Oil in noodle processing

In noodle processing, the frying is an important step which is conducted to dehydrate the gelatinized noodle strips in a short time such that dried noodles having quick reconstitutability are obtained.

Vegetable oil such as palm oil, sesame oil or rapeseed oil; an animal oil/fat such as lard; or a hydrogenated oil/fat thereof is used in general.

The frying process not only enables high productivity but also provides easy-to-eat property and favorable roast and savory flavor.

Oil uptake during the frying process in instant noodles is important in view that it imparts a distinct flavor, mouth-feel and improves product acceptability. However, higher oil uptake accounts for raising health concerns.

During frying process, the surface temperature of the instant noodles increases rapidly after being placed in the hot oil. The water on the instant noodles surface immediately goes into a boiling state, which causes instant noodles to dry out, and thus heat and mass exchange takes place.

The process leads to shrinkage and raises the level of porosity and roughness. The moisture contained in the gelatinized starch granules evaporates due to the high temperature. The empty spaces previously occupied by the moisture are next partially filled with oil.

When whole grain flour was used, the oil content of the fried noodles decreased by up to 30% compared with those made from white flour.

The wheat cultivar also affected the oil content of the fried noodle and the dough development time during noodle making was negatively correlated with oil uptake. Conversely, oil content has been found to increase as the dough mixing time increased.

Krokida in 2000 have reported an increase in oil content with longer frying times, especially for thinnerproducts, which has been related to the microstructure developed during frying. (J. Food Eng. 44, 39–46)

Pinthus and Sam Saguy (1994) have also stated that crust porosity increases with frying time thus contributing to increased oil uptake. (J. Food Sci.59, 804–807)
Oil in noodle processing

Expeller pressure

An expeller press is a screw-type machine. The principle of the expeller press is to force the material to be extracted into a tapering tube by means of a rotating screw. The tube is perforated along its length by narrow slits and terminates in an adjustable cone that gives a variables gap between the cone and the tube exit.

The machine uses friction and continuous pressure from the screw drives to move and compress the material. The fat is forced out through the tube slit.

In processing of natural oils, the oils are crushed from seeds or grain, using the hydraulic action of an expeller press. No heat is involved in the pressing and no chemical antioxidants are added to preserve the oils. The oils seeps though small openings that do not allow seed fiber solids to pass through.

Expeller pressing yields less oil than solvent extraction, usually 50 to 70 percent of the oil, so expeller-pressed oils are usually more expansive than conventionally processed oils.
Expeller pressure

The reasons of hydrogenation process

Hydrogenation is a major type of chemical process. Hydrogenation of triglyceride oils may be defined as the reaction of the carbon-carbon double bonds of the fatty acids with hydrogen. The reaction is carried out in the presence of a catalyst, to form a solid or semi-solid mixture.

Consequently the fatty acid become saturated and thus, less prone to oxidation and attain a high melting point.

The first patent for the hydrogenation process was by William Norman in 1903. The process has affected the whole food industry because the lipid by-product from the manufacture of high-protein feeds from soybeans, cottonseeds, etc.

The hydrogenation process is an important tool for the edible fats and oils processor. With hydrogenation, liquid oils can be converted into plastic or hard fats more suitable for a particular food product.

The purpose to hydrogenate fat or oil:
*To change the physical form for product functionality improvement
*To improve oxidative stability

It is a complex process, requiring the right catalyst type and quantity, the right combination of process conditions and the optimum processing time, reflecting upstream and downstream, capacity; it is mass transfer limited.

Hydrogenation is used to convert liquid oils to semi-solid plastic fats that are suitable for margarine, shortening and specialty products.
The reasons of hydrogenation process

Frying of food

Frying, especially deep frying has become the most popular food preparation technology during the last five decades.

The frying technology is important to many sectors of the food industry, including suppliers of oils and ingredients, food service operators, food industries and manufacturers of frying equipment.

Fried food is food that has been cooked in a large amount of fat (as in deep frying) or a small amount of fat. 

The fat is absorbed into the surface of the food, and the heat of the changes the character of the food, shrinking it slightly and changing its color.

Shallow frying is a dry heat method of cooking, where prepared food is cooked in a pre-heated pan or metal surface with a small quantity of fat or oil.

Shallow frying is a fast method of cooking because heat is conducted from the hot surface of the cooking pan directly to the food.

Deep frying is a dry heat method of cooking, where prepared food is cooked in preheated fat or oil.

It is a very important method of cooking because it is fast, convenient and deep fried foods are generally liked for flavor and texture.

The fats used for frying gradually undergo certain chemical changes during use. The most important changes are:
Color formation
Oxidation
Polymerization
Hydrolysis

The main change in the food composition during frying is the loss of water and its replacement with frying oil. In contact with hot frying oil, water is rapidly covered into steam at least in the surface layer of fried material.
Frying of food