Since food is harvested, collected, caught, or slaughtered, it will suffer damage. Based on the ease or absence of food spoilage can be divided into three groups, namely:
1. food ingredients that are not easily damaged (nonperishable),
2. slightly perishable foodstuffs (semi perishable), and
3. perishable foodstuffs.
All living things need food for the growth and maintenance of life. Bacteria, molds, yeasts, insects, and rodents (rodents) always compete with humans to consume their food supplies. Furthermore, highly sensitive organic compounds in foodstuffs, and the biochemical balance of these compounds, will be destroyed by almost all environmental variables in nature. Heat, cold, light, oxygen, humidity, dryness, the content of enzymes in the food itself, time, all can spoil food.
As an illustration, after harvesting vegetables, if they are not transported quickly from the garden and are properly protected and stored, all the work that has been done to produce them is in vain. This always happens in almost all foodstuffs. The speed of food spoilage can be seen from the shelf life of some foodstuffs, which can be seen in Table 1.1 below. From this table, we can know the shelf life of some foodstuffs (both vegetable and animal) at a temperature of 21.11°C.
At room temperature (27°C), meat, fish, and poultry go bad in 1 - 2 days. This will also occur in some types of fruits and leafy vegetables, as well as in raw milk and other fresh foodstuffs. At room temperature or field temperature, some foodstuffs can even become worthless (damaged, spoiled) within a few hours.
By studying Learning Activity 2 about the factors that cause food spoilage, you are expected to be able to know about the signs of food spoilage, types of damage, and the main factors that cause spoilage.
A. SIGNS OF FOOD DAMAGE
A food item is said to be damaged if it shows a deviation that exceeds the normal acceptable limits for the five senses or other usual parameters.
The fruit ripening process is a long series of chemical reactions, which can end in the degradation of the weave resulting in cell death and spoilage. Likewise with vegetables, so here the occurrence or start of rot is a sign of damage.
Some materials are considered damaged if they show deviations in consistency and texture from the normal state. A material that normally has a thick consistency, but if it is in a runny consistency, it means that a deviation has occurred which indicates damage. Likewise, agricultural products which normally have a hard texture such as potatoes, sweet potatoes, carrots, and others, if in a fresh state the material has a soft texture, it means that the material has been damaged.
The occurrence of further bruising can be used as a sign of damage. In sapodilla fruit, mango, apple, guava, and other fruits bruises often occur, which indicates damage to the inside.
Some fried ingredients are said to be spoiled if there is scorching caused by heating too long or using too high a temperature. Likewise, the occurrence of an unwanted browning reaction is a sign of damage.
Flours that clump and harden cause these flours to not be able to fulfill their function as expected. For example, albumen egg flour hardens during storage, causing the solubility and foaming power of albumen to below, or casein which hardens during storage so that its solubility is reduced. These signs are signs of damage.
Damaged cooking oil is characterized by a distorted odor arising, namely the occurrence of a rancid odor, which is caused by the oxidation and degradation of the unsaturated fatty acids contained in the oil.
Dried agricultural produce sometimes turns black and becomes moldy. Some agricultural produce overgrown with molds with signs of mycelium and spores growing on the surface of materials that are not normally present is a sign of damage.
Signs of physical damage can be found on agricultural products that are attacked by insects or rats so that their physical forms become hollow or have bite marks. The presence of cocoons, caterpillars, and so on is often used as a sign of damage.
Damaged eggs can be marked by cracks, the contents of the eggs become runny or candling shows signs of damage. Fresh, damaged meat will emit a foul odor, while some parts are sometimes wormy or have a distorted color. Slimy meats are considered to have started or are undergoing decay.
Fish are damaged if they show signs such as pale gills, sunken eyes, and very soft texture smells and is slimy. However, there is also damage that does not show clear signs, for example, the presence of caterpillars inside petai seeds is sometimes never seen or expected before because from the outside the fruit shows an intact condition no different from that which was not damaged.
B. TYPES OF FOOD DAMAGE
Foods that have undergone deviations and normal conditions usually have undergone "damage". When viewed from the cause, damage to food can be divided into several types, namely microbiological, biological, physical, chemical, and mechanical damage.
1. Microbiological Damage
This type of damage is caused by microorganisms such as mold, bacteria, and yeast (yeast). The type of food that can be damaged by microbes depends on the composition of the raw materials and their condition after processing. In general, groups of bacteria are easy to damage materials that contain lots of protein and high water content. Mold attacks materials that contain lots of pectin, starch, and cellulose, while yeast attacks materials that contain lots of sugar.
This type of biological damage to food is characterized by the emergence of mold, rot, mucus, the occurrence of discoloration. The method of destruction is by hydrolyzing or degrading the macromolecules that make up the material into smaller fractions. For example, carbohydrates are broken down into simple sugars or further breakdown of sugars into acids that have a low number of carbon atoms. Proteins can be broken down into peptide groups, amide compounds, and ammonia gas, while fats can be broken down into glycerol and fatty acids.
With the breakdown of carbohydrates (starch, pectin, or cellulose), the material can experience softening. The occurrence of acid can lower the pH, the gases produced can affect the smell and taste of the material.
This microbiological damage is a form of damage that is very detrimental and sometimes dangerous to human health, because of the toxins it produces, transmission, and rapid spread of damage. Microbiological damage does not only occur in raw materials, but also in semi-finished and processed materials. Foods in cans or bottles can spoil and are sometimes dangerous because they can produce toxins. Materials that have been damaged by microbes, can be a dangerous source of contamination for other ingredients that are still healthy and fresh. Decaying material contains microbes that are young and in malignant growth (lag phase), so they can spread to other nearby materials.
2. Biological Damage
Biological damage is damage caused by damage physiology, insects, and rodents.
Physiological damage includes damage caused by metabolic reactions in the material, or by enzymes present in it naturally, resulting in an autolysis process that causes damage and spoilage. The meat will quickly spoil or rot if stored at room temperature because of the autolysis reaction. A similar situation also occurs in some fruits.
If livestock is slaughtered, there will be a cessation of blood circulation that carries oxygen to muscle tissue (meat), this will limit the occurrence of aerobic metabolism. Because of these conditions, the metabolic system will change to anaerobic metabolism which produces lactic acid. This will cause the pH to drop to around 5.6 5.8. With a decrease in pH, anaerobic metabolism becomes slow and the amount of ATP is depleted so that the meat hardens (rigor mortise) and then becomes soft again. The autolysis process will take place, so the meat becomes damaged. Changes in pH will cause a type of pigment to change colors, such as chlorophyll and anthocyanins. The normal color deviation is often interpreted as damage. Denaturation and clumping of proteins can occur due to differences in pH or by heating.
3. Physical Damage
Physical damage is caused by physical treatments. For example, drying can cause case hardening. In refrigeration, chilling injuries or freezing injuries and freezer burn can occur in frozen materials. In frying or burning for too long it can cause scorching, as well as physical damage.
These chilling injuries may be caused by a toxin present in live fabrics. In a neutral state, this toxin can be neutralized (detoxified) by other compounds. It is suspected that the plant contains a toxin, namely chlorogenic acid which can be neutralized by ascorbic acid. But in the chilling process, the speed of toxin production will increase, while detoxification will decrease, so that the cells will be poisoned and die, then rot.
Another possibility is caused by the presence of 2 types of fat contained in mitochondria, namely fatty acids that are sensitive to cooling and fatty acids that are resistant to cooling.
It is suspected that the fatty acid that is sensitive to cooling is linolenic acid, while the fatty acid that is resistant to cooling is palmitic acid. If the linolenic acid content in mitochondria is greater than palmitic acid, the material will be sensitive to cooling. Vice versa, if the palmitic acid content is greater than linolenic acid, the material will be resistant to cooling.
There are several theories regarding the occurrence of freezing injuries, one of which according to the latest theory is that the water contained between the woven cells at freezing temperatures will become ice crystals, which will become larger over time by absorbing water from the inside. surrounding cells so that the cells become dry. As a result of this dehydration, the sulfhydryl bonds (-SH) of the protein will turn into disulfide bonds (-S-S) so that the protein is physiologically lost, as well as the enzymes will lose their function so that metabolism stops and cells will die and then rot. Freezing with the wrong temperature can cause damage in the form of rupture of cells so that liquid leaves the cells, the color of the material becomes dark, decay and softening occur. In frozen meat without wrapping, the outside of the meat becomes dry and hardened (freezer burn).
Storage in wet (moist) warehouses can cause agricultural products (food) to absorb water, for example, hardening occurs in dry flours so that the flours harden or become petrified. The improper drying process of albumen flour can cause the flour to lose its foaming power or cause very low rehydration power.
Humid storage can cause the water activity of the material to increase, thus providing opportunities for other forms of microbiological damage to be active. In general, physical damage occurs together with other forms of damage.
The use of too high a temperature in food processing causes distorted taste and damage to the vitamin content. The use of high temperatures causes thermal degradation of the compounds in the ingredients, resulting in a decrease in the quality (quality) of food ingredients.
Materials that are dried at temperatures that are too high and by drying too quickly will experience case hardening (the outside of the food hardens while the inside remains soft), other symptoms that occur are scorching, dark food color (brown) and caramelization occurs. The presence of light also stimulates the occurrence of material damage, for example in fat.
4. Chemical Damage
Chemical damage is usually related to other damage.
The presence of light can help chemical damage, for example, fat oxidation or the color of the material becomes paler (fading) the presence of oxygen causes the oil to become rancid.
To prevent the occurrence of rancidity, usually used antioxidant compounds. Antioxidants BHA and BHT provide better protection against oxidation of cooking oil when compared to tocopherols; tertiary butyl hydroquinone, and propyl gallate. Meanwhile, the chelating agents EDTA (Ethylene Diamine Tetra Acetic Acid) and isopropylcitrate are less effective.
The appearance of black stains on canned food, caused by the presence of FeS compounds, is chemical damage caused by the coating or enamel of the inner layer of the can that is not good and reacts with the H2S produced by the food.
Browning reactions in some materials can occur enzymatically or non-enzymatically. This non-enzymatic browning can cause an unwanted color to appear, namely brown. Non-enzymatic browning is a chemical breakdown.
5. Mechanical Damage
Mechanical damage is caused by mechanical impacts, For example, collisions between materials or due to collisions between tools and the material itself, or between food ingredients and processing containers. Examples of mechanical damage when fruits and vegetables are harvested with tools, for example, mangoes, durians harvested with bamboo poles can be damaged by the poles or bruised by falling on rocks or hard ground. Some tubers are deformed because they are torn or cut by a hoe or other digging tool. For goods that are transported by bulk transportation, the bottom will be crushed and compressed from the top and sides, causing bruises, especially in a moving vehicle, as if the materials inside were shaken vigorously, causing a lot of mechanical damage.
Symptoms of damage that arise include bruises (due to being crushed/stressed), flattened, cracked, broken, torn/cut, and others. Food commodities that are prone to mechanical damage are fruits (especially soft-skinned ones), especially fruit vegetables (tomatoes, cucumbers), eggs, and tubers.
C. MAIN FACTORS CAUSED FOOD DAMAGE
Food spoilage can be caused by the following factors:
1. microbial growth and activity, especially bacteria, molds, and yeasts,
2. the activity of enzymes in foodstuffs,
3. insects, parasites, and mice,
4. temperature including heating and cooling,
5. water content,
6. air including oxygen,
7. rays, and
8. time (long) storage.
1. Bacteria, Mold, and Yeast
Microbes that cause food spoilage can be found anywhere.
whether in soil, water, air, on the skin or fur of livestock and in the intestines. Some microbes can also be found on the skins of fruits, vegetables, seeds, and nuts. In the woven/living tissue normally no microbes are found. For example, cow's milk is in a sterile state in the mammary glands, but after being milked it will experience contamination from the air, the container, or from the milker itself. Beef from healthy cattle will also be contaminated immediately after slaughter. Fruits, vegetables, whole grains, and nuts will become contaminated after being peeled. Likewise in eggs, the inside of a healthy egg is sterile at first, but the shell contains a lot of bacteria from chicken droppings.
Bacteria have several forms such as cocci in Streptococcus sp, Micrococcus sp, and Sarcina sp, rod shape in bacilli, and spiral shape in spirilla and vibrios (Figure 1.1). Bacteria found in food have a very small size, which has a cell length between one to several microns (1 micron = 1/1,000mm).
Some bacteria can form spores and are resistant to heating, chemical influences, and other changes. Spores of these bacteria are much more resistant than yeasts or molds, and more resistant to high heat processing than enzymes. To kill these spores in foodstuffs need to be sterilized, namely an attempt to kill the sporing microorganisms, with a pressure of 1 atm and a temperature of 1210C.
Yeasts have a cell length of 20 microns or more. Most yeasts are round or oval (elliptical). Molds are larger and more complex. Molds grow like feathers or hairs called mycelia, and at the ends are shaped like fruit called conidia and contain mold spores. Molds have distinctive colored spores, for example, green or black in rotten bread, orange in income, or white and black in tempeh. This color difference is caused by differences in the color of the conidia or spores.
Bacteria, yeast, or molds that grow in foodstuffs can change the composition of foodstuffs. Some of these microbes can hydrolyze starch and cellulose or cause the fermentation of sugars, while other microbes produce enzymes that can hydrolyze fats and cause rancidity, or damage proteins that produce a bad smell. Some of these microbes can produce mucus, gas, foam, distorted colors, acids, toxins, and others. If food is spontaneously contaminated from the air, then in the food there will be the growth of a mixture of several types of microbes.
Bacteria, yeasts, and molds can grow well in warm and humid conditions. Most bacteria have a growth temperature range between 45 - 55 0C and are called thermophilic bacteria.
Some bacteria that have a growth temperature range between 20 – 450C are called mesophilic bacteria, and others have a growth temperature below 200C and are called psychrophilic bacteria. The spores of most bacteria can survive in boiling water, and when the temperature drops, the spores germinate and reproduce.
Some bacteria and all molds that require oxygen to live are called aerobic bacteria. Other bacteria cannot grow in the presence of oxygen, such bacteria are called anaerobic bacteria.
Under optimal conditions, bacteria multiply rapidly. From 1 cell to 2 cells it only takes 20 minutes and so it grows and multiplies according to an exponential function. For example, for example, milk which under certain conditions contains 100,000 bacteria per ml, if left at room temperature for 24 hours, the number of bacteria can double to 25 million, and in 96 hours the number of bacteria to 5,000 million per ml. Environmental factors that affect microbial growth include water, pH, RH, temperature, oxygen, and minerals.
2. Enzyme Activation
Enzymes present in foodstuffs can come from microbes or it is already present in these foods normally.
Enzyme activity can be prevented or stopped completely by heat, chemical treatment, radiation, or other treatment. From a food technology perspective, enzyme activity is beneficial. For example in the manufacture of fruit juices, several enzymes such as pectinase are required to purify fruit juices such as apple cider. Another example is the use of the enzyme papain (proteinase) to tenderize meat. But too much tenderization or ripening can lead to spoilage.
The maximum activity of enzymes generally lies between pH 4 to 8, or around pH 6. However, some enzymes, such as pepsin, still show activity up to pH 2, and phosphatase enzymes in the blood up to pH 9 as shown in Table 1.3.
If food is refrigerated, sterilized, or pasteurized to inactivate microbes, enzymes will be partially or completely destroyed or become inactive. Some enzymes are more resistant to heating, cooling, drying, radiation, or other preservation methods than microbes. For example, heating or radiation may be effective in killing microbes, but certain enzymes may still be active.
3. Insects, Parasites, and Rats
Insects can especially damage/injure the surface of food such as fruits, vegetables, grains and tubers, thereby causing contamination by bacteria, yeasts, or molds.
In grains or dried fruits, insects can usually be prevented by fumigation, using several chemicals such as methyl bromide, ethylene oxide, and propylene oxide. Other chemicals such as ethylene and propylene should not be used for foods that have a high water content because they may form toxins.
Insect eggs can be left in food before and after processing, for example in flour. To destroy the eggs of these insects, flour is usually passed in a centrifuge, so that with hard impacts from the walls of the centrifuge the eggs will break. Although the egg fragments still remain in the flour, they cannot reproduce further.
Parasites that are commonly found in pork are tapeworms (Trichinella spiralis). The tapeworms enter the pig's body through the remains of the food they eat. Uncooked pork can be a source of contamination for humans. Nematodes may be killed by freezing.
Rats are a threat in Indonesia, especially to grain yields before harvest and during storage in warehouses. Rats are harmful not only because of the amount of material eaten but also their feces, hair, and urine can be a good medium for bacterial growth and cause unpleasant odors.
4. Heating and Cooling
Heating and cooling that is not carefully monitored can cause food spoilage. According to the research results, for every 100C increase with a temperature range of 10 380C, the speed of enzymatic and non-enzymatic reactions will increase twofold. Excessive heating can cause protein denaturation, breakdown of emulsions, destroy vitamins, and degradation of fats or oils.
Freezing done on fruits and vegetables will cause the material to experience thawing after being removed from the freezing place so that the texture becomes soft and can
cause microbial contamination. This situation can also occur in liquid materials such as milk. If milk is frozen then the emulsion will break and the fat will separate, the protein will denature and cause clumping.
After harvesting, fruits and vegetables require optimum storage temperatures. A cooling temperature of about 4.50C can prevent or slow down the spoilage process.
5. Water content
The water content on the surface of the material is affected by the relative humidity RH the air around it. If the water content of the material is low while the surrounding RH is high, there will be the absorption of water vapor from the air so that the water content of the material will be higher.
If the temperature of the material is lower (cold) there will be air condensation on the surface of the material and can be a good medium for the proliferation of bacteria or mold growth. This condensation does not always originate outside the material. In packaging, some foodstuffs such as fruits and vegetables can produce water from respiration and transpiration. This water can help the growth of microbes.
Dried foodstuffs can also produce water, for example, if the temperature rises during packing, as a result, the relative humidity on the surface will change. This water vapor can then condense on the surface of the food, especially if the storage temperature is decreased.
6. Air and Oxygen
Air and oxygen can damage vitamins, especially vitamin A and C, food color, flavor, and other ingredients are also important for mold growth. In general, mold is aerobic, therefore it is often found growing on the surface of the food.
Oxygen can be reduced in quantity by sucking the air out by vacuum or adding an inert gas during processing, replacing the air with nitrogen (N) or CO2, or by capturing oxygen molecules with chemical reagents. In foods containing fat, oxygen can cause rancidity.
7. Ray (Light)
Light can damage some vitamins, especially riboflavin, vitamin A and vitamin C, can also damage the color of food. For example, if milk is stored in a translucent bottle, the flavor of the milk may change due to fat oxidation and light-catalyzed protein changes. Materials that are sensitive to light can be protected by packing in an impermeable container (material).
8. Storage Time
After slaughter, harvesting, or processing there are times in the where the food is of the best quality, but this is only temporary. Depending on the degree of maturity at the time of harvest, some foodstuffs may deteriorate within a day or two, or within hours of harvesting or cutting.
The effects of damage by microbial growth, enzyme activity, damage by insects, effects of heating or cooling, moisture content, oxygen, and light are all affected by time.
In general, a longer time will cause greater damage to the material, except for cheese, wine, and others that are not damaged during storage, ripening, or aging.
FOOD PROCESSING PROCESS STAGES
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