Issue link: http://read.dmtmag.com/i/717894
www.goodfruit.com Good Fruit Grower SEPTEMBER 2016 47 TR Turoni DA-Meter T he DA-meter nondestructively measures the dif- ference of absorbance (as I AD ) of two wavebands of light between 670 and 720 nm, which is used to calculate relative chlorophyll content, an indicator for the maturity progression of the fruit. However, while the parameter correlates closely with the SSC, TA and firmness for some varieties and regions, no major correlations have been found in the Pacific Northwest for Honeycrisp. When using the DA-meter in orchards, direct sunlight can interfere with the readings, so the WTFRC team has retrofitted a visor to the instrument to eliminate fluctuations in readings caused by light (see inset photo at right). The DA-meter alone cannot replace the most common destructive maturity indi- cators (SSC, starch, firmness), but it can be used as an additional parameter to track the speed of maturity progression, the spread of maturity within a tree or a block, and to separate lots for storage. Currently sci- entists are using the DA-meter to study the ripening behavior of pears. How they compare DA Meter Metrohm Titrator Accuvin Titratable Acidity Test Kit BSG wine acid test Atago PAL- BX|ACID5 Felix F-750 Parameter Chlorophyll quantity Titratable acidity Titratable acidity Titratable acidity Soluble solid content, titratable acidity Chlorophyll quantity, dry matter content, (soluble solid content) Price for device ($) $ 3,000 $ 30,000 - - $ 1,260 $ 6,950 Price per sample ($) - - from $1.82 ($52 for 20 test/kit) ($103 for 50 test/kit) ($182 for 100 test/kit) $ 0.25 ($10 for test kit - approx. 40 tests) - - Time requirement per sample 3 sec. 3 min. 1 min. 3 min. 3 min. 5 sec. Accuracy 100% 100% 73% 87% 69 - 88% - Training Easy- intermediate Difficult Easy Intermediate Intermediate Difficult Advantages -Quick calibration -For field use -Easy to use -Hand-held device -Exact value -High reliability -Auto sampler for high sample throughput -For field use -Fast & easy to use -No training needed -Cheap method -Good accuracy -SSC & TA estimation from the same sample -Measures up to 3 parameters at the same time -Hand-held device -High future potential Disadvantages -Low correlation between DA value and other fruit quality parameter -Difficult to download data with software provided by company -Acquisition and maintenance cost -Training required -Requires lab conditions -No exact value -Less accurate -Not comfortable for field use -Additional tools (electric pipette and glass beaker) are useful when analyzing larger sample set (>15) -Error susceptibility when making the 1:50 dilution -Low accuracy for TA reading -Models have to be developed -Many open research questions regarding the specifics for models -Not ready for field application DA Meter Metrohm Titrator Accuvin Titratable Acidity Test Kit BSG wine acid test Atago PAL- BX|ACID5 Felix F-750 SouRCE: WASHINGToN TREE FRuIT RESEARCH CoMMISSIoN Here's an overview of several devices and methods used to measure fruit quality parameters, including firmness, soluble solids content (SSC), titratable acidity (TA), dry matter content (DMC) and skin color. Find summaries of each method here and on the next page. (Images courtesy of the Washington Tree Fruit Research Commission.) Summaries continue on the next page. "One year after I watched my neighbor save most of his apple crop with Orchard-Rite ®wind machines (while I lost three quarters of mine), I decided I should do something on my farm to help ensure that I have fruit to sell every year. I purchased three Orchard-Rite ® wind machines and placed them where I had good trees but couldn't set good crops because of frost. One year the tart cherry orchard where I have a machine that covers the lower two-thirds of the orchard yielded 3 times more cherries than the one-third of the orchard that was not covered. That one machine in that one year paid for itself and half of another.We were able to raise the temperature 4 to 5 degrees (Fahrenheit). We have since added four more machines. With Orchard-Rite ® wind machines we are able to have a more consistent crop from the top of the tree to bottom every year on both apples and cherries. We are very pleased with the service we get on the wind machines. The Superior Wind Machine Service guys give them the once-over every year, keeping them in top-notch condition for the upcoming season!" -- Bob Bush Bush's Apples New Era, MI "With Orchard-Rite® wind machines we are able to have a more consistent crop from the top of the tree to bottom every year on both apples and cherries." 6919 Kra Avenue Caledonia, MI 49316 Phone: 616-971-8177 Fax: 616-971-8178