Aren’t You Glad There’s a New Way to Process Juice?
Thermosonication for Fruit and Vegetable Juices
by Danielle Rosen
Springtime is here again, and with it comes a new harvest of fresh fruit and vegetables. From juicy apricots to white asparagus, phytonutrient-filled seasonal produce can be found both in gardens and grocery stores, but consumers are looking for new ways to get their daily five. One trend that has become popular is to get the daily dose of fruits and vegetables in the form of fresh juices, however many juices that are available on the market are not as “fresh,” as consumers believe them to be. Traditional processing methods such as pasteurization for fruits and vegetable juices which often rely on high heat to reduce spoilage bacteria and enzymes to safe-to-consume levels, also degrade the color, taste, and nutrient composition of fruit and veggie juices. Because of the negative effects of traditional fruit and vegetable juice processing, many juice manufactures add preservatives, colorings, and flavors to get a more desirable product. Is a fruit or vegetable juice filled with preservative and reduced vitamin C content what consumers really want? The answer is most likely no, but new methods of processing can produce fresher juices with nutrients and taste that consumers love.
Thermosonication is a form of minimal processing that works by applying low heat and low frequency sound waves to the fruit and vegetable juices. By combining low heat forms of pasteurization with the novel processing technique of ultrasound, two different spoilage reduction processes are applied to the juice to create a safe to consume product without degrading important nutrients and sensory aspects like color and taste. Thermosonication has been used in many different types of fruit and vegetable juices, and generally applies a frequency of around 20 kilohertz (kHZ) anywhere between 40-80°C for several seconds to 10 minutes. Time, temperature, and frequency combinations change depending on the type of fruit or vegetable juice, the nutrient content, viscosity, and intended purpose (such as straight to the bottle, or used in another product), but all forms rely on low frequency and low temperature to preserve nutrients and sensory attributes like appearance and taste.
To understand thermosonication a little better, let’s look at how it works for processing a consumer favorite, fresh orange juice. First, the oranges are harvested and the juice is extracted. Once the raw orange juice is ready, it is put into a large vat surrounded by a pre-heated water bath of 45°C. An ultrasound probe is then put into the middle of the vat of orange juice, and waves of 20kHZ are administered for several minutes. As the invisible sound waves travel through the vat of juice, they pass through the spoilage bacteria, causing their cell walls to break and thus killing the bacteria. As the waves are destroying the bacteria, the water bath is destroying the spoilage enzymes bacteria that can lead to browning or mold growth in the juice.
Now that you know how thermosonication works, the question is, does it really work? Still looking at orange juice, the key nutrient, vitamin C, is retained at 85-98% whereas orange juice processed with pasteurization only has 85% retention or less. Spoilage enzymes are reduced by 90% or more, and dangerous bacteria like E. Coli and Salmonella are destroyed. Thermosonicated juices also tend have a more appealing appearance, flavor, and texture than juices treated with high heat alone. These benefits of thermosonication are amazing, because they are achieved without the addition of ANY preservatives, added vitamins, or colorings, and it results in a cleaner ingredient list, fresher product, and happier consumer.