Low Methoxyl Pectin (LM Pectin) is pectin that has esterification of less than 50%. It is usually extracted from sunflower discs or potatoes, or obtained from high ester pectin by acid or alkali treatment to reduce its methoxylation by de-esterification.
LM Pectin is low methoxylated pectin with high reactivity to calcium ions. Gelation of LM pectin can be controlled by adjusting the pH and by adding different calcium salts during the gelation process.
LM pectin can be further divided into normal LM pectin and LM amidated pectin.
Product Name | Low Methoxyl Pectin, LM Pectin | Esterification Degree | <50% |
Raw Materials | Apple, citrus, grapefruit, sunflower disc, etc. | Preparation Method | Alkali method, enzyme method |
Classification | Regular low methoxyl pectin, low methoxyl amidated pectin | Applications | Low-sugar jams, dairy products, bakery products |
Low Methoxyl Pectin can be further classified into regular low methoxyl pectin and low methoxyl amidated pectin (LMA pectin).
Low Methoxyl Pectin is slightly more stable at higher pH conditions. Under alkaline conditions, pectins can undergo de-esterification even at room temperature. If de-esterification is carried out with ammonia, some of the methoxys of the methyl ester is converted to the amino of the amide. Low methoxyl amidated pectins have better physical properties than other low methoxyl pectins and can be widely used as gelling agents.
The gel formation mechanism of Low Methoxyl Pectin is completely different from that of High Methoxyl Pectin. Its gel is the result of the ionic connection between the carboxyl groups of the two pectin molecule chains through the calcium bridge and the joint action of hydrogen bonding. This gel is influenced by the concentration of calcium ions in the system and is not obvious for sugars and acids on the contrary.
The gel conditions of Low Methoxyl Pectin: pH range 2-6, soluble solids content 10%-80%, the formed gel is thermally reversible.
The gelation of Low Methoxyl Pectin is influenced by the conditions of pectin esterification, relative molecular mass, calcium content, pH, other substituents, and cooling rate.
Among them, calcium is a necessary condition, and it is proved that about 25mg of calcium is required per gram of low methoxyl pectin. Low Methoxyl Pectin with different degrees of esterification has different calcium activity.
The relationship between gelling degree and esterification degree of Low Methoxyl Pectin is opposite to that of High Methoxyl Pectin. The gelling temperature of Low Methoxyl Pectin is inversely proportional to the esterification degree, and the gelation temperature of Low Methoxyl Pectin jelly has little or no difference from the melting temperature.
With high molecular quality, the binding zone of "egg box" model can be formed easily and the quality of gel formation is good.
If the DE value increases, the gel forming temperature decreases; If the DA value increases, the gel forming temperature also increases. However, if the DA value is so high that the gelation temperature is higher than the boiling temperature of the system, it will make the system form pre-gel immediately.
If the content increases, the gel strength and gel temperature will rise, but too high will lead to the formation of pre-gel, so that the gel strength will be reduced instead.
For certain pectins with DE and DA values, before reaching the optimum gel strength, the calcium ion concentration increases, and the gel strength and gel temperature increase; After reaching the optimum gel strength, the calcium ion concentration continues to increase, and the gel strength starts to become brittle and weak, and finally forms pre-gel.
Adding or presence of polyphosphate, citrate, etc. that can chelate calcium ions in the system, can reduce the effective concentration of calcium ions, thus reducing the risk of pregel formation, especially when the solids content in the system is high.
When the content increases, the gel strength increases and the gel formation temperature rises, but too high will lead to the formation of pregel.
Different substances affect the ability of pectin to bind calcium ions to different degrees. Under the fixed conditions of pH=3.0, solids content=31% and calcium ions content of 20mg/g pectin, for example, the magnitude of gel strength is decoction sugar>42DE glucose syrup>high fructose syrup>sorbitol, respectively. The sensitivity of different solids species to the calcium ions that produce pregel also all differ.
The pH can be in the range of 2.6-6.8. An increase in pH requires more pectin or calcium ions to form the same quality of gel; An increase in pH results in a lower gel formation temperature.
If the calcium ion solution is added to the pectin solution which is lower than the gel-forming temperature, it will cause the system to form pre-gel immediately.
Calcium ion solution should be added in a more dilute form, otherwise, it will lead to the local formation of pre-gel or local non-gel formation phenomenon.
If calcium salts that can only be dissolved slowly are used, the gel formation and strength can be enhanced over time.
The gels formed by Low Methoxyl Pectin, especially amidated pectin, are thermally reversible gels. If the DE value is high and the solids content is high, the gels formed will also have better thermal stability.
Low Methoxyl Pectin has good thixotropy and the gel becomes pumpable by shear force, especially for pulpy yogurt production.
At low solids content (20%), CMC or locust bean gum compounded with Low Methoxyl Pectin can improve the gel organization. Xanthan gum compounded with pectin reduces the gel organization.
The manufacture of pectin is generally extracted with hot water under low acid and alkaline values, and when powder pectin is produced, it is dried and powdered after precipitation with alcohols, and the extracted pectin is HM pectin.
If de-esterification is carried out under acidic or alkaline conditions, LM pectin can be produced, and various kinds of pectins can be obtained by changing the extraction or de-esterification conditions.
Put the pectin concentrate into a stainless steel pot, add ammonium hydroxide to adjust the pH to 10.5, and keep it at a constant temperature of 15℃ for 3h. Then add an equal volume of 95% alcohol and an appropriate amount of hydrochloric acid to lower the pH to about 5.
After stirring, let it stand for 1h, filter out the precipitated pectin, squeeze it dry, then wash it with 50% and 95% alcohol respectively for 1 time, press it dry and spread it on a baking tray, dry it in a vacuum drier at 65℃, take it away and grind it fine, pack it to get the finished product.
The yield is about 90% of the amount of pectin.
Enzyme method is to extract low methoxy pectin by lipase defatting method.
Compared with the traditional alkali and acid methods, it has the advantages of easy process control, high product quality, energy saving and cost reduction.
Low Methoxyl Pectin is used in a wide range of applications such as low sugar jams, dairy products, bakery products, mirror pectin and yogurt companions.
The solids content needs to be less than 60% and the product needs to contain calcium or other metal ions in order to form the final gel.
Low Methoxyl Pectin is used in systems with pH=2.6-6.8, solids content above 10% and the presence of calcium ions (at least 15mg/g of pectin), mainly for low sugar jams, yogurt pulp bases, gummy candies, sweets, baked goods glazes, etc.
The choice of pectin for a specific application depends entirely on the conditions of the system, production costs and product requirements.
Amidated pectin has greater versatility than regular Low Methoxyl Pectin.
Generally, pectin should be dissolved in pure water before mixing with other excipients.
Pure pectin solutions have a low viscosity and are Newtonian fluids. The general application of pectin in jams or jellies ranges from 0.3% (High Methoxyl Pectin, about 65% soluble solids) to 0.7% (Amidated or Low Methoxyl Pectin, about 35% soluble solids).
From the nature and function of pectin, it is known that any change in the system conditions will affect the use of the effect, if the formation of pre-gel, not only to increase production costs, but also to reduce product quality, change other factors may also make the pre-gel phenomenon disappeared.
Food | Function | Preferred Type | Reason for Selection | Application Concentration/% |
Low solids jam (suspended matter <55%) | Gelling agent | Amidated pectin | Gelling without adding calcium salts | 0.4-1.0 |
Soft sugar food jelly with natural flavor | Gelling agent | Acid hydrolyzed pectin (used in combination with starch) | Bears high soluble solids (76%-78%) | 1.0-2.0 |
Hot reversible bread jelly icing | Gelling agent | Amidated pectin | Gels in a slightly wider range of soluble solids | 1.0-2.0 |
Gelled sour cow milk products | Gelling agent | Amidated pectin | Â | 0.5-1.0 |
Canned fruit for the preparation of fruit buttermilk sweets | Gelling agent | Amidated or acid-hydrolyzed pectin | Need to add buttermilk to fruit products to control the gelling effect | 0.8-1.2 |
Instant pudding powder | Gelling agent | Amidated pectin | Requires rapid dissolution in water and rapid gelling when buttermilk is added | 0.8-1.2 |
Syrup base for ready-to-eat chocolate or vanilla pudding | Gelling agent | Amidated pectin | Syrup does not need to be overly thick, syrup must be neutral at pH with buttermilk for rapid gelling | 0.8-1.2 |
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