Monitoring natural phenolics and antioxidants in processing apple juice (AP10020)

This is a final research report from Hort Innovation’s historical archives. Please note that as these reports may date back as far as the 1990s, the content and recommendations within them may be superseded by more recent research.

What was it all about?

Apple fruit are nutritious and should be an integral part to a balanced diet. Besides their traditional nutritional benefits, such as vitamins, minerals, fibre etc, apples are a rich source of naturally-occurring phenolic compounds which significantly contribute to the antioxidants in the human diet. However, apples at the time were not just eaten whole as fresh apples; approximately one third of apples were processed, with apple juice being the most popular form of processed apples. There were two types of apple juices on the market; cloudy and clarified. Cloudy apple juice was made from crushed and pressed apples and had rapidly grown in popularity. Clarified juice was clear and was made by processing the cloudy apple juice. This study measured the antioxidant activity level and the concentration of naturally-occurring phenolic compounds in a range of 17 different commercial apple juices (6 cloudy and 11 clarified apple juices) purchased from supermarkets.

The results showed that the levels of naturally-occurring phenolic compounds were 2.8 times higher in the cloudy than in the clarified apple juices. Similarly, the cloudy apple juices contained 2.5 times more antioxidant activity compared to the clarified apple juices. Therefore, it was shown that the clarification process decreased the phenolic compound content and the antioxidant activity of commercial apple juices. Further research in the ‘healthiness’ of Australian apple juice would increase the consumer appeal of Australian apple juice. This project was partly funded through a voluntary contribution from ‘Appledale Co-op’ in Orange, NSW.