Specific Gravity Question

[Lamb Abbey Orchards]

Tom:

What are the benefits of having a high versus a low specific gravity potato? What is each type ideally best used for?

I'm also curious what the highest and lowest specific gravity numbers are that you've ever seen in a potato. Thanks!


John

[Tom Wagner]

John,

What seems like a simple question to many and I am sure many will have some simple answers, I cannot reply with any degree of simplicity.

I have had extremely low and high gravities. I do not think in terms of percent starch, or solids, but as specific gravities such as 1.040 as low and 1.117 as high.
I don't have my other computer handy so I can't tell you right off the exact extremes.

As a potato buyer, fieldsman, potato storage manager, variety development associate with Frito-Lay back in the late 60's and early 70's, specific gravity was important for making potato chips. The higher the better....less oil consumption, and higher lbs of finished product per truck load.

But conversely, I am selecting for low specific gravities now in order to get more low carb types.

Cooking with the various gravities tend to group potatoes by gravity for certain recipes and cooking venues. Those bits of information are readily available via Internet searches.

I cook new varieties all the time and can tell low, medium, and high gravities right away. I like Amey Russets, Tom Boys, etc., since the gravities are around 1.090 and that constitutes my favorite gravity range.

I would go on but the tomato seed extraction is going full swing.

[Lamb Abbey Orchards]

Tom:

Thanks for the info. It's very helpful.

One other question--is there a direct correlation between high specific gravity and a potato's ability to brown when fried? You mention that while at Frito Lay, you sought out a higher specific gravity number for making chips. I'm curious whether this was simply about less oil consumption and higher lbs of finished product, or whether chips actually browned better if a potato's specific gravity was on the high end.

Happy seed extracting . . .


John

[Tom Wagner]

After many years, breeders have tried to tie high gravity with low sugars to get the ideal potato chip. While I was at Frito-Lay, Monona was a featured variety for storage potatoes since it could be warmed up in storage and "burn" off the sugars accumulated during the 38 to 45 F. storage. It was, however, quite low in specific gravity and plant managers complained of the high oil usage. As Atlantic and others came along with high gravities, the cast was set.

So as most potato chip manufacturers have the sensitive jets of wind to knock out dark colored chips, the search is always on for round white potatoes that have both high gravities and low reducing sugars. As a consequence we think of rounds whites as having that and round reds...just the opposite.

I can produce through breeding efforts round reds with high gravities and low sugars and white potatoes vice versa.