Matured apple fruits of 11 cultivars were a source of fresh flesh and of an extremely variable phenolics composition in the biological medium of cut apple tissue. The content of epicatechin, chlorogenic acid, phloretin-xyloglucoside, and procyanidin B2 were quantitatively determined in extracts from tissue using HPLC method. Diffuse reflectance spectra were recorded every two minutes from the moment of flesh cutting till 12 min after, when enzymatic browning occurred. A two-beam reflectance spectrophotometer was used to collect the data within a wavelength range from 220 nm to 400 nm. The differential spectra calculated from diffuse absorbance data in the course of the browning kinetics were correlated with the phenolics concentration in apples. Chemometric graphs and analysis pointed to a specific time period and specific spectra bands linked to phenolics degradation (310 nm, 332 nm, 346 nm) or with the activation of certain new chromophores (258 nm, 280 nm, 310 nm, 380 nm) in apple tissue. The levels of biologically active compounds in fresh tissue will be correctly predicted from three linear regressions of diffuse-absorbance at characteristic bands of the spectra and browning time (from 0 to 12 min).