Effect of pH Changes on Antioxidant Capacity and the Content of Betalain Pigments During the Heating of a Solution of Red Beet Betalains

Red beets and their products are mainly consumed after processing. In this study, the effect of pH on changes in antioxidant capacity (AC) and the content of betalain pigments were analysed during the heating of a betalain preparation solution. With pH ranging from 4 to 9 during the heat-treatment, the content of red pigments decreased depending on the pH level of the sample. The losses of red pigments in the investigated betalain preparation solution increased along with rising pH levels of the heated solution. The greatest losses were recorded at pH of 9.0. An opposite correlation was observed for yellow pigments. The content of yellow pigments in the heated betalain preparation solution was increasing along with increasing pH. The most pronounced increase in the content of yellow pigments was found at pH of 6.5 and 7.0. At the same time, the heated betalain preparation solution was shown to exhibit a higher antioxidant capacity at pH of 6.0 (14.9 μmol Trolox/mL) than at pH of 4.0 (12.6 μmol Trolox/mL). It was observed that the increase in the antioxidant capacity in heated betalain preparation solutions with pH in the 6.0–6.5 range occurred as a result of increased concentrations of neobetanin, assessed by HPLC, within the pH range from 5.0 to 6.5

Content betalain pigments, nitrates and antioxidant capacity of beetroot juices depending on cultivars and the size of beetroot roots

Celem pracy była ocena zawartości barwników betalainowych, azotanów (III) i (V) oraz zdolności przeciwutleniającej soku z korzeni 14 odmian buraka ćwikłowego, o różnej masie korzeni. Surowiec podzielono pod względem masy na 4 grupy wielkościowe, a następnie przygotowano z nich sok. Stwierdzono, że zawartość barwników betalainowych oraz azotanów (V) w soku istotnie zależy od odmiany i wielkości korzenia buraka ćwikłowego. W badanych odmianach buraka ćwikłowego zaobserwowano duże zróżnicowanie zawartości barwników betalainowych i azotanów (V). Wraz ze wzrostem masy korzenia zawartość barwników betalainowych oraz zdolność przeciwutleniająca maleje. Zdolność przeciwutleniająca soku była istotnie skorelowana z zawartością barwników. Azotanów (III) nie wykryto w żadnej z badanych prób.The aim of this study was to estimate the content of betalain pigments, nitrate and antioxidant capacity of beetroot 14 cultivars, depending on the weight of root. The roots of red beet were divided into 4 groups according to their weight and then was prepared juice. It was found, that betalains and nitrate (V) contents of the juice significantly depends on cultivars and the size of beetroot roots. Large differences were found in betalains and nitrate (V) contents between cultivars. Betalains pigment contents and antioxidant capacity decreased with increasing root weight. The antioxidant capacity of juice is significantly correlated with pigment contents. Nitrate (III) were not detected in any tested samples