Antioxidant capacity and related parameters of different fruit formulations

Fruits and vegetables are known as good sources of phytochemicals, essential to prevent degenerative diseases like cancer and cardiovascular diseases (CVD). They contain a variety of antioxidants, which are useful to scavenge radical oxygen species (ROS). Besides smoothies, fruit purees, concentrates and juices - used by the food industry for these new beverages - were analysed. Total phenolics by Folin-Ciocalteu method, vitamin C content and antioxidant capacity (AOC) by FRAP, TEAC and ORAC assay were analysed by using high-throughput methods on a microplate reader. Vitamin C content ranged from 31 ± 3 mg/100 g in drinkable pomegranate concentrate to 1373 ± 125 mg/100 g in acerola puree; total phenolics content was quantified between 51 ± 1 mg gallic acid equivalents (GAE)/100 g in the mango-peach smoothie and 1152 ± 62 mg/100 g in the ascorbic acid rich acerola puree. The AOC differed depending on kind of fruit and antioxidant assay used. In most fruit products the major portion of AOC was generated by polyphenolic compounds, except acerola puree and orange juice. Very good correlations between total phenolics content and antioxidant capacity were found in the single fruit products, however not in the fruit and vegetable smoothies. Most of the analysed smoothies were able to supply with one package nearly the recommended dietary intake (RDI) of vitamin C for adults of 100 mg per day.     

The effects of treatment on quality parameters of smoothie-type ‘Hayward’ kiwi fruit beverages

Kiwi fruits contain high levels of bioactive compounds (ascorbic acid, total phenols, anthocyanins, chlorophylls, carotenoids, tannins, flavanols and flavonoids), which are important to preserve them in preparation of purees, beverages, juices and other varieties of food products. The purpose of the present study was to evaluate physicochemical parameters, including antioxidant and binding properties during different treatments in the preparation of ‘Hayward’ kiwi fruit smoothie-type beverages. Preparation of smoothie-type beverages from kiwi fruits involved the following stages: adding of different percentages of sugar content inside the mass, mixture and then freezing during long storage. The bioactive compounds were determined in fresh and treated smoothies. To assess the antioxidant capacity, four different methods were applied: 2, 2′-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺), Ferric-reducing/antioxidant power (FRAP), Cupric reducing antioxidant (CUPRAC) and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, showing high correlation coefficients with polyphenols from 0.894 till 0.969, because polyphenols mostly influence the antioxidant capacity. The decrease of total phenolic compounds (39%) and anthocyanins (31%) was higher than in ascorbic acid (25%) in preparation of smoothies after long cold storage. The proposed above preparation of smoothies preserved the decrease of bioactive compounds. The binding abilities of extracted polyphenols to human serum albumin (HSA) of smoothies determined by 3D-fluorescence and FTIR spectroscopy correlated with their amounts. The investigated kiwi fruit smoothies can be used as a source of antioxidants.     

Effect of lactic acid fermentation on antioxidant, texture, color and sensory properties of red and green smoothies

Weissella cibaria, Lactobacillus plantarum, Lactobacillus sp. and Lactobacillus pentosus were variously identified from blackberries, prunes, kiwifruits, papaya and fennels by partial 16S rRNA gene sequence. Representative isolates from each plant species were screened based on the kinetics of growth on fruit juices. A protocol for processing and storage of red and green smoothies (RS and GS) was set up, which included fermentation by selected lactic acid bacteria starters and exo-polysaccharide producing strains. Starters grew and remained viable at ca. 9.0 log cfu g⁻¹ during 30 days of storage at 4 °C. No contaminating Enterobacteriaceae and yeast were found throughout storage. Values of soluble solids, total titratable acidity and viscosity distinguished started RS and GS compared to spontaneously (unstarted) fermented smoothies. Color difference dE∗_ab and browning index were positively affected by lactic acid fermentation. Consumption of carbohydrates by lactic acid bacteria was limited as well as it was the lactic fermentation. Consumption of malic acid was evident throughout storage. Polyphenolic compounds and, especially, ascorbic acid were better preserved in started RS and GS compared to unstarted samples. This reflected on the free radical scavenging activity. A statistical correlation was only found between the level of ascorbic acid and free radical scavenging activity. As shown by a ?rst-order equation, the rate of degradation of ascorbic acid through storage were found to be higher in the unstarted compared to started RS and GS. Fermentation by lactic acid bacteria clearly improved the sensory attributes of RS and GS.