1. Foam affects the taste of food.
2. When there is too much foam, it will easily overflow, causing waste of materials and increasing the chance of contamination.
3. In severe cases, the respiration of the bacteria will be hindered, resulting in the destruction of the bacteria.
4. More foam will lead to less filling during canning.
5. For example: Soymilk contains a substance called saponin, which will make soymilk produce a lot of foam when it is heated to 80-90°C. These foams are like a "mask", it looks like it is boiled, but it is not completely boiled. cooked.
If you drink this soy milk, the saponins contained in it will affect the body's absorption of protein, which may lead to indigestion. If you drink too much, it is easy to cause nausea, vomiting, diarrhea, abdominal pain and other problems.
There are indeed many problems in food production. For example, a lot of foam is generated during the processing of juice, so the same problem exists when filling. If it is filled once, it must be unsatisfactory. If it is filled many times, it will increase the operation of the machine and increase the production cost. Quality of products.
For another example, one step in the process of making tofu is to boil soy milk. Soy milk has a lot of protein and some saponins. They are all surface active and can form a large amount of foam during heating and stirring. Soy milk contains quite a lot of protease inhibitors. If it does not lose its activity, it will inhibit the activity of protease and affect the digestion and absorption of protein by the human body. Saponins have a bitter taste, and high levels can cause nausea and vomiting. The temperature at which a large amount of foam is formed is only about seventy or eighty degrees, which is not enough to inactivate protease inhibitors and saponins. If it is not defoamed, the production of large amounts of foam will make it difficult for the temperature to continue to rise. Therefore, defoaming is an unavoidable operation [1].
To sum up, it can be said that the foam generated in the production not only affects the smooth progress of industrial production, but also affects the quality of the product, and also reduces the usable area of the equipment and increases the consumption of processing time.
There are two methods to eliminate foam: mechanical defoaming and chemical defoaming. Mechanical defoaming refers to breaking the foam with mechanical force, or breaking the foam with pressure. This method does not require additional substances, saves raw materials, and reduces the The probability of contamination by chemical reagents, but this method requires certain equipment and power, and cannot fundamentally eliminate the factors that cause foam. Chemical defoaming is the addition of defoaming agents. Compared with mechanical defoaming, this method saves time and effort, requires less investment, and has quicker results [2].
1. Brief introduction of defoamer
Defoamers are substances used to reduce surface tension and eliminate foam during food processing. Foam is a heterogeneous dispersion system in which insoluble gas enters the liquid under the action of external force, and a large number of bubbles formed are blocked by the liquid. Foams are thermodynamically unstable systems that have a tendency to shrink their surface area and rupture by themselves. Natural defoaming takes a long time, and it is necessary to use defoamer to achieve rapid defoaming to meet the requirements of food processing and production.
There are many types of defoamers, and their ingredients vary widely.
Defoamer is mainly composed of active ingredients, emulsifiers, carriers and emulsification assistants, among which active ingredients are the most important core part, which plays the role of breaking foam and reducing surface tension; emulsifier is to disperse active ingredients into small particles, so that Better dispersion in oil or water, better defoaming effect. The carrier occupies a large proportion in the defoamer, and the surface tension is not high, and it mainly acts as a support medium, which is beneficial to the effect of defoaming and defoaming, and can reduce the cost; the emulsification aid is to make the emulsification effect better.
Defoamers are mostly liquid compound products, which are mainly divided into three categories: mineral oils, silicones, and polyethers [3].
1. Mineral oil defoamer is usually composed of carrier, active agent, etc. The carrier is a substance with low surface tension, and its function is to carry and dilute. Commonly used carriers are water, fatty alcohol, etc.;
2. Silicone defoamer generally includes polydimethylsiloxane and the like. Silicone-based defoamer has poor solubility, and has the characteristics of fast defoaming speed and good foam suppression at room temperature, but delamination, slow defoaming speed, and poor foam suppression at high temperature.
3. Polyether defoamers include polyoxypropylene oxyethylene glycerol ether, etc. Polyether defoamer has the characteristics of long foam suppression time, good effect, fast defoaming speed and good thermal stability. For example, antifoaming agents are used in the production process of fruit and vegetable beverages, soy products, and sucrose.
The role of defoamer can be divided into three types: foam breaker, foam inhibitor, and defoamer.
The so-called foam breaker is added after the liquid is foamed, and enters the foam film through the action of adsorbing foam and surface tension to make the foundation thinner, which can quickly destroy the foam and reduce the liquid level. The foam suppressor is a substance that can inhibit the generation of foam. It adsorbs on the foam together with the liquid foam, reduces the surface tension, makes the foam film thin and damaged, and prevents the foam phenomenon.
The defoaming agent adsorbs on the bubbles in the liquid, and gathers the air in the bubbles. After the bubbles adsorb each other, large bubbles are formed at the adsorption interface, and the buoyancy increases to increase the speed and promote the defoaming.
Defoamers generally have various functions such as breaking foam, inhibiting foam, and defoaming. The defoamer selected for the foaming caused by different ways or reasons is different, so the formula screening of the defoamer is particularly important.
Second, the principle of defoamer defoaming
Defoamer defoaming principle 1:
There is still no unified understanding of the mechanism of action of defoaming agents. Ross (S.), an American colloid chemist, clearly stated that no defoaming mechanism covers all defoaming phenomena, and various complex defoaming agents can cope with various A defoaming mechanism. Next, two defoaming principles are explained.
Foam is a dispersion system in which gas is dispersed in a liquid, the gas is the dispersed phase, and the liquid is the dispersion medium, which forms a stable state because the gas is insoluble in the surfactant. After the bubbles are formed, due to the intermolecular action of the foaming system, the hydrophilic group and the hydrophobic group are adsorbed by the bubble wall to form a regular arrangement. , its stability is very strong, and it is not easy to break under normal conditions. At the same time, foam is a thermodynamically unstable system. Under the action of gravity, the liquid film continuously flows down, evaporates, and ruptures, as well as the liquid drainage and infiltration process between the foam liquid films.
The reasons for defoaming are mainly divided into two aspects: 1) the easily spreadable and adsorbed defoamer molecules replace the foaming agent molecules, forming a film with poor strength; 2) the defoaming agent molecules take away the adjacent surface during the spreading process The partial solution of the layer makes the foam liquid film thinner, the foam stability is reduced, and it is easy to be destroyed.
From the above, we can know that in order to play a role, the defoamer must first penetrate into the double-layer film of the bubble film, and its penetration ability can be expressed by the penetration coefficient E. After the defoamer penetrates, it needs to spread quickly, and its spreading ability can be expressed by the spreading coefficient S,
where γF is the surface tension of the foam medium; γDF is the surface tension of the defoamer; γD is the interfacial tension between the foam medium and the defoamer. When E>0, the defoamer can penetrate into the foam; when E<0, the defoamer cannot penetrate into the foam; when S>0, the defoamer can expand on the surface of the liquid film; when S<0 , the defoamer cannot expand on the surface of the liquid film. Therefore, only when E>0, S>0, the defoamer has a defoaming effect [4].
Defoamer defoaming principle 2:
The existence of foam in the liquid is caused by the adsorption of surface-active substances on the surface of the gas, resulting in the reduction of surface energy and the formation of an energy-stable system; the principle of defoamer is to change the distribution of surface-active substances on the surface of some bubbles, thereby changing the surface. The tension causes the internal pressure of these bubbles to change and merge into other bubbles, forming larger bubbles, but causing new imbalances and new mergers. The combined large bubbles are finally pushed out of the liquid by buoyancy, which is a process of defoaming; under the action of gravity, the bubble film on the surface of the liquid will gradually thin and finally rupture. The role of the defoamer is to accelerate the The process of thinning and breaking [5].
3. Standard basis for the application of defoamer in food production
Defoamers are divided into industrial-grade defoamers and food-grade defoamers. Food-grade defoamers that are not harmful to human body are added to food, so they can be eaten with confidence. However, as a food additive, the maximum dosage needs to be controlled, and excessive addition will also cause harm to the human body. Businesses who use defoamer as food additives must add them carefully in strict accordance with the requirements of my country's "GB 2760-2014 National Food Safety Standard_Standards for the Use of Food Additives". Industrial defoamer is strictly prohibited to be added to food.
At present, the defoamers licensed in my country include emulsified silicone oil, higher alcohol fatty acid ester compound, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropanolamine ether, polyoxypropylene glycerol ether and polyoxypropylene oxide. Vinyl glycerol ether, polydimethylsiloxane, etc.
This year, the price of raw materials in the chemical industry has generally risen, and some unscrupulous merchants have begun to make small calculations, such as using industrial-grade polydimethylsiloxane to pretend to be food-grade polydimethylsiloxane; industrial-grade emulsifier pretending to be food-grade emulsifier; What's more, in order to reduce the use of active substances and improve product performance, industrial-grade polyethers and silicone polyethers that are not listed in the list of raw materials are used in the production of food-grade defoamer. Outrageous!
However, according to national standards, it is safe to use a certain amount of food additives, and misuse of food additives will cause harm to the body, and even cause cancer and teratogenicity. At present, the problems of illegal use in the market mainly include the following four situations:
1. Use of additives that are not approved or banned by the state.
2. The use of additives exceeds the prescribed amount.
3. The use of additives exceeds the specified range.
4. Use industrial-grade additives instead of food-grade additives
Fourth, the development of the defoamer industry
According to Albany, NY, the defoamer market is expected to grow at a CAGR of 4.5% during the forecast period from 2022 to 2031. The silicone product type accounted for a prominent 44.7% share of the defoamer market in 2021 and is expected to maintain its dominance over the forecast period. Low surface tension, thermal stability, chemical inertness, and complete insolubility are promising properties that make silicone antifoams suitable for use in multiple industries including pharmaceutical, oil and gas, and food and beverage.
Relative to volume, Asia Pacific will hold a key share of 34.4% of the defoamer market in 2021. Rapid growth in several end-use industries including pharmaceuticals, paper and pulp, food and beverages, and textiles has created ample opportunities for the antifoams market in the region [6].
5. Research on the application of defoamer in food [7]
1) Defoamer in MSG production
The fermentation process of monosodium glutamate belongs to aerobic fermentation, and a large number of bubbles are generated in the process. The generation of bubbles will reduce the yield, inhibit the respiration of the bacteria, and reduce the acid production rate of the bacteria. Defoamers are the most economical and easiest way to suppress foam. Defoamers used in monosodium glutamate production usually include vegetable oil defoamers, polyether defoamers, and silicone defoamers. However, vegetable oil defoamers are not well stored, are easily deteriorated, have increased acid value, and are rarely used. Ether defoamers and silicone defoamers are widely used in the monosodium glutamate fermentation industry, and scholars have conducted many studies on this.
Domestic scholars Hu Ting and others used raw materials such as silicon paste, polyether, emulsifier, thickener, and water to obtain dimethyl silicone oil-organosilicon composite defoamer through stirring-heating-dissolving-layering-cooling operations. , the best experimental conditions are: high-speed centrifugation at 3000r/min for 30min, and storage at 75~85℃ for 72h. This defoamer is used in a monosodium glutamate factory fermentation tank, and the results show that this kind of organic silicon composite defoamer has better effect than the vegetable oil defoamer and organic silicon defoamer currently used, and has no effect on bacteria. The amount is small, the defoaming speed is fast, and the defoaming ability is strong, but its anti-foaming effect is general.
A foreign scholar M Stones has studied the silicone defoamer, and the result is that: because silicon refers to a special material with Si-O-Si backbone organic groups, it is the simplest polymer, namely polydimethylsilicon. Oxane (silicone rubber), these properties ensure that the silicone will migrate with a group into the bubbles at the gas-liquid interface, silicone and silicone copolymers are high polymer materials, polydimethylsiloxane, They can be combined to produce a wide variety of foam control agents with defoaming properties.
Li Yuee et al. conducted experiments on the polyether defoamer used in the fermentation of monosodium glutamate. The results show that the larger the molecular weight of the hydrophobic group of the polyether, the better the defoaming effect. When the molecular weight is greater than 3000, the polyether defoaming The defoaming effect of polyether defoamer is good. When the molecular weight is greater than 1500 and less than 2500, there is a good defoaming effect, while when the molecular weight is less than 1000, there is no defoaming effect; the defoaming effect of polyether defoamer increases with the increase of the hydrophilic group content. It will be reduced until the defoaming effect is lost, and it will even have the effect of assisting foaming. Only when the proportion of the hydrophilic group chain is within a certain range, the polyether defoamer will have a good defoaming effect. The comprehensive defoaming ability (including defoaming and anti-foaming) is affected by the concentration of the defoaming agent, and decreases with the increase of the concentration. The optimal concentration is: 5%~20%.
Some scholars have improved the use of polyether defoamer: first add a certain amount of defoamer to the culture medium, and heat and sterilize it into the tank together with the culture medium. In addition, the defoamer is formulated into a certain proportion of emulsion. After disinfection, the pressure is maintained with air. Depending on the rise of the foam in the fermenter, it can be "flowed" into the tank at any time, which can effectively reduce the amount of defoamer used.
2) Defoamers in sugar production
Different from the manufacture of monosodium glutamate, the sugar-making process adopts the concentrated crystallization method, and the defoamer is a commonly used industrial auxiliary in the sugar-making process. type, polyether type (such as PPE) and silicone type (such as F type), etc. Because polyglycerol fatty acid esters, namely N-type antifoaming agents, have good defoaming and antifoaming effects in the process of boiling sugar, the surface tension of syrup is greatly reduced, and it can also accelerate the sedimentation speed of sugar crystals and improve the filtration performance of syrup. Ester antifoams are the most widely used antifoams in the sugar industry.
Domestic scholars Chen Chaoyi and others have conducted experiments on N-type defoamer. The results show that the higher the concentration of N-type defoamer, the stronger the effect of defoaming and foam suppression. When the amount of defoamer added in syrup reaches 30mg/kg, it can be Obtain satisfactory defoaming and anti-foaming effects. There are also experts who use food-grade defoamer in the preparation process of isomalt oligosaccharides. The results show that food-grade defoamer can suppress foam and reduce surface tension, and food-grade defoamer can also prevent the product from being oxidized and protect the finished product. . Different defoamers are used for different sugars. In theory, non-toxic surfactants with a lipophilic and hydrophilic balance (HLB) in the range of 1 to 3 can be used as defoamers for sugar processing. difficult to determine theoretically
Links