Pectin is a polysaccharide derived from soluble plants which is obtained by water extraction from edible plant fibre (generally citrus fruits or apples), followed by precipitation with alcohol or salts.
It is a carbohydrate used as a gelling agent, thickener and stabiliser due to its hydrocolloid properties.
General characteristics of pectins
1. Incorporation:
The incorporation process to prevent
lumps from forming:
- Mix the pectin with the sugar stated in the recipe at a ratio of 1:5 respectively.
- Gradually sprinkle into the liquid part while mixing vigorously with a whisk.
It can also be dispersed, first, in a nonaqueous medium like oil, or in a concentrated sugar solution of > 65 °Bx.
2. Activation:
The gelling characteristics of pectin are activated from 80/85 °C. Slow and gradual boiling is good so that the pectin hydrates properly. The cooking time may be extended once it comes
to boiling point if the type of recipe requires so.
Dissolving may be difficult if the calcium content is too high (80 ppm Ca++). In this case, you should add more salt to neutralise the calcium.
3. Dispersion:
Correct dispersion of the pectin will depend on the medium and process.
It disperses best with thermal treatment and mixed or homogenisation.
4. Stability and preservation:
So as pectin’s characteristics remain unchanged, it must be kept in a cool, dry place. Higher temperatures compared to the ambient temperature lead to degradation of the pectin due to a
reduction in the molecular weight.
The optimum pH of pectin is between 2.8 and 4.7 inclusive.
5. Texture:
Gelation occurs during the cooling process.
It takes 24 hours to obtain the final texture.
Pectin classification
Pectin can be classified into 2 groups based on the degree of methoxylation (DM):
- HM (high methoxyl): DM ≥ 50% methoxyl groups.
- LM (low methoxyl): DM ≤ 50% methoxyl groups.
The relationship between the methoxyl groups and free acids present in the pectin molecular chain is defined as the degree of methoxylation.
The degree of methoxylation influences the properties of the pectin, particularly the gelatinisation conditions.
High methoxyl pectins (HM)
In an aqueous solution, these pectins produce suspensions with high viscosity that form strong and cohesive gels.
This type of pectins are heat resistant.
Gelation conditions:
- They can form a gel only if the total soluble solid (TSS) (Brix) content is equal to or higher than 60% with a maximum of 80%.
- The pH necessary for it to gelify is between 2.0 and 3.5.
Reactivity:
- The higher the concentration of soluble solids (TSS) (Brix), the higher the strength of the gel obtained and the higher the gelation temperature.
Excess soluble solids or Brix reduce the trength of the gel.
The lower the pH, the higher the gelation Temperature, and as a consequence, gelation will be quicker. pH values below 2.0 may encounter gelation problems.
pH variation it’s very important. 0.1 units of pH may make the gelation temperature fall to 10 °C.
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 gelify again.
- Depending on the dosing and hydration temperature they act as thickeners.
Gelation conditions:
- They form a gel in the presence of Calcium (Ca++) ions alone
- They gelify with low soluble solid values (brix) and a very wide pH range.
Reactividad:
- Low methoxyl pectins form gels with a pectin that has a greater gel strength the higher the amount of calcium. Too much calcium can destroy the structure of the gel.
- The presence of sugar or soluble sugars considerably reduces the quantity of calcium necessary for proper gelification.
- A low pH increases the reactivity of the pectin.
Conventional low methoxyl (LMC)
Conventional low methoxyl (LMC) pectins are low methoxyl pectins obtained from HM pectins via physicochemical procedures.
LMC pectins form transparent and thermoirreversible gels.
Amidated low methoxyl (LMA) pectins
Amidated pectins (LMA are low methoxyl pectins obtained from HM pectins through alkaline extraction
- LMA pectins are thermoirreversible.
- The calcium encourages greater reactivity and a harder end gel.
- The higher the amount of soluble solids and the lower the pH, the stronger and more cohesive gels are obtained.
- Depending on the type of pectin and the method of dispersion, different hardness values are obtained.
Masterclass about pectins
To learn more about the functionalities of pectins, their classification and the development of the graphics shown above, we have carried out a Masterclass with Jordi Bordas and Óscar Albiñana that you can see in the following link: