Fruit waste provides antioxidant source

During the production of pre-packaged fruit and juices, portions such as the skin are often unused. Some fruit by-products are currently used in animal feed, but most often they are sent as waste for disposal.

Now, Dr Said Ajlouni and PhD student Wei Wei Tow from the Melbourne School of Land and Environment are working with Dr Robert Premier, technical manager at Salad Fresh, to put this waste material to good use.

’Fruit has long been known for its health benefits, partly as a good source of antioxidants − the chemical compounds, including some vitamins, that protect body cells from damage,’ Dr Ajlouni says. ’So we decided to investigate if fruit waste also had these properties.’

The team analysed tomato, apple, plum, peach, pear, grape and apricot waste, such as the skin, revealing them all to be good sources of antioxidants. For example, results from the tomato study revealed that, compared to tomato juice, tomato waste contains double the amount of lycopene, a bright red pigment found in fruits and vegetables, which also acts as an antioxidant.

By heating, freezing and breaking up the strucure of the fruit waste with sound waves, the researchers concentrated it into a powder containing large amounts of antioxidants. For example, heating tomato extract increased the amount of extracted lycopene from tomato waste by at least threefold.

So far, the most promising results have come from apple waste. The antioxidant properties are present in compounds called polyphenols, a group of chemical compounds found in a wide array of fruits and vegetables, including apples, blackberries, blueberries, cantaloupe, grapes, pears, plums, strawberries, broccoli, cabbage, celery, onion and parsley. High levels of polyphenols can generally be found in the fruit skins.

Recently, Dr Ajlouni and Tow examined the antioxidant powder against standard laboratory cancer cell lines. Ms Tow visited China Agricultural University to perform the experiments and says that the studies revealed that the apple antioxidant powder reduced the growth of human cervical and liver cancer cells by 85-98 per cent.

The next steps will include the team refining their extraction method to try and further concentrate the antioxidant properties of the waste powder.

Working with a major food-production company in Victoria, the researchers are also establishing how the antioxidant powder can be incorporated into food products for extra health benefits. The powder is being tested for its use as a thickener in fruit products, as a covering for capsules and as an antioxidant boost in snack bars.