Process of crystallization

Crystallization is an example of a separation process in which mass is transferred from a liquid solution, whose composition is generally mixed, to a pure solid crystal. Butter, margarine, ice cream, sugar, and chocolate all contain different types of crystals, although they all contain fat crystals. Ice cream has fat crystals, ice crystals, and sometimes lactose crystals. Key elements in the candy making process are in sugar's physical properties. Specifically, its solubility with its effect on the water's boiling point.

Crystallization occurs in two major steps.
*Nucleation: The appearance of a crystalline phase from either a supercooled liquid or a supersaturated solvent. The solute molecules or atoms dispersed in the solvent start to gather into clusters.
*Crystal growth: The increase in the size of particles and leads to a crystal state.

Nucleation involves formation of a crystalline state from the supersaturated liquid state. Once nuclei form, they grow into product-sized crystals through incorporation of additional molecules into the crystal lattice. This is called spontaneous nucleation.

Seed crystals are small crystals, generally of the solute, which then grow by deposition on them of further solute from the solution. This growth continues until the solution concentration falls to the saturation line. Below the saturation curve there is no crystal growth, crystals instead dissolve.

Controlling crystallization to obtain the desired crystal content, size distribution, shape, and polymorph is key to manufacturing products with desired functionality and shelf life. The crystalline phase plays such a large role in appearance, texture, spreadability, and flavor release in many food products including chocolate, margarine, butter, and shortening..
Process of crystallization

Food processing of smoking

Smoking foods is one of the most ancient food preservation processes and is some communities one of the most important. The use of wood smoke to preserve food is nearly as old as open air drying.

At first smoking of food could be considered a side effect due to preservation by drying in the fireplace. Later on, the process was developed and changed and was combined with other processes such as salted dried, and fermented.

Smoking has been mainly used with meat and fish. The main purpose are it imparts desirable flavors and colors to the foods and some of the compound formed during smoking have a preservative effect due to the presence of a number of compounds. 

Depending to the smoking procedure, the moisture drops 10-40%. Compounds present in smoke with bactericidal and antioxidative properties are deposited on and penetrate into the food especially meat. 

Important smoke ingredients include phenols, acids and carbonyl compounds.

Smoking of meat uses the heat of burning wood to cook the meat while adding flavor to the meat through the variety of wood being used. The wood used to generate the smoke should be of the hardwood species. In America, the wood varieties that are used are hickory, mesquite, oak, pecan, alder, maple, apple, cherry and plum.

Curing and smoking of meat are closely interrelated and are often practiced together, that is cured meat is commonly smoked and vice versa.

Meat exposed to temperature s of 165 to 185 degrees will fully cook. The best methods ensure meat in the smoker is fully cooked is to use a meat thermometer and probe into the deepest part of the cut to ensure the heat has reached all the way to the center.
Food processing of smoking

Breakfast pastry of France - Croissant

The croissant is the quintessential breakfast pastry of France and is ingrained in the daily French culture as much as the baguette. In the culinary inventory of the Patrimoine Francais, mention is made of a cake in the shape of a croissant served during a banquet given in Paris by the Queen of France in 1549 to commemorate the alliance of François ler with le Grand Turc.

It is a time-consuming labor of love, requiring more than just a few passes of the rolling pin.

Croissant pastry dough must be repeatedly folded, not stirred or kneaded numerous times over the closure of several hours. This folding produces layers in the dough, alternating layers of butter and dough.

When baked, the moisture in the layers of butter cerate steam and acts as the primary leavening agent in the croissant, puffing out to separate the layers of dough and creating that famously flaky texture so sought after in a croissant.

Croissant dough is softer, therefore requiring a soft roll in fat. Finished croissants also are a softer eating product, requiring fat with low solids.

To maintain the desired softness, croissant roll-in fat also usually has an emulsifier to enhance the shelf-life of the finished product.

The wheat flour should a pure one with strength and baking qualities slightly superior to ordinary bread flour.

Fats used for croissants – whether butter or margarine – should have good plasticity and stability. The moisture content of the butter should be 15% at most, and the point of fusion of margarine should not be higher than 36 ° C.
Breakfast pastry of France - Croissant

What is retrogradation?

Retrogradation is another important property of starch. Retrogradation refers to the occurrence where starch reverts or retrogrades to a more crystalline structure upon cooling.

In most products, retrogradation causes deterioration of quality and therefore retrogradation has to be avoided.

Both amylose and amylopectin may participate in a textural change that makes them somewhat more ‘gritty’ with time.

In particular it appears that retrogradation is the recrystallization of the amylopectin where the amylose molecules clump together and separate from the sol or gel, thus destroying the semi-elastic network on which its properties depend.

Retrogradation is more likely to occur in a high amylose starch. Starches with a very high amylose content undergo retrogradation less readily than those with a lower amylose content and such starches are commercially available to food manufacturers,.

This occurrence is noted in baked products that become ‘stale’ no longer ‘fresh’ tasting or ‘fresh’ handling.  It is also observed in leftover, long-grain rice.

Moreover, the term retrogradation can also be used to describe changes occurring during cooling from gelatinization temperatures as well as changes occurring during long-term storage.
What is retrogradation?

Interesterification process of fats and oils

Interesterification is a catalytic process involving the exchange of fatty acids between existing esters to form new esters.

When applied to a mixture to triacylglycerols, the available fatty acids are redistributed over all the possible triacylglycerol types.

The process is used in the edible oils and fats industry to alter the composition and therefore the physical properties of triacylglycerol mixture.

Basically there are three kinds of interesterification reactions, namely, ester-ester interchange, acidolysis and alcoholysis. Interesterification can be done chemically or enzymatically. Chemical interesterification is used industrially to produce fats and oils used in margarines, shortening and confectionary fats.

The purpose of interesterification:
*Modify the melting point. The process rearranges the distributions of the fatty acids in the triglycerides, therefore producing products with melting and crystallization characteristics different from the original blend.

*To slow rancidification

*Create oil more suitable for deep frying

*Making margarine with good taste and low saturated fat content

Interesterification of palm oil with pam seeds or coconut oil (2:1) and to use of 6 parts of this product with 4 parts of sunflower provides a margarine which contains 20-25% w/w of linolenic acid and does not contain hydrogenated fat.
Interesterification process of fats and oils

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.
Hydrogenation process

Starch gelatinization

Starch is the most common carbohydrates polymer in foods. It is known to go through transformation and gives diverse physical structures and properties.

When starch granules are heated in the presence of water, the granules eventually lose the double-helical crystalline structure and the Maltese cross. This process is known as gelatinization.

Starches of different botanical sources and genetic backgrounds display different gelatinization properties, including gelatinization temperature, enthalpy change and melting of amylose-lipid complex.

The gelatinization of starch is an irreversible process, and each starch has its own characteristic gelatinization temperature.

Water acts as a plasticizer during starch gelatinization, lowering the melting temperature of starch. This decreases the glass transition temperature of the non-crystalline regions of native starch and leads to melting of the crystalline parts as temperature is increased.

Starch gels are composites of swollen gelatinized granules embedded in a continuous amylose network.

When the gelatinized starch is continuously heated in excess water, the starch granules swell, develop viscosity and become a paste. This is known as pasting.
Starch gelatinization

Process of mastication

Mastication is a complex process which pieces of food are crushed and ground by teeth and bought into a condition which is safe to be swallowed. When food is introduced into the mouth, it is moved by the tongue and then pressed against the palate which serves to indicate morphology.

A mouth-size portion of food is usually around 5 g. During mastication, this will usually be reduced by 2 to 3 orders of magnitude before going to the stomach.

During the chewing process, food particles are positioned on the surface of teeth by the cheek and tongue. The tongue, cheeks and lips are able to push the food between particular teeth.

As mastication continues, food is ground into fine particles, mixed with saliva and formed into a bolus. Oral secretion of saliva is by the salivary glands located under the tongue, between the jaw bones, at the lower jaw and beneath the ear.

A combination of mastication and saliva also causes aggregation of hard particles derived from brittle foods during mastication.

The rate of food is broken down during mastication are all important aspects of food texture. It is include the size, shape and mechanical properties.

The term ‘texture’ is used to describe how foods properties respond during the mastication process with respect to all mechanical and tactile.

The type of material strongly affects the average duration of mastication, for example an average mastication and swallow time of 22 seconds for hard solids such as peanuts and biscuits and 9 seconds for soft solid such as bananas and spreads, while low viscosity liquids reside in the mouth for around a second.

The reduction of the size of the food particles during the mastication process is also highly relevant to the flavor release of that food.

Flavor release is the substance in the food that finally reaches the flavor-sensitive organs located in the nose.

This process of mastication imparts pleasurable sensations that seem to fill a very basic human need. Chewing is a sensual that people enjoy throughout life, from the cradle to the grave.
Process of mastication

The process of gelatinization

Gelatinization occurs when starch granules are heated in a liquid. It is responsible for the thickening of food systems. The process is an important physic-chemical change associated with the cooking of starchy materials.

When the liquid is heated, the hydrogen bonds holding the starch together weaken, allowing water to penetrate the starch molecules, causing them to swell until their peak thickness is reached.

During the gelatinization, water will be absorbed into the individual starch granules and held there tightly, actually becoming bound water. Bound water is no longer able to flow; the water that is bound in the granules causes granule themselves to swell significantly.

The gelatinizes starch mixtures are opaque and fragile and the ordered crystalline structure of starch is lost.

Gelatinization takes place over a temperature range that varies according to the source of starch and its amylose/amylopectin ratio.

The most important factors that affect the gelatinization temperature are:
*Type of starch
*Amount of tenderizer: sweeteners and fats
*Amount of acid

The process of gelatinization

Crystallization in foods

The process of forming crystals from solution is known as crystallization. It is important unit operation for separation of solids in dissolved form in a solution by making used of the principles of saturation solubility, temperature or solubility and temperature.

Crystallization is a term that describes several different phenomenon related to the formation of a crystalline lattice structure.

Crystallization is often a four step process that includes:
*Generation of a supersaturated state
*Nucleation – formation of nuclei
*Propagation – crystal growth
*Maturation – crystal perfection or continued growth

The liquid phase remaining after the formation of the crystals is called ‘mother liquor’.

In the food industry, crystallization may serve for the recovery of crystalline products – (sugar, glucose, lactose, citric acid, salt), for the removal of certain undesirable components or for modification of certain food products in order to obtain a desirable structure.

Several materials may also crystallize during food processing.

Crystallization of triglycerides 

Crystallization of triglycerides is a complex phenomenon characterized by fairly slow growth rates and polymorphic transitions of their crystallized phases.

The crystallization of triglycerides is also complicated by the presence of minor components frequently contained in them. For examples, milk fat consists of 95-98% triglycerides but also contained diglycerides, free fatty acids, monoglyceride, phospholipids and sterols as minor components.

Crystallization of sucrose
Crystallization is the final step in the recovery of sugar from sugar cane or sugar beet. Also called ‘sugar boiling’, sugar crystallization of sugar is a complex process requiring precise control, skill and experience.

Crystallization process is used as a unit operation for separation of solids from the liquids or as a process tool for processing certain foods item.

In the separation process, in some cases the solids are the desired products, whereas in others liquid is the desired product.
Crystallization in foods

Food Safety In History

Food Safety In History
Before manufacturing traditional, farming practices and preserving techniques were used to ensure safe food.

During industrial revolution, food began to be processed and packaged. Lacking regulation, manufacturers were free to add whatever they liked to their products. Sweeping from the floor were included in pepper, lead salts were added to candy and cheese, textile inks were used as coloring agents, bricks dust was added to cocoa, and copper salts were added to peas and pickles.

In the 1880s, women started organizing groups to protest the conditions at slaughterhouses in New York City and adulterated foods in other parts of the country.

In 1883, Harvey W. Wiley, chief chemist of the U.S Agricultural Department’s Bureau of Chemistry, began experimenting with food and drug adulteration.

Meanwhile, Upton Sinclair spent several weeks in a meat packing plant investigating labor conditions and turned his discoveries into a book, The Jungle, published in 1906. Although the focus of that book was the conditions immigrants experienced in the early twentieth century, there were graphic descriptions of the filth and poor hygiene in packing plants. It caught the public attention.

People began complaining to Congress and to President Theodore Roosevelt. Pressure was also mounting from foreign governments that wanted some assures that food imported from United States was pure and wholesome.

Two acts were passed in 1906, the Pure Food and Drug Act and the Beef Inspection Act, to improve food safety conditions.

In 1927, U.S Food, Drug and Insecticide Administration (shortened to Food and Drug Administration) or FDA was created to enforce the Pure Food and Drug act.


The Pure food Act was later superseded in 1938 by Pure Food, Drug and Cosmetics Act. This act prohibited any food or drug that is dangerous to health to be sold in interstate commerce.

In 1958, concern over cancer led to the adoption of the Delaney Amendments, which expanded the FDA’s regulatory powers to set limits on pesticides and additives. Manufacturers had to prove that additives and pesticides were safe before they could be used.

The Fair Packaging and Labeling Act of 1966 standardized the labels of products and required that labels provide honest information.

The next major act was the Food Quality Protection Act of 1996. It set new regulations requiring implementation of Hazard Analysis and Critical Control points (HACCPs) for most food processor.

The Food quality Protection Act also changed the way acceptable pesticide levels are calculated. Now total exposure for all sources must be calculated.
Food Safety In History