Hydrothermal conversion of ice-cream wastewater

摘要

Ice-cream wastewater (WW) was subjected to a hydrothermal process (230 degrees C, 40 bar, and 240 min) to reduce the organic load and to produce functional hydrolysates of protein as value-added components. Samples of WW from six different production days were collected after a typical clean-in-place protocol. Untreated WW contained high values of total protein (12-22% on dry basis), biological oxygen demand (BOD, 8-38 g L-1), and chemical oxygen demand (COD, 7-30 g L-1). The hydrothermal process reduced 87-97 and 25-70% of the BOD and COD, respectively. Moreover, the hydrothermal process hydrolyzed between 38 and 56% of the protein fraction, and the resulting hydrolysates showed antioxidant activity (14-19% of the DPPH) and antihypertension (angiotensin I-converting enzyme) activity (60-97%). Additionally, the hydrolysates showed a high ratio of glutamic acid (20-26%) and proline (10-15%), which confirmed the relevant functional properties of hydrolysates. Practical Applications Virtually all ice-cream manufacturers experience the common challenge of managing WW from production and cleaning operations. In this study, we converted ice-cream WW into valued-added hydrolysates through hydrothermal process. Produced hydrolysates exhibited relevant functional properties. More importantly, the outcomes of this investigation help to address the environmental concerns associated with millions of tons of WW generated from manufacturing activities.