Comparison and conversion of fruit quality measurements obtained from three textural instruments and validation of the results with sensory evaluation data

Apple texture is an important attribute considered by customers in making purchase decisions, and also considered by experts in evaluating the fruit quality, maturity, storability and marketability. Different instruments are used to evaluate the fruit texture at different programs. This makes the comparison of their results challenging. In addition, long-term research programs (e.g., apple breeding programs) collect data on the same varieties for more than 20 years and as a result they cannot easily switch to use a new instrument and need validation and conversion models to be able to do so. As a result, the objectives of this study were: 1) comparing the data obtained from three widely used textural instruments, and investigating relationships between the obtained parameters; 2) validating the instrumental measurements with sensory evaluations; and 3) developing models to convert data obtained from one instrument to those that can be measured by another instrument.
Three computerized Penetrometers were used in this study: Fruit Texture Analyzer (FTA) which was used to measure maximum firmness on peeled fruit; Mohr Digi-Test-2 (MDT2) which was used to collect eight parameters on peeled samples; TA.XTplus Texture Analyzer which was used to measure five parameters on intact samples.
Eight apple varieties with a range of textural attributes were used in this study. Fruit was grouped into two lots of four cultivars and were warmed to room temperature overnight prior to conducting the tests. Sensory judges (n = 11) were recruited from staff at Summerland Research and Development Centre, and evaluated apples in triplicate in individual sensory booths under red light using Compusense five software (Compusense Inc., Guelph, ON). Food standards were presented for defined sensory attributes. The triplicate assessment of four apple varieties were completed in each session based on quantitative descriptive analysis techniques using apple slices (⅛ apple) excised from the sun/shade transition zones. The instrumental measurements were conducted on 10 apples from each cultivar, with two measurements on each apple as subsamples.
In summary, we were able to compare the measurements from three commonly used computerized penetrometers to evaluate apple texture, investigated their relationships with the sensory evaluations and developed models to convert data obtained from one instrument to those that can be generated with another instrument.