Apple flesh firmness, a common indicator of maturity and postharvest quality, can be measured destructively using several instruments. This study compared readings obtained with a Magness-Taylor tester, an Effegi device, and an electronic tester with Magness-Taylor testing in the on or off mode. Three trained operators measured firmness of 50-apple samples of three cultivars with a wide range in suspected maturity. In the instrument test, each operator measured firmness using a different instrument or mode on one half of each apple. In the operator test, the firmness of each apple was measured three times (once by each operator). Both soft and firm lots had consistent operator and instrument differences in readings. Ignoring the operator differences, five out of six comparisons of instrument and mode produced significantly different readings. Operator differences between instruments and modes were also significant in many instances. The results suggest that a single instrument and operator should be used in long-term experiments when multiple determinations of apple flesh firmness are planned.
Three apple (Malus domestica Borkh.) cultivars of various maturity levels and flesh firmness were used to compare firmness readings obtained by three trained operators using Magness-Taylor (MT), Effegi (EF), and Electronic Pressure Tester (EPT) penetrometers. For all cultivars and operators, use of the MT resulted in the lowest mean readings, while use of the EPT operated in the MT testing mode resulted in the highest readings. Operator differences were observed for all instruments except when the electronic tester was used in the default mode. Comparisons between instruments and modes resulted in significantly different firmness readings across operators, except for the comparison of EF vs. EPT in default mode. For most comparisons, firmness variance due to instrument or mode was larger than the variance due to operator. Apple maturity did not significantly alter firmness trends due to instrument or operator. Thus, caution should be used to interpret apple firmness changes of a single lot of apples when several instruments and/or operators are used.
Agricultural research often involves collecting numerical data in the field, orechard or greenhouse. Traditionally, horticulturists have recorded numerical data by hand and then manually entered the information into a computer or calculator for statistical analysis. In the last decade data loggers and portable computers have made data collection and analysis easier and more efficient. A palmtop computer is a small, lightweight instrument that combines the best characteristics of data loggers and portable computers. In our trial, palmtop computers equipped with a spreadsheet software program were ideal for numerical data entry in the field and were a cost-effective alternative to other devices.
In both experiments. 20-apple samples from 6 commercial orchards were harvested and stored in 208 liter containers at 0C for 4, 6, and 8 months. Additional samples were removed from CA and held at 0C for 14 days before evaluation. Gas composition was measured and controlled 6 times per day using automatic control equipment.
In the first experiment, samples were stored at constant 0.0% CO2 and one of three O2 regimes (constant 2.0%. 0.5 rising to 3.5%. or 3.5% falling to 0.5% O2). Apples stored at 3.5% falling to 0.5% O2 during the storage period were softer than apples held at constant 2.0% or those held at 0.5% rising to 3.5% O2 during the storage period. Variable O2 concentrations did not influence weight loss during storage and insignificant scald, flesh browning, core browning, rot, and low 02 injury were observed.
In the second experiment, samples were stored at constant 2.0% O2 and one of three CO2 regimes (constant 0%, constant 5%. or 0% rising to 6% CO2). Constant 5% or rising CO2 conditions did not significantly influence flesh softening or weight loss during storage. Negligible CO2 injury was observed.
York Imperial is an important processing apple cultivar in the mid-Atlantic region and is often stored for up to eleven months. This experiment was designed to further examine the optimum CA storage conditions for this cultivar. Six orchards were used as statistical blocks. The factorial experiment was set up with 2 temperatures (0 and 2C), 2 oxygen (1 and 2%) and 3 carbon dioxide concentrations (2,3.5 and 5%). Sample size was 20 fruit at all analysis periods (at harvest, 4, 6, and 8 months). The apples were stored in a recirculating CA research facility and evaluated for firmness, soluble solids and weight loss. In the overall statistical analysis, orchard blocks, harvest dates and storage times significantly influenced all 3 quality parameters. Differences between blocks at harvest were substantial with firmness ranging from 9.5 to 11.3 kg and the soluble solids ranging from 12.8 to 14.8%. At the third storage removal (8 months), low oxygen increased firmness and decreased weight loss during storage while at the lower temperature, apples were firmer, had higher soluble solids and less weight loss than at the higher temperature. Although statistically significant, the differences may not be commercially important Block differences were generally maintained throughout storage.
We present a method for predicting firmness of `York Imperial' apples after air or controlled-atmosphere storage. Firmness and soluble solids content in freshly harvested fruit can be plotted on a graph showing a “decision line.” If the prestorage firmness and soluble solids coordinates for a given sample are above the decision line, then firmness after storage is predicted to be greater than the target value. Prestorage flesh firmness and soluble solids content were the best predictors of poststorage firmness. There was no significant improvement in firmness prediction when ethylene, starch, or other indicators of maturity were included.