Application Note | November 15, 2011

Determining Pulp Concentration In Thick Orange Juice Using Guided Microwave Spectrometry

Source: Thermo Scientific Product Inspection

Samples of thick juice with declared pulp concentrations were used to create a dilution series with diminishing calculated pulp contents from 61% to 30%. This was done by removing measured amounts of thick juice from the original sample and replacing it with pulp-free orange juice, purchased from the local store. To calibrate the e scan analyzer, we used two methods. First, we poured each of the created samples into our static laboratory e scan analyzer chamber and tested them at 44°F. Then the regression results were validated by testing samples with known pulp concentrations and comparing the e scan analyzer readings with these known values.

In comparing the results of this first evaluation with those of the validation, we found the results were significantly less precise. We attributed this to the tendency of the high concentration juice to settle out more quickly in our static chamber. To prove this theory, we prepared a second dilution series and calibrated the e scan analyzer using a continuous-flow method. This was done by pumping each sample in a loop through the chamber for five minutes using a peristaltic pump at 3.4 L/min and then taking a reading. Once this second calibration was completed, the regression results were again validated in the manner explained above.

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