Application of cryogenic grinding pretreatment to enhance extractability of bioactive molecules from pumpkin seed cake

Pumpkin seed cake, a by-product of pumpkin seed oil production, is a potential source of nutraceuticals, which remain unexploited by current management practices. This research assessed its bioactive potential and investigated the effect of cryogenic grinding pretreatment on extractability of various nonpolar and polar bioactive molecules. Notable amounts of squalene (1,684 mg/kg), phytosterols (3,900 mg/kg), and tocopherols (220.3 mg/kg) were extracted from the untreated (control) pumpkin seed cake together with 72.6 mg/kg of protochlorophylls and 90.1 mg/kg of total phenols. Control pumpkin seed cake also yielded 16.75% of total fiber. Application of cryogenic grinding as well as its duration significantly increased the amount of bioactive molecules extracted from pumpkin seed cake as well as extracts antioxidant activity. Major increase was determined for phytosterols and protochlorophylls which were 2 and 2.5 fold higher, respectively, in pumpkin seed cake samples ground with cryogenic cooling during 12 min. Practical applications Yearly production of pumpkin seed oil leaves behind more than 11.500 tons of by-product in the form of pumpkin seed cake which is currently mainly used as livestock feed or for composting. Results of this study reveal high bioactive potential of pumpkin seed cake, which opens way to new possibilities of its utilization in functional food and dietary supplements production. In particular, it could be exploited as low cost raw material for the extraction of high added value extracts aimed for the treatment of benign prostatic hyperplasia. Application of cryogenic conditions during grinding additionally enhances bioactive potential of pumpkin seed cake.