Ripeness and Refractometers

One of our anatomy professors just informed me that he passed on something I taught him. While testing the specific gravity of their urine, a student asked him if a refractometer was useful for anything else. He remembered a conversation we had and pulled up a picture of someone using one in the wine industry, which is basically what I did in graduate school.

Refractometers can be used to tell ripeness of fruit. Indeed, I sometimes will use one at the market to test produce. Where I live there are a lot of foreign markets with produce of initially dubious value. I don't really know why they are selling 5kg of limes for $1. Are they bad? Did they buy too many? If I ask them in Italian, will they be able to explain it to me in Spanish? I just trust the refractometer.

Now, imagine what they see. A bearded male of Saxon ancestry pulls a refractometer and some plastic pasteur pipettes from his jacket. He squirts some juice on this lightsaber-looking thing and looks into it as he points it towards the light. Some fruit, he takes. Others he passes. It must look like something out of science fiction to them.

Well, it certainly is science. Using a refractometer to measure the Brix ratio (one degree approximates 1% sugar content and is relatively reliable as an indicator of sweetness), and pH paper to measure acids, one can tell almost exactly when fruit is at the perfect ripeness. As fruits mature, the sugars cease to be reducing, and the total amount of acids diminishes while sugars accumulate in the fruit. At an optimum range of sugar to acid ratio, a fruit is ripe and ready not only for harvest but for consumption.  Delicious!

As a practical matter, since you know I like practical science, this is a putative business model. You buy fruit if you live in the west hemisphere only once a week or more. You hope it will last on the counter until you need it and then only as much as you need to be ripe when you need it. With a refractometer, you could establish fruit in bins at various degrees of ripeness and classify fruit as 'ready now', 'ready within the week' and 'ready in more than a week' and thereby assist shoppers in planning their consumption without waste. Would it sell? I don't know. Could it? Most definitely. We have all seen people smelling mellons and scouring over berries, touching them all. No need for that. Science to the rescue!

You too could be like the wineries and know exactly when your fruits are ripe. Wouldn't that be nice?