Abstract
Fruit firmness is an important, but highly variable quality characteristic of strawberry (Fragaria xananassa Duch.) fruit. Both genetic background, growing conditions and fruit constitution at the time of testing (degree of ripeness, size, post-harvest handling, internal temperature, etc.) affect fruit firmness. Fruit firmness data is also influenced by the methods used, and there is no common standardized method for fruit firmness testing in strawberry. Many instruments and techniques are reported in the literature. Most of these methods measure the force needed to puncture, penetrate or deform the fruit. Despite of this, the physical differences in instrumentation, in the textural components they measure, or in fruit handling techniques associated with them, lead to variable results. Often, low correlations between results from different methods are found. In the present paper, the equipment and techniques for strawberry fruit firmness testing and their overall suitability for adoption as a standard method are reviewed and discussed. Considering cost, time efficiency, accuracy and reproducibility, methods using the Bareiss HHp-2001-Fff, a handheld electronic instrument, appear to be efficient for measuring the firmness of single berries. When measuring multi-fruited samples for firmness, the Eisenhuth method seems to be very useful. The Instron and the Texture Analyzer are advanced instruments, giving reliable results, but they are expensive and time-consuming. In many cases, two methods should be combined to obtain reliable results. In all cases, the sample size should be at least 25 fruits.