Evaluation of the extraction efficiency for polyphenol extracts from by‐products of green kiwifruit juicing

Abstract

The health benefits of fruits are attributable in part to their bioactive components such as phenolics and pectic polysaccharides. By-products derived from kiwifruit processing can be a good source of such bioactive compounds. Extracts were produced using different concentrations of ethanol in water (0%, 30%, 50%, 74% and 96% v ⁄ v) from by-products (skin, residue and pulp) of the green-fleshed kiwifruit (Actinidia deliciosa 'Hayward') juicing process. The amounts of phenolic compounds and uronic acid (UA) as well as the phenolic composition in each extract were determined. Results show that different by-products contained different concentrations of phenolics and pectic polysaccharides. Based on total phenolic contents, 96% v ⁄ v ethanol appeared to be the best extraction medium. The 30% or 74% ethanolic dilution was the second best medium for phenolic extraction from skin and pulp ⁄ residue, respectively. Water was a good medium for extracting satisfactory quantities of phenolics as well as the highest concentration of pectic polysaccharides. Phenolic profiling by high-performance liquid chromatography (HPLC) was used to detect individual phenolic compounds in an extract. Results using HPLC showed that alkali pre-treatment has improved the extraction efficiency of phenolics as a function of alkali concentration, fruit tissue type, extraction media, byproduct preparation method, and class of polyphenols. As a result more efficient methods for both extraction and characterisation of polyphenols could be evaluated.

Influence of Extraction Conditions on the Recovery of Phenolic Antioxidants From Spent Coffee Grounds

“…1, the composition of the solvent had a marked effect on the extraction yield and the use of the 60:40 ethanol-water mixture gave better results compared to pure ethanol or pure water. Similar results were obtained in studies on the extraction of phenolics from different materials, such as peanut skins (Nepote et al, 2005), olive leaves (Mylonaki et al, 2008) and the byproducts of kiwifruit juicing (Sun-Waterhouse et al, 2009). One explanation may lie in the fact that phenolic compounds exhibit a wide range of solubilities in polar solvents and are often more soluble in solvents less polar than water (Liu et al, 2000).…”

Spray-Drying of Green or Gold Kiwifruit Juice–Milk Mixtures; Novel Formulations and Processes to Retain Natural Fruit Colour and Antioxidants

“…Phenolic compounds identified in the spray-dried powders included caffeic acid derivatives, protocatechuic acid, chlorogenic acid, gallic acid, hydroxybenzoic acids, quercetin glycosides, epicatechin and/or procyanidin. The presence of these phenolics in the spray-dried powders confirmed that the phenolics intrinsically occurring in green or gold kiwifruit juice were significantly retained after spray drying in the presence of milk and maltodextran (Sun-Waterhouse et al 2009a, 2013aMcGhie and Ainge 2002;Dawes and Keene 1999). Differences in the concentrations of these compounds before and after storage indicate the different extractabilities and stabilities of these antioxidants in the green or gold kiwifruit juice-milk powder matrices at 4°C or 20°C.…”

“…The injection volume was 30 μL. Individual phenolics were identified through comparing their retention time and absorbance maximum (λ max ) with those of external standards (catechin, caffeic acid, chlorogenic acid, gallic acid, epicatechin, 2,4-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, ferulic acid, p-hydroxybenzoic acid, protocatechuic acid, salicylic acid, syringic acid, p-/m-/o-coumaric acids, phloretin, phlorizin, procyanidin B1, quercetin, rutin, quercetinglucoside and quercetin-rhamnoside), and based on our previous HPLC analysis of kiwifruit products (Sun-Waterhouse et al 2009a, b, 2013a. Most of the individual phenolics were quantified using the internal standard phlorizin at a wavelength of 280 nm while the flavonols were quantified using kaempferol at 370 nm.…”

Formulation and characterization of functional foods based on fruit and vegetable residue flour

“…anti-browning, antimicrobial, flavouring, colorants) have been extensively developed (as reviewed by AyalaZavala et al 2011;Sun-Waterhouse 2011). Furthermore, recent studies have shown functional food ingredients extracted from FVR, since they are rich in dietary fibres and antioxidants compounds (Sun-Waterhouse et al 2010;Nilnakara et al 2009;Aziz et al 2011Aziz et al , 2012Sun-Waterhouse et al 2009). …”