What are Pectins?

Pectins are soluble polysaccharides of plant origin obtained by aqueous extraction of edible vegetable fiber (usually citrus fruits or apples), followed by precipitation with alcohol and salts.

Pectins are carbohydrates used as gelling, thickening, and stabilizing agents due to their hydrocolloid properties.

General Characteristics of Pectins

1. Integration:

Integration process to avoid the formation of lumps:

• Mix the pectin with the sugar of the recipe in a proportion of 1-5 respectively.
• Gradually incorporate into the liquid part in the form of rain while mixing vigorously with rods.

It could also be dispersed first in a non-aqueous medium such as oil, or in a concentrated sugar solution > 65 °Bx

2. Activation:

The activation of the gelling characteristics of pectins is obtained from 80/85°C. A slow and progressive boil is convenient so that the pectin hydrates correctly. The cooking time can be extended once the boiling point is reached if the type of recipe requires it.

It may be difficult to dissolve if there is too high a calcium content (80 ppm a++). In this case, it would be necessary to add salts that neutralize the calcium.

3. Dispersion:

The correct dispersion of the pectin will depend on the medium and the process.

It disperses better with heat treatment and mixing or homogenization.

4. Stability and Conservation:

To maintain its characteristics unaltered, pectin should be stored in a cool, dry place. Temperatures higher than room temperature determine a degradation of the pectin due to a reduction in molecular weight.

The optimum pH of pectin is between 2.8 and 4.7.

5. Texture

Gelation is obtained during the cooling process.

The final texture is obtained after 24 hours.

Classification of Pectins

Pectins are classified based on the degree of methoxylation (DM) into 2 groups:

• HM (high methoxyl): DM ≥ 50% of methoxyl groups.
• LM (low methoxyl): DM ≤ 50% of methoxyl groups.

It is defined as degree of methoxylation, the relationship between the methoxyl groups and those free acids present in the molecular chain of pectin.

The degree of methoxylation affects the properties of pectin, in particular the gelling conditions.

High Methoxyl Pectins (HM)

These pectins in aqueous solution give rise to suspensions of high viscosity forming strong and cohesive gels.
This type of pectins are heat resistant.

Gelling conditions:

1. They can form a gel only if the content of total soluble solids (TSS) (Brix) is equal to or greater than 60% with a maximum of 80%.
2. The pH required for gelling should be between 2.0 and 3.5.

Reactivity:

• The higher the concentration of soluble solids (TSS) (Brix), the greater the strength of the gel obtained and the higher the gelling temperature.

An excess of soluble solids or brix causes the gel strength to decrease.

The lower the pH, the higher the gelling temperature, consequently a faster gelling will be obtained. pH values below 2.0 can cause gelling problems.

The pH variation is very important. 0.1 pH units can lower the gelling temperature by up to 10 ºC.

Low Methoxyl Pectins (LM)

Characteristics:

• The LM pectin family is divided into LMC (conventional low methoxyl) and LMA (amidated low methoxyl).
• They are thixotropic. After a cold mixing process, they gel again.
• Depending on the dosage and hydration temperature, they act as thickeners.

Gelling conditions:

1. They form a gel only in the presence of Calcium ions (Ca++).
2. They can gel with low values of soluble solids (Brix) and a very wide pH range.

Reactivity:

• Low methoxyl pectins form gels with a gel strength that is greater with a greater amount of calcium. Too much calcium can deconstruct the gel.
• The presence of sugar or soluble solids greatly reduces the amount of calcium needed for proper gelling.
• A low pH increases the reactivity of the pectin.

Conventional Low Methoxyl Pectins (LMC)

Conventional low methoxyl pectins (LMC) are low methoxyl pectins obtained from HM pectins by physicochemical procedures.
LMC pectins form transparent and thermally irreversible gels.

Amidated Low Methoxyl Pectins (LMA)

Amidated pectins (LMA) are low methoxyl pectins obtained from HM pectins by alkaline extraction.

1. LMA pectins are thermoreversible.
2. The contribution of calcium favors a greater reactivity and final hardness of the gel.
3. The greater the amount of soluble solids and the lower the pH, the stronger and more cohesive gels are also obtained.
4. Depending on the type of pectin and the dispersion medium, different hardness values are obtained.

Masterclass on Pectins

To go much further on the functionalities of pectins, their classification and development of the graphs shown above, we have created a Masterclass with Jordi Bordas and Óscar Albiñana that you can see in the following link: