Is your apple juice really made of apples?
When you purchase apple juice, you
are expecting to receive apple juice, but that isn’t always the case. Sometimes the juice will be a mix of apple
and pear juices. This mixture is done
for economic benefit to the producer.
Different fruit juice concentrates have different values on the
market. Adding some of the less valuable
concentrate to the mix makes it cheaper to produce.
This is possible because apple and pear juices are very similar in both their organoleptic properties, and their contained carbohydrates. The mixing of substance to reduce cost is called adulteration. Finding a way to accurately determine the composition of a juice mixture is important. The common method of determining specific juices is to use phenolic profiling. Phenolics are plant metabolites, that are different depending on type of fruit, location of growth, and age of the fruit. Different fruits will have different phenolic profiles. While this method usually works, it is not always accurate, and phenolics thought to be unique to one fruit have been found in others. To determine an accurate way to distinguish fruit juices, J.L. Willems and N.H. Low studied 27 apple juice samples and 31 pear juices samples from around the world to identify reliable finger-print molecules for these juices.
These concentrations include different varieties of the fruits, juice from different locations, and juice from different production dates. This style of sample was chosen to ensure that the method of determining juice type works effectively on all varieties of juice concentrate. Liquid chromatography with photodiode array detection was performed to identify unique compounds and then to be absolutely sure of the identities of the molecules the samples were tested using.
Two compounds specific to pears, and one specific to apples were identified. These compounds were found in large enough concentrations and stable enough as to be easily identified. The first pear juice compound was found to be a flavonol. Further analysis determined the specific flavonol to be isorhamnetin-3-O-rutinoside. The second compound was determined to be abscisic acid. The pear concentrates from China had different compositions than the other concentrates. These pear species are known as Asian pear (Pyrus pyrifolia). In three of the samples, isorhamnetin-3-O-rutinoside as not found, and in all four abscisic acid was not found. Fortunately, a previously known compound of arbutin could be used to identify these Chinese pear concentrates. The apple compound was found to be a phenolic and a hydroxycinnamic acid. Using results from mass spectral, UV-vis spectroscopy, and fragmentation pattern tests, the compound was determined to be 4-O-p-coumarylquinic acid.
This is possible because apple and pear juices are very similar in both their organoleptic properties, and their contained carbohydrates. The mixing of substance to reduce cost is called adulteration. Finding a way to accurately determine the composition of a juice mixture is important. The common method of determining specific juices is to use phenolic profiling. Phenolics are plant metabolites, that are different depending on type of fruit, location of growth, and age of the fruit. Different fruits will have different phenolic profiles. While this method usually works, it is not always accurate, and phenolics thought to be unique to one fruit have been found in others. To determine an accurate way to distinguish fruit juices, J.L. Willems and N.H. Low studied 27 apple juice samples and 31 pear juices samples from around the world to identify reliable finger-print molecules for these juices.
These concentrations include different varieties of the fruits, juice from different locations, and juice from different production dates. This style of sample was chosen to ensure that the method of determining juice type works effectively on all varieties of juice concentrate. Liquid chromatography with photodiode array detection was performed to identify unique compounds and then to be absolutely sure of the identities of the molecules the samples were tested using.
Two compounds specific to pears, and one specific to apples were identified. These compounds were found in large enough concentrations and stable enough as to be easily identified. The first pear juice compound was found to be a flavonol. Further analysis determined the specific flavonol to be isorhamnetin-3-O-rutinoside. The second compound was determined to be abscisic acid. The pear concentrates from China had different compositions than the other concentrates. These pear species are known as Asian pear (Pyrus pyrifolia). In three of the samples, isorhamnetin-3-O-rutinoside as not found, and in all four abscisic acid was not found. Fortunately, a previously known compound of arbutin could be used to identify these Chinese pear concentrates. The apple compound was found to be a phenolic and a hydroxycinnamic acid. Using results from mass spectral, UV-vis spectroscopy, and fragmentation pattern tests, the compound was determined to be 4-O-p-coumarylquinic acid.
These findings can be used to
identify the compositions of fruit juices sold on the market. The presence of adulteration in a juice
sample can be found, and it can also be determined if a product is 100%
pure. Checking purity is important, as
many products are labeled as 100% pure, but may be mislabeled. Additionally, the finding that Asian pears do
not contain isorhamnetin-3-O-rutinoside or abscisic acid can be used to
determine the location of origin of the juice.
This is useful as juices made in different places have different
values. Additionally, this can be used
to help consumers decide on a product if they are concerned about the location
of origin for the ingredients. While
this determination of juice composition may seem insignificant, it becomes
important when the scale of production, distribution, and sale of the product is
great, and international.
Read more here.
Image compiled by Max Hall using the following sources:
Read more here.
Image compiled by Max Hall using the following sources:
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