Tuesday, March 7, 2017

Oca a lost Crop of the Inca.

Oca. (Oxalis tuberosa)
What is Oca?
Oca belongs to the family of plants our native Irish wood sorrel belongs to, known in Irish Gaelic as Seamsóg.  This plant cousin comes from the mid level, wet, cool regions of the Andes Mountains which share a similar climate to the Irish climate. Our wood sorrel is botanically known as Oxalis acetosella whereas Oca is Oxalis tuberosa they are relatively closely related.  But for the vagaries of history should have been introduced as one of the Andean crops brought to Ireland by the explorers, for various reasons this wonderful tuber got left behind. Oca is the second most important tuber crop of the Andean people only second to potato but historically was always planted in addition to potato and on higher poorer soils. This strategic use of Oca is an interesting lesson in food safety strategy developed over thousands of years.  Another question for another day is if indeed it is a coincidence that our national plant the original Shamrock could possibly have been related to this plant but we leave this to the historians.
This reference from the International Potato Centre in Peru puts the importance of Oca succinctly.
“Oca produces the second most widely cultivated tuber after potato. It is hardy and frost resistant, with long, cylindrical tubers from white to deep grayish purple. High in protein, with a good balance of amino acids, it is also a good source of fiber, and high in antioxidants.

Described in the chronicles of the Spanish conquest, ceramic representations indicate that Oca was a highly revered staple dating back to pre-Colombian times. Its high yield and pleasant taste make it very popular in rural Andean cuisine where it is traditionally boiled in soups or stews. Tubers are also baked or roasted and often left in the sun to sweeten before cooking.  Most production is still for home consumption but CIP’s ALTAGRO project is helping smallholders produce Oca marmalades in a variety of colours. Repositioning the crop for new markets encourages the conservation of the crop’s diversity, and helps to overcome its reputation as a poor man’s tuber.”
CIP, International Potato Centre, Peru.
Five hundred years later we at Beotanics and the The Chefs Farm based at FitzGerald Nurersies in County Kilkenny have selected from 38 different varieties a small number of varieties that suit our farm environment and our palates. Who knows what might have happened in Irish history had this wonderful nutritious tuber been adopted alongside the potato all those years ago?  Meanwhile however as the mid 1850’s Ireland suffered famine and collapse of our only subsistence carbohydrate New Zealanders adopted this tuber with great vigour and today it is even called New Zealand Yam in that country and is a favourite niche carbohydrate tuber which is even eaten raw there as a snack. Unlike our potato you can eat Oca raw!  
Oca comes in many colours from whites to almost black and colours in between. The main colours of culinary interest are Yellow, Pink and Red, the more red the more acid they tend to taste and the more Yellow the more sweet. Some commercial breeding has taken place in New Zealand and in recent years Americans and Europeans including ourselves have been dabbling in saving seeds and making own selections. One of the draw backs in producing Oca is that it’s a short day tuberising plant. This means that the tubers can only begin to form when the days shorten to under 12 hours and of course this leaves them a very short window to develop size and weight. Breeding of lines that are day length neutral is being attempted but this requires breaking habits of thousands of years for this plant. In the meantime we work with the best selected lines we have based on taste and yield and we try to adapt our climatic conditions by protecting from early frosts to keep foliage into December which is a challenge and makes this an expensive crop to grow.
Why eat Oca?
Oca provides us with some interesting flavour, colour, nutritional and variety options for our carbohydrate intake and everyone and their mother is talking carbs these days! Me I am just a humble farmer / plantsman but I eat too and I’ve had some big challenges recently with maintaining my sugar levels to keep out of Type2 Diabetes territory. I am not recommending that any of the crops I grow will achieve my goals but I believe variety is important in diet and this little tuber is one of my carbs of choice purely based on taste. It however is deemed to be lower in Glycemic index than potato and has definite flavour difference. I have used it in sheperds pie, fish pie, roasted, deep fried as chips, raw, grated on salads, soups and simple mashed on plate like potato and mixed with potato and sweet potato mash.  One of the very interesting thoughts is that it can be used instead of baby potatoes as starters if you are having potato with main course and it’s a great conversation piece now that you are so well educated on Oca!  I have provided some recipes below. As you can see from the chart below Oca is low in Carbs just 10.4g per 100g serving and high in some important vitamins not commonly high in other vegetables, great source of fibre and put simply adds variety into your diet for that part of your meal.

Amount per 100 g
% Daily Value
87 g
Very high water content
0.8 g
1.5 %
Contains practically no fat
10.4 g
3.5 %
8 g
32 %
Excellent source of dietary fiber
Vitamin B1 (Thiamine)
0.05 mg
3.3 %
Vitamin B2 (Riboflavin)
0.94 mg
55 %
Better source of riboflavin than most root vegetables
Vitamin B3 (Niacin)
1.09 mg
5.5 %
Vitamin C (Ascorbic Acid)
39.7 mg
66 %
Calcium (Ca)
17.2 mg
1.7 %
Iron (Fe)
12.5 mg
70 %
Only some oca varieties provide this much iron
Phosphorus (P)
28.2 mg
2.8 %
Zinc (Zn)
1.8 mg
11.9 %

The absolute amounts in the nutrition facts table above are provided by two primary sources: 1) Marrou, Gonzalez, and Flores (2011). Composición química de "oca" (Oxalis tuberosa), "arracacha" (Arracaccia xanthorriza) y "tarwi" (Lupinus mutabilis) — Formulación de una mezcla base para productos alimenticios. Asociación RVCTA. 2) Tablas Peruanas de Composición de Alimentos, Centro Nacional de Alimentación y Nutrición, Instituto Nacional de Salud.
The percent daily values or %DV above have been calculated by healwithfood.org and are based on recommendations for a 2,000 calorie reference diet. Your daily values may be different depending on your individual needs.
Other sources:
Penarrieta (2009). Antioxidants in Bolivian Plant Foods. Antioxidant Capacity, Flavonoids and other Phenolic Compounds. Department of Chemistry, Lund University.
Albihn and Savage (2001). The effect of cooking on the location and concentration of oxalate in three cultivars of New Zealand-grown oca (Oxalis tuberosa Mol). Journal of the Science of Food and Agriculture, 81 (10), 1027-33.


How to eat Oca.
As mentioned earlier there are as many ways to eat Oca as there are potato. One thing to be aware of with Oca is that its higher than potato in Oxalates which are found in Spinach, Rhubarb and some other vegetables. More modern varieties in fact are lower in Oxalates especially the yellow forms. If you are prone to kidney or gallstones foods with Oxalic acid should not be taken in excess so consulting your dietician or doctor on this is a good idea. However research done in New Zealand on this topic has clearly shown that by boiling or half boiling Oca much of the oxalates are removed and most are removes when Oca is peeled as the skin holds the highest amounts of these Oxalates. So as a general note all vegetables that are high in Oxalates just require consumption levels to take this into account. The method of cooking will greatly determine the Oxalate level you ingest. Another thing to remember with Oca is that the beautiful colours you see on the Tubers when raw quickly fade when cooked
Some Oca Recipes.
10 things to do with Oca
1.     Ocas are a yummy addition to a roast.
2.     Try Oca mash; it's nice with grilled meat like lamb cutlets.
3.     A Oca cooked for 40-50 seconds in the microwave makes a good snack for toddlers.
4.     Sliced Ocas are great in stir-fries, especially if still slightly crisp.
5.     Lightly cooked and sliced with a lemon or lime vinaigrette, Ocas make a great salad base
6.     Ocas have a natural sweetness which works well with ginger, orange or sweet and sour type sauces.
7.     Ocas are delicious drizzled with honey and roasted in the oven until soft and caramelized.
8.     Roast Ocas with red onions and pumpkin and toss through pasta for a quick delicious dinner.
9.        Grate Ocas and use raw in salads - try Oca and carrot with a lemony dressing.
10.      Lightly cook Ocas in the microwave, then stir-fry with sliced almonds and freshly grated ginger.
Oca, cashew & coconut curry
Sauté 1 diced onion and 1 garlic clove.
Add green curry paste and sauté for 2-3 minutes.
Add 500g whole mellow yellow or apricot Ocas and 1 tin of coconut milk.
Simmer until Ocas are cooked, approximately 30-40 minutes.
Other options - green banana, prawns, pumpkin.

500g grated Ocas
1 cup plain flour
1 cup wholemeal flour
1/2tp baking powder
1/2tp baking soda
1/2tp salt
1/2cup brown sugar
1/2tp nutmeg
1/2tp cinnamon
1/2cup raisins/chopped dried apricots
4 eggs
1 cup vegetable oil

Mix dry ingredients and fold in Ocas, dried fruit, beaten eggs and oil.
Pour into muffin tins and bake at 180ºC for approximately 30 minutes. Top with your favourite icing.

Winter Gratin
Ocas sliced lengthways, sliced parsnip, pumpkin and kumara, layered in a baking dish with dots of butter, mixed herbs and cheese (mozzarella and tasty cheddar are good), and season each layer with salt.
Bake in a moderate oven covered for 45 minutes. Add a touch (1/4 cup) of stock, milk or cream if it gets too dry. Uncover, add a final layer of cheese, and fresh breadcrumbs and finish for 10 minutes or grill topping until golden brown
Great for the family!

Honey glazed Oca
In a roasting dish, place your Ocas and lightly cover with a mix of honey and butter (30 seconds in a microwave to soften), and sprinkle with cinnamon and salt.
Roast for approx. 30-40 minutes in a moderate oven (the longer they are cooked the sweeter the Oca gets

Roast Oca
Put Ocas around a roast of meat about 30 minutes before the meat is cooked or put into a baking dish with butter or dripping, sprinkle with salt and pepper and bake in the oven at a moderate heat for 30 minutes

Peruvian Oca & Banana Strudel
Using left over honey-glazed Ocas, mix with bananas (overripe is better), mash together with some dried fruit (apricots, sultanas, raisins) and add some fresh breadcrumbs, mixed spice and a pinch of nutmeg. Set aside. (You can use fresh grated Ocas but add more crumbs and a touch of honey.)
Meanwhile melt some butter and brush a sheet of filo pastry. Place another sheet on top of this and repeat again. Place 2 heaped tablespoons of Oca mix on pastry and fold sides over and brush with butter before rolling up.
Place in a moderate oven and bake. Strudel is cooked with it is brown and you can smell it. Serve with bush honey yoghurt or vanilla ice cream.
Delicious Winter Desert!