Food Spoilage

      FOOD SPOILAGE

Food storage is a complex process influenced by factors like temperature, moisture, light, and microorganisms. Foods deteriorate in terms of taste, nutrition, safety, and appearance due to physical, chemical, and biological factors, leading to changes in color, texture, and flavor. Various preservation methods are used in modern food technology to counter spoilage, considering the diversity of foods. Spoilage rates vary  based on factors like moisture, sugar, salt, and acidity, requiring regular stock rotation even in modern storage facilities. Rapid food spoilage can lead to starvation in less developed areas and affects advanced societies. Understanding and controlling food deterioration is crucial in food science, with many preservation methods evolving from early attempts to prolong storage life.

SHELF LIFE

Shelf life is how long food stays good to eat. It can vary from person to person because everyone has different standards for what's okay to eat. Food companies decide how long they'll sell a product based on its quality. They set a minimum quality level (MAQ) that tells them when to stop selling it. The shelf life of food depends on how it's made, packaged, and stored. Different dates on food packages help you know how fresh it is, like the date it was made, displayed, or when it should be sold by. Scientists use tools to guess how long food will stay good, especially for new products. They might use labels or tags that show if food has been exposed to too much time or temperature, which can make it go bad.

MAJOR CAUSES FOR FOOD DETERIORATION

Factors affecting food deterioration include:

- Growth and activities of microorganisms like bacteria, yeasts, and molds.

- Activities of food enzymes and other chemical reactions within the food.

- Infestation by insects, parasites, and rodents.

- Inappropriate temperatures for a given food.

- Gain or loss of moisture.

- Reaction with oxygen.

- Exposure to light.

- Physical stress or abuse.

- Passage of time.

These factors can be biological, chemical, or physical and often work together to spoil food. Effective preservation methods aim to minimize or eliminate these factors. For example, canned meats are protected from insects, light, and moisture by sealing them in metal cans. Vacuum or nitrogen flushing removes oxygen, and heat treatment kills  microorganisms and enzymes. Storage conditions are controlled to further prevent deterioration. It's important to consider each factor individually when preserving food.

Bacteria, Yeasts, & Molds

Key points about microorganisms and food deterioration:

- Microorganisms can make our food go bad, but not all of them are harmful.

- Bacteria, yeasts, and molds are the main types of microorganisms that can contaminate food.

- They can enter food from sources like soil, water, air, and animal skins.

- Bacteria are small, with various shapes, while yeasts are larger than bacteria and mostly spherical or ellipsoidal and molds are even larger, with complex structures, and grow by forming networks of fibers.

- These microorganisms can cause fermentation, rancidity, sourness, and toxin production in food.

- They thrive in warm and moist conditions, and bacteria can multiply rapidly through cell division.

- To keep our food safe, we need to control contamination and create unfavorable conditions for microorganism growth.

- This includes practicing proper sanitation and temperature control.

Insects, Parasites, & Rodents:

- Bugs like insects can damage our food and spread bacteria, yeast, and mold.

- Pesticides, cold temperatures, and special containers help control insects in stored food.

- Some processed foods may still have bug eggs, but we have methods to remove them.

- Food inspection by organizations like the FDA and USDA is important to check for insect contamination.

- Certain levels of insect contamination are allowed, but highly destructive bugs are not allowed in import/export.

- Parasites like the trichinosis nematode in pork and worms in fish can infect us if not cooked properly or frozen.

- Rodents eat our food and can contaminate it with bacteria from their urine and droppings.

- In areas with poor rodent control, they can cause food shortages and spread diseases like salmonellosis, leptospirosis, typhus fever, and the plague.

 Food Enzymes:

Even after harvest or slaughter, food retains enzyme activity, which, if not controlled, can intensify and lead to deterioration. Enzymes from living animals can break down tissues post-slaughter, while plant enzymes can cause ripening and tenderizing, but excessive activity can result in rotting. Without intervention like heat or chemicals, these reactions persist in food, posing a risk of spoilage over time.

Heat & Cold:

Temperature fluctuations affect food quality: in the typical handling range (10-38°C), reactions accelerate with every 10°C rise. Heat can damage proteins and vitamins, while cold causes discoloration and texture changes. Freezing harms foods like milk, and refrigeration at 4°C can also damage produce. Bananas and tomatoes, for instance, should be stored above 10°C for best results.

Moisture & Dryness:

Excessive moisture fluctuations can compromise food quality by facilitating chemical reactions and microbial growth. Changes in humidity can cause surface defects like lumping and caking, creating favorable conditions for bacteria and mold. Even in sealed packaging, fruits and vegetables may release moisture, encouraging microbial proliferation. Non-respiring foods can also impact package humidity, resulting in surface condensation, particularly in cooler storage environments.

Oxygen:

Oxygen in the air can be bad for food because it causes it to spoil faster. To prevent this, food is packaged in a way that removes the oxygen or replaces it with other gases like nitrogen or carbon dioxide. This helps keep the food fresh for a longer time. It's like putting food in a special container that keeps it safe from the oxygen in the air. This is called modified atmosphere packaging.

Light:

When food is exposed to light, it can damage vitamins like riboflavin, vitamin A, and vitamin C, as well as food colors. For example, milk left in bottles under the sun can develop a strange taste due to light-induced fat oxidation. Different types of light affect food differently, and sausages and meat can look different under natural light compared to fluorescent light. To protect light-sensitive foods, they are packaged in containers that block out light or use special materials that filter out specific wavelengths of light. So, by using opaque packaging or materials that block certain types of light, we can help preserve the quality of light-sensitive foods.

Time:

After food is harvested or made, there is a period when it’s at its best quality (period can be really short, like just a day, or a few hours).Factors like microorganisms, insects, and the effects of heat, cold, moisture, oxygen, and light can make it go bad. Some foods get better with age like certain cheeses, sausages, and wines, but most lose quality over time. Proper handling and preservation can help keep food fresh, but there's a limit to how long it stays good. That's why we have expiration dates on processed foods.

PRINCIPLES OF FOOD PRESERVATION

These are the principles on which food preservation methods are largely based. If foods are to be kept only for short periods of time, then there are two very simple rules:

 1. Keep food alive as long as possible; kill the animal or plant just before it is to be used. A good example of this is keeping lobsters alive in a tank in a supermarket or restaurant-while alive and healthy, they do not seriously deteriorate. This is also practiced with fish, poultry, fruits, and vegetables where possible. Unfortunately, the possibilities are limited. 

2. If the food must be killed, clean it, cover it, and cool it as quickly as possible. However, cleaning, covering, and cooling will only delay deterioration for a short time, for hours or perhaps at most for a few days. Microorganisms and natural food enzymes will not be destroyed or totally inactivated and so will take over very quickly. 

For longer-term and practical preservation, as required for most of our food supply, further precautions are necessary. These are largely directed at inactivating or controlling microorganisms, enzymes, and reducing or eliminating chemical reactions which cause food spoilage. 

CONTROL OF MICROORGANISMS  

To control bacteria, yeasts, and molds in food, we use heat, cold, drying, acid, sugar, salt, smoke, air, chemicals, and radiation. However, we need to find the right balance because these methods can also cause the food to deteriorate. It's all about finding the perfect amount of heat or preservatives that will kill microorganisms without compromising the quality of the food or our health. Food preservation is a science of compromise, where we strive to strike the right balance in dosage and treatments.

Heat:

To make food completely sterile, it needs to be heated to 121°C for at least 15 minutes. This is done using steam under pressure in machines like autoclaves or in the canning industry. Different foods require different levels of heat to be safe to eat. For example, acidic foods like tomatoes or orange juice can be made safe by heating them to 93°C for 15 minutes. Guidelines provide the right temperatures and times for different foods. It's important to note that not all microorganisms need to be killed in every food. Milk, for instance, is heated to 63°C for 30 minutes to eliminate most bacteria and germs, but it's not completely sterile because it's meant to be consumed within a few days. However, if milk is going to be stored for a long time, such as evaporated milk, it needs to be heated even more to ensure it's completely safe to eat.

Cold:

Cold temperatures can slow down the growth of bacteria, yeasts, and molds, but they don't necessarily kill them. Thawing frozen food can allow any surviving bacteria to become active again. It's important to handle and store food properly to minimize the risk of bacterial growth and foodborne illnesses.

Drying:

When microorganisms lose access to water in food, they can no longer multiply. Total drying is more effective at stopping their growth than partial drying. Mold prefers less dry foods, while bacteria and yeasts thrive in more moist conditions.

Acid:

Acid can denature bacterial and food proteins, making microorganisms sensitive to it. Controlled fermentation preserves food by inhibiting the growth of spoilage organisms. Adding acid-producing cultures or acids directly to foods increases acidity, but it is not enough to ensure food sterility. Acid combined with heat enhances the destruction of microorganisms.

Sugar & Salt:

When fruits are placed in sugar syrup or meat in salt brine, osmosis occurs. Water moves out of microorganisms' cells, causing dehydration and inhibiting their growth. Yeasts and molds are more tolerant to osmosis and sugar/salt, allowing them to thrive in high sugar or salt products where bacteria cannot.

CONTROL OF ENZYMES AND OTHER FACTORS

The chapter underscores the need to manage factors contributing to food deterioration, with microorganisms as the primary concern. Preservation methods such as heat, cold, drying, chemicals, and radiation are utilized to combat microbial decay but can also affect food enzymes. While techniques like irradiation and freezing can control microbial growth, they may not fully deactivate enzymes. Protective packaging and sanitation are essential for mitigating environmental risks and pest control. However, challenges remain in addressing contaminants like industrial pollutants and pesticides,necessitating strict oversight by regulatory agencies to ensure food safety standards are met.