Zaid Saleh

Pilot-scale resin adsorption as a means to recover and fractionate apple polyphenols

The purification and fractionation of phenolic compounds from crude plant extracts using a food-grade acrylic adsorbent were studied at pilot-plant scale. A diluted apple juice concentrate served as a model phenolic solution for column adsorption and desorption trials. Phenolic concentrations were evaluated photometrically using the Folin-Ciocalteu assay and by HPLC-DAD. Recovery rates were significantly affected by increasing phenolic concentrations of the feed solutions applied to the column. In contrast, the flow rate during column loading hardly influenced adsorption efficiency, whereas the temperature and pH value were shown to be crucial parameters determining both total phenolic recovery rates and the adsorption behavior of individual polyphenols. As expected, the eluent composition had the greatest impact on the desorption characteristics of both total and individual phenolic compounds. HPLC analyses revealed significantly different elution profiles of individual polyphenols depending on lipophilicity. This technique allows fractionation of crude plant phenolic extracts, thus providing the opportunity to design the functional properties of the resulting phenolic fractions selectively, and the present study delivers valuable information with regard to the adjustment of individual process parameters.

Separation and concentration of health compounds by membrane filtration

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 trans-membrane 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.

Extraction of Polyphenolics from Apple Juice by Foam Fractionation

This research was undertaken to test the feasibility of using the foam technology to separate polyphenols from fruit juices for use as functional food ingredients. The separation performance, expressed as enrichment ratio, selectivity and percentage recovery, was determined as a function of operating variables, namely air or N2 flow rate, initial feed concentration, bubble size, solution pH and the presence of alcohol to modify the surface tension. Measurements were made of the average bubble size and gas hold-up volume to calculate interfacial area. The bulk phase concentrations of the polyphenolics in the feed and foam fractions were analysed for total phenolic content by Folin assay and phenolic composition by reverse phase HPLC. Enrichment factors of up to 6 were found under optimum conditions of low sugar concentration (6-9 oBrix), low flow rate (0.2-0.6 ml min-1) and acidic pH (3-4). However recoveries were low at around 30% of total phenolics and selectivity was poor. It was concluded that foam fractionation represents a potential low cost technology to recover a proportion of the polyphenolic content in an enriched juice concentrate suitable for use as a functional ingredient.

Apple Polyphenol Extracts Protect Against Aspirin‐induced Gastric Mucosal Damage in Rats

The protective role of two apple polyphenol extracts, Douglas‐FB (FB) and Douglas‐EF (EF), on gastric mucosal damage following aspirin ingestion was investigated in healthy rats. Polyphenol content of the apple extracts varied, with the EF extract having 20% w/w polyphenols and a high proportion of flavanols as epicatechin and procyanidin, whereas the FB extract comprised 12% w/w polyphenols, which were mostly flavonols as quercetin glycosides. Male Sprague–Dawley rats were allocated to control, FB and EF groups and fed the experimental diet during the 10‐day trial. Control treatment rats received 1 mL of deionised water, whereas apple polyphenol treatment group rats, FB and EF received a concentration of 10−2 m polyphenols in 1 mL deionised water daily via oral gavage. At the end of 10‐day feeding period, rats were fasted overnight, and the following morning, aspirin (200 mg/kg) was given by oral gavage. Four hours after aspirin administration, the animals were euthanised, and samples taken for analysis. Both apple polyphenol extracts significantly reduced the ulcer area, ulcer lesion index and gastric injury score. The glutathione in gastric mucosa was increased significantly in rats given FB apple extract. Despite their different polyphenol compositions, FB and EF apple extracts assisted in protecting the gastric mucosa following acute aspirin administration in rats. Copyright