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Caramelization is one of the most important types of browning processes in foods, together with Millard reactions and enzymatic browning. Caramelization leads desirable colour and flavour in bakery's goods, coffee, beverages, beer and peanuts. Undesirable effects of caramelization are for example burned sugar smell and blackening.

Caramelization causes important changes in foods, not only in colour but also in flavour. As no enzymes are involved in the caramilization process, it is a non-enzymatic browning reaction.

Caramelization occurs during dry heating and roasting of foods with a high concentration of carbohydrates (sugars).

Simply speaking, caramelization is the process of removal of water from a sugar (such as sucrose or glucose) followed by isomerization and polymerisation steps. In reality the caramelization process is a complex series of chemical reactions, which is still poorly understood.

The process of caramelization starts with the melting of the sugar at high temperatures, followed by foaming (boiling). At this stage saccharose (sugar) decomposes into glucose and fructose. This is followed by a condensation step, in which the individual sugars lose water and react with each other to for example difructose-anhydride. The next step is the isomerization of aldoses to ketoses and further dehydration reactions. The last series of reactions include both fragmentation reactions (flavour production) and polymerization reactions (colour production).

Caramelization starts at relatively high temperatures as compared to the other browning reactions, and depends on the type of sugar. Table 1 below shows the initial caramelization temperatures of some common carbohydrates. This table is based on pure carbohydrates. In foods often several different carbohydrates and other components are present; all these may influence the caramelization temperature as well as the different steps and reactions, and thus the final flavours and colours that are produced.

Table 1: Initial caramelization temperatures of common carbohydrates

Sugar Temperature

Fructose 110° C

Galactose 160° C

Glucose 160° C

Saccharose 160° C

Maltose 180° C

The Maillard reaction is not a single reaction, but a complex series of reactions between amino acids and reducing sugars, usually at increased temperatures. Like caramelization, it is a form of non-enzymatic browning.

In the process, hundreds of different flavour compounds are created. These compounds in turn break down to form yet more new flavour compounds, and so on. Each type of food has a very distinctive set of flavour compounds that are formed during the Maillard reaction.

Enzymatic browning is a chemical process which occurs in fruits and vegetables by the enzyme polyphenoloxidase, which results in brown pigments. Enzymatic browning can be observed in fruits (apricots, pears, bananas, and grapes), vegetables (potatoes, mushrooms, lettuce) and also in seafood (shrimps, spiny lobsters and crabs).

Enzymatic browning is detrimental to quality, particularly in post-harvest storage of fresh fruits, juices and some shellfish. Enzymatic browning may be responsible for up to 50% of all losses during fruit and vegetables production.

What are emulsifiers and why are they used?

Add oil to water and the two liquids will never mix. At least not until an emulsifier is added. Emulsifiers are molecules with one water-loving (hydrophilic) and one oil-loving (hydrophobic) end. They make it possible for water and oil to become finely dispersed in each other, creating a stable, homogenous, smooth emulsion.

Bread

It is possible to make bread without emulsifiers but the result is often dry, low in volume and easily stales. As little as 0.5% emulsifier added to the dough is enough to achieve an enhanced volume, a softer crumb structure and a longer shelf-life. There are two types of emulsifiers used in bread: dough strengtheners (e.g. diacetyl tartaric acid esters (E472e) and sodium or calcium stearoyl-2-lactylate (E481, E482)) and dough softeners (e.g. mono- and di-glycerides of fatty acids (E471)). Dough-strengthening agents make the dough stronger and result in bread with an improved texture and volume. Dough-softening agents allow obtaining a softer crumb structure and increased shelf-life.

What are saturated and unsaturated fats ?

Fats in foods, or, more correctly, their fatty acids, are of three main types, saturated, monounsaturated and polyunsaturated.

Saturated fatty acids carry a full quota of hydrogen atoms in their chemical structure. This is the type that increases the amount of cholesterol in the blood and is considered a risk factor in heart disease; animal fats are the main source.

When one pair of hydrogen atoms is missing, the fatty acids are termed monounsaturated. They do not raise blood cholesterol and may even be beneficial. The main sources are olive oil and rapeseed oil (used in some margarines and low fat spreads).

When more than one pair of hydrogen atoms is missing, the fatty acids are termed polyunsaturated. They predominate in most vegetable oils. Most appear to have no effect on blood cholesterol levels but are useful if they replace saturates in the diet. However, those found in fatty fish and fish oils (termed omega-3 polyunsaturated) are considered to help to lower cholesterol and therefore to be beneficial.

What is a hydrogenated vegetable oil?

Vegetable oils, as the name implies, are liquid at room temperature. To make them suitable for use in margarines and shortenings, they are hydrogenated, i.e. treated with hydrogen, to solidify them. The hydrogenation process makes them more saturated.

BAKERY PRODUCTS pH

Bread 5.3 - 5.8

Eclairs 4.4 - 4.5

Napoleons 4.4 - 4.5

Biscuits 7.1 - 7.3

Crackers 7.0 - 8.5

Cakes

Angel food 5.2 - 5.6

Chocolate 7.2 - 7.6

Devil's food 7.5 - 8.0

Pound 6.6 - 7.1

Sponge 7.3 - 7.6

White layer 7.1 - 7.4

Yellow layer 6.7 - 7.1

Flour 6.0 - 6.3