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Have you ever tried sorting frozen avocado? After dicing, soft avocado is suitable as a vacuum packed salad, whereas the firmer product is further processed as a higher-priced dried product. Wouldn’t it be great if a machine test could reliably do this for you?
Presented with three sample batches, FTC was able to demonstrate a method to precisely apply a repeatable firmness test.
The test was performed using an FTC TMS-Pro Texture Analyzer fitted with a 2500 N intelligent loadcell (ILC). For this particular application, a custom fixture was designed to meet the requirements of the test, comprising a 3.5 inch (89 mm) sample cell and 3.25 inch (82.5 mm) plunger plate. This back extrusion method allows the compressed product to flow around the compression plate, so that resistance or firmness can be measured.
For each test, 250 grams of fruit from a single batch was loaded into the sample cell. To maintain consistency across all batches, the samples came directly from refrigeration, as the fruit degrades rapidly once defrosted. The TL-Pro test program moved the plunger at a constant speed of 400mm/min to compress the product, to a depth 5mm from the bottom of the cell. The software recorded the peak force achieved, and calculated the area under the curve, representing the total work done (energy) during compression.
The graphical representation from TL-Pro, of the test results for two representative samples from three batches, is shown here (force applied, against cumulative displacement).
The graph clearly shows that firmness can be distinguished by this test, and that the three batches are different. This enables mechanical testing to be used for determining product suitability for each destination: vacuum packed fresh salad or dried.
The shape of the curves signify meaningful characteristics of the samples also – the flat curve indicates softness in the fruit, while the jaggedness reflects a sample with firmer individual pieces.
This test method demonstrates the advantages of mechanical testing (or a food texture analyzer). A single quick test can be compared with standardized measures of firmness to determine the quality of the product. Over-firm avocado will not make its way into salad, nor over-soft fruit into the dried preparation stream. The value of the dried product can be maximized and the quality of salad mouthfeel optimized.