Optimisation of biologically active compounds ultrasound assisted extraction from potatoes using response surface methodology

R. Zarins¹*, Z. Kruma¹ and I. Skrabule²

¹Latvia University of Life Sciences and Technologies, Faculty of Food Technology, Department of Food Technology, Rigas iela 22, LV-3004 Jelgava, Latvia
²Institute of Agricultural Resources and Economics, Zinātne iela 2, Priekuli, Priekuli municipality, LV-4126 Latvia
*Correspondence: reinis-zarins@inbox.lv

Abstract:

Potato (Solanum tuberosum L.) is source of phenolic compounds and from plant matrixes can be extracted by several methods. In recent years ultrasound assisted extraction has become more popular due to its efficiency for recovery of phenolic compounds and antioxidants and response surface methodology is an effective tool for optimisation of extraction procedure by evaluating different variables and their interaction. The aim of the current research was to optimize ultrasound assisted extraction of biologically active compounds from potatoes by response surface methodology. For experiment purple-flesh potato variety ‘Blue Congo’ was selected. Control sample was extracted by stirring for 1 hour. Box-Behnken design was used for optimization of extraction conditions from fresh potatoes and as variables were selected: ethanol concentration (% v/v), hydrochloric acid concentration (molarity) and time (min). For extracts as responses total phenolic, total flavonoid, total anthocyanin content and antioxidant activity (DPPH, ABTS+ scavenging activity) were determined using a spectrophotometric methods. Significant models were obtained for antocyanins, total phenols and DPPH radical scavenging activity. Optimisation of extraction showed that for maximising all responses optimal HCl concentration is 2.5M, ethanol concentration 79.4% and extraction time 60 minutes, resulting in following responses: 57.41 mg 100 g^-1 of anthocyanins, 238.52 mg 100 g^-1 of TPC, 24.58 mM TE 100 g^-1 of DPPH scavenging activity and 12.99 mM TE 100 g^-1 of ABTS scavenging activity. Conventional extraction method showed significantly lower results. It could be concluded that ultrasound assisted extraction is effective method for recovery of phenolic compounds and solvents and extraction time is significant parameter influencing efficiency.

Key words:

Effect of germination and extrusion on the phenolic content and antioxidant activity of raw buckwheat (Fagopyrum esculentum Moench)

I. Beitane¹*, G. Krumina–Zemture¹ and M. Sabovics²

¹Latvia University of Agriculture, Faculty of Food Technology, Department of Nutrition, Riga Street 22, LV–3004 Jelgava, Latvia
²Latvia University of Agriculture, Faculty of Food Technology, Department of Food Technology, Riga street 22, LV–3004 Jelgava, Latvia
*Correspondence: ilze.beitane@llu.lv

Abstract:

The aim of the research was to determine the total phenolic content, antioxidant activity and phenolic compounds in raw and germinated common buckwheat grain and their extruded products in order to estimate the effect of germination and extrusion on the total phenolic content, antioxidant activity and phenolic compounds in buckwheat. A total of 10 buckwheat samples were analysed, where the raw buckwheat grain was the control sample, four samples were germinated and then extruded. The total phenolic content was determined using the Folin–Ciocalteu assay. The antioxidant activity was determined using a micro plate assay and phenolic compounds with Liquid Chromatography –Time of Flight Mass Spectrometer method.
The results showed that germination of buckwheat significantly affected the total phenolic content, antioxidant activity, radical scavenging activity and content of phenolic compounds. The decrease of the total phenolic content, antioxidant activity, radical scavenging activity and the content of some phenolic compounds depended on germination time – 48 h of germination provided greater concentrations at the end of a 24 h germination period, whereas the content of some phenolic compounds like rutin, quercetin and vitexin increased substantially after germination, besides, the increase of phenolic compounds depended on the germination time. In total 26 different phenolic compounds were detected in raw and germinated buckwheat samples and only one compound with an m/z value 385.1282 was unidentified. The data of extrusion revealed a significant decrease of total phenolic content, antioxidant activity, radical scavenging activity and phenolic compounds content in buckwheat samples (P < 0.05). In the extruded buckwheat samples novel phenolic compounds like 4–hydroxybenzoic acid, homovanillic acid, catechin, ferulic acid, and hyperoside were detected.

Key words:

antioxidant activity, buckwheat, extrusion, germination, phenolics