Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 22, 2001
Publication Date: N/A
Interpretive Summary: Aroma is an important contributor to flavor of fresh strawberries. It was hypothesized that the concentration of strawberry aroma compounds could be modified by far-red and red light reflected from the soil surface to the berries as they ripen. To test the theory, strawberry plants of two popular varieties,"Chandler" and "Sweet Charlie", were grown in raised soil lbeds that were trickle irrigated and covered with plastic mulch to conserv water, control weeds, and keep the fruit clean. The plots were covered with either standard black plastic mulch or with a red plastic mulch that was formulated to reflect a ratio of far-red to red light that could act through the plants natural growth regulating system to favor increased yield and quality. Freshly picked strawberries that ripened over the red mulch during sunny weather released greater amounts of the aroma compounds desired by consumers. Berries of both varieties responded similarly to ripening over the red mulch. This information is important to home gardeners and to growers who specialize in "You-Pick" or other fresh strawberry markets.
Technical Abstract: Strawberry (Fragaria ananassa Duch) is a high value food crop, the aroma of which is important in consumer satisfaction. We hypothesized that the concentration of fresh strawberry aroma compounds could be enhanced by growing the berries over a red plastic mulch that was formulated to reflect more far-red (FR) and red light (R) and a higher FR/R photon ratio than is reflected by standard black plastic mulch. Strawberries of the cultivars "Chandler" and "Sweet Charlie" were grown in trickle-irrigated field plots over the two colors of mulch, the berries were harvested when ripe, and aroma compounds isolated by dynamic headspace sampling. Entrained compounds were quantified by gas chromatography and identified by gas chromatography/mass spectroscopy. Twenty-three compounds were identified, most of them were aliphatic esters. Strawberries that ripened over the red mulch during periods of sunny weather had significantly higher concentrations of aroma compounds than berries grown over the black plasti mulch. Total levels of aroma compounds from berries grown over red plastic mulch were higher for both Chandler and Sweet Charlie. We conclude that FR and R in light reflected from the red mulch acted through the natural phytochrome system to modify gene expression enough to result in greater concentration of aroma compounds in fresh strawberries.