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Welcome to the first of Food Surveys' Food Quality video guides. We will be taking you through a range of subjects over the coming months but today, we are going to start off with one of the most commonly used pieced of equipment, the penetrometer.
What is a penetrometer and what is it measuring? Strictly speaking all this device measures is PSI (pounds per square inch). In terms of how those measurements are valuable, they help to determine the firmness of the flesh of fruit, giving us an indication of the ripeness.
Lets have a look at whats in the box...we have a number of attachments. Usually included in your kit you will find an 8mm plunger and an 11mm plunger. The larger is typically used for harder fruit such as apples and pears. You will also find a washer which goes on the penetrometer before the plunger to prevent the plunger going to deep. Finally we have a peeler which are generally supplied with all pentrometers.
To measure the firmeness of the flesh, these heads will be presed into the fruit until they penetrate until you get to this line here.
What products can this be used for? Well here we have some typical produce we use to take pressure readings.
Once you have selected your food product, be sure to discard if there are prominent defects that may affect your reading.
To prepare your sample you take your peeler and remove a couple of layers, just enough to test the flesh rather than the peel. We typically take 2 slices in order to give a good area to push the plunger into the fruit.
Now we are ready to use the device. Take care not to hit the stone if the fruit has one, press firmly into the product until you reach the line on the plunger we identified previously. Ideally you want to press for 2 seconds.
Dont forget to reset the device using the button on the side.
Then, peel, repeat the process on the opposite side of the fruit, 2 readings per fruit which can either be reported individually or averaged. For some fruits such as apples with a blush, the blush side can sometimes provide a firmer reading so averages are usefult in these circumstances.
In terms of equipment maintenance, this really is a low tech piece of equipment. After every use, wipe the juice from the penetrometer in order to prevent the juices getting onto the spring inside the penetrometer.
You can see a recent calibration sticker here on the side, a third party calibration is the best way to make sure that your food quality data is accurate and dependable.
In between calibrations if you have any reason to doubt the accuracy of your tool, there is a simple way to check them using a set of calibrated weighing scales.
Remove the plunger from the penetrometer, simply apply firm presure into the top of the scales and using a whole kilo number and check this against the number on the penetrometer. Here you can see on the dial that our equipment is accurately calibrated.
That finishes our first food quality guide tutorial. Visit our website for more tutorials