Chlorophyll fluorescence emission and its relation to skin color and firmness during ripening of guava fruit

Abstract

Introduction . Chlorophyll fluorescence (chl-fluorescence) has been used in postharvest studies as a non-destructive technique for evaluating fruit ripening. Since there are no available studies using chl-fluorescence in guava fruit, the aim of this work was to verify the relations between chl-fluorescence parameters and fruit quality attributes, such as skin color and fruit firmness, and to measure the chl-fluorescence during ripening of guava fruit. Materials and methods . Firstly, maximal (Fm ), minimal (Fo ), variable (Fv ), and variable to maximal [Fv /Fm ] fluorescence yields, skin color (Ho) and fruit firmness were evaluated in guava fruit harvested at three ripeness stages: dark-green (I), light-green (II) and yellowish-green (III). Secondly, changes in the above chl-fluorescence parameters and Ho were measured during 7 days of ripening. Relations between the evaluated parameters were also studied. Results and discussion . The three ripeness stages were well segregated using the Ho, Fm and fruit firmness parameters. Fo was insensible to early changes in fruit ripening, maintaining relatively stable values until fruit firmness of 20 N. When considering changes in chl-fluorescence and Ho during ripening, there were no significant differences between guava fruit harvested at stages II or III. The [Fv /Fm ] value decline was only evident on the fifth day of ripening, whereas Fv , Fm and Ho began to decrease on the first day. Regardless of [Fv /Fm ], the relations between chl-fluorescence parameters and Ho tended to increase from ripeness stages I to III, with Fm having the highest correlation with Ho. The results show that chl-fluorescence can be used to evaluate the ripening and senescence of guava fruit, with Fm being a good ripening indicator.