Association between the concentration of n-alkanes and tolerance to cracking in commercial varieties of sweet cherry fruits

Abstract

Fruit cracking is one of the major economic losses in cherry production worldwide. Factors involved in differential tolerance among varieties are unknown. This phenomenon is mainly caused by rainfall during the harvest period and is related to osmotic factors and fruit water permeability. The cuticle is a hydrophobic extracellular membrane and soluble waxes represent a mixture of aliphatic very long chain fatty acids, its derivatives and cyclic compounds like triterpenes. Analysis of waxes from enzymatic isolated sweet cherry fruit cuticles showed that the main components are triterpenes (76%), alkanes (19%) and alcohols (1%).Cracking in vitro was investigated in five sweet cherry varieties. After removal of cuticular wax fruit cracking was significantly increased. Nuclear magnetic resonance analysis (1H and 13C NMR), revealed that fruits of different sweet cherry varieties contain primarily n-alkane with 29 carbons and no iso-alkane. Gas chromatography–mass spectrometry (GC–MS) enabled identification and quantification of n-alkanes. Varieties with significantly higher concentrations of nonacosane (Kordia, Regina and Lapins) were more tolerant to cracking compared to varieties with lower amounts (Bing and Rainier).We hypothesized that there is an association between the amount of C 29 n-alkane and cracking tolerance in sweet cherry fruits. This difference could be an important factor to explain the different tolerances to cracking in fruits of sweet cherry varieties.