Exergy, energy, and sustainability assessments applied to RSM optimization of integrated convective air-drying with pretreatments to improve the nutritional quality of pumpkin seeds

Abstract

Pumpkin seeds are generally discarded but they are a source of protein, fibers, and other nutrients. This paper aimed to define the drying conditions for obtaining the optimal effective diffusivity (Deff) by applying the RSM (Response Surface Method) and Box–Behnken design (BBD) and random search also focused on energetic, exergetic, and environmental assessments. Pumpkin seeds were subjected to pretreatments by immersion in NaCl solutions at 0, 2, 7, and 14 % (w/w), and blanching at 373 K during 0, 2, 7, 12, and 14 min. The pretreated samples presented shorter drying times than the non-pretreated ones at all temperatures studied. The optimal conditions are 356.8 K, 12.65 % NaCl, and 0.5 min. The lipid and protein contents did not show significant variations at the optimal conditions concerning fresh pumpkin seeds; however, the crude fiber contents decreased. The energetic and exergy efficiency of the dryer were 13.4 % and 41.77 %, respectively. The Improvement Potential (IP) and Sustainability Index (SI) values are associated with the losses of exergy. The CO2 emissions during the global process were 0.165 kg/kg of fresh seeds, and their values were related to the specific energy consumption.