the consumer for more natural food products, the trend toward replacement of synthetic colorants by natural product has been increasing. Betacyanin pigment could be a good candidate for natural colorants in some alcoholic beverages. Our findings in this study provided the information of how to maintain the pigment stability in betacyanin‐containing beverages by proper alcohol and pH control, which is necessary for the Djulis wine industry.

UPLC-QTOF-MS fingerprinting combined with chemometrics to assess the solvent extraction efficiency, phytochemical variation, and antioxidant activities of Beta vulgaris L.

“…Interestingly, conventional red beet extracted by aqueous methanol mixed with organic acids (S17, S18, S19) had higher betanin contents than the other methanol solvent extract (S16). This result is in agreement with Narkprasom and others, who demonstrated that organic acids enhanced betalain retention through oxygen scavenging and complexation of metal cations [ 16 ]. Another study indicated that slight acidification of the extraction medium enhanced betacyanin stability and avoids oxidation by polyphenol oxidases [ 22 ].…”

Influence of extraction parameters and stability of betacyanins extracted from red amaranth during storage

“…The changes in color throughout the storage period are due to degradation of betacyanins and the generation of other isoforms, such as betaxanthin, methyl derivative of arginine betaxanthin, and betalamic acid. Narkprasom et al (2012) showed that the formation of isoforms of betacyanins is dependent on pH, heat, and temperature and the alcohol concentration. In our study, L* and b* values were much lower, whereas a* values were higher compared to the powder of different parts of the Amaranthus species (Li et al 2015).…”

Investigation of the Antioxidant Capacity, Insecticidal Ability and Oxidation Stability of Chenopodium formosanum Seed Extract

“…Chenopodium formosanum , also known as djulis, is a native cereal plant of Taiwan that is a major source of colorants and antioxidants [ 11 , 12 ]. Chenopodium formosanum has colorful leaves, but its bright red seeds are most likely why it is called “Hung Li” in Chinese [ 13 ].…”