Dietary fiber sticks obtained by fluidized bed drying from pear bio-wastes from the canning industry

RETAMAL, E. ; GOMEZ MATTSON, M.; GARRIDO MAKINISTIAN, F.; SETTE, P.; DIEZ S.; FRANCESCHINIS, L.; MAZZA, G.; ZAMBON, M.; SALVATORI, D.

CABA

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

Asociación Argentina de Ingenieros Químicos (AAIQ)

Fruit industry generates large amount and variety of bio-wastes, which constitute an important source of bioactive compounds. Considering the environmental hazards related to the accumulation of solid residues with high organic content, it is interesting to consider them as potential substrates for the design of new food products [1]. In particular, the pomace resulting from the manufacturing of canned fruit, composed of peel and the flesh tissue that remains after mechanical peeling mainly contains cellulose, hemicellulose, lignin, and pectin, and can then be used to develop fiber-rich products. Fluid bed drying is an effective process for drying particulate materials and was proposed in this work as an alternative to the extrusion process for the production of fiber sticks. The objective of this work was to study the feasibility of applying the fluidized bed drying process on different formulations made with pear (var. Williams) wastes generated by mechanical peeling of the fruit used for canning (CERES S.A industry, Río Negro province, Argentina). After collection, the wastes were immersed in acid solution to reduce browning and subjected to juice extraction process by cold pressing. The remaining solid residue called RSR (water content = 89.8 kg water/100 kg, wet basis) was used for two feed formulations prepared by using: 80% of RSR and 20% of ingredients added from different source: lupine flour (LF) or wheat bran (WB). Both mixtures were subjected to manual mechanical profiling and subsequent cutting for achieving the shape of small sticks (2 cm long and 0.45 cm diameter). Once molded, the wet sticks were dried in a fluidized-bed equipment operated at 4.5-6 m/s air-flow rate,  5 % air relative humidity and three air temperature conditions (50 °C, 60 °C and 70 °C), until constant weight was reached. Different semi-empirical mathematical models (Page, Modified Page, Logarithmic, and Henderson & Pabis) were used to describe the obtained drying curves, being the Page´s model the most suitable to predict the waste formulations drying behavior. Very short drying times were required to achieve aw < 0.2 in all cases, showing a high efficiency of fluidized bed drying without the addition of inert material often necessary for biomass fluidization. Drying rate was lower in LF formulation compared to that of WB, increasing with air temperature in both cases. For instance, at 60 °C 13 min were required to reach a humidity value of 0.2 kg/kg (dry basis) in WB while at 70 °C the time decreased by  35 %. In LF  23% reduction in drying time was observed (from 15.5 till 12 min).It was possible to obtain by fluidized-drying dry fiber sticks similar to those existing on market but with different nutritional value. According to the current legislation, the products obtained from both formulations were “high in dietary fiber”. The sticks formulated with lupine flour could be also considered “high in protein" products and the sticks containing wheat bran could be considered "source of protein".