Question

Explain how foods are preserved and fermented.

Answer 1

Methods of Food Preservation

A number of methods of prevention can be used that can either totally prevent, delay, or otherwise reduce food spoilage. Preservatives can expand the shelf life of food and can lengthen the time long enough for it to be harvested, processed, sold, and kept in the consumer’s home for a reasonable length of time.

Maintaining or creating nutritional value, texture and flavor is an important aspect of food preservation, although, historically, some methods drastically altered the character of the food being preserved. In many cases these changes have now come to be seen as desirable qualities, as with cheese, yogurt, and pickled onions.

Drying is one of the most ancient food preservation techniques, which reduces water activity sufficiently to prevent bacterial growth.

Refrigeration preserves food by slowing down the growth and reproduction of microorganisms and the action of enzymes which cause food to rot.

Freezing is also one of the most commonly used processes for preserving a very wide range of food including prepared foodstuffs which would not have required freezing in their unprepared state.

Vacuum-packing stores food in a vacuum environment, usually in an air-tight bag or bottle. The vacuum environment strips bacteria of oxygen needed for survival, thereby slowing spoiling. Vacuum-packing is commonly used for storing nuts to reduce the loss of flavor from oxidation.

Salting or curing draws moisture from the meat through a process of osmosis. Meat is cured with salt or sugar, or a combination of the two. Nitrates and nitrites are also often used to cure meat and contribute to the characteristic pink color, as well as inhibition of Clostridium botulinum.

Sugar is used to preserve fruits, either in syrup with fruit such as apples, pears, peaches, apricots, plums, or in crystallized form where the preserved material is cooked in sugar to the point of crystallisation and the resultant product is then stored dry. This method is used for the skins of citrus fruit (candied peel), angelica, and ginger. A modification of this process produces glacé fruit such as glacé cherries where the fruit is preserved in sugar but is then extracted from the syrup and sold, the preservation being maintained by the sugar content of the fruit and the superficial coating of syrup. The use of sugar is often combined with alcohol for preservation of luxury products such as fruit in brandy or other spirits. These should not be confused with fruit flavored spirits such as cherry brandy.

Smoking is used to lengthen the shelf life of perishable food items. This effect is achieved by exposing the food to smoke from burning plant materials such as wood. Most commonly subjected to this method of food preservation are meats and fish that have undergone curing. Fruits and vegetables like paprika, cheeses, spices, and ingredients for making drinks such as malt and tea leaves are also smoked, but mainly for cooking or flavoring them. It is one of the oldest food preservation methods, which probably arose after the development of cooking with fire.

Preservative food additives can be antimicrobial. These inhibit the growth of bacteria or fungi, including mold, or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.), and disodium EDTA. Antioxidants include BHA and BHT. Other preservatives include formaldehyde (usually in solution), glutaraldehyde (kills insects), ethanol, and methylchloroisothiazolinone.

Pickling is a method of preserving food in an edible anti-microbial liquid. Pickling can be broadly categorized into two categories: chemical pickling and fermentation pickling.

Canning involves cooking food, sealing it in sterile cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. Foods have varying degrees of natural protection against spoilage and may require that the final step occur in a pressure cooker. High-acid fruits like strawberries require no preservatives to can and only a short boiling cycle, whereas marginal fruits such as tomatoes require longer boiling and addition of other acidic elements. Low acid foods, such as vegetables and meats require pressure canning. Food preserved by canning or bottling is at immediate risk of spoilage once the can or bottle has been opened.

There are several benefits to fermenting food. First, fermentation serves to enhance the digestion of food. Your body needs adequate digestive enzymes to properly absorb, digest, and utilize nutrients in food. When vegetables like cabbage and cucumbers are left to steep and sit until the sugars are broken down to promote the growth of bacteria, this is when the vegetables are fermented.

Fermented foods are also filled with beneficial bacteria that work as reinforcement for the good bacteria in the digestive system. Since 70 percent to 80 percent of the immune system lies in the gut, having proper balance of gut flora is important.

During fermentation, organisms produce acetic acid, alcohol and lactic acid, which are all “bio-preservatives” that retain nutrients and prevent spoilage. Lactic acid acts as a preservative by reducing pH, which inhibits the growth of harmful bacteria.

Bacteria in the absence of oxygen convert sugar into alcohol which in turn preserves the food.

Best Fermented Foods

1. Kefir

Kefir is a unique cultured dairy product due to combined lactic acid and alcoholic fermentation of lactose in milk. Kefir is produced by microbial activity of kefir grains, which have a relatively stable and specific balance of lactic acid bacteria and yeast.

The benefits of kefir make it a “functional food,” meaning it can potentially help treat or prevent disease. It’s been associated with a reduction in lactose intolerance, better immune system activity, lowered cholesterol and anti-cancer actions. Consequently, research on kefir has increased in the past years.

2. Kimchi

Kimchi is a spicy and popular fermented food enjoyed in Korea. Since it is low in carbohydrates, fat, and has a high content of vitamins, minerals, dietary fiber and phytochemicals, it is a perfect fermented food for weight control.

3. Kombucha

Kombucha is a fermented tea that can be made from home or bought commercially. Benefits of kombucha include reducing blood pressure, improving cholesterol levels, increasing the body’s resistance to cancer and detoxifying the body.

4. Miso

Miso is a paste-like, half-solid food with sweet and salty taste, which has been gaining popularity worldwide. It has been a staple food in Japan and is used to cook miso soup and side dishes as seasoning. The bioactive compounds formed or released by the enzymes during miso production have been shown to exhibit antioxidant, antidiabetic, anticancer and antihypertensive properties.

5. Natto

A traditional Japanese food made from fermented soy with Bacillus subtilis is natto. The enzymes during the fermentation process produce mucilage that contains nattokinase. Natto is a natural blood thinner.

6. Sauerkraut

Sauerkraut is finely chopped cabbage that has been fermented by lactic acid-producing bacteria. By fermenting cabbage, it can become more functional by protecting blood vessels and increasing vitamin C, folate and manganese.