# Volatiles in Berries: Biosynthesis, Composition, Bioavailability, and Health Benefits
## 1 Introduction  
Berries, one of the most common fruits in the human diet (strawberry, blueberry, red raspberry, blackberry, and cranberry in the United States), are rich in minerals, vitamins, dietary fibers, and especially polyphenols and volatiles [1; 2; 3]. Volatile compounds in berries are responsible for the unique aroma of berries [4]. Fruit volatile compounds are mainly comprised of diverse chemicals, including esters, alcohols, terpenoids, aldehydes, ketones, and lactones [5]. The volatile composition of berries is complex and different by many factors, including the cultivar, ripeness, pre- and post-harvest storage conditions, fruit samples, temperature, and experimental conditions [6; 7; 8; 9; 10; 11]. Blueberries (_Vaccinium ashei_) showed linalod increasing and \(\alpha\)-terpineol and \(\beta\)-caryophyllene decreasing during the maturation of the blueberry [6]. Full-red harvested strawberries contained more volatile compounds than \(\forall\)-red harvested strawberries, regardless of the storage duration [12]. Raspberries (raw, frozen, or frozen for a year) were examined to compare the long-term frozen storage. The changes in volatile composition during long-term frozen storage were negligible except for an increase in \(\alpha\)-ionone and caryophyllene [8].  
Volatile compounds are small and light molecules (below 250-300 Da) with low polarity and high vapor pressure [13]. Plants synthesize and release volatile compounds to communicate and interact with environments, compensating for the immobility of plants [14]. Volatile compounds play an important role in pollination by attracting pollinators, protecting from pathogens and herbivores, and even communicating with inter- and intra-plants [15]. Volatiles can be divided into primary compounds and secondary compounds. Primary compounds are synthesized during maturation by anabolic or catabolic pathways of the plant [16]. Secondary volatile compounds are produced from tissue disruption by autoxidation or enzyme catalyzing reactions [17; 18; 19].  
A mixture of many different volatile compounds makes a unique aroma. Although a lot of compounds were found as volatile compounds in fruits, only a few compounds have beenidentified as aroma compounds of fruit flavor based on their quantitative abundance and olfactory thresholds [20]. With the increasing consumption of berries and berry products such as fruits, juice, puree, jams, and other berry ingredients, there have been many studies conducted about identifying aroma volatile compounds of berries for developing consumer acceptability [21] and the studies about the health beneficial effect of berries, especially berry polyphenols. Berry polyphenols are composed of flavonoids, phenolic acids, tannins, stilbenes, lignans, and others and have been shown to possess many health effects, such as antioxidant, anti-inflammatory, and anti-cancer activities [22; 23; 24]. Unlike berry polyphenols, although there have been extensive analyses of volatile berry composition, there is still a very limited number of studies on the bioavailability and health benefits of berry volatiles. Recently, volatile compounds in plants have been reported to have health-promoting activities such as anti-inflammatory effects [25; 26]. Many review articles mainly focused on the composition of berry volatiles and affecting factors such as different locations, ripeness, cultivar/genotypes, harvest and storage conditions, etc., but there is a lack of information about the bioavailability and biological activities of berry volatiles in our body. In this article, the biosynthesis of volatiles in plants, the chemical composition of some berries commonly consumed in the U.S. (blackberry, blueberry, cranberry, raspberry, and strawberry), bioavailability, and the health benefits of volatile compounds that are rich in berries were reviewed.