7/28/2019 BK9780854048663-00001 http://slidepdf.com/reader/full/bk9780854048663-00001 1/8 Introduction - Progress in Amorphous Food and Pharmaceutical Systems Harry Levine NABISCO R&D, KRAFT FOODS, EAST HANOVER, NEW JERSEY 07936, USA When the conference convener, Felix Franks, asked me to kick-off the opening session by chairing an introductory panel discussion on ‘progress since 1990’, I thought it might be interesting (to all the conferees, not just to me) to begin that discussion by presenting a chronology of key milestones on the subject, from my own personal and admittedly biased perspective. That chronology is shown in Table 1. For me, the story began in 1979 (at General Foods [GF], where I had started working as a polymer chemist in 1976, following a 2-year post-doctoral fellow- ship) when I happened to find and read a paper by Felix Franks and co-workers’ on biological cryoprotection. In that seminal paper, the concept of Ti, a charac- teristic subzero glass transition temperature for a maximally freeze-concentrated aqueous solution, was introduced for the first time. As illustrated in Figure 1, T,’ was shown on a differential scanning calorimetry thermogram and a solute- water state diagram, and was identified as % Tr, the recrystallization tempera- ture, for water-compatible polymers such as poly(viny1 pyrrolidone) and hy- droxyethyl starch. It occurred to me that Franks’ new conceptual approach to biological cryoprotection might be applicable to the storage stabilization of ice-containing frozen foods. I thought I should try to meet Prof. Franks and discuss the matter with him. In early 1980, during a multi-purpose business trip to Europe, I had an opportunity to visit Cambridge University in England and meet Felix Franks for the first time. That was a turning point in my life, both professionally and personally. When I returned to GF, I arranged to invite Felix to visit our Technical Center in Tarrytown, NY and present a guest seminar, which was co-hosted by two of my young colleagues in Central Research, Tim Schenz and Louise Slade, along with myself. As a consequence of that first visit to Tarrytown, Felix became a paid consultant to General Foods from 1980-87, as well as a scientificmentor (and lifelong friend)to Louise and me. [Twenty two years later, I still enjoy telling people that Felix was the person responsible for bringing Louise and me together, first professionally and then personally.] 1
Progress in Amorphous Foodand Pharmaceutical Systems
Harry Levine
NABISCO R&D, KRAFT FOODS, EAST HANOVER, NEW JERSEY07936, USA
When the conference convener, Felix Franks, asked me to kick-off the openingsession by chairing an introductory panel discussion on ‘progress since 1990’, Ithought it might be interesting (to all the conferees, not just to me) to begin thatdiscussion by presenting a chronology of key milestones on the subject, from myown personal and admittedly biased perspective. That chronology is shown inTable 1.
For me, the story began in 1979 (at General Foods [GF], where I had startedworking as a polymer chemist in 1976, following a 2-year post-doctoral fellow-
ship) when I happened to find and read a paper by Felix Franks and co-workers’on biological cryoprotection. In that seminal paper, the concept of T i ,a charac-teristic subzero glass transition temperature for a maximally freeze-concentratedaqueous solution, was introduced for the first time. As illustrated in Figure 1, T,’was shown on a differential scanning calorimetry thermogram and a solute-
water state diagram, and was identified as % Tr,the recrystallization tempera-ture, for water-compatible polymers such as poly(viny1 pyrrolidone) and hy-droxyethyl starch. It occurred to me that Franks’ new conceptual approach tobiological cryoprotection might be applicable to the storage stabilization of
ice-containing frozen foods. I thought I should try to meet Prof. Franks anddiscuss the matter with him.
In early 1980, during a multi-purpose business trip to Europe, I had anopportunity to visit Cambridge University in England and meet Felix Franks forthe first time. That was a turning point in my life, both professionally andpersonally. When I returned to GF, I arranged to invite Felix to visit ourTechnical Center in Tarrytown, NY and present a guest seminar, which wasco-hosted by two of my young colleagues in Central Research, Tim Schenz andLouise Slade, along with myself.As a consequence of that first visit to Tarrytown,
Felix became a paid consultant to General Foods from 1980-87, as well as ascientific mentor (and lifelong friend) to Louise and me. [Twenty two years later,I still enjoy telling people that Felix was the person responsible for bringingLouise and me together, first professionally and then personally.]
Table 1 A chronology -from a personal perspec tive
Introduction - Progress in Amorphous Food and Pharmaceutical Systems
1979 Seminal paper on ‘biological cryoprotection’ found and read -Franks et al., J .
Microscopy, 1977.’ Tg’ z ,) shown for the first time [Figure 11on a DSC thermogram and solute-water state diagram
Levine met Franks at Cambridge, then Levine, Slade and Tim Schenz hostedFranks at a General Foods, Tarrytown seminar. Franks became G Fconsultant (1980-87) and mentor to Levine and Slade
1980-82 Other historical papers found and read -White &Cakebread (1966)2- glassystate in foods; Luyet, MacKenzie, Rasmussen (1939-77)3-6- biological
1980
1982
1985
1987
1989
1991
1992
19941995
2001
cryoprotection; Parks et al. (1928-34)7,8-glucose glasses;van den Berg (1981 thesis)’ -glass transition in starchSlade and Levine attended Franks’ Cambridge Conference on BiologicalCryoprotection-met, e.g. Angell and the CrowesSlade attended Franks’ Cambridge Conference on ‘Water Activity? and gaveground-breaking lecture” on ‘Food Polymer Science’ approach ‘Beyond
“Water Activity”. . ’Levine and Slade began teaching their Food Polymer Science short course[Figure 2-magazine cover]Levine and Slade organized ACS ‘Water Relationships in Foods’ symposium+edited 1991 Plenum book’’ (>600 citations to date)Slade and Levine’s CRC Crit. Revs. monograph ‘Beyond Water Activity.. .’I2
published +>470 citations to dateBlanshard’s ACTIF program at Nottingham University (1989-92) +1992Easter School -+1993 ‘Glassy States in Foods’‘What are Harry and Louise talking about? [media Figure 31Franks and Levine organized ‘AMORPH 1’ conference at Cambridge -‘Discussion Symposium on Chemistry and Application Technology ofAmorphous Carbohydrates’ -,Summary report on current status[Highlights - Table 21Franks’ list of ‘outstanding questions’ on Solid Aqueous Solutions of
carbohydrate^'^ [Table 31 -+
5/15/01 ‘AMORPH 2001’at Cambridge- The Amorphous State -A Critical Review’
During the period from mid-1980 through 1982, while Louise and Tim and I
were busy building a very large experimental database of DSC-measured T,’
values for hundreds of food ingredients, materials and products, I also found and
read many other historical papers on glasses, glassy states and the glass transi-
tion in food and biological systems. They included: White and Cakebread’s 1966
paper on the glassy state in sugar-containing foods;2 an extensive series of works
by Luyet, Rasmussen and MacKenzie, published from 1939 to 1977, on frozen
aqueous solutions of small carbohydrates with application to biological cryop-
r ~ t e c t i o n ; ~ - ~n even earlier series of papers by Parks et al. (1928-34) on the
physical chemistry of glucose and a 1981 doctoral thesis by van den
Berg on the glass transition in starch-water ~ ys tem s . ~
In 1982, Louise and I managed, after much difficulty with corporate prohib-
itions, to obtain GF approval to attend our first scientific conference at Cam-
bridge’s Girton College, on the subject of biological cryoprotection and organ-
ized by Felix. There, we met for the first time such well-known workers in this
field as Austen Angell and the Crowes, John and Lois, whose many papers we
6 Introduction - Progress in Amorphous Food and Pharmaceutical Systems
on the topic of ‘The Glassy State in Foods’, the proceedings of which werepublished as a major book in 1993.13
And now for a touch of humor [at least, friends of ours thought it washilarious]. In 1994, during the political campaign season in the US, there was a
series of TV advertisements featuring a married couple named ‘Harry andLouise’, who discussed in excruciating detail the pros or cons (I forget which) of aClinton (Hilary!) health care proposal of that time. Those several commercialsran so frequently and for so long that they generated various derogatory com-ments and reactions in the media of the day, two pieces of which are shown inFigure 3. Since by this time, we had been teaching our short course for eight years(and even had it videotaped once or twice), had published many voluminousreview papers, and never seemed to be able to deliver an invited presentationwithout going well over our allotted time, we were unhappily accustomed tohearing people often say ‘what are Harry and Louise talking about?’. But seeing
that written in large bold print in a newspaper was something else again.In 1995, Felix and I organized the first ‘AMORPH’ conference at Cambridge,
a ‘Discussion Symposium on the Chemistry and Application Technology ofAmorphous Carbohydrates’. The previously unpublished summary report fromthat conference, compiled by Felix, is reproduced here in its entirety in Felix’sPreface. For my Introduction to the AMORPH 2001 conference, I summarized
I
What are Harry and Louise talking about?glad you don’t have friendsUke Harrg and Louise?
Figure3 Humorous media pieces fr om 1994 on ‘Har ry and Louise’
highlights from Felix’s 1995 summary report, which are shown in Table 2.
Among our preparations for AMORPH 2001 at Cambridge, Felix produced a
list of ‘outstanding questions’ on Solid Aqueous Solutions of carbohydrate^,'^which are reproduced here in Table 3. Those questions were intended to form the
basis for the presentations (plenary lectures and invited contributions), posters
and discussion sessions during AMORPH 2001 on ‘The Amorphous State - A
Critical Review’. The rest of this book comprises the written proceedings from
that conference, which I’ve had the honor and pleasure of editing, for publication
by the Royal Society of Chemistry.
Table 2 Highlights rom ‘AMORPH 1’ Summary Report
Topic 1-Relationship between Molecular Structure and Glass Transition
Angell’s ‘strong/fragile’ classification scheme for glass-formers, along with TJTg ratio,may be useful in distinguishing behaviors among various common mono- anddisaccharide sugars.
Topic 2 -Chemical Reactivity of Solid Sugars
Some chemical reactions, especially those that do not rely on translational diffusion, canand do occur below Tg’hemical reaction rates (e.g. for Maillard browning), both belowand above T,, depend on mobility of reactants that may include water (e.g.hydrolysis).
Topic 3 -Chemistry and Biochemistry in Supersaturated Carbohydrate Mixtures
Accounts of survival of microorganisms, seeds, and viruses in glassy matrices, and of
varying storage stability of enzymes, proteins and drugs, after drying in ‘protecting’
sugar glasses, were discussed.Topic 4-Physical Processes (e .g . Crystallization) of and within AmorphousCarbohydrates; Kinetics; Effects of Residual MoistureandTopic 5 -Solid Solutions involving Carbohydrates
According to crystallization kinetics theory, crystallization does not occur below T,. utvery slow crystallization at T < , as been reported, e.g. for the drug indomethacin.However, at 50“C below T,, indefinite stability against crystallization can be achieved.
Topic 6 -Dynamics, especially of Small Molecules within Amorphous Carbohydrates
Translational diffusion of small molecules (with low T,),even including water, at T< T g
of an amorphous carbohydrate matrix of higher T, (due to higher MW) can occur, butwill be much slower than the diffusion of the same small molecule in a bulk liquid state.
Topic 7 -Model Systems and Analytical Methods
After a search for a ‘single best’ method for determination of T, or solid carbohydrates,the consensus was in favor of a combination of techniques, which could include DMTA,DSC (or MDSC), DETA, NMR, ESR, dielectric permittivity, X-ray diffraction,IR/Raman spectroscopy, microscopy, and computer simulation.
Topic 8 -Amorphous Carbohydrates as Biostabilizers
Amorphous carbohydrates find widespread application as stabilizers (excipients) of
labile biologicals. The glassy solid state can be a necessary but not sufficient conditionfor stability. Stabilization with trehalose can be more successful than with sucrose,which can be due to the higher T, and lower chemical reactivity of trehalose.
[Note added in 2001- rehalose is now FDA-approved and commercially available (butexpensive) for use in foods in the United States.]
Table 3 Solid aqueous solutions of carbohydrates - utstanding questions
Introduction - Progress in Amorphous Food and Pharmaceutical Systems
Supersaturated carbohydrate solutionsSolvent effects on intram olecula r mo bilityMolecular structure an d thermomechanical propertiesRelationship between crystal structure a nd glass ‘structure’Me thods for studying hydrogen b ond topologyCrystallization of oligosaccharides from aqueo us glassesParad oxes posed by su gar hydrates: the raffinose mysteryDynam ics within aq ueous glasses: uncoupling of molecular motionsRelaxation rates an d fragility: analysis of D SC scansCom plexities of terna ry (m ulticom pone nt) systemsSug ar glasses as stabilizing principles: ecology and technology
References
1 . F. Fra nks, M.H. Asquith, C.C. Hamm ond, H.B. Skaer and P. Echlin, J . Microscopy,
2. G.W. White and S.H. Cakebread, J . Food Technol., 1966,1,73.
3. B. Luyet, J . Phy s. Chem., 1939,43, 881.
4. D. Rasmussen and B. Luyet, Biodynamica, 1969,10,319.
5. A.P. MacKenzie and D.H. Rasmussen, Wa ter Structure at the W ater-Polymer Inter-
face , H.H.G . Jellinek (ed.), Plenu m Press, New Y ork, 1972, 146.
6. A.P. MacK enzie, Phil. Trans. R oy . SOC.Lond. B, 1977,278,167.
7, G.S. Parks, H.M . Huffman and F.R. Cattoir, J . Phy s. Chem., 1928,32,1366.
8. G.S. Parks, L .E. Barton, M .E. Spaght an d J.W. Richardson, Physics, 1934,5,193.
9. C. van den Berg. Vapou r Sorption Equilibria and O ther W ater-Starch Interactions: A
Physico-Chemical Approach, P h D thesis, Agricultural University, Wageningen, Ne th-
erlands.
10. L. Slade and H. Levine, Faraday Division, Royal Society of Chemistry, IndustrialPhysical C hemistry G rou p, Conference on Concept of W ater A ctivity, Cambridge,U K , 1985.
11. H. Levine and L. Slade (eds.), W ate r Relationships in Foods, Plenum Press, New Y ork,
1991.12. L. Slade and H. Levine, Cr it. Reus. Food Sci. Nut r., 1991,30, 115.
13 . J.M.V. Blanshard and P.J. Lillford (eds.), The Glassy State in Foods, Nottingham
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