Dual Color-Space Image Analysis Reveals Maturity-Dependent Responses to L-Cysteine Pretreatment in Dried ‘Gala’ Apple Slices

Drying is a traditional fruit preservation method often combined with pretreatments to improve product quality. Slices from six “Gala” apples at three successive consumption maturity (storage) stages were immersed for 1 min in 0.3% or 0.6% aqueous L-cysteine solutions and dried under controlled laboratory conditions. Color changes were quantified from calibrated digital images in the sRGB and CIE L*a*b* color spaces. Treatment, storage stage, and their interaction were evaluated using hierarchical analysis of variance supplemented by cluster-robust inference. L-cysteine significantly reduced color deterioration, with particularly strong treatment effects for ΔL*, Δa*, ΔsR, and ΔsG. Component-wise sRGB analysis revealed differences in treatment responses among individual color channels that were less apparent from the overall color difference (sRGB ΔE) alone. Treatment effectiveness varied across consumption maturity stages, highlighting the importance of maturity when evaluating L-cysteine pretreatment.