It is nice to see the second special issue derived from the International Forum on arabinogalactan protein.
It is well known that the role of hydrocolloids to control the texture, which is one of the most decisive factor for the palatability, is important and that hydrocolloids are widely used in food industry. Since the recent change in legislation on food additives, it is admitted to display on a label “thickening polysaccharides” when more than two different natural polysaccharides without specifying the individual names such as pectin, carrageenan, xanthan gum, gellan gum, arabinogalactan etc. For those who know some ingredients, this method of display seems to be too simple and they may wish to know more about the polysaccharides used in such processed foods. However, with the advent of small package of foods sold in a so-called convenience store, it is difficult to display the details of all ingredients on a limited space of a label.
It is nice to see that there is a growing interest in hydrocolloids when people talk about the importance of educational aspect of food and eating. As is well known, most food polysaccharides except starch are useful not only for the texture control, but also are dietary fibres and have beneficial physiological functions, which is now a hot topics in food science. FFI Journal has been contributing to the spread of useful knowledge in food science for both scientists and technologists and general public. We are all expecting that the journal continues to publish interesting articles in food science and arts. Since the variety is the most important aspect in foods, there should be no end of the journal, and so it is never ending.
The details of the organization process of the International Forum and the importance of the international cooperation between academia and industry were already written by Professor Phillips and Dr. Ogasawara in the first issue, and it is expected that the international cooperation will be developed further in the near future. There are still many unknown problems and characteristics in food hydrocolloids although there have been extensive efforts to understand the relation between structures and properties, which is very important for developing further application in food processing. Food engineers and technologists are sometimes too busy to examine the structure and properties of each polysaccharide, and are apt to do only trial and error method or at most to start from the “established” fact. It is important to have stimulating interaction between fundamental science and industrial application. It is indeed wonderful to see that the International Forum was successful and that the organizer Prof. Phillips has been organizing the long run international conference “Gums and Stabilisers for the Food Industry”, so-called Wrexham Conference or Gums Conference for more than 25 years. Another series of international conference on hydrocolloids (IHC), which has been organized every two years when there is no Gums Conference, has been also effective to activate the cooperation between academia and industry. The 8^th IHC will be held in Trondheim in June 2006, and the 14th Gums Conference will be held in Wrexham in June 2007. It is a pity to see not so many participants from Japan to these international conferences, but I hope that many researchers will be interested in the near future.

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The International Forum is one of the instruments of the International Cooperation for Global Innovation programme being implemented jointly by Phillips Hydrocolloids Research Ltd (PHRLtd) and San-Ei Gen FFI Inc to explore the boundaries of scientific areas related to our commercial interests. There is great excitement in exploring inter-disciplinary subjects, and the Arabinogalactan Proteins (AGPs) represent one such area.
They are a large family of glycoprotein found in plants membranes, cell walls and plant secretions, and are ubiquitous throughout the plant kingdom. The Forum was planned to bring together experts in the various aspects of these fascinating materials, which span all the way from controlling plant development to providing important industrial commodities and technical products. Chemical botanists, plant biologists, genetic manipulators, medical doctors, cell biologists and microbiologists have joined chemical and industrial research scientists in the quest to understand these incredibly diverse yet related materials. The two editions of the Journal are the result. The second edition here concentrates on a specific AGP of industrial importance derived from Acacia trees in Africa.
Gum arabic or gum Acacia is a tree gum exudate and has been an important article of commerce since Ancient times. It was used by the Egyptians for embalming mummies and also for paints for hieroglyphic inscriptions. Traditionally the gum has been obtained mainly from the Acacia senegal species. The trees grow widely across the Sahelian belt of Africa situated north of the equator up to the Sahara desert and from Senegal in the west to Somalia in the east. The gum oozes from the stems and branches of trees (usually after five years of age or more) when subjected to stress conditions such as drought, poor soil or wounding. Production is stimulated by 'tapping', which involves removing sections of the bark with an axe taking care not to damage the tree. The sticky gummy substance dries on the branches to form hard nodules which are picked by hand and are sorted according to colour and size.
In the food industry the most commonly used species is Acacia senegal and is a major food additive and ingredient. It is the most versatile of all food additives because it combines so many diverse functionalities. These include emulsification when the AGP can coat an oil or a fat droplet in beverages and confectionary, encapsulation of flavour, essential oils and vitamins, adhesion to form glazes and to prevent sugar crystallization, texture modification. They can bind water, so enhance water absorption, provide foam stabilization and yield a large elastic modulus to give tenacity in such products as chewing gum and pastilles.
But how can they achieve all this range of functionalities? This is the subject of the second edition of the AGP Forum. The structure while still holds some secrets has to some extend been unlocked, as demonstrated by Professor Peter Williams and Dr S. Al-Assaf. Its composition is complex but it is this very diversity of protein and carbohydrate in the glycoprotein which gives it its special quality. The AGP component is central to its effective action. For example, if its AGP component is removed, destroyed or hydrolysed to its component shorter peptide chains it will not coat an oil droplet to prevent their coalescence or aggregation, which is the necessary property to enable the Acacia gum to be the best natural emulsifier. Professor Nishinari explores the rheological properties of these systems which make them so valuable, being fluid over a range of concentrations, but able to form foams and viscous solutions also – again a consequence of their combined hydrophobic and hydrophilic glycoprotein AGP character.
The way in which this specific and important industrial AGP operates has been examined by Dr Sasaki and Mr Sakata. 「View PDF for the rest of the abstract」

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This paper provides an overview of the literature concerned with the physicochemical characterisation of gum arabic and discusses current concepts regarding the molecular structure.

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Gel permeation chromatography (GPC) coupled on line to a multi angle laser light scattering, refractive index and ultra violet (UV) detectors was used for the characterisation of gum arabic and particularly the high molecular weight arabinogalactan protein (AGP) fraction.
Factors influencing the molecular weight determination of the gum arabic such as characteristics of the column, data processing method, hydration and filtration through different pore size filters are discussed. Examination of a large number of gum arabic samples provided by several different suppliers and user companies revealed wide variation in the weight average molecular weight for the whole gum ranging from 400K to 2 million as well as variation in the AGP content and molecular weight. The variation was found to be mainly due to the presence of ultra high molecular weight aggregates which elute in the void volume. Filtration through small size filters removes this aggregate fraction and brings the molecular weight parameters of the whole gum and AGP fraction closer to characteristic norms. A method whereby the contribution from the aggregate peak is removed electronically has been shown to correlate well with the filtration treatment.
Characterisation of the AGP fraction from another acacia species, namely A. seyal reveals two components that are included within the high molecular weight peak. Only one of these components is degraded by protease.

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The series of control Acacia senegal gums and the samples which had been matured to produce the Acacia (sen) SUPER GUM™ samples (FR-2877, FR-2878 FR-2879, EM1 and EM2) were examined by NMR, FT-IR spectroscopy and dynamic light scattering. No chemical difference in any of the samples could be detected by ¹³CNMR or 2D NMR (COSY) spectroscopy. The ¹H NMR and ¹H NMR spectra confirmed these observations, but showed that at the highest level of maturation to average molecular weights in excess of 2.5 x 10⁶, some changes could be observed, which probably is due to dehydration of the COOH uronic acid group. The selection of the matured gums for commercial use ensures that no observable changes are evident in these gums.
Dynamic light scattering data showed these gums are highly heterogeneous in molecular size. In extreme dilute solutions, two distinctively separated populations of particles were observed with the sizes of each group almost identical for the control gum (EM0) and SUPER GUM™ samples (EM1 and EM2) (~20 nm and ~70 nm, respectively). However, the relative amount of the larger size group was in the order of EM0<EM1<EM2, corresponding to an increase in molecular weight. On increasing the polymer concentration, the two groups seem to form aggregates of their own independently, giving two new groups of particles. The maturation treatment resulted in a significant increase in the size of the larger size group which suggests the maturation treatment not only increased the molecular weight of gum arabic, but also modified the surface properties of the molecules in a way that makes them more able to aggregate.

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The structure of the arabinogalactan protein of gum arabic and its mode of supramolecular association have been investigated by atomic force microscopy. Gum arabic samples and fractions derived by hydrophobic interaction chromatography were dissolved in H₂O and deposited on surfaces for imaging by tapping mode atomic force microscopy in air. Two different surfaces were used: mica and graphite. The mica surface is hydrophilic, negatively charged, and acquires a thin layer of water from atmospheric water vapor. Graphite is a hydrophobic surface, and is poorly hydrated. The two surfaces provide complementary information about the samples.
On mica, rounded globules were observed. This reflects weak attraction to the mica surface, and consequent intramolecular condensation of the sample components. The globules appear to fall into two classes differing in size. The diameters at half height, uncorrected for tip broadening effects, were approximately 20-40 nm and approximately 50-60 nm for the two classes. Real diameters would be smaller. The globules are tentatively identified as arabinogalactan (AG) and arabinogalactan protein (AGP), respectively.
On graphite, both globular and extended forms were observed. Resolution was generally superior to that obtained on mica. Small globules less than about 20 nm in diameter were observed as isolated features, and as subunits in assemblies, where close packing allowed a globule diameter of 10-16 nm to be determined. The small globules were attributed to partially dehydrated AG polysaccharide. They were the most prevalent feature imaged, in accord with the gum composition of 89% AG component, and a hydrodynamic diameter measured in solution of approximately 20-30 nm for AG. Extended structures, with both thin linear sections and linear arrays of globules, were observed and attributed to the AGP component. The AGP structure observed was consistent with the "wattle blossom" model.

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The rheological behaviours of aqueous solutions of gum arabic were investigated in this study. The gum arabic solutions at concentrations of 10 wt% and 30 wt% showed shear thinning flow behaviour. Viscosity of the non-centrifuged solution was higher than that of the centrifuged solutions at low shear rate region, suggesting that the air bubbles in the solution contribute to increasing of viscosity. The gum arabic solution can contain many air bubbles in the dissolving process, since the gum arabic has high surface activity in the aqueous solution. Air bubbles in the solution of gum arabic can be partially removed by centrifugation of the solution. The Newtonian regime can be observed at high shear rate region in the both non-centrifuged and centrifuged solutions and the viscosity of non-centrifuged solution was the same as that of centrifuged solutions. In dynamic rheological behaviours, the storage modulus of non-centrifuged solution was higher than that of centrifuged solution at low frequency region. The storage modulus of both non-centrifuged and centrifuged solutions increases with time when temperature is changed from 10℃ to 32℃, as in the gelling process.

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The relationship between emulsion stability and oil adsorbed component of gum arabic was studied using gum arabic of two molecular weights. The emulsion using high molecular weight gum arabic was more stable than the emulsion using low molecular weight gum arabic. The adsorbed component on to the oil surface of emulsion was desorbed and analyzed using GPC-MALLS. The adsorbed fractions of gum arabic are the arabinogalactoan protein (AGP) and glycoprotein (GP) components, which containing protein, but make up only 7~10% in the whole gum arabic. There is no significant difference in the amount adsorbed on to the oil surface in the emulsions made with high molecular or low molecular weight gum arabic. The molecular weight of adsorbed component on to the oil surface is more important for emulsion stability than the amount of gum arabic adsorbed.

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Two gum arabic samples of high (GA-H) and low molecular weight (GA-L) were used in this study to investigate the effect of high pressure homogenisation. The effect of pressure homogenisation on gum arabic solutions and ultimately adsorption of the gum on to oil droplets has not previously been reported. In this study, the effect of high pressure homogenisation on gum solutions was monitored using the GPC-MALLS technique, which enabled the oil adsorbed component to be measured. Moreover, the relation between the stability of the emulsion and the pressure homogenisation treatment was evaluated. Gum arabic solutions were treated by dispersion or high pressure (1 or 3 pass at 25, 50, 75, 150 MPa). No significant changes were observed following dispersion treatment while a decrease in molecular weight and AGP content was confirmed by high pressure homogenisation a behaviour which was similar for both GA-L and GA-H solutions.
The droplet size distributions of the emulsion were determined initially, then the emulsion was treated for 3 and 7 days at 60℃ in order to accelerate the evaluation of stability. The results show a droplet size of 1 micron or greater is formed, with only a small fraction adsorbed on to oil droplet following this dispersion treatment only. The amount of adsorbed component increased with high pressure homogenisation , and was accompanied by lower droplet sizes but these decreased when the pressure increased to 150 MPa. High pressure homogenisation had a pronounced effect on the amount of adsorbed component and droplet size in GA-L but not on GA-H. The number of passes at a given pressure resulted in a reduction in initial droplet size and decreased amount of adsorbed component.
A decrease in molecular weight and AGP content was observed with gum arabic solutions treated by high pressure (75 MPa) compared with 25 MPa or 50 MPa. However, emulsions made with GA-L and GA-H which when treated with 75 MPa were found to be more stable compared with those treated with 25 MPa and 50 MPa. It is concluded that the stability of the emulsions is related not only to the amount of adsorbed component but also to the conformational and de-aggregation changes induced by high pressure homogenisation. It is, therefore, necessary to properly select the pressure homogenisation conditions to obtain stable emulsions.

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Evidence regarding the molecular structural basis of the emulsifying activity of gum arabic is reviewed. Emphasis is placed on tests of the hypothesis that some of the arabinogalactan proteins in gum arabic contain intact glycosylphosphatidylinositol lipid anchors that assist in binding to the surface of oil droplets and thereby contribute to the stabilization of dilute oil-in-water emulsions. Corn fiber gum, in which the proportion of protein content is similar to that of gum arabic, is evaluated as an alternative to gum arabic for use in dilute oil-in-water emulsions.

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The role of proteinaceous materials, especially the fraction bound to polysaccharide (i.e, AGP type fraction), in emulsifying was investigated using sugar beet pectin. Enzymatic modification of the pectin using acid proteinases decreased the total protein content from 1.56 to 0.13 % without altering the content of ferulic acid or the composition of constitutional sugar. The modification also decreased slightly the molecular size of the polysaccharide without marked change in the molecular mass. Emulsifying properties of the pectin with or without the modification were compared by the changes in droplet size and creaming stability of O/W emulsion (pH3.0) containing 15 % middle-chain triglyceride and 1.5% pectin as main constituents. The mean droplet size of the emulsion increased from 0.45 to 4.06μm and its creaming stability decreased after the modification. Mass distribution of the pectin within the emulsion elucidated that the modification apparently decreased the amount of the fraction existing in the oil phase from 5.4 to 2.1 % and that the molar mass of the fraction in the oil phase was approx. 2-4 times as large as that in the aqueous phase. Results from the present study suggested the important role of AGP type fraction to explain the emulsifying mechanism of sugar beet pectin.

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The aim of this study was to evaluate the nature of the protein in sugar beet pectin, with particular emphasis on determining whether the protein is linked to carbohydrate in an AGP-type structure, similar to gum arabic.
GPC-MALLS, coupled online to light scattering, refractive index and UV was used to determine the molecular weight and distribution. The contribution of ferulic acid to the UV response was quantified by monitoring the elution profile at three different wavelengths (214, 254 and 280 nm). The molecular weight for sugar beet pectin was found to be in the range of 4.7 to 5.8 x 10⁵ with a mass recovery of 70-80%, indicating the presence of 20-30% hydrogel particles which cannot pass through 0.45μm filters. In an effort to improve the mass recovery it was found that treatment such as longer hydration times, high shear mixing, hydrolysis, and sonication increased the mass recovery by bringing the hydrogel materials into solution. Reproducible data was obtained with high shear mixing and therefore, it was concluded that the molecular weight of sugar beet pectin sample is ~ 1 x 10⁶ when 100% mass recovery is obtained. Complete mass recovery was also achieved by enzymatic digestion using Viscozyme and filtration through small size filters which resulted in a drastic decrease in the molecular weight. There was only a small decrease in the molecular weight following protease digestion, which could be an indication of a covalent linkage between protein and carbohydrate moieties.

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Gum Ghatti, otherwise known as the Indian gum, is an exudate of the Anogeissus Latifolia tree belonging to the family Combretaceae. This tree species is widely found in all regions of India This gum has been known for many generations and has been mentioned in the ancient Greek and Hindu systems of medicine. The earliest mentions of this gum in the British/US Pharmacopoeia have been in early 1900’s.
Gum Ghatti was originally developed around 1900 as a substitute for gum arabic. It has higher viscosity compared to gum arabic and is a better emulsifying and suspending agent. Gum Ghatii has been used in a range of emulsions, suspensions and as a sizing agent in the paper industry.
The aim of this paper is to provide a background of Gum Ghatti dealing with its origins, chemical properties, features, journey from the tree to the industry, grades and the uses within the food industry. The regulatory status of this gum in different countries is also noted.

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In the fall of 2004, thanks to a generous fellowship grant from the Japan Society of New York, I spent 10 weeks gathering oral histories about how globalization, Westernization and modernization have affected culinary past-times in both rural and urban Japan. I am a radio reporter by training, so I took my microphone and tape recorder everywhere I went, capturing the sounds and voices of places as diverse as bustling depachika and typhoon-ravaged rice farms. Three experiences in particular left large impressions on me and helped me form my understanding of the current state of the Japanese mealtime. The first was a very chic, very international picnic with busy Japanese urbanites in Tokyo’s Shinjuku Park. That experience underscored how global a village urban Japan has become. With its lush offerings of French breads and cheeses and Italian meats and sweets, it also made me wonder just how far to the West the Japanese diet would lean in coming years, and at what cost to cherished Japanese culinary past-times and foods. The second experience was a journey north of Tokyo to Iwate Prefecture, where, in Towa-cho, I learned how rice farmers are coping with the combined pressures of natural disasters, globalization and a sagging local economy. I learned that even remote, rural areas are not immune to the downside of a global economy. The third experience took me into vast department store food emporia known as depachika. The range of foods sold and the kinetic energy of the places were themselves somewhat startling, but what I found most revealing was the edible evidence of Japanese innovation by way of imitation. Green tea éclairs and squid ink baguettes are just two examples of the way that Japanese chefs have fused the East and the West in a single dish that is, by way of its very inventiveness, uniquely Japanese. My many hours spent in depachika made me appreciate the peculiarly Japanese ability to preserve tradition by shaking it up. It also gave me hope that no matter how great a stake foreign influence claims on the Japanese palate and the Japanese table, the most innovative chefs and home cooks, farmers and artisans will always figure out a way to preserve their food’s essential “Japaneseness.”

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