Effect of cooking techniques on the retention of anthocyanins and vitamin C in potatoes

Abstract

Potato (Solanum tuberosum L.) is a great source of vitamins and minerals as well as a supplier of energy and quality protein. As a source of vitamin C it is usually underestimated. Anthocyanins are the compounds responsible for the color found in the pigmented potatoes. Vitamin C is an essential water-soluble vitamin that is cofactor involved in many central biochemical processes. There are two major forms of vitamin C: L-ascorbic acid (AA) and L-dehydroascorbic acid (DHAA). The aim of the study was to evaluate the effect of different cooking techniques on the retention of anthocyanins and vitamin C.

Four different cultivars were used (ʻRikeaʼ, ʻRosamundaʼ, ʻBlue Congoʼ, ʻSynkeä Sakariʼ) and four different cooking methods were applied (baking, boiling, microwaving and frying). Raw tubers were analyzed in order to estimate the retention of the bioactive compounds after cooking. Anthocyanins were extracted using 70 % acidified methanol. Hydrolysis of anthocyanins was carried out using 2.7 M HCl. Vitamin C was extracted with 3 % metaphosphoric acid (MPA) with 1mM EDTA. Samples were analyzed with HPLC-DAD.

The highest content of anthocyanins was present in the Finnish cultivar ʻSynkeä Sakariʼ (2.96 mg/g FD). The main anthocyanidins in the purple cultivars ʻSynkeä Sakariʼ and ʻBlue Congoʼ were derivatives of petunidin. In ʻRosamundaʼ (red skin cultivar) the main anthocyanins were derivatives of pelargonidin. The most effective method for preserving anthocyanins in the purple cultivars is baking and for the red-skin cultivar microwaving. The white cultivar ʻRikeaʼ showed the highest content of vitamin C (2.77 mg/g FD). The highest retention of vitamin C was in baked and microwaved samples.