Saturday, March 12, 2011
Though fresh foods are considered best, frozen foods too have their own benefits: they lock in nutrition and quality and keep food safe. Ritu Raizada speaks to a Dubai-based nutritionist about frozen foods.
A dietician highlights the benefits of frozen fruits and vegetables.
For a long time, I thought she was crazy. Here we were at the fresh vegetables section in the supermarket and she would not consider stopping there even for a second. With a cheery ‘See ya at the checkout counter in 20' she would whiz past me to the frozen foods section to pick up nearly the very same vegetables I was stocking up on, except hers were all frozen and packaged.
How can you want to eat this stuff, I would wail. But I knew her answer. Frozen foods are healthy. They are convenient. They are not dead foods. Blah, blah, blah. For a long time, I thought she was deluded, lazy and a negligent cook.
Well, what do you know, I am wrong. Well, mostly.
Freezing foods, as I discovered during a conversation with Sajita Sunil, nutritionist, Emirates Diagnostic Clinic, Dubai, "is a quick, convenient and a very popular method of preserving fruits and vegetables. If properly done, it helps in retaining more nutrients in the food." More nutrients? Yes, you read that right.
"This method of food preservation," Sunil continues, "retards the growth of bacteria, moulds and yeasts, which means that it delays spoilage and keeps foods safe by preventing micro-organisms from growing on them."
The science of frozen foods is quite simple. "In this method of preservation, the water in the food gets frozen into ice crystals," explains Sunil, "thus becoming unavailable to micro-organisms that need it to thrive and proliferate."
But, and there is always a but isn't there when there is overt good news, these micro-organisms do not die; they simply become inactive. Therefore, even while frozen vegetables are a healthy alternative to fresh ones, if not handled properly once taken out of the deep freezer, they could turn into a breeding ground for the inactive micro assailants. Once the food is thawed, the micro-organisms may continue to grow.
Having said that, negligence by humans does not detract from the essential virtues of frozen vegetables.
Of course, the baseline truth about nutrition is that fresh is always best. "Healthy eating is all about eating fresh foods; they are always a better choice," says Sunil. "Fresh vegetables and fruits are best when in season, but frozen vegetables come to our rescue when we wish to eat them out of season."
And now the picture gets more argumentative, so to speak. When fresh produce is not consumed quickly and is allowed to linger on the shelf for too long, it begins to lose its nutritional value.
So, if you are buying aubergines that have been hanging about in their containers at the supermarket well into their ripe old age, they might not be the powerhouses of nutrients they were at the time of plucking.
Frozen foods on the other hand, due to being flash frozen soon after they leave the farm end up locking in the goodness. "A frozen product is packed when the freshness and quality is at its peak," says Sunil. "So, its nutritional value does not deteriorate, while fresh food if left for too long in a grocery store deteriorates in quality."
Interestingly, frozen foods are also known as ‘shocked' foods. "As the foods to be frozen are suddenly or rapidly exposed to such a low temperature these foods are also known as ‘shock treated' or ‘shocked' products."
There is practically no loss of nutrients, like vitamins and minerals from frozen meats, fish and poultry because protein, vitamins A and D and minerals are not affected by freezing.
The most important aspect to freezing is the rapid reduction of the temperature to between -2˚C and -7˚C," explains Sunil. "In this temperature range, maximum ice crystals are formed in the cells of the product that is frozen. If water in the cells gets frozen quickly, then the ice crystals so formed remain small, causing minimal damage to the cells. In other words, rapid freezing prevents formation of large ice crystals which can damage the cells of the frozen product. This helps maintain the quality of the frozen product."
An economical option
Slow freezing, she says, results in the formation of large ice crystals, which damage the cells of the food that is frozen, thus adversely affecting the quality of the product.
"Defrosting on the other hand," says Sunil, "leads to a loss of liquid which contains water-soluble vitamins and mineral salts. This water could also be lost during the cooking process if it is not recovered."
Frozen foods, many a time, also end up as less expensive options for rustling up a quick meal. After all they are a snip, dip and stir away from a ready meal as they require minimal or no chopping, peeling or cleaning. They also cook faster. And, you can stack up your freezer with a variety of frozen vegetables which means fewer trips to the supermarket.
But, wait, the happiness quotient of frozen foods sort of takes a beating here. One of the main disadvantages of frozen fruits and vegetables is that "when you defrost them, the texture or firmness gets altered". Fresh foods on the other hand, taste good and have better texture. Plus, "not all fruits and vegetables can be frozen. For example, freezing salad vegetables like lettuce can ruin its crispness. Also fruits like watermelons or tomatoes don't freeze well."
Are any artificial ingredients used to freeze fruits and vegetables? Sunil says, "Frozen foods do not require any preservatives because during the freezing process itself, many of the microorganisms get destroyed or inactivated.
Fresh fruits and vegetables continue to undergo chemical changes which results in spoilage and a reduction in the quality of the product. These changes occur due to chemical compounds called enzymes present in fresh produce. The enzyme activity alters and loss of nutrients, flavour and colour occurs."
The reason why "these enzymes should be inactivated to prevent such losses by blanching (a process where the vegetables are exposed to either boiling water or steam for a short period and immediately immersed in ice water to prevent it from getting cooked). It also helps in destroying micro-organisms that may be present on the surface of vegetables. This is why this process is not recommended for fruits."
The most commonly used chemical compounds in the freezing process are ascorbic acid, citric acid and sodium bisulphite and sodium metabisulphite," she says. These chemical compounds are also known as stabilisers and act as antioxidants, which basically means they prevent oxidation or browning of fruits.
The two commonly used chemical preservatives are sodium benzoate and sulphur dioxide. Thus, fruits having deep colours (blue grapes, black plums, watermelons) tend to bleach the colour. The use of chemicals in this case is desirable. What about frozen meals?
Frozen meals, says Sunil, can help one lose weight provided portion control is maintained. Most frozen meals come in small portions which, if eaten as such, are adequate sources of calories for an individual.
The odds stacked against freshly-cooked food are they do not necessarily encourage portion control. "A person does not measure portions while serving himself fresh food," she says. "The portions of food go up or down depending on the taste of the food as well as the hunger levels of the diner at that moment. "In comparison, ideally, one could have a smaller portion of a frozen meal and add a salad, a fruit or yoghurt to go with it. This would help fulfil one's nutritional needs and also stop you from reaching for a second helping of the same frozen food."
According to Sunil, "Most frozen meals available in the supermarkets are high in calories as well as in saturated fat" therefore one needs to constantly read the nutrition labels. "While some frozen meals are not unhealthy, a majority of them could be. Yes, they are convenient foods but they need to be chosen with care."
Sunil also advises on checking the sodium levels of frozen meals. "They could be unhealthily high." The other thing to keep in mind is the date of production and expiry of packaged frozen foods. "The product should be consumed when it is closer to the production date rather than the expiry date." For home-cooked meals that are frozen, the FIFO (first in first out) rule is a must.
The bottomline? "Both fresh as well as frozen foods have their share of advantages and disadvantages. It is entirely up to an individual to choose between the two and eat a diet rich in a variety and nutrition."
On fresh versus frozen vegetables: "Be it fresh or frozen, a lot depends on the way the food is prepared. For example, boiling the vegetables in a lot of water can drain a lot of the water-soluble vitamins. In order to retain the nutrients either in fresh or frozen vegetables, it is best to bake, steam or stir-fry them. If you choose to eat vegetables raw, fresh is better."
On cooked and frozen packaged meals: "Frozen foods, regular or diet, are not always healthy on their own," she says. "Planning and incorporating frozen meals in one's daily diet with care can help you to eat healthily."
Top foods to freeze
Vegetables like potatoes, pumpkin, butternut squash, corn and pulses like lentils, dried beans, peas and chickpeas freeze much better and there is hardly any change in its texture when defrosted.
Baked pasta dishes freeze well before cooking. Foods such as macaroni or lasagna with cheese are saucy in consistency and hence will thicken during the freezing process. So incase you want to freeze them after cooking, it is better to prepare them in a little more liquid consistency before freezing them.
Though creams face a problem during the freezing process, butter can be frozen for quite a long period without any change in its texture.
Any kind of breads like white, brown or whole meal in either baked or unbaked form can be frozen.
Rice also freezes well and there is no change in texture when defrosted.
Meat, fish, poultry, seafood either in the cooked or raw form freeze well. Also there is no loss of nutrients when thawed.
A raw product will have a better nutrient value than its cooked counterpart. This is because some amount of nutrient loss does take place during cooking.
Eggs freeze well but not with the shells; because the shells burst. Hence the best way to freeze eggs would be to crack open them and freeze them in air tight containers. Both the white and the yolks of the eggs freeze well, while only the yolks freeze well when they are cooked.
Some herbs like basil, thyme, oregano, mint, rosemary and lemongrass can be frozen well. While some others loose their texture and become soggy. But the nutritional value and flavor does not get affected; hence the herbs can only be used for cooked dishes like in stews, soups and sauces and not for garnishing.
Freezer bags, plastic airtight containers or heavy duty aluminium foil can be used to freeze the foods. Whatever the method, ensure you remove as much air as possible before closing the containers.
Care should be taken to keep the raw and the cooked food products in different sections of the freezer to avoid cross-contamination.
Date the containers or bags so the foods frozen first can be used first (remember, First In, First Out). This is particularly important because when a product is stored in the freezer for a long time, its quality and nutritional value depreciates.
How to thaw frozen foods
There are a few methods which can be used to thaw or defrost frozen foods:
Take the food out from the freezer and leave it in the refrigerator to thaw all day, or overnight. This way of defrosting is useful for people who plan their meals beforehand. This is the best and the safest way of thawing food.
Keep the food in a watertight container or bag and submerge it in cold water. Keep changing the water every half an hour until the food thaws completely. This method of defrosting is beneficial to those who have enough time to defrost. Care should be taken to ensure the bags are leakproof as bacteria from the surrounding environment could act on the food leading to spoilage.
One can also use the defrost setting in a microwave oven for the quickest results. Care should be taken to leave at least about an 2-inch space between the food and the sides of the microwave for better heat circulation. When defrosting food in a microwave, cook it immediately after thawing because some areas of the food may become warm and may also begin to cook during microwaving (bringing the food to ‘Danger Zone" temperatures). Hence it is always recommended to immediately grill the food in the microwave itself or in the oven.
In this method of defrosting, the food should be defrosted for half the time recommended and check on it. This is to ensure that the food especially fish, poultry and meat, does not get cooked during the thawing process. Then turn the sides and continue with the defrosting process for the next half time. The food should still be cold to touch and soft. Let it stand for five minutes so that whatever little ice is left on the food melts away.
The best way to thaw meat and poultry would be to take it out from the freezer and keep it in the refrigerator overnight. Since the meat and chicken take longer to thaw, it's better they do so in the refrigerator where temperatures are controlled.
On the other hand thawing meat and poultry at room temperature is faster than in the refrigerator but ensure the food is still in its packing while thawing to reduce penetration of household bacteria.
Another way to defrost food is to cut it food into smaller pieces after it is partially thawed (if you can do so at this point) and allow it to thaw evenly.
Foods that should not be frozen:Water-rich fruits and vegetables. They do not freeze well due to their high water content. The change in their texture is evident when they thaw.
Some examples of fruits and vegetables that fall under the high-water content category are lettuce, celery, radishes, strawberries, melon, cucumber, cabbage, raw grapes, apples and tomatoes.
Mayonnaise, cream and milk do not freeze well. The product itself may get damaged due to the freezing process and either curdle or split into two layers of liquids.
The same goes for cream puddings and fillings, custard, cakes, tarts, jellies, gelatin salads, cheese, the whites of hard-boiled eggs, gravies made with wheat flour and spices.
How and where to use frozen foods:Experts often recommend intake of both frozen as well as fresh fruit and vegetables as part of a healthy balanced diet. Hence five portions of fruit and vegetables should be incorporated in one's meal on a daily basis. Frozen foods can be used in:
Flavoured yoghurt (prepared at home)
Fruit and vegetable juices, soups
Vegetable salad with frozen prawns, grilled fish or chicken
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