In North America Berries are consumed both in fresh or frozen forms and also in foods such as yogurts, beverages, jams, canned fruits, jellies. Recently, interest in berry fruits has intensified around the world because of the multiple health-promoting phytochemicals found in berries. Berry extracts are being commercialized as nutraceuticals and as dietary supplements to meet consumers’ demands.
Anthocyanins represent one of major phytochemicals present in most colorful berries and are of interest to nutritionists because of their postulated health benefits, as well as to food processors because of their colorful character as a natural alternative to the use of synthetic dyes.
Anthocyanins are responsible for most of the wonderful orange-red, red, purple, blue and even some deep black colors in berries. Visual appearance of fresh and processed berries is the first factor influencing acceptability and quality perception regarding flavor and texture by consumers. Anthocyanin-rich berries and anthocyanin pigments from berry fruits have been suggested as potential chemoprotective agents, and a large and growing body of evidence from in-vitro cell culture studies, in-vivo animal model tumor systems, as well as human epidemiological studies.
However, color appearance and cancer preventive properties are closely associated with the concentration of the pigments as well as their chemical structures. Therefore, accurate data about anthocyanin content and distribution in berry fruits are important. The most commonly consumed berry fruits in North America include strawberries, blueberries, cranberries, red raspberries, blackberries, and black raspberries.
Anthocyanins belong to the class of flavonoid compounds and are commonly known as plant polyphenols. The anthocyanin pigments consist of two or three main chemical units: the flavylium ring or aglycone base (anthocyanidin), sugars, and sometimes acylating groups. Anthocyanidins present the basic structure of a C6-C3- C6 carbon skeleton typical of flavonoids. They are polyhydroxy and polymethoxy derivatives of 2-phenylbenzoprylium or flavylium salts.
There are 27 known anthocyanidins present in nature, however, only six (cyanidin, pelargonidin, peonidin, delphinidin, petunidin, and malvidin) are commonly found in berries. One of the unusual anthocyanidin structures found in berries was a 4-substituted aglycone, recently found in strawberries.
Anthocyanidins rarely occur in their free form in nature because of their high reactivity. Anthocyanins are mainly glycosylated with one or more sugar moieties that enhance their stability and solubility.
Although not common in berries, some anthocyanins may be acylated. Acylated anthocyanins have acids attached to the sugar moiety, either aliphatic (such as acetic or malonic) acids or aromatic (such as p-coumaric or caffeic) acids. Acylated anthocyanins have been reported in boysenberries and marionberries.
Different combinations of types and numbers of sugars and/or acids attached to the different type of aglycons lead to a wide range of different anthocyanins found in berries. However, the most predominant berry anthocyanin is cyanidin-3-glucoside. The anthocyanin composition in berries has been used as a botanical tool for taxonomic classification of plants, as the anthocyanin profile tends to be characteristic of a plant, similar to a fingerprint. Anthocyanin profiles vary largely among different species but tend to remain quite similar within the same species. Some profiles are rather simple, such as the cases of strawberry, where 80–90% of the pigment composition is just one pigment, pelaronidin-3-glucoside.
Other berries are characterized for their complex anthocyanin profiles, such as Vaccinium corymbosum commonly known as highbush blueberries that exhibit 5 of the different aglycones (cy, dp, pt, mv and pn), 3 different glycosylating sugars (glu, gal, and ara), and also exhibit some acylated derivatives of these anthocyanins – the acetylated monoglycosides. The most widespread anthocyanin in berries is cyanidin 3-glucoside. Differential anthocyanin profiles can be also used for the detection of adulteration in specific commodities of berry fruit products.
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