Recovery of bioactive compounds in kiwifruit juice by ultrafiltration A. Cassano ⁎, L. Donato, C. Conidi, E. Drioli Institute on Membrane Technology, ITM-CNR, c/o University of Calabria, via P. Bucci, cubo 17/C, I-87030 Rende (Cosenza), Italy ABSTRACT ARTICLE INFO Article history: Received 31 August 2007 Accepted 19 March 2008 Editor proof receive date 12 May 2008 Keywords: Kiwifruit juice Bioactive compounds Ultrafiltration Food quality is not only a function of nutritional values but also of the presence of bioactive compounds exerting a positive effects on human health. This research was undertaken to study the influence of the ultrafiltration (UF) on the composition of some bioactive compounds of the kiwifruit juice in order to develop a natural product which can be used to fortify foods and beverages. At the same time the effect of transmembrane pressure (TMP) and temperature on the permeate flux was also investigated in order to identify the optimal operating conditions for the processing of the juice. An optimal TMP value occurred at 0.6–0.65 bar in different conditions of cross flow velocities. Steady-state permeate fluxes increased linearly with temperature in the range 20–30 °C. The kiwifruit juice was clarified in optimal operating conditions, according to the batch concentration mode, up to a final volume reduction factor (VRF) of 2.76. The analyses of flux decay according to fouling models reported in the literature revealed that the formation of a cake layer covering the entire surface of the membrane is the main cause of the membrane fouling. Most bioactive compounds of the depectinised kiwifruit juice were recovered in the clarified fraction of the UF process. The rejection of the UF membrane towards total phenolics was 13.5%. The recovery of glutamic, folic, ascorbic and citric acids, in the clarified juice, with respect to the initial feed, was dependent on the final VRF of the UF process: an increase of the VRF determines an increase of these compounds in the clarified juice. The rejections of the UF membrane towards these compounds were in the range 0–4.3%. Industrial relevance: Among different substances contained in the kiwifruit a primary role, in the safeguard of the human health, is carried out by some bioactive compounds such as ascorbic, folic, citric, glutamic acids and polyphenols. This research was undertaken to study the influence of ultrafiltration on the composition of these compounds in order to develop a natural product which can be used to fortify foods and beverages. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction Foods characterised by protective and health-promoting potential, in addition to their nutritive value, are recognised as functional foods. The beneficial components in functional foods have been called by various terms such as phytochemicals, functional components and bioactive components. These components may exert their effects by acting as antioxidants, activating liver detoxification enzymes, block- ing the activity of bacterial or viral toxins, inhibiting cholesterol adsorption, decreasing platelet aggregation, or destroying harmful gastrointestinal bacteria (Pennington, 2002). Epidemiological studies have shown that there is a significant positive association between intake of fruits and vegetables and reduced risk of chronic diseases, such as cancer, cardiovascular disease, diabetes, osteoporosis, Alzheimer's disease and immune disorders (Kaur & Kapoor, 2001; Willet, 2002). The fruit of the Actinidia plant is known more commonly as kiwi- fruit: its cultivation is very significant in Italy which is the world's largest producer of kiwifruit with a production of about 330,000 tons/ year (about 33% of the world-wide production). Other than for the production of derivatives addressed to the consumers or for the food industry (nectars and whole or sliced fruits appertized in syrup, whole or dried kiwifruit, powder of dried puree, clarified juice to be used in juice blending, jams, sugared and dried pulp, concentrated juices, fermented beverages and wine), the kiwi fruit can be exploited as a source of interesting components (Dalla Rosa, Mastrocola, Maltini, & Sacchetti, 1999). It is characterised by a high content of benefit substances for human health such as vitamins, minerals, polyphenols. Furthermore, it is low fat and contains no cholesterol (Kassardjian, Ferguson, Ferguson & MacRae, 2006). Among different substances contained in the kiwifruit a primary role, in the safeguard of the human health, is carried out by some bioactive compounds such as ascorbic, folic, citric and glutamic acids. Ascorbic acid is a water soluble vitamin important for its antioxidant function. It reduces the risk of heart disease by preventing the oxidation of low-density lipoprotein (LDL) cholesterol. Kiwifruit Innovative Food Science and Emerging Technologies 9 (2008) 556–562 ⁎ Corresponding author. Tel.: +39 0984 492067; fax: +39 0984 402103. E-mail address: a.cassano@itm.cnr.it (A. Cassano). 1466-8564/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2008.03.004 Contents lists available at ScienceDirect Innovative Food Science and Emerging Technologies journal homepage: www.elsevier.com/locate/ifset