Polydextrose – from seed to Eureba

Consumers demand less sug­ar to keep calo­ries in check and reduce the effect on blood sug­ar lev­els. But it is rarely as sim­ple as adding less if any sug­ar at all. We can eas­i­ly com­pen­sate the sweet­ness with a high-inten­si­ty sweet­en­er, for exam­ple, ste­vi­ol gly­co­sides. The big chal­lenge is to main­tain the per­fect mouth­feel. No one wants an ice cream that doesn’t melt the right way in the mouth or an ener­gy bar that crunch between teeth in a wrong way between. Then poly­dex­trose can be the solu­tion. It is an ingre­di­ent that pro­vides soft­ness and juici­ness in the same way as fat and pro­vides vol­ume, tex­ture and mouth­feel like sugar.

A successful recipe

In the 1960s, Hans Rennhard and his research team at Pfizer exper­i­ment­ed with nat­ur­al ingre­di­ents to pro­duce low-calo­rie sub­sti­tutes for sug­ar, fat, flour and starch. The exper­i­men­ta­tion gave results in 1965. They mixed 89 per cent glu­cose, 10 per cent sor­bitol and 1 per cent cit­ric acid, heat­ed the mix­ture and got polydextrose.

Although poly­dex­trose is pro­duced from nat­ur­al ingre­di­ents, the sub­stance itself is not found in nature, and could, there­fore, be patent­ed. Pfizer did so in 1973. Then, years of stud­ies fol­lowed on the food’s tech­ni­cal prop­er­ties and how safe it is for humans. It turned out to have suit­able tech­ni­cal prop­er­ties and not only be harm­less but even great for peo­ple. It was approved as dietary fibre in the United States in 1982. The EU fol­lowed 1995.

Glucose

The main ingre­di­ent in the pro­duc­tion of poly­dex­trose is glu­cose. The mono­sac­cha­ride is abun­dant in fruits and berries, but for food pro­duc­tion, glu­cose is made from starch from nat­ur­al sources such as corn, wheat, pota­toes and cassava.

Manufacturing starts with dis­solv­ing starch in water and adding acid or enzymes (or both) and heat­ing every­thing up. This makes the starch, which con­sists of long chains of glu­cose mol­e­cules, to break up into increas­ing­ly short­er and short­er chains. A chain reac­tion if you wish. The treat­ment is called hydrol­y­sis and the result is glu­cose syrup – a caloric bomb with sky-high gly­caemic index (GI).

Sorbitol

The oth­er ingre­di­ent in the pro­duc­tion of poly­dex­trose is sor­bitol. It is a sug­ar alco­hol found nat­u­ral­ly in plums, pears, peach­es, apples and a host of dif­fer­ent fruits and berries. The sub­stance is also found in rowan berries, and this is where it was first dis­cov­ered. However, indus­tri­al­ly, sor­bitol is pro­duced from glu­cose. You can read how it’s done in a sep­a­rate arti­cle on sor­bitol.

Citric acid

The third and last ingre­di­ent in the pro­duc­tion of poly­dex­trose is cit­ric acid. As the name sug­gests, it is found in cit­rus fruits, but also in a vari­ety of oth­er fruits and berries.

Citric acid can be extract­ed from, among oth­er things, unripe lemons and oth­er cit­rus fruits. That is how it usu­al­ly was pro­duced from the end of the 19th cen­tu­ry and well into the 20th cen­tu­ry. But as ear­ly as 1917, the American food chemist James Currie dis­cov­ered that the fun­gus Aspergillus niger – com­mon­ly known as black mould – is a capa­ble pro­duc­er of cit­ric acid. Practically all cit­ric acid sold today is pro­duced by black mould.

The fact that black mould is used to pro­duce food is a hot top­ic in some cir­cles on the inter­net. But there is no cause for con­cern. There are non-tox­ic strains of black mould used in the pro­duc­tion of cit­ric acid. Thus, it is not the same strains that cre­ate harm­ful mould in damp houses.

Citric acid pro­duc­tion begins with the hydrol­y­sis of starch to pro­duce glu­cose syrups with which the fun­gus than are fed. In return, they pro­duce cit­ric acid, which is extract­ed in sev­er­al steps which includes purifi­ca­tion, evap­o­ra­tion, crys­tal­liza­tion and drying.

Preparation of polydextrose

We now have all the ingre­di­ents nec­es­sary to make poly­dex­trose: glu­cose, sor­bitol and cit­ric acid. Note that in prac­tice, all three are made from starch, which comes from wheat, corn, pota­toes, cas­sa­va or anoth­er starch-rich crop.

Polydextrose is pre­pared by mix­ing 89 parts of glu­cose, 10 parts of sor­bitol and 1 part of cit­ric acid and heat­ing the mix­ture till it becomes liq­uid. Then the cit­ric acid acts as a cat­a­lyst and makes glu­cose and sor­bitol to react with each oth­er to form short­er, and longer glu­cose chains, which in turn are attached to each oth­er and form branched mol­e­cules of glu­cose parts.

It is these branched mol­e­cules of glu­cose that are poly­dex­trose. On aver­age, they have twelve glu­cose mol­e­cules, but the num­ber can vary from three to over one hun­dred. That is why they are called poly­dex­trose; poly means many in clas­si­cal Greek, and dex­trose is anoth­er name for glucose.

But all glu­cose and sor­bitol are not con­vert­ed. And the cit­ric acid, which was just a cat­a­lyst, remains. Also, some lev­oglu­cose, which is a nat­u­ral­ly occur­ring organ­ic sub­stance, has been formed.

Polydextrose is dietary fibre

So what makes poly­dex­trose a fibre? The answer lies in how the glu­cose mol­e­cules are attached to each other.

When a car­bon atom in one glu­cose mol­e­cule and a car­bon atom in anoth­er glu­cose mol­e­cule hold the same oxy­gen atom in their hands, they become linked. The two car­bon atoms and the oxy­gen atom is called a gly­co­side bond. These are denot­ed by α or β fol­lowed by two num­bers, for exam­ple, α-(1→4) and β-(1→6). The num­bers tell which car­bon atoms hold the oxy­gen atom in their hands, and the Greek let­ter says whether the car­bon atoms are turned in dif­fer­ent or the same direc­tion. (You will find a more detailed descrip­tion with illus­tra­tions in the arti­cle on dex­trin.)

A poly­dex­trose mol­e­cule has a jum­ble of gly­co­side bonds: α- and β-(1→2), (1→3), (1,→4) and (1→6). There are most of α-(1→6) and β-(1→6).

Although they are called almost the same thing, our bod­ies han­dle them very dif­fer­ent­ly. Our diges­tive sys­tem quick­ly breaks down α-(1→4) bonds, which are the gly­co­side link­age in starch and com­mon sug­ars, but strug­gle with α- and β-(1→6) bonds. If a glu­cose chain has more than one α- or β-(1→6) bind­ing, the body does not have time to break it down before it reach­es the large intes­tine. Such car­bo­hy­drates are called dietary fibres.

Since α- and β-(1→6) are com­mon in poly­dex­trose, most of it will pass the stom­ach and small intes­tine before with­out being touched. This, togeth­er with the fact that poly­dex­trose has a favourable phys­i­o­log­i­cal effect as sci­en­tif­ic demon­strat­ed, makes poly­dex­trose approved as dietary fibre.

Better on the stomach

Polydextrose is bet­ter on the stom­ach than sug­ar alco­hols. Studies show that you can eat up to 50 grams of poly­dex­trose at one time, and up to 90 grams dur­ing a day with­out stom­ach prob­lems. The lim­it val­ues are well above the 25 to 35 grams of fibre that an adult should eat per day (and few­er than half come up to). Therefore, poly­dex­trose may be used with­out restric­tion in most foods, but not more than necessary.

Several features in the same ingredient

Polydextrose has many use­ful prop­er­ties that make it a pop­u­lar ingre­di­ent in every­thing from drinks, ice cream and pas­tries to dress­ings and jams. With neu­tral taste, it’s a chameleon that fits in many contexts.

The gas­tric-friend­ly dietary fibre, made from nat­ur­al ingre­di­ents, is a good start­ing point for cre­at­ing a sweet­ened fibre. Since poly­dex­trose is not sweet in itself, it must be sup­ple­ment­ed with a sweet­en­er such as ste­vi­ol gly­co­sides and/​or sug­ar alco­hols. Precisely what to com­ple­ment poly­dex­trose and in what pro­por­tions vary from appli­ca­tion to application.

We can help you

Don’t hes­i­tate to con­tact us if you want help find­ing the right ingre­di­ents and pro­por­tions to replace sug­ar with sweet­ened fibre. Chances are that we already have a ready-made solu­tion for you. If not, we can help you devel­op one.