Reversibility of thermal degradation of betacyanins under the influence of isoascorbic acid

Structural and chromatic stability of purple pitaya (Hylocereus polyrhizus [Weber] Britton & Rose) betacyanins as affected by the juice matrix and selected additives

“…Maximum pigment stability was obtained for purple pitaya juice at pH 4 with a 1% ascorbic acid supplementation, affording a pigment retention of 91% after heating and CS. Since in this study isoascorbic acid addition showed less pronounced stabilising effects than ascorbic acid, the assumption of stereoselective reaction mechanisms during heating and regeneration (Bilyk & Howard, 1982) is supported. According to the authors, differing stabilisation potential of ascorbic acid and isoascorbic acid is due to different configuration which would affect the formation of an imidium ion intermediate with betalamic acid, thus precluding betalamic acid dimerisation counteracting recombination with cyclo-Dopa glucoside.…”

“…Hence, no stabilising effect of matrix constituents was found. In contrast, betacyanins isolated from red beet were reported to be less stable compared to pigments in the red beet juice matrix (Bilyk & Howard, 1982). After 24 h of cool storage (CS), the pigment preparation exhibited higher colour retention than directly after heating, thus indicating betacyanin regeneration, as previously described to proceed in betanin solutions (Huang & von Elbe, 1985) as well as red beet (von Elbe, Schwartz, & Hildenbrand, 1981) and purple pitaya juice (Herbach et al, 2004a), respectively.…”

“…Betacyanin stabilisation by supplementation prior to heating was preferred in this study, because it was found to be superior to addition after heat exposure (Bilyk & Howard, 1982;Han et al, 1998). While purple pitaya juice was reported to contain nearly 600 mg/L citric acid, it was found to be devoid of ascorbic acid (Stintzing, Schieber, & Carle, 2003).…”

“…In contrast, several findings on betalain stability improvement by ascorbic acid were reported. Ascorbic acid concentrations of 0.003% (Máriás-syová & Š ilhár, 2000), 0.1% (Barrera, Reynoso, & Gonzá-les de Mejía, 1998;Bilyk & Howard, 1982), 0.2% (Attoe & von Elbe, 1985), and 40 mmol/L (about 0.7%; Han, Kim, Kim, & Kim, 1998), respectively, were found to enhance betalain stability, while Attoe and von Elbe (1985) reported a reduction of headspace oxygen by 87% when adding 11 mmol/L (about 0.2%) ascorbic acid. The stabilising effects of ascorbic and isoascorbic acid were ascribed to oxygen removal, since oxygen was shown to accelerate betanin degradation (Attoe & von Elbe, 1982).…”

“…Several authors reported further enhancement of betanin stability by employing isoascorbic instead of ascorbic acid (Attoe & von Elbe, 1985;Barrera et al, 1998;Bilyk & Howard, 1982), which could be due to superior oxygen conversion by isoascorbic acid exhibiting a higher redox potential (Attoe & von Elbe, 1985). Furthermore, improved betanin stability was ascribed to sequestering effects of citric acid, partially neutralising the electrophilic center of betanin by associating around the positively charged quaternary amino nitrogen (Pasch & von Elbe, 1979).…”