Extraction of Polyphenolics from Apple Juice by Foam Fractionation

Abstract

The performance of nano-filtration (NF) for separating phenolic compounds from sugar in apple juice was studied using 1 and 0.25 kDa molecular weight cut-off (MWCO) spiral wound membranes. If these phenolic compounds could be recovered, they could stabilize the juice from haze formation or be added as antioxidants to foods and beverages in order to increase their health properties. Batch experiments were conducted on a pilot scale rig using a diluted clear apple juice concentrate. For the 1 kDa MWCO membrane, the research determined the effect of operating conditions on process efficiency and membrane fouling. The concentration of polyphenolics on the retentate side increased by a factor of up to 4 and the sugar concentration increased by 1.5 times under optimum conditions of lower temperature (30oC), acidic pH (2), lower transmembrane pressure (5 Bar) and higher initial sugar concentration (20 oBrix). Despite the increase in polyphenolics in the retentate, there was little difference in the phenolic composition between retentate and permeate solutions. As the molecular mass of the rejected phenolics was smaller than the membrane cut-off, this indicated that the rejection was related to the formation of a secondary membrane formed as a result of fouling. A mass balance of polyphenolics in the final retentate and permeate compared with the initial feed solution indicated that up to 4.3 gm of polyphenolics were bound per m2 of membrane. The permeate solutions collected from the 1 kDa MWCO membrane were then filtered using a 0.25 kDa MWCO membrane. Most phenolic compounds were retained by the membrane and the concentration increased by a factor of up to 2. Catechin, rutin, phloridzin and quercetin derivatives were concentrated on the retentate side. However, around 20 -40% of chlorogenic acid and epicatechin was observed on the permeate side. It is concluded that membrane separation represents a potentially efficient and cost-effective technology to separate the phenolic fraction of fruit juice in a form suitable for use as a functional ingredient.

Foam Fractionation as a Means to Recover and Fractionate Bioactives

“…Recovery on the other hand was seen to increase with initial concentration as with increased amount of polyphenols in the initial solution means increased amount of polyphenols separated out by the foam. This result correlates with literature results [20].…”

“…This then led to decreased absorption surfaces, so less polyphenols separated and thus a lower ER and recovery at 5mL/min. Above 10mL/min, the increased superficial gas velocity decreased the residence time of the bubbles [20], so there was less time for adsorption to occur and less time for the foam to drain. The increased flowrate also causes greater entrainment of liquid in the foam, which effectively diluted the foam, but increased foam volume.…”

Concentration of Rutin Model Solutions from Their Mixtures with Glucose Using Ultrafiltration

“…The optimum could have been different if the fouling had been considered in addition to the rutin concentration factor [ 36 – 38 ].…”