The influence of edible coatings and natural antioxidants on fresh-cut potato quality, stability and oil uptake after deep fat frying

The effect of four edible hydrocolloid coatings (carboxymethyl cellulose, chitosan, pectin and gum arabic) on fresh-cut potato's colour, pH and moisture content during storage was studied. Possibility of coating enrichment with natural olive leaf extract and sodium ascorbate was also evaluated. Coatings scored as the best ones straight after coating or during storage for 7 days at 10 ± 1 °C, were used for deep fat frying of potato. Chitosan was shown to cause significant decrease in pH and browning of potato strips. Pectin was classified as good coating alone but in combination with olive leaf extract showed lower quality parameters of fresh-cut samples compared to control. Only carboxymethyl cellulose and gum arabic itself or enriched with olive leaf extract or sodium ascorbate were shown not to affect colour, pH and moisture during storage. Moreover, these coatings significantly reduced fat content in deep fat fried potato strips, without influence on L*, b*, whiteness index (WI), and ΔE.

Microencapsulation of Olive Leaf Extract by Spray Drying

The aim of this research was to obtain a high value powder of olive leaf extract (OLE) rich in polyphenols by spray drying. Since carrier, polyphenols/carrier ratio, and inlet temperature could have an impact on process yield and polyphenol retention, to define the most promising drying conditions for OLE experiment with gallic acid model solutions (GAS) was conducted. Influence of carrier type (maltodextrin, inulin, gum arabic, and their two-component blends), polyphenols/carrier ratio, and temperature on process yield of spray dried GAS was examined, and for each carrier the most promising temperature and ratio were selected. Optimal temperature for all GAS samples was 150 °C, and optimal gallic acid/carrier ratio for samples with inulin or gum arabic was 3:1, while for all other combinations it was 5:1. In OLE powder produced under these conditions, polyphenol content and physical properties (rehydration, bulk density) were determined. Mixture of maltodextrin and gum arabic resulted in the highest OLE product yield (54.48%) and the highest polyphenol retention (56.50%) obtaining good physical properties (bulk density=0.31 g ml–1, rehydration time=98 s), while use of inulin resulted in the lowest yield (32.71%), polyphenol retention (28.24%), bulk density (0.25 g ml–1), and the highest rehydration time (140 s).

Pectin microgels and their subunit structure

High-performance size exclusion chromatography revealed that alkaline-extracted peach fruit pectin dissolved in 0.05 M NaNO3 comprised a hierarchy of at least four aggregated, macromolecular-sized species. Each of the three largest species was found to be comparable in length to the three smallest subunits of an interconnecting gel network visualized by transmission electron microscopy of pectin, rapidly dried from solution. The interconnecting subunits of the gel network were rods or segmented rods and the integrated network formed a circular gel about 1 micron in diameter. Shadowed samples prepared from 5 and 50 mM NaCl or aqueous glycerol solutions produced images of partially dissociated subunits.