The Effect of Smoke Content on Products

Has a great influence on the composition of the smoke. When burning, the more oxygen there is, the more wood resin oil in the smoke, while the aldehyde and phenol components decrease.

+ Fuel moisture (about 30-40% is good)

High fuel humidity, when burned, will have a lot of dust, smoke, ash particles and acid, making the product smell and taste worse. If the amount of dust and ash is too much, the product will be black and dirty, the amount of acid (especially formic acid) will make the product have an unpleasant smell and taste.

The high humidity of the fuel, the small amount of heat released will prolong the smoking time, but if the humidity is too low, when burning strongly, little smoke will be emitted, high temperature will produce harmful components.

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2.4.3.4 Effects of smoke on products

- The deposition of smoke on the surface of the product: is the first step of the smoking effect (called dialysis).

+ Colloidal properties of smoke: smoke is a very complex air-dissolved colloidal system.

+ Main factors affecting the deposition of smoke: the more unstable the smoke system, the greater the deposition effect; the impact of various forces; the impact on the surface properties of the product.

- Smoke penetration: after settling on the surface of the product, it begins to gradually penetrate into the product. When smoke particles adhere to the product, the ingredients in the smoke will penetrate, especially those that are soluble in water.

+ Main factors affecting the absorption of smoke: composition, temperature, humidity, smoke concentration; structure and condition of the product itself; smoking method and time.

2.4.3.5 Antiseptic and antiseptic effects of smoke

Through research, smoke has the ability to disinfect and therefore has the ability to prevent rot, but the anti-rot effect of smoke is stronger, these two points are closely related to each other.

2.4.3.6 Antioxidant effects of smoke

Smoked products have a pronounced antioxidant effect, which is the most important characteristic of smoke.

2.4.3.7 Effect of smoke composition on products

- Affects the color and taste of the product

When smoked, smoked products have their own flavor and color. The formation of color and flavor is due to the complex synthesis of many substances left for the senses.

- Affects nutritional value.

Phenols and polyphenols react with sulfhydryl groups of proteins, and carbonyl groups from smoke react with amino acids. Both of these reactions reduce the nutritional value of proteins, as they reduce the nutritional value of amino acids, especially lysine.

Smoking can degrade the structure of thiamine but has little effect on niacin and riboflavin. The antioxidant role of wood smoke will help stabilize fat-soluble vitamins and will also prevent oxidation of the surface of the product. Therefore, smoking is considered to be a processing method with high nutritional value.

- Affect human health

There has never been any discovery of poisoning from smoked products. However, we must also admit that there are some harmful substances of the phenol and aldehyde type. [9]

2.4.3.8 Effects of basic smoke components on products

+ Phenolic compounds

There are about 20 different phenolic compounds in the composition of smoke, the most common being guaiacol. 4-methylguaiacol, phenol, 4-ethylguaiacol, o-crezol, etc. It is found that phenolic compounds have the effect of resisting oxidation processes, giving flavor to products and destroying microorganisms that contaminate food.

+ Alcohol compounds

Various alcohols have been found in smoke, the most common and simplest being methanol. Alcohol does not play a significant role in imparting colour or flavour to smoked products although it does have a minor effect in killing microorganisms.

+ Organic acids

Organic acids in smoke have carbon chains ranging from 1 to 10 carbon atoms, of which acids with carbon chains from 1 to 4 atoms are the most numerous.

such as formic acid, acetic acid, propyonic acid, butyric acid, etc. appear in the vapor phase of smoke. Acids appear in the solid phase of smoke (plastic droplets).

Organic acids do not affect the smell of smoked products, they only have a small preservative effect in reducing the pH of the product surface, at the same time they have an effect in coagulating the protein on the surface of the smoked product, together with the temperature it forms the outer shell of the smoked product.

+ Carbonyl compounds

There are about 20 carbonyl compounds found in the composition of smoke: 2-pentanone, 2-butanone, butanal, acetone, propanol,…

In carbonyl compounds, the volatile type will give flavor to smoked products, partly giving color to the product, especially carbonyl compounds with short carbon chains.

+ Hydrocarbon compounds

Many polycyclic hydrocarbon compounds are found in smoked foods. These include Ben[ ] anthracene, dibenz[ , h] anthracene, ben[ ] pyrene,… Of these, at least dibenz[ , h] anthracene, ben[ ] pyrene are substances that are recorded as carcinogens in animals. However, these compounds exist at very low levels. Nowadays, by special smoking methods, these hydrocarbon compounds are eliminated.

+ Other gases: Components of smoke such as CO2 , CO penetrate into fish meat to create carboxylmyoglobin, carbonmonoxide-myoglobin, at the same time oxygen combines with myoglobin to form oxy-myoglobin or met-myoglobin to create red pigment. [3]

2.4.4 Drying process

2.4.4.1 Changes during the drying process

a. Purpose

Separates part of the water in the raw material itself, reducing the mass of the products. Increases crispness and flexibility, maintaining the characteristic properties of the product. At the same time, limits the growth of microorganisms, prolonging the storage time.

b. Physical transformation

It is the movement of moisture from the inner layer to the surface, from the surface to the environment due to the evaporation of water from the surface, creating a humidity difference between the inner layers and the surface of the material, leading to some changes such as:

 The phenomenon of volume contraction, density increase, mass decrease.

 Thermal transformation creates temperature gradients on the outer and inner surfaces of the material.

 Changes in physical properties include deformation, shrinkage, increased brittleness or cracking.

c. Chemical change

As the temperature increases, it promotes the following reactions: oxidation-reduction reaction, Maillard reaction, protein decomposition reaction, but then the reaction rate gradually decreases due to the decrease in water content in the raw material.

d. Biological transformation.

Temperature has a great influence on the outer surface as well as the internal structure of the product:

 Regarding cell structure: temperature irreversibly denatures protoplasm and water. In addition, it also changes the structure of tissues.

 Regarding microorganisms: they are inhibited or destroyed on the surface of the material. However, some species can still grow, such as molds.

 Regarding enzymes: most of the enzymes in the raw materials themselves have been denatured under high temperature conditions.

e. Sensory

- Color: strongly changed, most of the original color of the raw material is lost, forming characteristic colors of the product due to caramelization reaction, melanoidin and oxidation reaction of polyphenols.

- Odors: some odors are formed but some aromatic substances are also carried away by moisture, some are destroyed by heat.

- Taste: reduced moisture leads to increased product taste, especially sweet and salty.

- State: associated with physical and chemical changes such as increased elasticity, toughness, swelling, brittleness and changes in shape. Regarding size, some products shrink in size, which can cause the product to become distorted, bent, etc.

2.4.4.2 Factors affecting the drying process

- Drying temperature: increasing the drying temperature increases the drying speed, but within a certain range, if the drying temperature is too high, the product will be burnt, discolored, some amino acids will be destroyed and the product may take a long time to dry. If the drying temperature is too low, the drying time will be prolonged, creating conditions for microorganisms to grow and damage the product.

- Drying air humidity: the lower the drying air humidity, the faster the drying speed. If the humidity is too high, the outer surface will become dry and hard, affecting the moisture release ability of the material.

- Wind speed or air circulation inside the device: low speed means long drying time but too high speed means uneven drying temperature. Average speed is about 0.4-0.6 m/s. Parallel air circulation means faster drying speed.

- Characteristics of the raw material to be dried: the thickness of the raw material is the distance for moisture to move from the inside to the surface. The thicker the raw material, the larger this distance, the longer the drying time. The porous the raw material, the faster the drying time and vice versa. The ingredients of the dried raw material such as soluble substances that can bind with water will limit the speed of moisture movement.

2.4.5 Preservation process

Changes during storage:

2.4.5.1 Moisture absorption

When the air humidity is high, the product will absorb moisture. When the saturation pressure on the surface of the raw material is less than the partial pressure of water vapor in the air, the product will absorb moisture.

Products will rot after absorbing moisture. Therefore, preventing moisture absorption is the most important issue in the preservation process.

2.4.5.2 Putrefaction and deterioration

The more water in the product, the faster the rate of spoilage. In addition, discoloration may also occur.

2.4.5.3 Product oxidation

The fat of aquatic animals contains many unsaturated fats, which are easily oxidized when exposed to air. The oxidation process usually occurs automatically and continuously. But when a certain substance is produced, it automatically stops.

2.4.5.4 Product quality and shelf life

+ Quality of smoked products

Smoked fish has high nutritional value, the Protein and Lipid content is much higher than the original fresh material due to the loss of moisture during the drying process. Although a certain amount of water-soluble Protein is lost, the content is not greater than 1% of the total Protein. Smoke affects amino acids, changing some chemical properties of functional groups within a limited range and does not significantly affect the nutritional value of protein in the product.

+ Product storage time

Smoked fish is generally a highly perishable product and should therefore be stored at cold temperatures. Shelf life depends on many factors, but the most important are the starting materials, salt concentration and moisture content of the product. Smoking temperature, smoke composition, packaging type, hygiene conditions and storage temperature also greatly affect shelf life.

2.4.5.5 Effects of smoked foods on human health

Although smoked products contain some substances of the phenol and aldehyde type that are harmful to human health, in reality there has been no case of poisoning from eating smoked food. The reason is that the amount of these substances is very small, as prescribed, the amount of formaldehyde in food is not more than 20mg%, so it cannot be toxic to humans. On the other hand, when people eat smoked food, through chemical and biochemical effects, their toxicity is reduced or eliminated. [2]

2.4.5.6 Research situation at home and abroad

Doan Thi Kieu Tien. 2002. Through the experiment " research on smoked seasoned snakehead fish fillets ", it was concluded that: a salt ratio of 10% and a salting time of 60 minutes will create a delicious taste for the product; preliminary drying for 60 minutes at a temperature of 50-60 0 C will bring the raw material to the appropriate humidity for the smoking stage; for 30-40 minutes at 60-70 0 C will be the best for smoking; for the finished product, continue drying at 60-80 0 C for 8 hours will create a product with the best quality and sensory value, and be stored at a cool temperature (20-22 0 C).

Pham Thi Can Tho,. 2003. Through " research on smoked pangasius fillets ", it was concluded that: the seasoning ratio of 5% salt and 7% sugar, marinating time of 60 minutes will create a delicious taste for the product; pre-drying for 180 minutes at a temperature of 45-50 0 C will bring the raw materials to the appropriate humidity to enter the smoking stage.

Smoke; in 70-80 0 C for 9 hours will produce a product with the best quality and sensory value, and is stored at 10-15 0 C.

Ngo Thi Thu Phan, 2010. Through the experiment " researching the process of seasoned and smoked tuna fillets ", it was concluded that: the ratio of salt 5%: sugar 10% and the salting time of 60 minutes will create a delicious taste for the product; pre-drying for 45 minutes at 55 0 C will bring the raw materials to the appropriate humidity to enter the smoking stage; for 45 minutes at 55 0 C will be the best smoked; for the finished product, continue drying at 60-80 0 C for 3 hours will create a product with the best quality and sensory value, and can be preserved at 5 0 C for 7 days.

Huynh Thanh Long. 2011. Through the experiment " Research on the production process of smoked seasoned mackerel fillet products ", it was concluded that: the ratio of salt 10%: sugar 10% and the salting time of 60 minutes will create a delicious taste for the product; pre-drying for 40 minutes at a temperature of 80-85 0 C will bring the raw materials to the appropriate humidity to enter the smoking stage; for 60 minutes at 80-85 0 C will be the best smoked; for the finished product, continue drying at 80-85 0 C for 4 hours will create a product with the best quality and sensory value, and be stored at room temperature (30 ± 2 0 C) for 10 days.

From there, this study with different salting ratios and times; pre-drying, smoking, drying temperatures and times; and different preservation methods and times for small and fatty raw materials.

Originating from Europe and America, there are many research topics on smoked products with diverse products: smoked pork, smoked beef, smoked chicken, smoked sausage, ... and smoked seafood is also very rich, you can refer to the documents of Antonios E. Goulas, Michael G. Kontominas. Effect of salting and smoking-method on the keeping quality of chub mackerel (Scomber japonicus): biochemical and sensory attributes. Department of Chemistry, Laboratory of Food Chemistry and Technology, University of Ioannina, GR-45110 Ioannina, Greece, but the survey on smoked mackerel raw materials has not found any foreign sources.

PART III: RESEARCH METHODS AND METHODS

3.1 Place and time of implementation

Location: Laboratory of Department of Nutrition and Processing, Faculty of Aquaculture, Can Tho University.

Internship period: January 2012 to May 2012.

3.2 Experimental equipment

3.2.1 Materials

- Knife

- Cutting board

- Tray

- Basket

3.2.2 Machinery and equipment

- Electronic scale accuracy is ± 0.01g