Learn the science behind:
HM, LMA, LMC, rapid-set, slow-set. There are a lot of different types of pectin, some of which sound like code names! But which one do you need to make a sugar-free jam? Or a tart raspberry gummy? Or a new application, that doesn’t typically use pectin?
We’ll cover it all, but first, let’s dive into what a pectin really is.
- What is pectin?
- Pectin is extracted from citrus and apples
- HM vs LM pectins
- HM – Some are slow, others fast
- Two types of LM: LMA and LMC
- Experimenting with pectin
What is pectin?
Pectin is a component that’s naturally present in most plants. There, it serves crucial functions to ensure plants thrive. Fruits especially tend to be high in pectin.
There isn’t just one pectin either. Instead, pectins are a group of molecules that all have a similar basic structure, with slightly different functionalities. They’re all large carbohydrates, also called polysaccharides. These polysaccharides are long chains of smaller carbohydrates. In the case of pectin, the most important building block of this chain is galacturonic acid.
|Fruits low in pectin||pineapple, banana, kiwi, mango, pear, pumpkin, strawberry, blueberry, cherry|
|Fruits high in pectin||apple, lemon, orange, cranberry, passionfruit|
Pectin is a gelling agent
Since pectin is naturally present in so many fruits, you’ll encounter it when cooking or baking with them. For instance, in a pumpkin pie pectin contributes to that creamy texture. And when you make fruit jam, the naturally present pectin contributes to the final consistency.
But pectin can also be used pure, as a gelling agent. Under the right conditions, pectin can form a firm, transparent gel. The most well-known applications are probably fruit jam, marmalades, and related products.
Did you know? In some countries you can find special sugars for making jams. These sugar mixes are regular sugar (sucrose) mixed with pectin!
Pectin is extracted from citrus and apples
To use pectin as a gelling agent it has to be extracted from a plant. Even though it is a very common component, it is only actively extracted from a few types of fruits. This is in part because the concentration of pectin has to be high enough, and because the quality of the pectin needs to be up to scratch.
It’s why most pectin is extracted from two types of fruits: apples and citrus fruits. The leftover product after pressing apples for juice and cider, apple pomace is a valuable source. In citrus fruits, the rind contains a high concentration of pectin, making it a suitable candidate as well.
To extract the pectin, manufacturers break down the fruits and cook them for a set time under acidic conditions. This sets the pectin free. In subsequent steps, the pectin is precipitated and then dried to make a pectin powder.
The basic pectin: HM
This standard method results in the production of so-called HM pectin where H stands for high and M for methoxyl. The methoxylation of a pectin is a measure of the degree of esterification (DE). Pectins contain a lot of acid (-COOH) groups. If these groups react with alcohol (-OH) an ester is formed. The pectin production process mentioned above makes pectins with a large number of these esters, hence the name high methoxyl.
An extra process step gives LM pectin
On the other side of the spectrum, we have LM pectins, which are low methoxyl pectins. In order to make such an LM pectin an additional process step is required to get rid of some of those esters.
The cut-off between high and low is a degree of esterification of roughly 50% anything above that is considered high, while anything below that is low.
To understand pectins, it helps to understand what acid and alkaline mean. The aciditiy and alkalinity are measured using the pH scale which runs from 0 to 14. A pH-value of 7 is neutral, anything below 7 is acidic, and above 7 is considered alkaline.
HM vs LM pectins
Those ester groups on pectin molecules have a big impact on how pectins work. As a result, HM and LM pectins work quite differently. Even though both form a gel, the way in which they do so is very different. It’s why they are suitable for different applications.
HM requires sugar and acid
HM pectins disperse well in water, no matter the acidity of the liquid. When it’s dispersed in water HM pectin won’t immediately form a gel. Instead, the individual HM pectin molecules repel each other. They prefer to be surrounded by water instead of other pectin molecules.
One of the reasons for this phenomenon is that a pectin molecule contains some negatively charged areas. These negatively charged areas repel one another, in the same way the two negative poles of a magnet would. In order for an HM pectin to form a gel, this repulsive force needs to be overcome. That way, they can come together and form a network. Once the pectins form this network, they form a gel. To ensure HM pectins come together, you need two key ingredients:
- Sugar: a high amount of sugar dissolved in water binds water molecules. As a result, pectin can no longer surround itself with these water molecules. They’re scarcer. This helps pectin molecules find one another. HM pectin tends to need over 60w% of sugar to form a gel.
- Acid: an acidic environment contains a lot of protons (H+). These protons neutralize the negative charges of the pectins, making it easier for them to approach each other. The pH-value needs to be below 3,5 for HM pectins to come together and gel.
LM requires calcium (divalent ions)
Remember that LM pectin contains fewer esters and as a result more free acid (-COOH) groups. These groups are negatively charged in a neutral or slightly acidic environment (-COO–). It enables a completely different mechanism for forming a gel. It doesn’t need as much sugar, nor as low a pH-value. Instead, it can form a gel by creating a structure with calcium ions.
Calcium ions (Ca2+) have a positive charge. These positive charges can neutralize and attract two negatively charged acid groups from two pectin molecules. The two pectins serve as an egg box carton that encases these calcium ions, the eggs. Pectin molecules again form a network, but one that’s connected through these calcium ions. This network doesn’t depend as much on the pH-value, it can gel from a pH of roughly 2,0-6,0.
The eggbox needs a divalent ion to form. It does not have to be calcium, but in food applications it generally is.
Choosing LM vs. HM pectins
Before diving into some more variations of LM and HM pectins, let’s quickly summarize what we’ve learned so far:
- HM pectin is suitable for applications that:
- contain a lot of sugar
- are acidic
- LM pectin is suitable for applications that:
- contain calcium.
- does not depend on sugar content.
- doesn’t need pH to be controlled tightly.
As an example, when you want to make jam from fruit, you’d use HM pectin for a version with plenty of sugar. For a low-in-sugar jam you’d need the LM pectin.
Other HM vs. LM differences
Whereas the differences mentioned above are the most important ones when choosing a pectin, there are a few more considerations to keep in mind:
- Thermal reversibility: some gels lose their gel-like structure when heated, whereas others do not.
- HM gels are not thermally reversible, they soften when warmer, but don’t turn liquid again.
- LM gels are thermally reversible, you can heat them, liquify them and re-set them again.
- Shear reversibility: LM products can be pumped (shear resistant) whereas HM products cannot.
HM – Some are slow, others fast
As we mentioned, for a pectin to be called HM, it needs to have a degree of esterification (DE) above 50%. Any value below that is an LM pectin. However, seeing as how pectins can have a DE-value up to 80, that still leaves quite a wide range of pectins.
Since the DE of a pectin greatly influences how fast a pectin sets and forms a gel, pectins are further grouped by how fast they set. This works as follows:
- Extra slow-set HM pectin: has a DE-value of 50-60%, it takes the longest to set.
- Slow-set HM pectin: has a DE-value of 60-70%
- Rapid-set HM pectin: has a DE-value above 70%, it sets fastest and at the highest temperature
The degree of esterification can depend on the source of the pectin, but also on the production process used to make the HM pectin.
Yellow and apple pectin are types of HM pectin
Not all pectins will have a name that describes their chemical makeup. Sometimes, these pectins have a name similar to the application that they’re best suited for. Other times, names sound quite generic. Such is definitely the case for yellow pectin and apple pectin. These names are used somewhat, but not 100%, consistently.
Yellow and apple pectin generally refer to the same type of pectin. Comparing over five different brands of yellow pectin, they all need acidity and high sugar content to set. This clearly indicates that they’re HM pectins. Generally speaking, people seem to refer to the slow-set variety.
It’s not clear to me why yellow pectin is called that way, except for one brand (Sosa) carrying yellow pectin. As to why it’s called apple pectin, a lot of pectins are made from apple. Hence the name, despite it not being very descriptive.
Two types of LM: LMA and LMC
Manufacturers can use one of two ways to transform an HM into an LM pectin. These two routes result in slightly different products with different functionality. First of, manufacturers can use the so called conventional method, in which they use an acid to get rid of estergroups. LM pectin made this way is appropriately called LMC (LM conventional). Alternatively, manufacturers can use an alkaline material (NH3, an amine). This gives amidated LM pectin, referred to as LMA.
Both LMA and LMC need calcium to form a gel function quite similarly. However, there are a few differences in how they work:
- LMC sets at a higher temperature than LMA (under otherwise the same circumstances).
- LMA can gel under a wider range of conditions:
- For instance, the use of LMC is limited to 55w% sugar any more and it no longer forms a gel. LMA though can handle sugar concentrations from 0 to just about any reasonable maximum value.
Experimenting with pectin
Despite there being some very clear differences between the different types of pectin, there’s a lot of overlap in how the different pectins can be used. Also keep in mind that the texture and structure of the final pectin strongly depend on how you use it. More or less sugar, acid or calcium will all impact how the pectin gel turns out! As such, see this as a starting point in your pectin journey.
If you’d like more specific tips on how to best use pectin, read our detailed pectin troubleshooting guide.
Milda E. Embuscado, Kerry C. Huber, Edible Films and Coatings for Food Applications, 188.8.131.52 Pectin (E440), p. 74, 2009, Springer, link
Janine, Pectine, Dat is jammie, 10-Dec, 2021, link
Martin Lersch, Texture v.3.0, Feb-2014, p.75 – Pectin, link
Martin Masuelli, ed. Pectins – Extraction, Purification, Characterization and Applications (London: IntechOpen, 2020). 10.5772/intechopen.78880
Patesserie, Pectinegehalte van Fruit, link
Pornsak Sriamornsak, Chemistry of Pectin and Its Pharmaceutical Uses : A Review, link
Thakur, Bablu & Singh, Rakesh & Handa, Avtar. (1997). Chemistry and Uses of Pectin – A Review. Critical reviews in food science and nutrition. 37. 47-73. 10.1080/10408399709527767. link
Vickie A. Vaclavik, Elizabeth W. Christian, Essentials of Food Science, Pectins, p.70-74, 2007, Springer, link
edited by Reginald H. Walter, The Chemistry and Technology of Pectin, 1991, link