Propylene Glycol Alginate (PGA) is a polysaccharide biomolecule synthesized by esterification reaction of alginic acid extracted from brown algae, with excellent emulsification, thickening, expansion, acid resistance and stability, etc. It can be widely used as food additives in all kinds of food in the U.S.A., Japan, South Korea, Russia, etc., with mature use methods and standard requirements; China approved its use as a food additive in 1988. In the United States, Japan, Korea, Russia and other countries and regions can be widely used as food additives in various types of food, with mature methods of use and standard requirements; China approved its use as a food additive in 1988.

Now PGA, as a new type of emulsification stabilizer, has been widely used in the production of yogurt and acidic milk drinks.

The application for expanding the scope of PGA for fermented pasta products, bread, pastries, etc. has been announced through the National Health Commission in November 2017, therefore, propylene glycol alginate, as a marine food additive with excellent performance, will surely play a greater role in the application fields of milk and dairy products, all kinds of beverages, ice creams, pasta products, as well as breads, pastries, and other baked foods.

Emulsification, stabilization and acid resistance of PGA

PGA has both hydrophilic and lipophilic groups in its molecular structure, and has good emulsification properties.PGA can be dissolved in water to form a viscous colloid, and can be dissolved in organic acid solution, 1% of the solution itself pH=3~4, with good acid resistance, and can form a gel in acidic solution pH=3~4, but will not produce a precipitation.

PGA has strong salt resistance and is stable to metal ions such as calcium and sodium, which can improve the stability of alginic acid in foodstuffs, and can also prevent the precipitation effect caused by calcium and other high-valent metal ions in foodstuffs.

Combining the properties of emulsification, acid resistance and stabilization, PGA is widely used in products such as yogurt, milk beverages and fruit juices.

1.1 Application in yogurt
The application of PGA in yogurt can give yogurt a natural texture and taste, effectively prevent the formation of unattractive rough and bumpy surfaces, and make the product smooth and glossy; in actual production, it blends well with all other ingredients and can be used in acidic environments of pH 3~5 to improve the viscosity of yogurt, prevent protein precipitation and whey uplift.

Wei Xiaoying et al. added different amounts of PGA to raw milk for yogurt fermentation, and found that after adding PGA, the viscosity of yogurt was 1 times higher than that of yogurt without PGA at the same rotational speed, and different amounts of PGA could affect the structure of yogurt to different degrees, and the best effect was achieved with the addition of 0.2%; at this time, the water-holding capacity of yogurt increased by 10.9%, the amount of whey precipitation decreased by 26.0%, and the hardness reached 8g, and the recoverability reached 8g. At this time, the water holding capacity of yogurt increased by 10.9%, the whey precipitation decreased by 26.0%, and the hardness reached 8g, with the best recovery.

Chen Yingqi added different mass fractions of propylene glycol alginate (PGA) and pectin to make stirred yogurt, and found that PGA had a better effect on the thickening of yogurt when the added amount of PGA and pectin was greater than 0.13%. And the inhibition of acid production after yogurt and the stability of acid resistance of PGA were better than that of pectin, which could make yogurt maintain the stability of texture, taste and flavor in a relatively long storage time.

Another study showed that PGA and modified starch as a combination of thickening agent in the application of stirred yogurt has a good synergistic effect, the optimal amount of the two were 0.15% and 1.20% (W/W), the quality of yogurt under these conditions is optimal.

1.2 Application in Milk Drinks
The most common quality problems in the production and storage of blended milk beverages are sedimentation and delamination. Fan Suqin et al. added 0.2% (W/W) PGA, 0.3% sodium carboxymethylcellulose, 0.1% high ester pectin and 0.015% sucrose ester to acidic milk beverage processing, which resulted in the best taste and the highest stability of milk beverage.

Tang Zhenrui studied the effect of seven thickeners including propylene glycol alginate on the stability of coffee milk beverage, and found that the additive amount of each monomer thickener was 1.1 g/kg of propylene glycol alginate, 1.4 g/kg of microcrystalline cellulose, 1.7 g/kg of gum arabic, 0.25 g/kg of xanthan gum, 0.15 g/kg of jellied colloidal gum, and 0.10 g/kg of ι-carrageenan, respectively, κ-type carrageenan 0.05 g/kg had relatively good effects on the stabilization system of coffee milk beverage.

Zhong Huafeng’s research on the formulation and stability of formulated pineapple juice milk beverage resulted in the optimal formulation as follows: pineapple juice concentrate 11%, milk powder 4.5%, sugar 4%, lactic acid 0.24%, sodium tripolyphosphate 0.06%, sodium citrate 0.04%, pectin 0.25%, acid-resistant sodium carboxymethylcellulose 0.02%, propyleneglycol alginate 0.02%, molecularly distilled monoglycerol 0.01%, sucrose 0.01%, and sodium carboxymethyl cellulose 0.02%. 0.01%, sucrose fatty acid ester 0.05%.

1.3 Application in Fruit Juice Drinks
The ideal appearance of fruit juice suspension drink should be juice clarification, fruit particles suspended uniformly or pulp mixed uniformly, without obvious layering phenomenon. In actual production, the suspension of fruit juice drinks has been a technical challenge.

In juice drinks, both pulp particles formed by the suspension, but also pectin, protein and the formation of the true solution, and even lipids formed by the emulsion, suspension. There is a large density difference between the particles of the emulsion and the beverage juice, which is the main reason for instability.

Adding a small amount of PGA to the juice drink can greatly alleviate this technical difficulty, which can make the fruit particles evenly suspended, and there will be no delamination phenomenon during the storage period, and at the same time, improve the stability of the fruit pulp, so that the juice has a thick taste and better texture.

Kong Jin et al. studied the best stabilization effect of the bifidobacteria fermented fruit pulp drink made when adding four compound stabilizers, namely 0.15% gelatin, 0.08% sodium alginate, 0.08% xanthan gum, and 0.01% PGA.

1.4 Application in ice cream
Ice cream is loved by consumers for its smooth and delicate organization, compact and soft shape, mellow and long-lasting flavor as well as rich nutrition and cool taste, but due to the complex component system and processing technology of ice cream, it is prone to quality problems in the production and storage process.

It has been found that the addition of PGA to ice cream can significantly improve the dispersion of fat and fat-containing solid particles and the taste, internal structure and appearance of ice cream, as well as improve the dispersion stability and anti-melting properties of ice cream. In addition, PGA can prevent the formation of lactose ice crystals in ice cream.

Hydration, anti-aging and tissue improvement of PGA

When PGA is applied to pasta products and baked goods, the amino group of gluten protein in flour will form a complex with the anionic group of PGA through electrostatic interaction, which will reduce the hydrophobicity of gluten protein and improve the water absorption rate of dough;

In the process of product storage, PGA can control the migration of water in the product system and keep the water molecules in a relatively stable state;

With its excellent emulsification characteristics, PGA interacts with starch molecules to form a stable composite structure, which can significantly slow down the aging of starch;

The combination of PGA and gluten protein in the dough on the other hand will also improve the network structure of gluten, thus improving the texture characteristics of the product and achieving better organization improvement effect.

The hydration, anti-aging and tissue improvement properties of PGA are applicable to raw and dry noodle products, raw and wet noodle products, convenient rice and noodle products, frozen rice and noodle products, bread, pastry and other baked goods.

2.1 Application in noodles

Noodles as China’s traditional food, has a long history, the current market noodle brand, color is very much, but there will be a lot of noodles taste saccharine, gluten-free, broken rate increased, muddy soup is more serious and other phenomena, the application of PGA in noodle products can be a better way to improve these problems.

Yu Peipei et al. studied the effect of PGA on the breakage rate and cooking quality of purple potato noodles and showed that PGA improved the breakage rate and cooking loss of purple potato noodles to different degrees, and the optimal additive amount was 0.3%~0.4%.

Liu Ranran found that the application of low ester PGA in noodles can effectively improve the quality of noodles, and when the addition amount of low ester PGA is between 0.2% and 0.3%, it can increase the hardness, chewiness and viscosity of noodles to a greater extent, and at the same time, reduce the rate of water absorption and starch dissolution, so as to make noodles glutenous, smooth, and achieve the best eating taste. (b);

Yang Yan et al. found that when PGA was added to noodles at a level of 0.3%, it had the most obvious effect on improving the quality of noodles, and produced noodles with a sinewy and elastic texture.

2.2 Application in dough

Frozen dough technology was first applied in the bread baking industry, and people have been researching ways to improve the problems in frozen dough, such as moisture loss, poor stability, and the phenomenon of frozen cracks in the finished product. The use of colloids to improve the quality of frozen dough is also more mature.

Yin Xiaojie investigated the effect of PGA on the quality and properties of frozen dough by adding different amounts of PGA on the tensile properties, water loss rate and freezable water content. The results showed that the quality of frozen dough showed a decreasing trend with the prolongation of freezing time, and under the same freezing time, the internal structure of frozen dough was stabilized, the water loss rate and freezable water content were reduced, and the quality of dough was better when the amount of PGA added was 0.2%.

2.3 Application in bread

Bread with the prolongation of storage time, prone to aging, texture and flavor deterioration, product shelf life shortening, which is the many bread manufacturers abhor the problem. Therefore, bread improver came into being, and studies have shown that hydrocolloids have good application advantages in the baking industry, which can improve the quality of bread.

Liu Haiyan found that the addition of PGA could improve the powder quality and tensile properties of dough, significantly increase the water absorption of dough, prolong the stabilization time of dough, improve the powder quality evaluation index, and increase the extensibility, tensile resistance, and tensile ratio of dough when studying the effect of PGA on the rheological properties of dough and the baking characteristics of bread.

When evaluating the baking characteristics of bread, it was found that the addition of PGA could increase the specific volume of bread, significantly improve the elasticity of bread, reduce the hardness of bread, improve the texture of bread, and improve the sensory score of bread.The most significant improvement of dough and bread and the best quality of bread were obtained with the addition of PGA in the range of 0.2% to 0.3%.

During long-term storage, cake will also show aging phenomena such as rough structure, loose and dry hardness, and deterioration of elasticity and flavor. Zhang Juanjuan et al. researched the formulation of cake quality improver: sodium alginate 0.15%, propylene glycol alginate 0.15%, xanthan gum 0.10%, which can improve the specific gravity of cake batter, improve the textural characteristics and sensory scores of the cake, so that the cake elasticity is better, the hardness is significantly reduced, and the degree of aging in the storage stage is significantly reduced year-on-year.

Foam Stability of PGA

Propylene glycol alginate has good foaming and emulsifying ability, widely used in beer foam stabilizer, can increase the foaming performance of beer, make the foam delicate and long-lasting.

Zhang Liqun et al. added an appropriate amount of PGA in beer, and found that PGA can significantly increase the stability of beer foam and foam holding power, even when encountered with grease or sterilization and washing residues can also resist rupture.

Liu Changhai et al. studied the effects of various food additives on the foam properties of beer and found that PGA was a good foam improver, and the addition of 30 mg/L could significantly improve the foam persistence of beer.

Synergistic properties of PGA and other colloids

PGA has good mutual solubility with sodium carboxymethyl cellulose, modified starch, sodium alginate, gum arabic, pectin, peach gum and so on, and can be mixed and compounded. Yinna screened out three stabilizers with better stabilizing effect and compounded them to improve the stability of horse milk beer.

The optimal amount of the stabilizers was CMC-Na %:PGA %:pectin % = 0.02:0.03:0.03, under which the centrifugal sedimentation rate of horse milk beer was 4.85%, and the sample state was the most stable.

Wang et al. showed that the stabilizing effect of the compound stabilizer of PGA 0.2% + monoglyceride 0.1% + NaH2PO4 0.05% was better than that of the PGA monomer stabilizer in stirred orange juice yogurt by studying the sensory quality and stability of stirred orange juice yogurt.

In addition to the functional properties of PGA in the above categories of food, it also has the properties of emulsifying flavor, beer modifier, etc., which are also widely used.

Prospect of PGA application

With the development of society, the direction of global food tends to be healthier. As a functional food additive from the ocean, propylene glycol alginate, with its unique acid resistance, emulsification stability, hydration and tissue improvement, will certainly be applied to various industries of food, exerting great functional effects and creating more opportunities and application values.