SEQUENTIAL HYDROTHERMAL EXTRACTION FOR THE RECOVERY OF VALUABLE BIOACTIVES FROM POTATO PEELS

Jose Salomon Martinez Fernandez

Agriculture and food industries generate significant quantities of by-products that become wastes if not properly managed. Disposal of these is challenging because they are prone to microbial decay, drying them is too costly, and storage is impractical. Yet, these are inexpensive sources of valuable compounds, such as bioactives and cell wall materials, which may be retrieved and used as functional ingredients. However, the major barrier for effectively utilizing these resources is the lack of technologies that can recover the desired components. Thus, new methods for the cost-effective extraction of the bioactives from the by-products need to be developed. In this study, Sequential Hydrothermal Extraction (SeqHTE) was investigated as a “green” and versatile alternative for recovering valuable bioactives to repurpose wastes such as potato peels. The maximum polyphenol recoveries were 22.48 and 32.87 mg/g for the Russet and mixture sample, respectively. The extracts displayed significant antioxidant functionality, ranging from 40–92% of free-radical inhibition. Additionally, SeqHTE allowed the retrieval of glycoalkaloids (20–610 mg/kg) and good amounts of polysaccharides (up to 35.7wt%). Based on the chemistry assessment, acid-catalyzed acyl bimolecular and unimolecular nucleophilic substitution reaction mechanisms were proposed as the means by which SeqHTE breaks down the solids to release bound metabolites. According to the kinetic study, the ideal conditions to enhance recovery and minimize degradation, were from 140–160°C and from 170–190°C for the first and second stage, respectively. The techno-economic analysis showed that SeqHTE costs were ~1.5–2 times of that for single-stage subcritical water extraction. However, this analysis revealed that the production costs of the process compared favorably with the one-stage approach, because it offered a more complete biomass utilization and multiple products. Under the analysis conditions, the unit production cost of SeqHTE with filtration was $0.43/kg of refined product. Alternatively, for SeqHTE with adsorption the cost was $67.00/kg. The results highlighted the potential and suitability of SeqHTE for the recovery of valuable and structurally diverse bioactives from wastes such as potato peels. The knowledge generated lays the groundwork for advancing the technology, which could become an effective yet versatile system for processing different wet biomass.

SEQUENTIAL HYDROTHERMAL EXTRACTION FOR THE RECOVERY OF VALUABLE BIOACTIVES FROM POTATO PEELS

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