Fruits and vegetables are good for you! While most of us have heard that statement since early childhood, it is only recently that numerous epidemiological studies and clinical trials have – perhaps unsurprisingly – provided solid scientific evidence indicating to what extent this is actually true. One of the primary mechanisms by which fruits and vegetables are thought to exert their beneficial effects on human health is by virtue of their ability to reduce oxidative stress. Phytochemicals such as polyphenols are the main plant constituents responsible for this antioxidant activity, and there is perhaps no better source of beneficial phytochemicals than the açaí berry.
Açaí berries, also referred to as açaí fruits or palm berries, are produced by palm trees of the species Euterpe oleracea. The fruits produced by these tall, slender palms (which can reach up to 30 meters in height), look very much like grapes but have quite a bit less pulp. In fact, about 80% of the fruit consists of the seed. When ripe, the skin of the fruit is dark purple or green, depending on the variety and maturity of the palm tree. The açaí palm grows its fruit in branched clusters containing up to 900 berries each, which can normally be harvested twice per year. Açaí palms are native to many regions in Latin America, from Belize to Peru, and can be found growing primarily in floodplains and swamps.
In Brazil, where açaí palms are also a native species, açaí berries are an economically valuable crop and are widely consumed in juices, smoothies and as part of other beverages such as sodas. Remarkably, açaí berries are a substantial part of the traditional diet of indigenous tribes in the Amazon basin, comprising in some cases over 40% of the total food intake by weight. Brazil probably has the longest history of consuming açaí berries, and, as a result, there are many different foods and drinks based on these healthy fruits. In northern Brazil, for example, açaí berries are traditionally served in cuicas with tapioca and sugar, and a popular new dish in the south of the country is açaí na tigela (“açaí in the bowl”), which is served cold.
Açaí also has a history of use in Latin America for traditional medicine, primarily for the treatment of gastrointestinal ailments using extracts derived from both fruits and roots. The sap of the açaí palm is employed as an astringent. In addition, the seeds of the açaí berries are ground for use as livestock feed, or to mix into soil as an organic fertiliser for plants.
One important disadvantage of açaí berries is their rapid deterioration after harvest. As a result, raw açaí berries are usually only available in the form of fruit pulp that has been frozen or dried (or freeze-dried). However, this limitation has not stopped a growing number of companies from developing and marketing a variety of juices and other health drinks that contain açaí berries, usually in combination with other fruit juices and flavours.
As a prerequisite to the successful growth of açaí as an ingredient in functional foods, and to the ability of manufacturers to promote these foods on the basis of various health claims, a full understanding of the phytochemical and nutrient composition of açaí is necessary. Towards this end, the nutrient analysis of açaí was recently carried out by a consortium of academic and commercial laboratories based in the United States and Singapore, who published their results in the Journal of Agricultural and Food Chemistry. Led by Alexander Schauss of AIMBR Life Sciences in Washington, the group examined the phytochemical and nutrient composition of a standardised freezed-dried açaí fruit pulp/skin powder.
Among the multiple findings obtained by this analysis, açaí berries were found to contain over 44% dietary fibre, which comprise the large majority of the carbohydrates (52% of the total weight). As such, a 100-gram serving of açaí powder would provide consumers with the recommended daily allowance of dietary fibre.
The standardised açaí powder was also found to contain high levels of oleic acid, a monounsaturated fatty acid known to have a variety of benefits for human health. Of the 32 grams of fat contained in 100 grams of açaí fruit pulp and skin powder, over 56% consists of oleic acid, making açaí berries one of the richest known natural sources of this important fatty acid. Another intriguing finding is that açaí contains relatively high levels of β-sitosterol – around 90% of total sterols, which were present at approximately 0.5 mg per gram of dry weight. β-sitosterol is a phytoesterol that is thought to reduce blood cholestrol levels by competing with dietary cholesterol for absorption.
In terms of antioxidants, which is what açaí are most famous for, the standardised açaí powder was found by the AIMBR-led consortium to contain high levels of anthocyanins and proanthocyanins as the most abundant phytochemicals, as well as several other flavonoids (including homoorientin, orientin, isovitexin, scoparin, and taxifolin deoxyhexose, in addition to numerous unknown flavonoids). However, only low levels of resveratrol were found, in contrast to the high levels of this life-extending molecule found in grape skins. Açaí berries also contain only trace quantities is vitamin C, so any açaí-containing functional foods should rely on other ingredients for this particular antioxidant.
The phytochemical content of açaí berries gives an important insight into the potential of this plant product as an attractive ingredient for the development of novel functional foods. Various studies have been carried out for this purpose over the years, but with conflicting results. An important feature of the AIMBR study was that it was based on the analysis of a standardised açaí powder, which takes into account and normalises the variations in phytochemical and nutrient content due to geographical, environmental, and seasonal differences in the harvesting of açaí berries. As with any food ingredient, it will be key for manufacturers of açaí-containing foods to know the composition of this complex plant product, and to be able to rely on sources of açaí berries which promise a minimum in compositional variation. Supplier of açaí products will be at an advantage if they can meet this standard.
The author
Camila Alexander
Nutraventures, a Belgium-based consulting group focusing on functional foods and nutraceuticals.
