These method is useful for routine drying where the moisture content of product is crucial. Laboratory moisture analysis is costly and time consuming. On the other hand, moisture content of sample can be approximated using weighing scale and a piece of sturdy container. This is rapid and economical.
Follow these steps:
1) Secure a container of known volume like a one or two liters metal can. A sturdy durable can is preferred. It will be used for a routine moisture analysis.
2) Verify the exact volume of the chosen container. Fill it with water up to brim and transfer to a graduated cylinder – use only graduated cylinder. Record the exact volume. Lets assume that volume is really two liters. Weigh the can.
3) Prepare three to ten batches of sample. Each batch should be more than enough to fit the container from number “2” and provide adequate for laboratory moisture analysis. Lets assume four kilograms for each batch.
4) Dry the samples using whatever method specified ( sun drying, oven drying, vacuum oven, etc….). Gather some literature about the drying time of the specified sample, need a wild guess otherwise.
5) Set your drying period. e.g. 1 day, 2 days, 3 days, 4 days etc…. at specified temperature or 2 hours, 4 hours, 6 hours, 8 hours etc… at specified temperature. Drying period and temperature are sample dependent.
6) Get a part of each sample for moisture analysis after the first specified interval (e.g. after one day). Send it to trusted laboratory for moisture analysis.
7) If your target moisture content is attained (e.g. 12 %), then stop drying. Otherwise continue drying and moisture testing until the desired moisture content is attained.
8) Fill each sample to the test container (container from “2“, the metal can). Filling should be free fall. Then scrape the top gently with a straight ruler or rod. Weigh the sample and container then subtract the container weight.
9) Get the average moisture content. e.g. 12 %.
10) Get the average sample weight of all batches or the average weight of 2-liter sample (from method “8“). e.g. 1.5 kilograms.
11) Get the average drying time at specified temperature. e.g. one day at 70 °C.
So the specific commodity should be dried for one day at 70 °C. As quality check, a 2-liter can of sample should weigh 1.5 kg. Excess weight means insufficient drying while underweight is over drying. Adjust drying time accordingly.
Please never ask me for sources/references cause I personally got the idea when I was working as Food Research Assistant. Comments, suggestions and recommendations are welcome!
The method is commodity specific. If you set parameters for drying ampalaya seeds then you should set another method for corn seeds. You need to shed sweats setting the parameters but the next routine analysis will be very very easy.
Marvin is the lead chocolate maker of Ben and Lyn Chocolate Inc. Has strong background in food research and development. Occasionally conducts training and lectures. Lecturer of Cocoa Foundation of the Philippines. Do coaching and consultancy services on his free time.