Food side streams contain useful compounds such as proteins, sugars, polyphenols, and amino acids that might get discarded during processing. The concentration of these components may be low (e.g., fruit side streams are mainly composed by water, around 90%, while polyphenol content in rapeseed meal is less than 3% dry weight) and therefore effective separation techniques should be evaluated. The aim of this review is to identify the different process steps (like pretreatment, volume reduction, phase change, solid removal, purification, and formulation) required to recover high-value products from agri-food residues. It reviews different plant-based byproducts as sources (cereal bran, fruit pomace, oilseed meals, fruit wastewater) of valuable compounds and discusses the relevant technologies required for processing (such as extraction, adsorption, crystallization, drying, among others). A structured approach to design recovery processes presented focused on high purity products. This work demonstrates that multiple high-value products can be recovered from a single agri-food side stream depending on the processing steps and the origin source (strong and soft structures and wastewater).

Efficient recovery and utilization of valuable components from industrial food side streams is a main driver towards a circular economy. Among different available purification techniques, adsorption can effectively recover these components. However, the conventional batch mode of operation can limit its applicability in food processes due to limited efficiency. This work compares conventional batch packed bed adsorption with semi-continuous adsorption (so-called CaptureSMB) for the recovery of sinapic acid at industrial scale, using a food grade resin Amberlite^TM FPX66. A mathematical mechanistic model able to describe semi-continuous operation is successfully validated and used to identify optimum operating parameters to maximize productivity and resin capacity utilization in batch and semi-continuous operating modes. The results indicate that CaptureSMB outperforms batch operation, increasing productivity from 5.18 g/L/h to 10.3 g/L/h for a given yield (>97%). A resin capacity utilization (RU) of around 70% is observed in both operating modes when productivity is maximized. A 92% RU can be accomplished for a given yield using the CaptureSMB process at a productivity of 7.0 g/L/h, higher than for conventional batch operation. The use of semi-continuous adsorption operation in food industry contributes to more efficient processes at reduced purification costs.

Proteins derived from plant resources such as oilseed meals, canola and sunflower, are considered a viable alternative to animal proteins for food consumption. This work presents a rational methodology, using high throughput experimentation (HTE), for the separation of cruciferin and napin, the two major proteins of canola meal, by chromatography. Eight different mixed mode and ion exchange resins were evaluated at different conditions with the aim of capturing napin and identifying adsorption/desorption behavior, ease of desorption and selectivity. POROS 50 HS resulted as the most promising resin. The obtained equilibrium adsorption data for napin and cruciferin was used in a mechanistic chromatography model and compared with experimental results showing a very good agreement. The model was used to identify column operating parameters that lead to >98% yield and purity for both proteins. Subsequently a conceptual downstream processing was proposed.

Sinapic acid is a potential valuable compound to be recovered from rapeseed meal extracts as it processes antioxidant and antimicrobial properties. However, the concentration of this compound might be low and the presence of other low value compounds could complicate its downstream processing. Adsorption is an alternative technique that might allow selective recovery of this compound. This work was focused on establishing the foundation of an industrial process design to recover sinapic acid by adsorption. The obtained results from multicomponent experiments indicate that, resin Amberlite^TM FPX66 is the best performing one showing a maximum adsorption capacity of 102.6 + 11.7 mg/g_resin, easy sinapic acid recovery by desorbing it with 70% ethanol and high selectivity to sinapic acid over glucose, phytic acid and glucosinolates. The obtained equilibrium information was applied as input in a dynamic column model and compared with experimental results, showing a good agreement (r² = 0.98). The model can be further applied for a large-scale chromatography process design to recover sinapic acid from rapeseed/canola meal extracts.

This paper describes a new option for integrated recovery and esterification of carboxylates produced by anaerobic digestion at a pH above the pK_a. The carboxylates (acetate, propionate, butyrate, valerate and lactate) are recovered using a strong anion exchange resin in the bicarbonate form, and the resin is regenerated using a CO₂-expanded alcohol technique, which allows for low chemicals consumption and direct esterification. Paper mill wastewater was used to study the effect of pH and the presence of other inorganic anions and cations on the adsorption and desorption with CO₂-expanded methanol. Calcium, which is present in paper mill wastewater, can cause precipitation problems, especially at high pH. Esters yields ranged from 1.08 ± 0.04 mol methyl acetate/mol of acetate_in to 0.57 ± 0.02 mol methyl valerate/mol of valerate_in.