A few things stand out about oxygen: 1. It is practically everywhere; even in water in small quantities. 2. It owes its properties, life-sustaining ones included, to its reactivity. 3. It can be indiscriminate in its reactivity i.e. it will not spare anything crossing its path under the right conditions. 4. Its presence is not noticeable to senses and hence its effects look mysterious.  5. Air, its only natural source, must be kept as clean as possible. 6. Its adverse effects need to be managed effectively, especially those that affect food and life.

We will soon see how our diet which is expected to sustain and grow and repair us can be cause of diseases like obesity, cancers, cardio-vascular disease and diabetes if it is too much in quantity or poor in quality. Oxygen can have similar effects.

Adverse effects of oxygen on food

Obviously, these stem from what reactions with oxygen do to food constituents and their adverse sensory and physiological after-effects.

Heat processing of moist or water-containing foods: As a general rule, in presence of water, the temperature of processing – whether domestic (i.e. cooking) or industrial – cannot exceed 100 deg C by much and hence oxygen-mediated damage will be minimal. This applies to steam/water cooking of fruits, vegetables, cereals and grains (and their flours), lentils and legumes (daals and kathol) etc. Moreover, heat processing in presence of water in open vessels raises steam which normally pushes air away from the food being cooked/processed.

Dry foods: As a corollary, all dry foods (sugar, oils, flours, seeds, cereals, grains, nuts, dry spices, etc.) must be roasted or fried carefully. (Industry can resort to doing it under vacuum in some cases).  We have already seen how sugar, excessively roasted spices and caramelized food (e.g. burnt bread) can be damaged because of their dryness, at higher temperatures. Actually, such damages to food are quite wide-spread and their adverse effects indirect but serious which we will see when we relate food with disease.

Ref (i) Post 6 – Industrial processed foods: Part III: The dark side of processing, a case for cautious consumption and (ii) Post 10 – https://letfoodliftlife.com/cost-benefit-analysis-of-cooking-with-milk-powder-introducing-the-environmental-cost-of-food-processing/. 

Edible oils: Refined soybean oil, canola oil (high linolenic variety) and flaxseed oil are inherently susceptible to oxidation by atmospheric oxygen because of their natural composition. Ironically, this stems from a desirable characteristic – their omega 3 fatty acids or PUFA in general. Obviously, such refined oils become even more vulnerable when they are heated for any type of cooking or processing. (Be careful while smearing refined soybean oil on an iron hot griddle or hot plate as in dosa or chilla making). Such ‘oxidized’ oils carry oxygen-rich molecules and oxygen-containing ‘free radicals’. These (especially the latter) are highly reactive and have been implicated in a series of adverse effects, principally onset of cancers and arterial and heart conditions.

Synthetic anti-oxidants are quite effective in reducing this effect but they are themselves susceptible to oxidation and are, ultimately, alien to our body. Not all refining can be eliminated but, obviously, there is a case for finding ways of using edible oils without refining and using susceptible oils smartly. Coming soon: a series of posts on edible oils familiarizing you with all these aspects, clear guidelines on which oils to use when, minimal processing of edible oils and how to work-in unrefined oils into our food.

Frying is an extremely popular process both at home and in the industry. The changes occurring during frying are complex and varied but, generally: water evaporates, starch gelatinizes, (i.e. its large molecules link up thru bridges of water molecules thereby forming water bound in a solid matrix), proteins get de-natured or distorted, carbohydrates caramelize, proteins and carbohydrates brown by Maillard Reaction, some volatiles are lost, oil makes inroads into the fried food, oil oxidizes (and sometimes polymerizes and becomes viscous), etc.

Some oxidation is inevitable even if antioxidants are present. Alarmingly, just-initiated oxidation in oils is often not sensorily noticeable. Be careful while frying nuts, starchy ‘fryums’, wafers, batters with low water content and even foods with a lot of bound water like bread slices. Never lose sight of the presence of oxygen everywhere and oxidizables in your frying input. Hearteningly, high water batters produce enough steam during frying to push away air, at least, in the initial stages. Don’t take frying or roasting too far. Frying and roasting, like baking, is both an art and a science and, we the people behind this blog are avid students.

Spices: Spices in general and ground spices in particular are stored for extended periods and are affected by air because of that length of time even at room temperatures. Oxygen-damage is a part of this effect, the others being some lumping or caking because of humid air and loss of volatiles. Now you know why stored powdered spices begin to look flat. A dedicated post is planned on whole and ground spices. General rule: grind in smaller quantities, store in air-tight bottles with white cotton plugs to fill up top empty space and cold-store. If you do grind larger quantities, even freezer sections would work.

Miscellaneous: Walnuts are the commonest among nuts to get bruised in the trade channel. You have already noted slight rancidness in them because of oxygen damage. Importantly, such oxygen-affected foods do send out a signal of caution by having altered flavor; don’t always ignore it. They act as oxygen-carriers and cause damage within our body.

Darkening of potatoes, brinjals or eggplant, sweet potato, apples etc. on cutting is an atmospheric oxygen-mediated reaction. While not particularly harmful, it certainly lowers the natural anti-oxidant potential of food.

 

Adverse effect of oxygen in nature: USA and Canada have reported rampant forest fires on vast swathes of forest land. The reasons are complicated, but obviously, oxygen in the air is what initiates and sustains them by being a direct reactant. The only real solution is minimizing the favouring factors; oxygen cannot be wished away. In fact, oxygen plays the same role in all fires everywhere and most fire-fighting is centered around making oxygen unavailable to the combusting matter. Water additionally cools down and slows down the burning reaction by lowering temperature support.

Most metal rusting in nature is oxygen-mediated and its effect on critical infrastructure like bridges can be serious. In fact, clothes, tapestry, buildings, our bodies, hair, paints…are all affected by atmosphere.

Obviously, not all oxidative damage to food occurs during cooking or processing. Everything, especially high IV oils, are slowly oxidized even during storage and unrefined oils are only relatively protected because of their natural anti-oxidants. Industry uses ‘sturdy’ oils like palmolein, cottonseed oil, ricebran oil and hydrogenated oils and processing under vacuum to minimize this. It helps but damages are never absent totally. At the same time, it is neither possible nor necessary to banish fried and heat-processed foods from our lives. Just be careful while cooking at home and prefer home-cooked foods. Buy reputed brands; you already know which categories to minimize. Always stay up-to-date with fruits and vegetables.

Minimizing food-mediated adverse effects of oxygen on health: With the adequate background on how oxygen can harm us, especially thru food, the following strategies become obvious:

1. Use edible oils smartly at home. Follow ensuing posts for more.
2. Minimize fried bought-outs.
3. Fry, toast, roast and, in some cases even bake, carefully.
4. Store powdered spices (and flaxseed oil, if stored at home) in air-tight bottles with minimal headspace. Ideally in the fridge, even in the freezer, in some cases.
5. Never exclude natural antioxidant-rich products from diet for long.
6. The importance of oxygenation of blood cannot be overemphasized. It not only helps release energy but also partially gets rid of ‘oxygen-carrying reactive molecules’ by oxidizing them and helping get rid of them. Deep breathing (if not formal Yoga) is a great practice.

A failed but interesting commercial experiment to save food from air: Some thirty years ago, TV was agog with the announcement of the launch of a revolutionary domestic food storage system. At a particular point of time (and there were only a handful of channels then), this product was to be demonstrated on live TV. It turned out to be a ‘kit’ containing a series of tightly lidded containers with a valve at the top and a small vacuum pump. The idea was to fill the container with your thing, close it tightly, connect it with the vacuum pump with a tube, suck out most of air from the container and close the valve. Obviously, the headspace developed adequate vacuum and the reduced oxygen concentration in contact with the content was to protect it. The system did not catch on but do note how, decades ago, the desirability of isolating foods from oxygen was recognized.

Conclusion: Oxygen is our friend; life is impossible without it. We have deliberately kept out gory details of what even short duration oxygen-deprivation (‘anoxia’) can do to the brain. Suffice it to say that deep-breathing exercises are good. Nothing presented here is meant to be fear-mongering; it simply exhorts you to understand how oxygen can be harmful.  Happy CAREFUL frying, baking, toasting, roasting. But not reckless buying of fried snacks. Some day, we will talk about convenient, delicious and novel ways of working colored, anti-oxidant-rich fruits and vegetables into our diets. We can’t banish fried snacks from our life, can we?!

All this may look like much ado about nothing but remember the gain is health and happiness thru routine, if mindful life.

Next post: Edible oils: an introduction

Understanding what they are.

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