This study aims to assess kinetic modelling of the solid–liquid extraction process of total polyphenolic compounds (TPC) from apple pomace (AP). In this regard, we investigated the effects of temperature and solvent (i.e. water, ethanol, and acetone) on TPC extraction over various periods. The highest TPC yield of 11.1 ± 0.49 mg gallic acid equivalent (GAE)/g db (dry basis) was achieved with a mixture of 65% acetone–35% water (v/v) at 60 °C. The kinetics of the solvent-based TPC extraction processes were assessed via first-order and second-order kinetic models, with an associated investigation of the kinetic parameters and rate constants, saturation concentrations, and activation energies. The second-order kinetic model was sufficient to describe the extraction mechanism of TPC from AP. This study provides an understanding of the mass transfer mechanism involved in the polyphenolic compound extraction process, thus facilitating future large-scale design, optimization, and process control to valorize pomace waste. Graphical Abstract

This study aims to valorize chitin polymer from the side stream of an insect farm and to determine the chitin content and its physicochemical properties obtained from different processing steps in the insect farm (Adult Black Soldier Fly insect, Puparia, and Flake). We used an acid-base method (using 1M HCl and 1M NaOH) as a conventional technique and the acid detergent fiber (ADF) with acid detergent lignin (ADL) methods. The chitin samples are then characterized for thermal stability (TGA-DTA), crystallinity (XRD), chemical compounds (FTIR), and C/N content, and the results were compared to the commercial shrimp chitin. The Puparia had the highest chitin content of 21-33%, followed by the Flake 20-28% and the Adult insect with 7-13% chitin, depending on the extraction method. The chitin yield from ADF-ADL method was on par with the conventional method, while the ADF results were approximately 3-10% higher than the ADF-ADL results. The insect farm side stream is an abundant rich source of high-quality chitin with physiochemical properties comparable with the commercially available shrimp derived chitin.

Keratin dissolution is the first step toward reusing protein-rich biomass such as waste wool, hair, and feather.

Highlightso Keratin recovery from wool using deep eutectic solvent was assessed o The basis for the use of the new deep eutectic solvent was discussed o The effects of the process variables on keratin yield were explored o Keratin recovered was optimised and characterised..

Highlights o Production of multiple biochemicals from pomace was assessed; o Environmental and economic performances of the production process investigated;o Multi-objective optimisation of the production process undertaken.

In this study, the solubilisation of waste coarse wool as a precursory step for the large scale valorisation of keratin was investigated using a green deep eutectic solvent (DES) based on L-cysteine and lactic acid. The investigation was undertaken via the response surface methodology and based on the Box-Behnken design for four process variables of temperature (70-110 C), dissolution time (2-10 h), the mass of L-cysteine (0.5-2.5 g) in 20 mL of lactic acid, and wool load in the DES (0.2-0.6 g). The effect of variations in temperature was established to be the most significant process variable influencing keratin yield from waste coarse wool in the current work. An optimum keratin yield (93.77 wt.%) was obtained at the temperature of 105 C, 8 h dissolution time, with 1.6 g L-cysteine in 20 mL of lactic acid using 0.5 g of wool. This study suggests L-cysteine and lactic acid as a green solvent with the potential to scale up keratin recovery from waste wool without significant destruction in the structure of the recovered keratin.

Subcritical water extraction (SWE) technology, as an environmentally sustainable technique, was applied to optimize the recovery of polyphenolic compounds from apple pomace (AP). Box–Behnken experimental design approach was used to investigate the effects of four process variables; extraction temperature (100-220 ºC), extraction time (30-120 min), mean sample particle size (500-1000 µm) and solid to solvent ratio (1-10 g/100 mL) on total polyphenolic compounds (TPC) yield. The SWE conditions for the optimal TPC of 39.08 ± 1.10 mg GAE per g of AP on dry basis (db) were determined to be temperature of 203.71 ºC, time of 75 min, solid to solvent ratio of 1 g/100 mL and a mean sample particle size of 500 µm. The temperature and solid to solvent ratio were determined as the most statistically significant process variables that influenced TPC yield. At the optimum conditions, antioxidant activity (% DPPH inhibition activity) of the polyphenolic extract was found in the range of 15.38–92.90% as compared to ascorbic acid (8.64–95.90%). The findings of this study proposed that SWE as a green and efficient technology provided significant advantage in term of polyphenolic compounds yield, and AP could be utilized as potential raw material for SWE of valuable antioxidant polyphenolic compounds.

Apple pomace (AP) from the food industry is a mixture of different fractions containing bioactive polyphenolic compounds. This study provides a systematic approach toward the recovery and evaluation of the physiochemical and biological properties of polyphenolic compounds from AP. We studied subcritical water extraction (SCW) and solvent extraction with ethanol from four different AP fractions of pulp, peel, seed, core, and stem (A), peel (B), seed and core (C), and pulp and peel (D). The subcritical water method at the optimum condition resulted in total polyphenolic compounds (TPC) of 39.08 ± 1.10 mg GAE per g of AP on a dry basis compared to the ethanol extraction with TPC content of 10.78 ± 0.94 mg GAE/g db. Phloridzin, chlorogenic acid, and quercetin were the main identified polyphenolics in the AP fractions using HPLC. DPPH radical scavenging activity of fraction B and subcritical water (SW) extracts showed comparable activity to ascorbic acid while all ethanolic extracts were cytocompatible toward human fibroblast (3T3-L1) and salivary gland acinar cells (NS-SV-AC). Our results indicated that AP is a rich source of polyphenolics with the potential for biomedical applications.