MDT Agricultural FAQ
This page contains answers to frequently-asked questions concerning the Mohr Digi-Test.
- What is the MDT? Is this another electronic firmness tester?
- Is it expensive? I'm not sure my organization can afford it.
- What is the point of testing internal fruit quality? Isn't Magness-Taylor type fruit firmness good enough?
- I'm concerned that the MDT would be difficult to use / complicated / require me to know a lot about computers.
- How fast is it? Is this going to slow down my operation?
- Can I take this out in my field truck? (i.e. is this thing going to break easily?)
- I need special features: testing fruit multiple times, diameter measurement, etc. Can the MDT do these things?
- Does the MDT test soluble solids, titrable acidity/pH, starch, etc?
- Can I test an apple with the skin on? / Do I have to remove the skin from the apple I'm testing?
- I want a non-destructive test. / Isn't a non-destructive test inherently better? / Can the MDT be adapted for online testing?
- How does barcode scanning streamline my fruit QA/QC process?
The MDT is not just another electronic firmness tester. It is the first device designed to measure the internal quality of all types of agricultural products, including tree-fruit. The MDT can act as a highly accurate Magness-Taylor type test device, but also has the capability of measuring internal fruit firmness under constant rate, creep (fruit material deformation under constant pressure -- a standard engineering materials test we believe measures the level of cell turgor / cell wall breakdown), and crispness (energy released by fracturing fruit material -- essentially quantifying the crunch produced by a mechanical bite). The result of these tests is the Quality Factor, a simple and accurate measure of fruit quality that is immune to most types of testing error and standardized for all types of fruit. In addition, the MDT can non-destructively test some agricultural products, including tomatoes and cherries.Top
There are no other test devices on the market with comparable features, so comparisons are difficult. However, the MDT costs about 1/5 to 1/3 what a complicated materials test platform with programmable features would cost -- about the same or slightly more than other electronic or computerized fruit testing devices, which have limited capabilities (e.g. cannot measure internal fruit quality) and lack true portability and other key MDT features (e.g. barcode reading, GPS capability).
If you or your organization employ QA/QC or field personnel who frequently test fruit, you can expect the MDT to save between 20-50% of the time your organization spends on testing, transcription, and data analysis. For many operations, this means that the MDT will pay for itself within 2-3 months on time savings alone. This does not take into account the fact that the MDT's unique and accurate fruit quality information has the potential to change the way your organization handles its fruit -- allowing for improved customer satisfaction and increased retail market share. If used properly, the MDT will pay for itself as well as help your organization increase its business volume. Top
M-T type fruit firmness is often a poor predictor of overall fruit quality. This is because fruit structure breaks down internally at a different (faster) rate than external fruit structure. Measurement of external fruit pressure can therefore be deceiving. For example, it is well known that fruit can appear to plateau in terms of fruit pressure under certain circumstances (e.g. Fuji apples held on the tree for water-core or color). However, the MDT lets you see that internal fruit pressure, creep, and crispness values are indeed changing a great deal as fruit structure degrades.
For this same reason, two apples with M1 firmness (external firmness) of 13.5 lbs may have Quality Factor values as much as 80 or more points apart -- one apple may be of near-optimal retail quality while the other is near the limit of consumer acceptability. If you are relying on traditional fruit firmness measurements when making picking, CA storage, or retail decisions, you might be just as well-served by flipping a coin.Top
The MDT was designed to be as easy to use as a calculator. We have had 4 years of intensive pre-release field testing by industry professionals who rely on our unit every day to make fruit quality decisions. Their suggestions have helped us make the MDT an instrument that is easy to use. After the unit is turned on, you are within two key-presses of testing. The barcode option makes the interface even easier.
The Windows software included with the MDT is also designed to be user friendly. Anyone able to use typical software (e.g. word processor) should have no trouble. For those users who are more technically savvy, the MDT offers a host of programmable features that allow for individual customization.Top
In Magness-Taylor compatibility mode (only tests the external portion of the apple), the MDT can reach 25+ tests/min, faster than a person can physically manipulate an apple. In full test mode, the MDT can reach 20+ tests/min.
What is more important than physical test speed is the fact that each test requires only one key-press. Date, time, fruit diameter, all fruit maturity data, barcode data, and optional GPS location are stored automatically. Statistics can be viewed immediately after testing. When uploaded to a desktop or notebook computer, automated fruit quality reports are prepared automatically. These features alone can translate to savings of several hours per day.Top
We have designed the MDT with portability in mind. The MDT is a fully portable, stand-alone unit with internal battery power good for as much as a week of regular testing. It is lightweight and comfortable to carry with its integral handle. You can take it in your field truck and carry it with you when you walk around your orchard if you like -- that is what it was designed for. The MDT is made of ABS plastic, stainless steel, and aluminum; it will not break easily, nor will it rust.Top
We've been listening to the needs of industry professionals and have added a number of features, including automatic diameter measurement, integrated multiple-punch testing (the MDT keeps track of how many times you punch a fruit and records individual test data for each punch but can also display composite or average values for each multiple-punched fruit), easy record editing, re-testing of fruit, and test deletion among other features. Further, when your organization decides it needs a particular feature, our software engineers are dedicated to adding it in as little time as possible (often in as little as 48 hours). The automatic upgrade feature of the MDT lets you easily upgrade your tester's internal software.Top
No. But the MDT does have the ability to record individual fruit and/or lot averages for these values in its electronic record, allowing you to sort and analyze these values with the MDT software. Furthermore, with the MDT Server software, any worker with a notebook computer (no MDT is necessary) can scan in any kind of fruit maturity information (starch, soluble solids, titrable acidity, color, defects, shape, etc.) from any location into a central relational database that will soon be accessible from MS Access or any other SQL-capable database program. A simple process using the MDT Server described here. These capabilities make the MDT and MDT Server central to any efficient fruit maturity management system.Top
Yes, you can use the MDT to test an apple with the skin on. Note that doing this changes the mechanics of the test because the plunger is forced to push a rough piece of fruit skin through the rest of the fruit. This results in 1) an initial spike indicating skin tension (which may be a valuable measurement, although we have not spent much time evaluating this possibility) and 2) elevated fruit pressure through the remainder of the test. The MDT software can correct for this discrepancy and approximate skin-off firmness values from the skin-on data. We have not done extensive testing to determine what changes, if any, occur in creep, crispness, and Quality Factor measurements. If saving time is very important to your organization, you may wish to institute consistent skin-on testing. It is a perfectly valid way to test.Top
The MDT can perform non-destructive squeeze tests on most fruits and vegetables; the cherry and tomato tests are excellent non-destructive maturity tests, for instance. Other soft fruits such as grapefruit and kiwis look promising. However, harder fruit such as apples can often give unreliable results when tested non-destructively in this way. We have designed the standard MDT test to be the most rigorous and reliable measure of fruit quality available. That said, the MDT fills a different niche than an online test device. The MDT gives growers, packers, and retailers solid, real-world information about their fruit. There is no guessing or correlation necessary, just excellent fruit quality information that can help the industry make informed decisions. In contrast, packing-line oriented non-destructive tests are correlative measures of fruit structure and are actually inherently worse.
There is a great deal of attention given to non-destructive testing in the tree-fruit industry; some of this attention is valid, and some is not. Mohr and Associates recently completed a 1-year retail fruit quality survey in CA, OR, and WA retail markets involving several thousand fruit from several retail chains. We found that fruit quality was remarkably consistent within a given sample. That is, fruit we tested from any particular retail location tended to form a bell-curve, which meant that statistical sampling was a valid and time-saving way to get a good idea of the quality of the fruit. We found that when fruit quality was poor, generally all the fruit we purchased was poor. Testing only one apple from a particular bin of overripe apples gave us more information about the quality of every apple in the bin than testing every apple with a non-destructive test could have.
A rapid non-destructive test is the best way to kick out a particularly malformed or diseased fruit (say 1 in 20 or 100). But if our retail fruit quality surveys are accurate and the real problem with Red Delicious apples is that 50% of retail fruit is of less-than-acceptable quality, no packing house we know of would be prepared to kick out 50% of its product (assuming packing quality was unacceptably poor, even though we find that usually it is not). That would be a wasteful and extremely inefficient way of doing business. A much better way of doing business would be to statistically sample fruit with an accurate, destructive test prior to the time fruit quality dropped to unacceptable levels and use this information to prevent fruit from becoming unacceptably mature. This would require quality measurements at every level of the distribution chain, particularly those parts of the distribution chain after packing (i.e. retail storage and presentation methods need to be scrutinized).
To reiterate, the MDT fills a different niche than that of an online non-destructive test. The MDT is an accurate, time-saving, and standardized way of measuring fruit quality. We have designed the MDT to meet an industry need for a standard method of highly accurate statistical sampling of fruit quality at the time of picking, packing, shipment, and at point of sale; one that can be tracked easily by barcode identifier. Only such standardized surveillance will allow the grower and packer to optimize picking, packing and shipment methods, keep tabs on the retail presentation of their fruit, and increase consumer confidence and market share.
Regarding the last portion of the above question, the MDT can be completely automated and would form the basis of an excellent online statistical quality assurance method at the packing-line level. If your organization wishes to pursue this possibility, we are willing to work with you to make it happen.Top
For those representing operations with QA/QC personnel who spend a lot of time testing fruit, MDT Server's networkable relational database and barcode scanning capability simplifies the fruit maturity testing process and lets multiple QA/QC personnel at different locations (with or without an MDT present) record their fruit quality data (e.g. soluble solids, starch-iodine, titrable acidity, color observations, defects, etc.) simultaneously in a central database without handwriting, confusion, or transcription errors.
The MDT keeps track of all test information that your company currently records by barcode so that an individual at a particular test station does not need to know anything about the fruit being tested -- their only task is to scan the tray or bin barcode identifier, then scan a test result value for each sample being tested. Using the MDT as a test device saves 20-50% of your test time; incorporating the MDT server software as your primary fruit maturity database tracking software saves even more time while eliminating transcription errors and improving the accessibility of your data. Automated reports generated from simple customized templates (created in MS Word, Excel, FrontPage, or other html-capable editor) create fruit quality reports that are consistent, professional, and instantly available for printing, e-mail, or posting to the web.Top