The humble potato-Do we know all that we ought to know ?

No doubt Potato is an important food crop grown and consumed all over the world.Though it had originated from Chile almost 7000-10000 years ago, Interestingly Asia predominates in production to day. Paradoxically Potato consumption is high in European countries, America and Canada while China and India, with small consumption base, contributes almost 35% of the annual global production, estimated at 380 million tons. The mode of consumption of potato varies from country to country with developing countries consuming it in house hold cooking while in developed contries bulk of the production is consumed by the processing industry. Why is that potato cultivation is preferred by many over others like cereals and similar staple foods? There could be several reasons including the farm income that can be earned with least cost and minimum efforts.

In terms of economics, the potato yield from a given area of land can be as high as 60-88 tons per hectare as reported from New Zealand though globally the average figure stands at around 18 tons per hectare. In a major potato consuming country like the United States, farmers have been able to harvest about 45 tons per hectare. With the flourishing of industries making several potato based consumer products like potato chips or French Fries there is never a dearth in demand for potatoes and grower-processor linkage is very strong in that country for mutual benefits. Such close linkages enable the processing industry to motivate the growers to adopt better processing varieties and incorporate best cultivation practices. It is interesting that of all the crops, potato has the unique position of yielding the highest calories estimated at 9.2 million kC per acre while corn (7.5 milliuon kC/acre) or rice (7.4 million kC/acre) or wheat (3 million kC /acre or soybean (2.8 million kC per acre) are no where nearby. 

Nutritionally potato cannot boast of any important credentials that can be cited in its favor but its content of resistant starch, 7-13% is rather unique because of its fiber like properties. It is well recognized that the resistant starch as it denotes, resists the action of digestive enzymes in the body passing into the large intestine some what unchanged providing a "fodder" for the intestinal microorganisms for conversion into a variety of beneficial biologically beneficial artifacts.Regular potato consumption is supposed to provide protection against colon cancer, contribute to improved glucose tolerance and insulin sensitivity, lowering the plasma cholesterol and triglycerides levels, increasing the satiety and hence the urge to eat unnecessarily and reducing the tendency to store fats. How far these attributes have been confirmed through human nutrition studies is not very clear. Interestingly cooked potato if consumed while hot contains lesser resistant starch while cooked and cooled potato preparations have highest resistant starch concentrations. Is it not a puzzle that potato chips can have a lower glycemic index of about 51 compared to its cooked counterparts with GI values varying from 77 to 85!  Potato is a rich source of Potassium, about 600 mg per 100 gm besides Vitamin C content is 20 mg per 100 gm. 

Does it occur to a layman that potato can be toxic if not properly handled and stored? It is true that the potato family of plants have the deadly toxic substances going by the name glycoalkaloids which the plant produces to protect itself from predators and self survival in nature. Fortunately the domesticated varieties of potatoes unlike their wild growing counterparts have much lesser levels of gycoalkaloids which can be controlled through variety improvements and controlled storage. Of the glycoalkaloids, Solanine and Chaconine, the first one is predominant and they are present in the crop at relatively small levels about 200 ppm which can go up to 1000 ppm, especially if exposed to light accompanied by the greening process. When potato develops green spots the solanine content can reach up to 1500 ppm locally around these green spots. Scrapping, trimming and dressing can save the potato from wasting. In spite of such alarming findings, potato poisoning cases are rarely reported. High concentrations can cause headaches, diarrhea, cramps, coma and even death. On an average a prolific potato consumer in a western country where the consumption is about 60-70 kg per year, daily intake of solanine is estimated at just about 12-13 mg per capita, an insignificant level not of so much concern.   

Agricultural technology during the last 100 years has been focusing on achieving increased yield through well proven cross breeding between high yielding strains and commonly used ones besides deploying efficient fertilizers and effective pesticides. With yields from land plateauing off for most commodities the interest shifted to changing the quality characteristics of the crop to get favorable traits like disease resistance, better nutrition and biochemical make up through intervention at the genetic level using biotechnological tools. Getting desirable features like virus resistance, solanine reduction, reduced vulnerability to enzymatic browning etc is a dream of the growing as well as the processing industries. However the deep suspicion about genetically modified or genetically engineered crops among the consumers has not allowed the biotech industry to fully tap the potentials for improvement. Though the food safety authorities in the US hold the view that genetically modified food, in no way alters the basic nature of the food, implying that the products is as natural as the original one, majority of consumers still do not seem to be agreeing to this view, 

Recent alarms raised about the formation of the toxic artifact viz Acrylamide during frying or baking of potato have focused the attention of health experts internationally and the precise dangers posed by this chemical is still debated. While it has been clearly brought out that Acrylamide is a carcinogen by animal studies, its effect on humans as a carcinogen is still to be unraveled. But Acrylamide definitely is implicated in many human disorders and therefore its intake needs to be controlled.  As the proteins in potato contain Asparagine amino acid and in presence of glucose present in potato,  Acrylamide a reaction product between the two is formed usually facilitated by high temperature conditions like frying and baking. This had necessitated renewed efforts to develop varieties of potatoes low in glucose for processing under high temperature conditions. Generally if the potato storage conditions are not optimal, there is an increased formation of glucose which contributes high acrylamide content in the fried or baked products. Storage at 7-10 C is considered suitable for short term storage while for storage up to an year a temperature of 4 C is recommended. Ironically lowering the temperature of storage below 4 C can increase glucose generation which is not desirable. Cold stored potatoes when exposed to ambient conditions tend to lose glucose and therefore it is always preferable to "cure" the cold stored potato for some time at ambient conditions before processing at high temperatures.

Another issue of concern to potato users is the color loss experienced during processing which happens because of enzymatic oxidation of polyphenols present with oxygen in the atmospheric air. Potato contains natural phenols like chlorogenic acid and as long as this is not exposed to the enzyme poly phenol oxidase (PPO), the bright color is maintained . But when potato is sliced or diced or mashed the enzyme PPO, polyphenols and atmospheric oxygen have a chance to react resulting in red colored products which further interact to give dark brown compounds. Though these brownish tinge so conspicuous in the fried products are not considered dangerous, the product loses its aesthetic appeal adversely affecting consumer acceptance. While in house hold kitchens the potato slices can be immersed in water to cut the access to air, commercially either heat preheat treatment to deactivate the enzyme PPO or other pre-processing steps will have to adopted to reduce the browning phenomenon. It is here genetic intervention has been able to evolve potatoes with low levels of PPO and the reduced susceptibility to generate Acrylamide during frying and baking. 

The so called GE potato developed by a US company has recently been approved as safe though the technique deployed does intervene at the gene level. According to the claims made by the developers, GE potato is a result of using a technology called RNA interference unlike the addition of genes from other species.. It is only silencing a DNA which is responsible for the production of PPO or transferring DNA for another variety of potato. There is no formation of any new protein during the process making it absolutely safe. This development has been welcomed by the processing industry and the consuming public which feels confidant about the safety of the potato both because of a better quality products and absolute safety guaranteed because of the uniqueness of the gene level intervention deployed in developing this variety. What is indisputable is that gene silencing or transfer of genes from the same species is more acceptable because such genetic changes are part of a natural process taking place for hundreds of years at a slow pace and therefore expediting the same by biotechnological techniques should be considered natural. Ultimately the consumer will decide whether such potatoes are acceptable or not. This is an uncertainty the new GE crop must face considering the fate of the famous FlavrSavr Tomato developed in 1992 and marketed between 1994 and 1997 after duly approved by the safety agencies but conked off in the market for many reasons.       

V.H.POTTY
http://vhpotty.blogspot.com
http://foodtechupdates.blogspot.com

IS POTATO UNHEALTHY?-A NEW CONTROVERSY IN THE OFFING

Agreed that Potato is a vegetable viewed from any angle and invariably it is considered one of the best naturally nutrient-dense vegetables available all over the world. Calorie wise it contains about 70 kC per 100 gm and is considered a better source of potassium than a banana. Though it is rarely known that Potato is a rich source of Vitamin C, the fact is that it can provide almost half the daily need of this nutrient in a single serve. Although notable is its usefulness as a source of Vitamin B6, Copper and Iron. Added to these positive features, it contains no fat, sodium or any other undesirable substances of any consequence. Some protagonists have changed the age old slogan of "apple a day keeps doctor away" replacing apple with potato. How far this claim can be substantiated is a matter of debate. .

If potato is claimed to be so good why is it that weight watchers generally avoid consumption of this vegetable regularly? Probably it is not potato that is doing any harm but calorie rich ingredients like fat and cheese and liberal addition of salt that is bringing the bad name for potato as a unhealthy food. Baked potato preparations doused with lot of butter and salt and deep fried foods like wafers and finger chips containing high fat and salt can create nightmarish situation when consumed in mega quantities regularly. These industrially manufactured products, in fact, contributed largely to the obesity epidemic that is raging in countries like the US.

Of course the golden rule for incorporating potato in the diet is that it should not be fried or baked with lot of fat and if just cooked potato is consumed there is unlikely to be any long term impact on weight gain. Recent move by the US government to restrict the level of potato in the school lunch program has created an avoidable controversy as it conveys a message that potato is not that good for health. Considering the overall nutrition provided by potato such a step can be only a retrograde on.Is it possible that such a decision is influenced by a recent study in the UK which implicates potato consumption as a hindrance to any program that aims at obesity abatement? Possibly yest. On the flip side of this issue, potato economy in the American continent is closely linked to the survival of the farmers as a major portion of production is absorbed by the school lunch programs across that country.

Interestingly China, which accounts for more than 20% of world production of potato, about 315 million tons, does not suffer from obesity epidemic as being seen in the west and probably this is a clear evidence that potato is not an obesogenic food if consumed properly. The world average annual consumption, about 33 kg per capita, is also not considered high working out to just about100 gm per day per person. Similarly the US produces about 20 million tons of potato annually for a population of 300 millions which averages the consumption at less than 70 kg per capita an year or less than 200 gm a day per person which is also not very high. What makes the difference is the way it is consumed using lot of fatty ingredients causing the health problem.

Just because Potato contains some starch, does it mean it cannot be considered a vegetable? If so what about vegetables like green peas, soy bean, fresh corn etc which when fresh are considered vegetables but on drying they become a pulse or an oil seed or a cereal?

Similarly common vegetables like squash, pumpkin, yam and a few others have starch content comparable to that in Potato. More important is the Glycemic Index (GI) of the vegetables that decides whether it will create a Glycemic over Load (GL) leading to weight gain. Potato has a relatively low GI, about 48 while a vegetable like Pumpkin has a GI pf 75. Ultimately moderation is the key when it comes to weight lose or gain and that is the need of the hour indeed!

V.H.POTTY
http://vhpotty.blogspot.com/
http://foodtechupdates.blogspot.com