Original article Comparison of bioactive peptides prepared from sheep cheese whey using a food-grade bacterial and a fungal protease preparation Grace Welsh, 1 Kate Ryder, 1 Jodi Brewster, 1 Christina Walker, 1 Sonya Mros, 2 Alaa El-Din A. Bekhit, 3 * Michelle McConnell 2 & Alan Carne 1 1 Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand 2 Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin, New Zealand 3 Department of Food Science, University of Otago, PO Box 56, Dunedin, New Zealand (Received 13 November 2016; Accepted in revised form 13 January 2017) Summary Novel bacterial (HT) and fungal (FPII) food-grade protease preparations were evaluated for their ability to hydrolyse sheep cheese whey (SCW) and the generation of bioactive peptides. Both protease prepara- tions hydrolysed the whey proteins to small peptides over 24-h hydrolysis time, but the time course hydrolysis profiles were different as evaluated by SDS-PAGE. The HT whey hydrolysate had considerably higher antioxidant and angiotensin-I converting enzyme (ACE)-inhibitor activity than the FPII hydroly- sate. Neither hydrolysate was cytotoxic towards Vero cells. OFFGEL electrophoresis of the small peptide pool fraction (<15 amino acids) of each hydrolysate indicated differences in the pI distribution of the bioactive peptides. This likely reflects the diverse hydrolytic specificity of the proteases. Although the antioxidant activity of both hydrolysates was not significantly affected by simulated gastrointestinal diges- tion, the loss of ACE-inhibitor activity was greater with the FPII hydrolysate. Keywords Angiotensin-I converting enzyme-inhibitor, antioxidant, bioactive, hydrolysates, sheep cheese whey. Introduction Small ruminant sheep dairying has been prominent for a long time in many countries where geography and climate are not suited to cow dairying (Pandya & Ghodke, 2007). There has also been growing interest elsewhere internationally in sheep dairying (Ardern et al., 2013), for the production of processed dairy products such as cheeses, in addition to providing alternatives for people who have an allergy to cow milk (Pandya & Ghodke, 2007). The recent expansion of sheep dairying in New Zealand and the use of sheep milk for special cheese manufacture generate consider- able quantities of SCW that is currently an underuti- lised co-product. Management of cheese whey as a high volume potential pollutant has been reviewed recently (Prazeres et al., 2012). While whey proteins themselves are well known for their health-promoting properties (Krissansen, 2007; Pihlanto, 2011; Tariq et al., 2013), it is widely recognised that whey proteins contain particular amino acid sequences that exhibit bioactivity only when released as peptides following hydrolysis with proteases (Mills et al., 2011). On consumption of milk, milk proteins are hydrolysed by gut proteases, generat- ing bioactive peptides that confer health-promoting benefits. A number of studies have reported that hydrolysates of cow milk and cow whey protein isolate generated using proteases of gut origin contain consid- erable bioactivity (Madureira et al., 2010; Adjonu et al., 2014). A few studies have reported the use of proteases of nongut origin to hydrolyse bovine milk and whey proteins (Hern andez-Ledesma et al., 2005; Dry akov a et al., 2010; del Mar Contreras et al., 2011; Tavares et al., 2011; De Gobba et al., 2014). The gen- eration of hydrolysates from whey can also improve various functional properties of the material, including solubility and emulsifying capability, that can be advantageous, in addition to the bioactivity manifested by the peptides (Sarmadi & Ismail, 2010). The potential for production of bioactive peptide- containing hydrolysates of food-grade natural product *Correspondent: E-mail: aladin.bekhit@otago.ac.nz International Journal of Food Science and Technology 2017 doi:10.1111/ijfs.13392 © 2017 Institute of Food Science and Technology 1