Developing palatants for pet food from leather industry wastes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand

Abstract

The leather industry generates substantial waste streams, which are presenting a significant challenge in terms of both environmental sustainability and economic efficiency. Adding value to leather waste streams is a popular research idea. Most previous research has focused on recycling and reusing collagen from leather waste or turning leather waste into bioenergy. This project concentrated on turning one leather waste stream into ingredients for pet food because the commercial value of the pet food industry is increasing. Cats are strict carnivores, and they find ingredients from animal sources highly palatable. Therefore, the aim of this project is to produce and develop edible and palatable products which are attractive to cats and analyse these novel products in order to understand more about increasing palatability in cat food. Chapter 2 is the literature review. The first part of the review summarises and compares research into the utilisation of leather waste streams, especially in the food industry. The second part contains basic information on palatability, and how improvements in cat food manufacture and methods for testing palatability have been made. The final part of the review considers methods for food flavour instrumental analysis especially to characterise key factors associated with palatability. Chapter 3 details attempts to explore collagen hydrolysis. Collagen hydrolysed by water mixtures were produced for in vivo testing by cats using two-bowl palatability tests. However, the hydrolysed collagen solutions only had the same levels of palatability as water for cats. Chapter 4 describes further palatability sample development and production processes. A series of samples were prepared and tested by cats using the same method in Chapter 3. The best performing of these was a raw sheep skin sample hydrolysed by phosphoric acid at 105°C and then adjust its pH to 5.5, which showed that a novel palatable product for cats can be produced from leather waste. This sample was further analysed in Chapter 5. Proximate analysis, volatile compounds characterisation, total amino acid, free amino acid and fatty acid analyses were carried out. Those tests allowed full nutritional mapping of the sample. The future work chapter indicates the remaining gaps in the finished lab work and the suggests further work that needs to be carried out.