Effect of mechanical bruises on optical properties of mature peaches in the near-infrared wavelength range

To date, studies have indicated that near-infrared technologies can be used to detect peaches with mechanically induced bruises. However, it is not clear whether different mechanisms of bruising have similar effects on optical properties of peaches, and which property has greater potential for identifying bruises in peaches. To answer these ques-tions, the absorption coefficient (ma) and reduced scattering coefficient (ms') of non-bruised, collision-bruised and compression-bruised peach pulp and skin were measured using an integrating sphere system over 950-1650 nm and up to 3 days after bruising. The changes in soluble solids content (SSC), water content, firmness, and microstructure of peach pulp or skin were also investigated. The results showed that the SSC of non-bruised and com-pressed peaches increased, and the SSC of collided peaches decreased with time after bruising as did the water content and firmness of all samples. Bruises caused cell structure damage and cell rupture. Three absorption peaks (980, 1175 and 1420 nm) and two ab-sorption peaks (1175 and 1440 nm) were noted for pulp and skin, respectively. Compression had more obvious effect on ma of pulp than collision. Except for shortly after bruising, ms' of bruised pulp was significantly lower (P < 0.05) than that of non-bruised fruit. The corre-lations between optical properties and quality indices were affected by bruises. Mechanical bruising had a significant effect on ms', from which we conclude that measurements of the reduced scattering coefficient has great potential for identifying bruised peaches. (C) 2021 IAgrE. Published by Elsevier Ltd. All rights reserved.