Preparation of functional foods from selected plant materials and their by-products

The aim of this project was to prepare innovative functional foods with potential health-promoting components from selected plant materials and their by-products. For this purpose, Arbutus unedo L. fruits, Myrtus communis L. purple and white berries, Acca sellowiana (O. Berg) flowers, Crocus sativus L. flower juice, Malus domestica L. Borkh. var. Shampion fruits and Diospyros kaki L. var. Rojo Brillante fruits were used to prepare juices and smoothies (thick beverages made mainly from pureed raw fruit). The final products (smoothies and juices) were created from 3 different bases: B1 - apple juice, B2 - persimmon fruit purée and apple juice, and B3 - strawberry tree dry fruits and apple juice, respectively, with an addition of 0.1 % or 0.5 % saffron flower juice or 0.5 % purple myrtle berry extract or 0.5 % feijoa flowers or 0.5 % strawberry tree fruits or persimmon fruit purée. Moreover, the stability of the final products was assessed during a 6 month period of storage. Potential health-promoting components were investigated in both the plant materials and the final food products. The total polyphenol content was estimated spectrophotometrically (Folin-Ciocalteu’s assay) and phenolic compounds were determined in the examined samples using ultra-performance liquid chromatography photodiode detector-quadrupole time of flight/mass spectrometry (UPLC-PDA-QTof/MS) and quantified by UPLC-PDA. Furthermore, proanthocyanidins analysis, determination of colour, total soluble solids (TSS), titratable acidity (TA), dry matter, ashes, pH, and total sugars content by HPLC-ELSD, organic acids and vitamin C content was performed. Moreover, biological activities like antioxidant activity and inhibition on targeted digestive enzymes were investigated with different assays. Antioxidant activity was determined by evaluating total reducing power (FRAP and CUPRAC assays), free radical scavenging activity (ABTS•+ and DPPH• assays), and oxygen radical absorption capacity (ORAC assay). On the most interesting products, in vitro analysis on Caco-2 cells (cytotoxic activity and determination of intracellular ROS production) was also performed. Estimation of inhibition on targeted digestive enzymes (α-amylase, α-glucosidase and pancreatic lipase) was performed to evaluate the potential benefits for consumers with health problems such as diabetes and weight management. Finally, consumer evaluations of the new functional foods were evaluated using 5° hedonic scale. Products with the base B3 (strawberry tree fruits + apple juice) and 0.5 % addition of purple myrtle berry extract, feijoa flowers and persimmon fruit purée, as well as with 0.1 % of saffron flower juice, were shown to be the most interesting to consumers thanks to the large amount of bioactive compounds, the best antioxidant activity and digestive enzyme inhibitory activity, as well as the highest quantity of organic acids and simple sugars. Positive evaluation of the sensory properties and ageing stability at 6-month timespan support the potential commercial use of this new functional food in smoothie form. The study has been performed in collaboration with Prof. Aneta Wojdyło and Paulina Nowicka from the Department of Fruit, Vegetables and Plant Nutraceutical Technology (Faculty of Biotechnology and Food Science, Wrocław University of Environmental and Life Sciences, Poland).