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.
