This research is based on answering the following question: Why does meat decompose faster than gelatin? The following topics were addressed: water activity, which is an intrinsic activity that is related to the moisture content in the food, the pH of the gelatin that could be taken as neutral since as we will see below is a food that is derived only from water mostly and gelatin, the pH of the meat in this there may be changes that notably affect this food so important for human consumption, meat components these are very important due to their great nutritional contribution that is derived mainly from essential amino acids and gelatin which is also composed of amino acids but of low biological value, the distribution of water in food,as well as various intrinsic and extrinsic factors that intervene in bacterial development in these foods, such as the atmosphere, temperature, humidity, availability of nutrients, redox potential, etc.
GELATINE COMPOSITION
Jellies are products that are attractive to children for their smooth consistency and soft texture, as well as for their striking colors and varied flavors. This food is taken as is after being reconstituted with water, although it also serves as an ingredient in various preparations, sweet or savory.
Regarding its nutritional composition, the proteins (although of low biological value) and the absence of fats and cholesterol stand out.
Gelatin is a substance of animal origin that is obtained from collagen, a protein that is abundant in the connective tissue of animal skins, bones and tissues. Proteins are its most abundant natural component, however, they are of low biological value because they lack some essential amino acids. This means that the quality of these proteins is not as good as that of meat, fish, eggs or dairy.
For this reason, gelatins should not be considered as a food with a great nutritional contribution, especially when most of those sold on the market have a high amount of added sugars to sweeten and flavor the food itself, neutral.
On the market there is a wide variety of jellies with fruit flavors and colors that mimic them, thanks to the addition of various additives (chemicals that are added to food in order to improve its appearance and extend its shelf life). Many of them are enriched in vitamins A, C and E, although their nutritional content is not compatible with that of fresh fruits. A serving of fruit gelatin contains approximately 30 milligrams of vitamin C, three times less than orange.
Gelatins are obtained by mixing with water a powdered element called gelatin, a solid, colorless, translucent and not very tasty substance that is obtained from collagen when water is boiled.
MEAT COMPOSITION
Meat is defined as all parts of an animal that have been determined as safe and suitable for human consumption or are used for this purpose. Meat is made up of water, proteins (amino acids), minerals, fats (fatty acids), vitamins and other bioactive components, as well as small amounts of carbohydrates.
From a nutritional point of view, the importance of meat derives from its high-quality proteins, which contain all the essential amino acids, as well as highly bioavailable minerals and vitamins. Meat is rich in vitamin B 12 and iron, which are not available in vegetarian diets.
WATER ACTIVITY AND GROWTH.
Beginning
Water activity (Aw) is a measure of the availability of water for biological functions and is related to the free water present in food.
In a food system, water or total moisture is present in a free and restricted form. Restricted water is the fraction that is used to hydrate hydrophilic molecules and to dissolve solutes, and is not available for biological functions; therefore, it does not contribute to the activity of the water.
The water activity of the food can be expressed by the portion of the water vapor pressure in the food (P, which is <1) with the pure water (Po, which is 1); that is, Po between P, varies from 0 to 1 or more exactly> 0 to <1, because no food can have water activity 0 or 1. The water activity of a food is determined from its equilibrium relative humidity (ERH), dividing ERH / 100 (because ERH is expressed as a percentage).
Water activity
The water activity of the food varies almost 0.1 to 0.9, the water activity values of some foods are as follows:
| FOODS | WATER ACTIVITY |
| Cereals, cookies, sugar, salt, dry milk. | 0.10 to 0.20 |
| Noodles, honey, chocolate, dry egg. | Less than 0.60 |
| Jam, jelly, dried fruit, Parmesan cheese, nuts. | 0.60 to 0.85 |
| Fermented sausages, dried cured meat, sweetened condensed milk, maple syrup. | 0. 85 to 0.93 |
| Evaporated milk, tomato paste, bread, fruit juices, salted fish, cold cuts, processed cheese. | 0.93 to 0.98 |
| Fresh meat, fish, fruits, vegetables, milk, eggs. | 0.98 to 0.99 |
Water activity and bacterial growth
Free water in food is necessary for microbial growth. The need to transport nutrients and remove waste materials, carry out enzymatic reactions, synthesize cellular matter, and take part in other biochemical reactions, such as the hydrolysis of a polymer to monomers (proteins to amino acids) Each microbial species (or group) It has an optimum, maximum and minimum water activity level for its growth.
In general, the minimum values of water activity for the growth of bacterial groups, the majority of molds 0.8 and 0.6 as minimum with xerophilic molds; most yeasts, 0.85, with osmophilic yeasts, 0.6 to 0.7; most bacteria. (1)
The activity of water is an intrinsic property and is related in a non-linear way to the moisture content by absorption and desorption curves or isotherms. To understand this, consider a food with water, stored at a specific temperature in a hermetically closed chamber; after some time, its vapor pressure will cause the transfer of water molecules and the chamber will acquire a constant relative humidity that will be in equilibrium (without movement in any direction) with the water content in the food. This humidity is a function of the degree of interaction of the solutes in the water, which is a reflection of how easy it is to escape from the food. On the contrary, if you start from a dry product and are subjected to high atmospheres of relative humidity,a mass transfer of the solid gas will be observed until reaching an equilibrium.
Hysterisis occurs with a hydrated protein that dries in an atmosphere of 35% relative humidity and reaches equilibrium at a content of 10% water (desorption curve); on the other hand, if the same totally dehydrated protein is placed in that atmosphere, it absorbs moisture and reaches equilibrium with only 7% water. The absorption isotherm represents the kinetics with which a food absorbs moisture and it is important to know it since it reflects the behavior of the dehydrated products stored in humid atmospheres (hygroscopicity). Similarly, the desorption is equivalent to the dehydration process and reflects the shape in which it loses water. Based on both curves, the storage, drying, rehydration, etc. systems are designed.In addition, they help to predict the stability of food stored in different conditions.
Isothermal solution of water showing hysterysis. At the same percentage of water, Aw is reduced more through desorption than absorption.
DISTRIBUTION OF WATER IN FOODS
Water Retention Capacity
The water retention capacity of proteins and polysaccharides is defined as the amount of liquid that can be trapped in a network, without exudation or syneresis; in each case this parameter varies depending on the type of food.
There are three hypothetical zones into which the water contained in a product can be divided.
- ZONE III: In this zone the water is considered "free", it is found in macrocapillaries and is part of the solutions that dissolve low molecular weight substances, it is the most abundant, easy to freeze and evaporate and its elimination reduces the activity of the water at 0.8. ZONE II: In this zone the water is located in different more structured layers and in microcapillaries; it is more difficult to remove than the previous one, but when doing so, water activity values of approximately 0.25 are obtained. This fraction would correspond, together with the monolayer, to the "bound" water.
- ZONE I: In this zone the water is equivalent to the monomolecular layer and it is more difficult to remove in commercial drying processes; in some cases it can be partially reduced in dehydration, but this is not recommended since, in addition to requiring a lot of energy and the food is damaged, its presence exerts a protective effect, especially against lipid oxidation reactions it acts as a barrier oxygen.
WATER ACTIVITY AND FOOD STABILITY
The various methods of food preservation are based on the control of one or more of the variables that influence its stability, that is, water activity, temperature, pH, availability of nutrients and reagents, oxidation reduction potential and presence of preservatives.. In this sense, the activity of water is of fundamental importance and based on it, the behavior of a product can be known.
The higher the water activity and the closer s 1.0 is, the greater the instability of the food; For this reason, fresh meats, fruits and vegetables need to be refrigerated for their conservation, on the other hand, stable foods at room temperature (except those thermally treated and commercially sterile, such as canned goods), are low in water activity, as happens with those of intermediate humidity in which microbial growth is retarded.
The influence of water activity on various chemical and enzymatic reactions that occur in food (browning, rancidity, etc.), as well as the growth of fungi, yeasts, bacteria; but also, the activity of the water influences the degradation of vitamins and pigments, loss of lysine and other transformations.
For their growth, microorganisms need favorable conditions of pH, nutrients, oxygen, temperature, and water activity; as a general rule, the latter will have to be higher as the parameters become less favorable. For every 0.1 unit increase in water activity, microbial growth can increase by up to 100%. Those that require the most water are bacteria (Aa> 0.91), then yeasts (> 0.88), and then fungi (> 0.80); of all, pathogens are the ones most needed for their development, contrary to osmophilic yeasts. As a rule, the minimum water activity for producing toxins is higher than for microbial growth. Reducing the availability of water inhibits this growth, but in turn increases the thermal resistance of microorganisms,which indicates that to destroy them it is better humid heat than dry heat. Microorganisms respond to low humidity, which prolongs their initial phase, lowers the logarithmic phase, and reduces the number of viable cells.
FREEZING FOODS
In accordance with the reduction in temperature, it inhibits chemical and enzymatic reactions and microbial growth, even when refrigeration (4-10 0 C) and freezing (<0 0 C) also develop. This is due, in part, to the fact that because they have low molecular weight substances dissolved, such as salts and sugars, foods have areas rich in solutes whose freezing temperature drops considerably and not all the water turns into ice when frozen. rather, solute-rich liquid sections remain.
In the microenvironment of the non-freezable phase, different from the rest of the food, the pH, the reagent concentration, the water activity, the ionic strength, the viscosity, the redox potential, the oxygen solubility, the surface tension are modified., etc.; Consequently, despite the low temperature, many chemical reactions such as protein denaturation, lipid oxidation, sucrose hydrolysis, non-enzymatic browning, etc. can occur under these conditions.
The stability and properties of macromolecules within food cells depend on the interaction of their reactive groups with the aqueous phase that surrounds them; freezing causes an increase of 10 to 15% in volume, alters these interactions and ice crystals modify the texture of fruits, vegetables and meat. The turgor of the tissues is called by the hisdrostatic pressure of the cells and the membrane retains the water; therefore, it is also responsible for maintaining freshness. The components of the membranes are lipoproteins formed by weak bonds (hydrogen bonds and hydrophobic bonds) highly dependent on temperature, which leads to their easy dissociation and the release of water during thawing; This causes the food tissues to lose their rigidity and freshness and,sometimes, nutrients such as water-soluble vitamins are removed from the thawing water.
The rate of freezing determines the formation and location of ice crystals; when done quickly (a few minutes at very low temperature), many small needle-like crystals are produced along the muscle fibers of the meat for example; On the contrary, if it is carried out slowly, fewer but larger crystals are induced, in such a way that each cell contains a single central mass of ice. Slow freezing is more harmful than fast freezing since it affects, above all, the cell membrane and also establishes intercellular crystals that have the ability to unite cells and integrate large aggregates.
Ice crystals do not maintain a constant size in storage at low temperatures, but continue to grow at the expense of smaller ones, because these have a greater area than large ones that increase their vapor pressure, therefore, the water molecules migrate more easily.
CAUSES OF FOOD DETERIORATION
There are several causes that intervene in the deterioration of food, these can be:
- PHYSICAL: light, oxygen, pH, humidity and temperature. ABIOTICS: -Biochemical: oxidation of lipids and browning.
-Chemicals: natural toxins, pollutants and additives.
- BIOTICS: microbiological and parasitological.
CLASSIFICATION OF FOODS BY EASE OF ALTERATION
Food can be classified as follows:
- STABLE: They do not alter unless they are handled improperly (sugar, flour) SEMIALTERABLES: If they are handled and stored properly it can last a long time (potatoes, apples, onions) ALTERABLE: They are easily altered, so it requires to be preserved properly (meat, fish, milk, fruits).
FACTORS INFLUENCING MICROBIAL DEVELOPMENT IN FOODS
The factors that influence microbial development in food are divided into two: intrinsic and extrinsic.
INTRINSIC FACTORS (substrate limitations)
NUTRIENT AVAILABILITY: The concentration of essential nutrients can determine the growth rate of a microorganism.
PH INCIDENCE: Most BACTERIA develop at a pH between 4.5 and 9 (optimum 6.5 to 7.5) except acetic and lactic bacteria up to 3.5, acid resistant FUNGI, optimal growth pH between 4 and 6 (extreme values between 2 and 11 for molds), and yeasts at pH 2 to 9.
REDOX POTENTIAL: It has a fundamental effect on the microflora of the food.
Although microbial growth can occur over a wide range of redox potential, microorganisms are usually classified as follows:
- Strict aerobes: they need oxygen as the final electron acceptor and a high redox potential (pseudomonas, bacillus, micrococcus). Facultative aerobes: enterobacteria (staphylococcus). Strict anaerobes: they need low or negative redox potentials (clostridium, propionibacterium). Microaerophils: aerobic or aerobic incapable of aerobic respiration but grow in the presence of air (lactobacillus, streptococcus, pediococcus) WATER ACTIVITY: minimum Aw values for the growth of microorganisms in food.
| MICROORGANISMS GROUP | Aw MINIMUM |
| Bacteria | 0.91 |
| Yeasts | 0.88 |
| Mushrooms | 0.80 |
| Halophytic bacteria | 0.75 |
| Xerophytic fungi | 0.65 |
| Osmophilic yeasts | 0.60 |
MICROBIAL COMPONENTS: There are first barrier and second barrier components.
- First barrier: Structures made up of macromolecules, quite resistant to physical, chemical or biological aggressions. Second barrier: One of the enzymatic browning functions in plants. 1.- Release of enzymes and substrates by tissue breakdown but for specifically antimicrobial purposes. 2.- Presence of other active compounds (thymol, eugenol, cinnamic aldehyde, benzoic acids).
EXTRINSIC FACTORS (environmental limitations)
RELATIVE HUMIDITY (RH): In equilibrium RH = Aw, relative humidity is very sensitive to temperature, with low temperatures it tends to increase and vice versa, enhancing condensation
TEMPERATURE:
| MINIMUM | OPTIMAL | MAXIMUM | |
| Thermophiles | 40-45 | 55-75 | 60-90 |
| Thermotrophs | 15-20 | 30-40 | 45-50 |
| Mesophiles | 5-15 | 30-40 | 40-47 |
| Psychrophiles | -5 + 5 | 12-15 | 15-20 |
| Psychrotrophs | -5 + 5 | 25-30 | 30-35 |
Greater resistance: Gram + bacteria than Gram- and the sporulated form instead of the vegetative form.
COMPOSITION OF THE ATMOSPHERE: The atmosphere is composed mainly of CO 2 this have mainly bacteriostatic effects, however; For some microorganisms it has a lethal effect, very sensitive to its presence are Gram- molds and bacteria and more resistant Gram + bacteria and some yeasts.
NATURAL AND INDUCED POST-MORTAL BIOCHEMICAL CHANGES THAT AFFECT THE QUALITY OF MEAT
Consumers' choice of meat purchase is strongly influenced by various product attributes, including water-holding capacity, color and fat content, and meat tenderness.
After maturation of the meat, the characteristics of the tissue differ substantially from those of live muscle. Postmortem metabolism leads to a decrease in pH from the physiological value of approximately 7.4 in muscle metabolism to a final value between pH 5.5 and 5.9 in red meat and poultry. Also. Before the formation of the complex of rigor, a certain contraction has occurred in the tissue.
The consequences of lowering the pH are both beneficial and undesirable for the value of the product. Clearly, the acidic pH of meat will retard microbial growth and thus extend shelf life compared to pH neutral muscle. The isoelectric point of myosin (the dominant protein in muscle) is approximately 5.0; at this pH, the sum of the positive and negative charges is equal to zero, the protein-protein interactions are maximum and the protein-water interactions are minimum. Consequently, the myofibrils shrink and lose a large part of their water-holding capacity. This loss of water during storage of fresh or cooked products (sometimes called <
THE pH IN MEAT
The pH is a measure of the concentration of protons or hydrogen ions, that is, of the acidity of the medium. In food numbers, pH constitutes an important factor for its stability since it determines the growth of specific groups of microorganisms.
In the case of meat, the pH of the live muscle is close to neutrality, when the death of the animal occurs, the supply of oxygen to the tissues ceases, and anaerobic processes (anaerobic glycolysis) predominate that generate the formation of acid. lactic acid from muscle glycogen. The formation of lactic acid causes the decrease of the pH in the muscle so that this value is an index of development of post-mortem biochemical modifications. When the meat maturation process has been completed, it must have a pH between 5.4 and 5.6 as the ideal meat pH, which allows a good commercial life by inhibiting the growth of microorganisms, and provides it with adequate physical-chemical characteristics..
However, in certain situations, the pH of the meat is altered because the anaerobic glycolysis processes do not develop properly. In this case we can find two situations:
- If the pH decreases rapidly after the death of the animal due to accelerated glycolysis the final pH falls below 5.4 and gives rise to PSE (pale, soft and exudative) meats. This type of meat contains a lower water retention capacity and exudes water to the outside that favors microbial proliferation. This type of meat occurs mainly in pigs If, on the contrary, the animal arrives tired at slaughter after carrying out an intense exercise in which muscle glycogen has been depleted, anaerobic glycolysis ends before reaching the final pH due to the fact that there is no substrate, leaving the muscle pH above 5.6. In this case, DFD (dark, firm, hard) meats are produced which are characterized by having a high water retention capacity and a high pH favors microbial proliferation.This type of meat is typical of fighting and game meat.
CONCLUSION
For the conclusion of said investigation, I will answer the question for which said investigation was initiated.
Why does meat break down faster than gelatin?
Well, first of all we would say that it is almost impossible for this to be the case, since it is known that a food is more perishable when it has a high water content and that food that contains less water is less perishable, this would indicate that gelatin would be more perishable than meat due to its high water content, but many important factors intervene in this phenomenon that were already mentioned above, well in the first place the two foods we are dealing with are of animal origin and are mainly composed of proteins, but meat has a all essential amino acids, which makes it have a higher biological value than gelatin, which also contains amino acids but of low value, less biological value,The most important factor in this is the activity of the water in these two foods since considering their physical, chemical and biological composition of the two when putting them in an atmosphere, and equal temperature, and taking their corresponding pH that are between 5.4 and 5.6 for the meat and almost neutral for the gelatin, we have that the activity of the water in the meat is 0.97 and that of the gelatin is 0.7 putting the two in a relative humidity of 10%, it gives us an indication that the meat is less prone to bacterial growth due to the activity of the water it has, but as its pH intervenes, it becomes more suitable for it to be invaded by microorganisms and these incite their decomposition since we would be dealing with a DFD type meat (dark, firm, hard) with a pH above 5.6 Due to the fact that glycolysis did not end properly to reach the normal pH of the meat, therefore the gelatin lasts longer than the meat, there is also another reason why we could explain this phenomenon in which, as in the previous one, the water activity and its distribution in said foods since the water retention capacity of these is derived from the capacity of the proteins that compose it, and from the distribution area in which the water is found for said foods, Taking this as a reference, the water in the gelatin and the meat would be found in zone III where the water is considered free and they are found in the macrocapillaries, and it is easy to freeze and evaporate and its elimination reduces the water activity to 0.8,Here we would take into account that gelatin has a high water content with respect to the content in meat, but with the intervention of water activity, the following phenomenon would occur: gelatin, which, as already mentioned, has a higher water content by placing it at a temperature For example, when it is frozen for a long time, its vapor pressure will cause the water molecules to transfer from its interior to the exterior, which will cause crystals or ice to form which will make it less prone to invade microorganisms,On the contrary, if we do the same with meat that has a lower water content in relation to gelatin, the phenomenon will occur in a different way, since in this case the meat would be taken as a dry product and when subjected to this humid environment it would cause that the water molecules from outside pass into it and this becomes a good medium for the invasion of microorganisms, and for this reason we again realize the reason why meat becomes more perishable in relation to gelatin when said factors to which both are exposed.and that is why we once again realize the reason why meat becomes more perishable in relation to gelatin when these factors to which both are exposed intervene.and that is why we once again realize the reason why meat becomes more perishable in relation to gelatin when these factors to which both are exposed intervene.
REFERENCES
- Bibek R. Fundamentals of food microbiology. 4th ed. Mexico: Mc Graw-Hill; 2008.Baudi S. Chemistry of foods.5th ed. Mexico: Pearson; 2013 Owen R. Food Chemistry, 3rd ed. Spain: Acribia; 2010. http://www.fao.org/Ag/againfo/themes/es/meat/backgr_composition.html http://bioquimicacarnicos.blogspot.com/2010/02/1-componentes-quimicos-de-la-carne.html
