Fermenting Sweet Potatoes

Pressing sweet potatoes to create brine

     It was a simple question. My son asked, “Are these sweet potatoes or yams?”

      I confidently answered, “they are sweet potatoes.” My mind however was exhibiting some doubt; I visualized standing in the produce section in front of the sweet potato display—Jewell yams. I had brought home Jewell yams but I also knew I had identified Jewell yams, Garnet yams, Japanese sweet potatoes, and Beauregard, all as sweet potatoes. Uh-Oh, I thought, what is the difference? My first pass of “asking google” left me more confused than enlightened.  The important thing I came away with was that sweet potatoes and yams are not related botanically, the nutritional content is very different and that sweet potatoes are soft and sweet while yams are starchy.  I read posts that referred to the yam as white and the high beta-carotene content of the yellow and orange-fleshed sweet potato. This did not map to my experience in the grocery store. The tubers that were labeled as sweet potatoes had white flesh and the tubers labeled as yams had rich orange flesh.

     It was getting late; I am a morning person and I was realizing this was a bigger project. The next morning I went and talked to the produce manager. He told me about the orange-fleshed yams and the white or creamy-colored sweet potatoes.  I realized the confusion was bigger than my own. It was in the markets and marketing. 

     All my supposed “sweet potato” ferments had been with the orange-fleshed “yams” for no other reason than they are my personal favorite and the color is beautiful. I bought 10 pounds of a creamy pale variety of sweet potato thinking I had not even begun to try to ferment sweet potatoes.  I shared my confusion with Christopher; “I bought sweet potatoes for an emergency ferment."

     He said, “I wonder if the phrase ‘I bought sweet potatoes for an emergency ferment’ has ever been uttered in human history.”  I wasn’t sure he got the gravity of the situation.

     I went back to researching the difference, it turns out most tubers in the grocery stores in this country are indeed sweet potatoes even when labeled yams. I had been fermenting sweet potatoes along.  True yams are grown in Africa and in the Caribbean and very few ever end up in our US grocery stores—especially not in rural southern Oregon. If you happen to find a true yam you will not be confused. They are larger, they have rounded ends, their skin is tough—almost bark-like, and the flesh is sticky.

     So why all the confusion?

     I did learn there has been confusion for many years. Here is the beginning of the second chapter of a book written on sweet potatoes in 1896: “Since the little word “Yam” is the cause of great confusion in the nomenclature of sweet potatoes, especially in the Southern States, it may be well to give some space here to the discussion of the vegetable of which the word is more properly the name.  The word Yam…is of African origin and means “to eat” in several dialects…”

     It is believed that when orange-fleshed, softer-textured sweet potatoes were introduced in the southern United States, growers wanted to differentiate them from the more traditional, white-fleshed types.  The African word nyami was used by the slaves to describe the southern sweet potato as it reminded them of the starchy, edible root from lily family of plants that they knew from their homeland. It was adopted as yam for these softer sweet potatoes, which incidentally are in the morning glory family and most likely native to the Americas.

     Now that we know the difference let’s talk about fermenting them.

“Lactic-acid fermentation also has some other distinct advantages, e.g., the food becomes resistant to microbial spoilage and to development of toxins (Kalantzopoulos 1997). Sweet potato, in tropical regions, is consumed in the households of small farmers and poor people. Night blindness is a major physiological disorder among these people due to vitamin A deficiency, which can be alleviated by regular consumption of orange-flesh (b-carotene-rich) sweet potato either fresh, boiled and as lacto-pickles.”–S.H. PANDA, M. PARMANICK and R.C. RAY

 

     Sweet potatoes are considered the world’s seventh most important food crop. A study was done in India in 2006 to see if lactic acid sweet potato pickle would be viable for small-scale industries. They deemed lactic-acid fermentation as “an important technology” in developing nations. They were interested not only in the nutritional benefits but also the “hygienic” potential because it is a safe way to process food. The study concluded that sweet potatoes could be pickled and that the flavor was pleasing.

 

     We are going to say the flavor is more than pleasing. It is amazing.

 

     Use sweet potatoes as you would carrots. They respond and look quite similar in a ferment.

Sweet Potato Ferment

Makes 2 quarts

5 pounds sweet potatoes, peeled and thinly sliced

1 medium onion, diced

1 green bell pepper, diced

5 cloves garlic, finely minced

3–4 dried tomatoes, thinly sliced

1 tablespoon fresh ginger root, grated

1 tablespoons whole coriander seeds

2 teaspoons cayenne powder

1–2 tablespoons salt

In this ferment there is no shredding. Instead we are slicing the sweet potatoes quite fine. This is best done with the slicer side of a grater or the slicing blade in your food processor.

Add the rest of the ingredients, then it is the same—salt and submerge.

Allow to ferment for about 2 weeks.