Ariestya Arlene Arbita1,3, Nicholas A. Paul2, Julian Cox1, Jian Zhao1,*
1Food Science and Technology, School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
2School of Science and Engineering, University of the Sunshine Coast, Maroochydore, Queensland 4558, Australia
3School of Chemical Engineering, Faculty of Industrial and Technology, Parahyangan Catholic University, Ciumbuleuit 94, Bandung 40141, Indonesia
Cheese-making involves milk coagulation as a crucial step. Rennet, a substance derived from the abomasum of a young calf stomach, has been used traditionally as milk-clotting enzyme in the cheese industry. However, the supply of rennet is limited and unable to meet the growing demands in cheese production. Moreover, there is an issue for vegetarians to consume cheese products made from rennet as it is derived from an animal-based source. A number of rennet substitutes have been explored, including pure chymosin produced by molecular technology, animal pepsin, plant and microbial proteases. However, these milk coagulants still have various drawbacks, including limited availability, low yields, high bitterness, and consumer concerns about animal ethics and genetically modified organism (GMO). Therefore, the continual search for rennet alternatives is necessary. Seaweeds are a potential source of milk clotting enzymes that have not been well explored. This study evaluated a milk-clotting enzyme from seven species of seaweed including different post-harvest processing, extraction and purification procedures. Protein extracts of all seven species of seaweeds exhibited some caseinolytic activity, but the extract of unprocessed (whole, dried) samples had higher protein yields and stronger caseinolytic activity. The extract from one species, Gracilaria edulis, demonstrated the ability to clot milk. The evaluation of the purification method for G. edulis extract revealed an optimum single step of 50% saturation and ammonium sulphate precipitation with dialysis as the desalting method.