What does pgpr stand for

Another important application of PGPR is its use as a water-in-oil emulsifier for the production of low-fat spreads.

However, the main application of PGPR is in the chocolate industry. It is especially important for chocolate coatings to flow properly during the enrobing process. Cocoa butter is an expensive raw material, and chocolate manufactures prepare low-fat products to use them only for these applications.

Since lecithin and PGPR have complementary rheological properties, they are often used in combination for an optimal control of chocolate rheology [ 23 , 43 ]. This allows a more even coating of confectionary pieces while reducing the consumption of expensive cocoa butter in the recipe. Lowering yield value also improves the release of entrapped air in chocolate, leading to a smoother and more efficient molding and depositing.

This is achieved without compromising quality and taste and with cost savings. Fat bloom is not always caused by a simple set of circumstances, such as the chocolate becoming wet. Fat bloom is more complicated, and oftentimes it may be more difficult to discover the actual source of the problem.

Fat bloom typically appears as lighter color spots on the chocolate. As the name implies, the bloom is composed of fat, in this case the naturally occurring fat that comes from the cacao bean-cocoa butter.

When discussing the reasons for fat bloom, it is important to note that when cocoa butter hardens, it forms crystals. Some of the crystals are stable, but other crystals are not and will actually change form over time. During chocolate manufacturing, a process called tempering is used to ensure that only stable crystals form, while the chocolate hardens. Fat bloom is caused by the interaction of the various types of crystals or the tempering process or lack thereof.

When they recrystallize, they recrystallize slowly, since the ambient temperature is close to that of the chocolate. This allows the crystals to grow much larger than the original small, compact crystals.

In addition to projecting above the surface of the chocolate, these larger crystals may displace cocoa butter, forcing it to the surface. The second type of bloom is created when the crystals have softened instead of melted. It is during this period that cocoa butter that has slightly melted migrates toward the surface. When it breaks the surface, it pools ever so slightly, and when it cools the cocoa butter appears as spots.

Many people are surprised to learn that fat bloom also occurs in cocoa powder. Since some cocoa butter is present, it must be tempered during manufacturing, just as chocolate is.

Cocoa powder that has been improperly tempered or undergone temperature fluctuations may cause bleaching of the cocoa powder and may cause clumping, as the cocoa butter helps the particles of the cocoa powder adhere to each other. As with chocolate, when bloom occurs it does not affect the edibility of the cocoa powder but may have an aesthetic impact. Other forms of cocoa butter crystals are not present in fat bloom.

Fat blooming actually occurs in a third process. This case affects not so much the chocolate industry directly but the ancillary confectionary industry. When chocolate is used to coat nuts or fillings that contain oils or fats such as nut butters that are incompatible with chocolate, the oils may actually seep into or through the chocolate over time. This is called fat migration. As the oils displace the cocoa butter, cocoa butter may sweep onto the surface of the piece of confectionary and recrystallize as bloom.

When this occurs, the manufacturing process needs to be examined, or the confectionary needs to be reformulated [ 44 — 47 ]. The safety of PGPR consumption has been widely studied. PGPR has been used continuously in greasing emulsions since , following short-term rat feeding trials undertaken in It was also first used in chocolate couverture in the UK in During and , 4. However, new requirements for biological testing led to the withdrawal of the product for this purpose, and it was not used again in chocolate production until onwards [ 38 ].

The results of these studies have been published in several papers [ 40 , 48 — 52 ]. There was no interference with normal fat metabolism in rats or in the utilization of fat-soluble vitamins. Despite the intimate relationship with fat metabolism, no evidence was found of any adverse effects on such vital processes as growth, reproduction, and maintenance of tissue homeostasis.

PGPR was not carcinogenic in either 2-year rat or week mouse feeding studies. This ADI, without the temporary prefix, was raised to 7. On the other hand, the maximum PGPR levels of use in foodstuffs ready for consumption in Europe are listed in Table 2 [ 55 ].

These are listed in Table 3 [ 56 ]. It is well known that chemical production of PGPR [ 40 ] is carried out in four stages: 1 preparation of the castor oil fatty acids, 2 condensation of the castor oil fatty acids, 3 preparation of polyglycerol, and 4 partial esterification of the condensed castor oil fatty acids with polyglycerol.

This acid value is equivalent to an average of about four-five fatty acid residues per molecule of the condensed product. The operation conditions can be found in several papers. Either carbon dioxide [ 40 , 59 ] or nitrogen [ 51 , 57 , 58 ] can be used to ensure an inert atmosphere.

During the condensation phase, ricinoleic acid may react in a number of ways as shown in Figure Simple linear esterification is the desired reaction, but cyclic esterification, which is a chain terminating process, is theoretically possible.

However, no evidence was found for the presence of this type of cyclic material in the polyricinoleic acid. Dehydration is also possible but occurs to only a small extent. The reaction takes place immediately following the preparation of the latter and in the same vessel, while the charge is still hot. The esterification conditions are the same as those for fatty acid condensation. The major components have the general structure shown in Figure 11 a , where the average value of is about 3.

Some of the specifications listed in Table 3 with the exception of refractive index are weight average analysis and do not indicate specific structural characteristics of PGPR. Taken on the whole, however, these weight average-related specifications do indicate correct chemical structure, but with limited accuracy. Refractive index, however, is directly indicative of final chemical structure; for example, if the oligomer distribution of PGPR is not correct or distributed differently on the polyglycerol backbone, the refractive index measurement will not comply with the specifications as described in Table 3.

One problem with this conventional process is that the step of polymerization of ricinoleic acid is complicated by the fact that there is a requirement to follow the refractive index see Table 3 of the mixture, while polymerization of ricinoleic acid and esterificaction of polyglycerol and polyricinoleic acid is under way and to stop the reaction when the key value is indicated by the analysis.

It is therefore difficult to run the refractive index test at the kettle, and this often requires that the instrument is used in a laboratory setting, usually in a quality control laboratory, which is both time consuming and inconvenient. Moreover, the refractive index requires a high degree of technical training and precision. The four-step conventional process also reduces efficiency of production and adds cost to the product.

Therefore, recently, a more economical and simplified chemical method for manufacturing PGPR was developed [ 60 ]. Further, in the conventional process, there is a tendency to produce compositions of darker color.

This is most likely due to the added processing steps of preparing two separate ingredients, each having its own cycle of heating and cooling, along with the additional handling associated with the manufacture of each ingredient.

Figure 12 shows different PGPRs with different colors. The new process proposed in this patent produce noticeably lower color end product, such a clear yellow liquid rather than amber liquid. The chemical procedures above describe have the disadvantage of requiring very long reaction times, involving high energy costs.

This fact, together with the high operating temperature, can adversely affect the quality of the final product because of problems related with coloration and odours, making it unsuitable for the food industry [ 57 ]. As an alternative, a biocatalytic synthesis of PGPR using enzymes has been recently proposed by the author research group [ 61 — 66 ].

Lipases are able to act in mild reaction conditions and produce a final product more suitable for use as a food additive. Lipases E. The wide berth for employment in a variety of reactions, endowed by this broad substrate specificity, is further enlarged by the fact that lipases are capable of catalyzing the reverse reaction of synthesis just as efficiently.

In fact, some lipases are better suited for synthesis than for hydrolysis applications [ 67 ]. The two main categories in which lipase-catalyzed reactions may be classified are as follows [ 67 ]. The ability of lipases to catalyze the reaction of synthesis is used in the manufacture of several products: pharmaceuticals, cosmetics, leather, detergents, foods, perfumery, medical diagnostics, and other organic synthetic materials [ 68 ]. On the other hand, lipases have been employed to catalyze reactions involving hydroxyl fatty acids like ricinoleic acid to narrowly shape the product distribution via their region- and stereoselectivities [ 69 ].

Esterification mixtures generally contain only the substrates and enzyme, and water is the only by-product of the reaction [ 67 ]. Many reported lipase-catalyzed syntheses are carried out in organic solvents. However, residues of organic solvents in products are undesired, and many solvents which could be used are even toxic and are not allowed for processing procedures to make products for food applications.

As well as that, removal of organic-solvent traces in products requires extra expense and increases manufacturing costs. Solvent-free processes are thus desired [ 70 — 73 ] due to their advantages [ 72 ] and because they fulfill the twelve principles of the Green Chemistry, as defined by Anastas and Warner [ 74 ].

The potential of this relatively easy to perform bioconversion for industrial purposes seems to be enormous, but there are only few examples of successful production processes in practice. There are some important reasons for this. The use of dried enzyme powders, although often reported in laboratory scale experiments, is generally unsuitable for large scale processing in nonaqueous media. Development of the enzymes into active and stable biocatalysts, usually by appropriate immobilization techniques on support materials suitable for large scale production processes on a multitons basis, is very important.

At the moment there are only a few off-the-shelf purpose made biocatalysts commercially available which are suitable for industrial production [ 73 ].

Taking into account all these considerations, we developed a novel method for PGPR production, using immobilized lipase and in a solvent-free system [ 61 — 66 ]. This process is environmentally friendly and avoids side reaction, so that the product has a higher purity and quality.

The enzymatic procedure consists of two steps similar to chemical procedure. First, the ricinoleic acid is polymerized to obtain the polyricinoleic acid, PR, also known as ricinoleic acid estolide [ 62 — 64 ].

Then, it is esterified with polyglycerol to obtain polyglycerol polyricinoleate, PGPR [ 61 , 65 , 66 ]. Figure 13 shows the reactions involved in the biosynthesis. The studies about the first reaction step are based on previous works [ 69 , 75 — 80 ] and a result of this conscientious bibliographical search; Candida rugosa lipase has been selected to catalyze the autocondensation reaction of ricinoleic acid to obtain the polyricinoleic acid.

Immobilization of Candida rugosa Lipase First of all, efforts have been devoted to obtaining an immobilized derivative with a high immobilized protein percentage and enzymatic activity for the present application [ 63 ]. It has been described that adsorbed lipase on a ceramic carrier SM [ 79 ] is suitable for producing ricinoleic acid estolide.

However, the difficulty of acquiring the support led the authors to test different immobilization matrices in an attempt to obtain an immobilized derivative, which could be successfully used to catalyze the production of ricinoleic acid estolide [ 63 ].

Eight inorganic supports two types of BioLite, Celite R, Chromosorb W, nonporous glass beads of two particle sizes, and porous glass beads of different pore sizes and two organic carriers cationic and anionic exchange resins, Dowex and Lewatit MonoPlus MP 64, resp.

Twelve different immobilized derivatives have been obtained, six of them by physical adsorption and the other six by covalent coupling via the amino groups of the enzyme. Immobilization on glutaraldehyde-activated aminopropyl glass beads was selected because it has been widely used by the authors with different enzymes [ 81 , 82 ] and has been shown to be very versatile. The results obtained are shown in Table 4 where percentages of immobilized protein and protein contents are summarized.

The best results have been obtained when porous glass was used as immobilization matrix and covalent binding as coupling method. In these cases enzyme loading increased, as the pore size became smaller because of the greater internal surface available for immobilization. Celite R was also shown to be suitable for Candida rugosa lipase immobilization.

The five above mentioned immobilized derivatives were used to catalyze the polymerization reaction of ricinoleic acid. The extent of the reaction was monitored by acid value measures [ 84 ].

Figure 14 shows the results obtained. It can be seen that there was a large difference between the activity of the derivative obtained on the anion exchange resin and the activity of other derivatives. Moreover, other studies showed that the activation of the support with soybean lecithin has a beneficial effect on the enzymatic activity and that the optimum pH for enzyme immobilization is 7 [ 63 ].

Optimization of the Reaction Conditions The optimization of some reaction conditions is especially important in an experimental system like the described one. It is known that temperature is a crucial parameter in every enzyme catalyzed reactor, but in this case, due to the special characteristics of the reaction medium solvent free , temperature greatly influences viscosity, mass transport phenomena, and, as a consequence, the esterification rate [ 85 ].

While high temperature favors the medium fluidity, enzyme has to be prevented from thermal deactivation [ 62 — 64 , 85 , 86 ].

Lower reaction rates have been detected below this value, and a slightly unfavourable effect could be observed at high temperature [ 63 ]. Another decisive parameter in this process is the water content. Water plays multiple roles in lipase-catalyzed esterifications performed in nonconventional media.

It is widely known that water is absolutely necessary for the catalytic function of enzymes because it participates, directly or indirectly, in all noncovalent interactions that maintain the conformation of the catalytic site of enzymes [ 62 — 64 , 87 — 89 ]. However, it has been found that the amount of water necessary for enzyme activity might be very small, and, in the case of lipase, just a few layers around the enzyme surface are needed [ 90 ].

Particularly, in the case of estolides production, the water formed by the reaction must be removed from the reaction mixture if polyricinoleic acid with a high degree of condensation is to be obtained [ 62 — 64 , 79 ]. In the light of the above considerations, a study on the optimal initial amount of water in the reactor was deemed necessary. With this purpose, the authors carried out four experiments using the immobilized derivative as obtained soaked , adding different amounts of water and drying the derivative under vacuum at room temperature before use [ 64 ].

The time course of these experiments is shown in Figure 15 where the acid value is represented against operation time. With these experiments it was demonstrated that an optimum in the initial water content exists, although this optimum seems to be quite wide. The same results were obtained when derivative was used as obtained and when small amounts of water were added.

However, drying the derivative or adding higher amounts of water led to a lower initial rate specially the high water content and a higher final acid value [ 64 ]. Production of PR in a Vacuum Reactor All the experiments described above were carried out simultaneously, in an air open tank reactor, within a month of each other.

Obviously, this poor reproducibility of the results is unacceptable if the process is to be applied on an industrial scale [ 64 ]. For this reason, the production of PR should be carried out in a closed system with controlled atmosphere, a suitable level of stirring and low pressure. Once we are able to produce polyricinoleic acid with the appropriate acid value, it is used as substrate of the second reaction, that is, the esterification of PR with polyglycerol.

Selection of Lipases Lipase from Candida rugosa was used to carry out the autocondensation of ricinoleic acid to obtain the estolide, which is the first step in PGPR synthesis. Obviously, it would be very convenient if the same lipase could serve as catalyst for the two reaction steps. However, several studies revealed that Candida rugosa lipase was unsuitable for PGPR synthesis, and therefore others lipases were assayed for this purpose [ 65 ].

A further twenty lipases from different sources were used, and the corresponding experiments of PGPR synthesis were performed. Table 5 shows the lipases tested, their specific activities as declared by the manufacturer , and the amounts of protein used in each experiment. It is important to note that many of the lipases were part of two kits [ 91 ] and the amount available was limited. In such cases, the total available protein was added to the reactor.

The evolution of the acid value with time for the enzymatic production of PGPR with the above mentioned lipases is plotted in Figures from 16 a to 16 d. The lipase from wheat germ exhibited a particular behavior. When it was tested to produce PGPR, the acid value of the reaction mixture increased, which indicates that polyricinoleic acid is being hydrolyzed, and therefore, under the experimental conditions, the hydrolytic activity of this lipase is greater than its synthetic activity.

It was thought that any acid value decay in the reaction mixture might be due to two possible reactions: i the synthesis of estolides with a higher polymerization degree and ii the esterification of polyricinoleic acid with polyglycerol-3 the desired process.

In case of the reactions catalyzed by the remaining lipases tested, there is no doubt about the cause of the decrease of acid value, because they are 1,3-specific and cannot act on hydroxy fatty acids [ 69 ].

On the other hand, it may be surprise that Mucor javanicus and Rhizopus sp. If polyglycerol-3 is a linear molecule, only two of the five hydroxyl groups available as acyl acceptor groups are primary, and the acid value reached when these lipases are used indicates that more than two hydroxyl groups have been esterified.

This fact can be explained if condensation of glycerol takes place between secondary-primary or secondary-secondary hydroxyl groups. In that case more than two primary hydroxyl groups may remain available as acyl acceptor groups. As can be seen in Figure 16 , satisfactory results were obtained when the twelve mentioned lipases were used to catalyze the production of PGPR, and some graphs are indistinguishable. Table 6 shows the acid values reached after 7 days of reaction, which permits a better comparison of the obtained results.

It can be observed that the lowest acid values were reached when lipases from Pseudomonas 3 enzymes and Chromobacterium viscosum were used. However, some of the lipases used in the present work are very expensive, which is an aspect that should be carefully considered if the long-term purpose is to develop an industrial procedure for PGPR production.

Therefore, in order to finally choose one or more of these lipases, we took into account not only kinetic aspects reaction rates and final acid value of the reaction mixture but also the cost of the procedure. In order to evaluate this economic aspect of the enzymatic biosynthesis of PGPR and because lipase is the most expensive material involved in the reaction, the cost of biocatalysts that cause a decrease of one unit of the acid value was calculated, and the results are showed in the last column of Table 6.

These results, together with those shown in Figure 16 , led us to select lipases from Rhizopus oryzae , Rhizopus arrhizus , and Mucor javanicus to catalyze PGPR synthesis [ 65 ]. Therefore, the three chosen lipases were immobilized by physical adsorption onto an anion exchange resin Lewatit MonoPlus MP What does PGPR mean? Couldn't find the full form or full meaning of PGPR? Notify me of new comments via email. Cancel Report. Create a new account.

Log In. Know what is PGPR? Got another good explanation for PGPR? Don't keep it to yourself! Add it HERE! I recently ate a Hershey bar for the first time in a long time. I had a violent allergic reaction with a very itchy rash that lasted for a week. I required a doctor visit and two prescription medications before I got some relief.

How is this not natural?? What are you not telling us?? Please reply! A food additive claimed natural usually meet two requirements: 1 can be found in natural 2 made from extraction or fermentation or other manufacturing process that can be called natural instead of chemical synthesis. Never noticed this ingredient until recently. Thanks for the info. When I ate a quarter of the bar yesterday I had severe bloated indigestion when eaten in conjunction with bread.

I tried another quarter of the bar today with plain dry water biscuits [i. I will just eat the water biscuits tomorrow evening and by process of elimination if my problem disappears I will totally avoid PGPR chocolate? Thanks for the information. I have not had a reaction to it but will probably refrain from purchasing chocolate with PGPR.

Thank you for the article! I also will avoid buying any chocolate with PGPR. I feel like I am chewing on a candle. I will happily pay more to have the good chocolate back that you used to make — get rid of PGPR and start putting cocoa butter back!!! I ate a Twix candy bar today.

I will never buy this product again: PGPR has ruined the flavor of my former favorite candy. As in the deadly poison made from castor beans. Just like PGPR. How is it made? The brief 3 step manufacturing processes as follows: 1.

Solubility Insoluble in water and in ethanol; soluble in ether. Structure Image Source. James Han Founder of FoodAdditives.