Strawberry Flavor: Diverse Chemical Compositions, a Seasonal Influence, and Their Effect on Sensory Perception

Fresh ripe strawberries are valued globally for their characteristic red color, juicy texture, distinct aroma, and sweet fruity flavor. To ensure continued consumption, flavor must be consistently high in quality, but defining this complex trait has proven to be difficult. Human perception of flavor is the integration of multiple sensory inputs, the most influential being the chemical senses of taste and olfaction. Olfaction is divided into orthonasal (smell) and retronasal (flavor). Previous efforts detailing strawberry flavor have supplied an index of volatile constituents, in which the significance of an aroma volatile to flavor is determined indirectly by the orthonasal odor threshold. This is an inappropriate methodology, as orthonasal olfaction does not integrate with taste perception like retronasal olfaction. In this study, genetic and environmentally induced variation among strawberry fruit is exploited by simultaneously assaying fruit for: biochemical inventories of volatile compounds, sugars, and organic acids; physical measures of titratable acidity, soluble solids content, and firmness; and consumer hedonic and sensory responses. Data are analyzed to determine seasonal effects, gross variation across genotypes, and fruit attributes influencing hedonics and sensory perception of strawberry fruit using a psychophysical approach. This approach, previously only applied to tomato, garners insights into flavor chemistry, the interaction between taste and olfaction, and a paradigm for enhancing liking of natural products. Seasonal progression exerts a negative influence on soluble solids content in subtropical Florida and sucrose is identified as the waning primary metabolite, leading to decreased volatile content. These alterations are perceivable as sweetness intensity, flavor intensity, and texture liking have significant influence on overall liking of strawberry fruit through variations in sugar concentration, specific volatile compounds, and fruit firmness. Interestingly, some of the most abundant volatiles do not contribute to consumer liking, whereas other less abundant volatiles contribute significantly. Thus reducing the importance of previously determined volatiles and recognizing novel components with a positive influence on flavor. In strawberry, a subset of specific aroma volatiles make contributions to perceived sweetness independent of sugar concentration in the fruit. More volatiles have been identified as having a positive effect on perceived sweetness in strawberry than previously observed in tomato.  This observation suggests that strawberry is a more appropriate system for studying the effects of aroma volatiles on perceived sweetness. Volatiles that increase perception of sweetness without adding sugar will have far-reaching effects in food chemistry, and also provide metabolic targets for future breeding efforts of consumer defined traits.