Valorisation of frozen chestnut by-products: technological challenges for the production of gluten-free flour

The industrial process of freezing chestnuts generates 5560% of by-products. This study aimed to valorise these low-value by-products by producing high-value chestnut flour. Two flour production processes were evaluated, using raw (RCF) and cooked (CCF10, CCF30, CCF50) chestnut by-products during 10, 30 and 50 min. The highest production yield was obtained for RCF (43.6±1.0%) followed by CCF10 (38.0±1.0%). Regarding flour composition, CCF50 presented the smaller protein, fat, fibre and ash contents (P0.05). The CCF10 flour also presented the smallest particle size. The highest peroxide index was found in CCF50 penalizing its acceptance by consumers due to the evidence of rancidity, emphasizing that long time-periods of cooking must be avoided. Finally, up to 129 days of storage, under no temperature or lighting controlled conditions, all chestnut flours showed to be stable overtime.Part of this work was supported by the program CENTRO2020, under the code 02/SAICT/2016, financed by the Portuguese Government and FEDER. Project nº 023631: SoSValor-Sustainable solutions for the valorisation of plant natural products and industrial waste, and by PRODER-Inovação na cadeia de produção da castanha: competitividade e sustentabilidade—Medida 4.1, Cooperação para a Inovação, Ref.ª 53590. This work was also supported by Project POCI-01-0145-FEDER-006984—Associate Laboratory LSRE-LCM, Project UID/BIO/04469/2013 — CEB and strategic project PEst-OE/ AGR/UI0690/2014—CIMO, all funded by FEDER through COMPETE2020—POCI and by Portuguese funds through FCT.