High hydrostatic pressure effects on spectral-optical variables of the chlorophyll pool in climacteric fruit

• High hydrostatic pressure (HHP) effects on chlorophyll Q band was tested in mature green and breaker tomato.
• Bathochromic shift of Q band peak position and decline of peak intensity appeared with ethylene burst.
• HHP induced hypsochromic shift of peak position, but had no effect on peak intensity.
• Hypsochromic shift of peak position increased with enhanced pressure and pre-ethylene burst.
• Variable peak position marks non-destructively the pressure-induced physiological changes of climacteric fruit.

High hydrostatic pressure (HHP) has been widely used for producing plant-based food of fresh-like quality. In this study, HHP-induced changes in the spectral-optical properties of the chlorophyll pool was approached in climacteric tomato fruit. The pericarp in pre- and post ethylene production stages was treated with 250 MPa and 400 MPa at room temperature. The chlorophyll pool, consisting of chlorophyll a, chlorophyll b, and pheophytin, was measured at the Q band of chlorophyll absorption considering the spectral intensity at peak maximum (IPP) and the peak position (PP). The IPP remained unchanged after HHP treatments. This finding confirms earlier studies on the stable, total chlorophyll pool. The single chlorophyll types, however, were affected with decline of chlorophyll a and increase of pheophytin content, suggesting that HHP is enhancing the chlorophyll breakdown process. When comparing fruit developmental stages, the relatively enhanced pheophytin caused the observed bathochromic (red) shift of PP of the Q band. After HHP treatment, however, this effect was outweighed by a strong hypsochromic (blue) shift of PP, assumingly due to enhanced electron state when pigments were allocated out of the stable matrix. The strong hypsochromic shift of the Q band PP may serve as a non-destructively measurable, general variable for optimizing HHP conditions in climacteric fruit.