Aroma of fresh strawberries is enhanced by ripening over red versus black mulch

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 were isolated by dynamic headspace sampling. Entrained compounds were quantified by gas chromatography and identified by gas chromatography/mass spectroscopy. Twenty-three compounds were identified, and 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 plastic mulch. Total levels of aroma compounds from berries grown over red plastic mulch were higher for both Chandler and Sweet Charlie. We postulate 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.