Louise Slade

Publications (20) View all

• Article: Melting and Crystallization of Sugars in High-Solids Systems.

  Yrjö H Roos, Marcus Karel, Theodore P Labuza, Harry Levine, Mohamed Mathlouthi, David Sinclair Reid, Evgenyi Shalaev, Louise Slade
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  ABSTRACT: Crystalline structures of sugars, particularly that of sucrose, depend on crystallization conditions and the presence of impurities. Sugar crystals show melting that often occurs at low temperatures with time- and temperature-dependent characteristics. Melting at low temperatures can be accounted for by the presence of impurties and defects. Sugar crystals also contain noncrystalline regions that may undergo decomposition and subsequent dissolution at the decomposition interface and acceleration of decomposition reactions. Such processes with melting establish a supersaturated condition for the remaining crystals, leading to a time-dependent melting-point depression and subsequent melting of the remaining crystals. Decomposition of sugars, as well as dissolution and melting of sugar crystals, are separate phenomena, although they are commonly found to coincide. Decomposition of sugars requires the presence and mobility of molecules for reactions outside of the crystal lattice, i.e., molecular mobility of amorphous or melted regions is a prerequisite for decomposition, while melting of sugar crystals occurs as a separate thermodynamic process with no chemical change of the molecules.
  Journal of Agricultural and Food Chemistry 03/2013; · 2.82 Impact Factor
• Article: Comment on the melting and decomposition of sugars.

  Yrjö H Roos, Felix Franks, Marcus Karel, Theodore P Labuza, Harry Levine, Mohamed Mathlouthi, David Reid, Evgenyi Shalaev, Louise Slade
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  ABSTRACT: Melting of sugars has been studied by numerous authors, including Roos (1) and many others, as summarized in Lee et al. (2). Lee et al. (2-5) published a series of papers on melting of sugars, studied almost exclusively using variations of differential scanning calorimetry (DSC). These publications have opened up a serious discussion on the melting of sucrose and other sugars. A misinterpretation of the data published in the Journal of Agricultural and Food Chemistry was used in public media and the 2011 Annual Meeting of the Institute of Food Technologists and Food Technology magazine (6) to proclaim that "sugar doesn't melt, as previously believed, but rather decomposes". We present here arguments that clearly refute the conclusions of Lee et al. (2-5) and express our concerns on published statements lacking scientific validation prone to devalue the food science discipline and mislead readers by fostering a misbelief that sugars do not melt.
  Journal of Agricultural and Food Chemistry 09/2012; 60(41):10359-62. · 2.82 Impact Factor
• Article: The “food polymer science” approach to flour functionality and ingredient technology in biscuit baking

  Harry Levine, Louise Slade
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  ABSTRACT: An overview is made on the “food polymer science” approach developed by the authors. The quality and performance of flours for the production of cookies and crackers have been shown to depend upon the major functional polymeric components of flour: gluten protein, damaged starch, and pentosans. Of these, damaged starch and soluble pentosans in soft-wheat flours are detrimental to the commercial production of low-moisture cookies and crackers. The detrimental effects of soluble pentosans in flours can be eliminated through the use of pentosanase enzyme in cookie and cracker doughs. Three commercialized applications of this industrial enzyme technology have been patented by Nabisco. The “food polymer science” approach to baking technology has also been used to study finished-product attributes such as texture, in the context of the thermomechanical properties (e.g. modulus) of glassy solid and rubbery liquid matrices. Results of various studies have clearly demonstrated that products in a glassy solid physical state (at T < Tg) are hard and crisp in texture, but upon increasing plasticization by water (such that Tg is depressed below the observation T), are transformed to a rubbery or viscous liquid state, wherein textural hardness (and mechanical modulus) and crispness are dramatically reduced.
  Macromolecular Symposia 03/2011; 140(1):77 - 80.
• Article: The glassy state phenomenon in applications for the food industry: Application of the food polymer science approach to structure–function relationships of sucrose in cookie and cracker systems

  Louise Slade, Harry Levine, James Ievolella, Martha Wang
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  ABSTRACT: This review of the glassy state phenomenon in applications for the food industry comprises two main parts. The first is a broad but brief overview of the so-called ‘food polymer science’ approach and its importance to food R&D studies of glassy solid and rubbery liquid states and glass transitions in food products and processes. The following elements of this approach are discussed: (i) the glass transition temperature (Tg) and methods for its measurement in foods; (ii) plasticization by water and its effect on Tg; (iii) the concepts of ‘water dynamics’ and ‘glass dynamics’ in non-equilibrium food systems; (iv) Williams–Landel–Ferry kinetics in the rubbery state above Tg, (v) state diagrams; and (vi) the effect of molecular weight on Tg. A comprehensive and up-to-date listing of more than 400 literature references on the glassy state phenomenon and glass transitions in food materials and systems is featured in that part of the paper, and these references are also compiled and tabulated according to specific subject headings. The second part of this review highlights the application of the food polymer science approach in recently reported studies on the structure–function relationships of sucrose in cookie and cracker systems. This part describes (i) the sucrose–water state diagram as a tool in understanding cookie and cracker baking; (ii) shortcomings of the traditional AACC sugar-snap cookie method as a test-baking system, in contrast to a new test system based on a model commercial-type wire-cut cookie formula; and (iii) a revealing illustration of sucrose functionality in cookie baking. The review concludes with a word about future prospects.
  Journal of the Science of Food and Agriculture 09/2006; 63(2):133 - 176. · 1.44 Impact Factor
• Source

  Available from: ncbi.nlm.nih.gov

  Article: Staphylococcus aureus growth boundaries: moving towards mechanistic predictive models based on solute-specific effects.

  Cynthia M Stewart, Martin B Cole, J David Legan, Louise Slade, Mark H Vandeven, Donald W Schaffner
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  ABSTRACT: The formulation of shelf-stable intermediate-moisture products is a critical food safety issue. Therefore, knowing the precise boundary for the growth-no-growth interface of Staphylococcus aureus is necessary for food safety risk assessment. This study was designed to examine the effects of various humectants and to produce growth boundary models as tools for risk assessment. The molecular mobility and the effects of various physical properties of humectants, such as their glass transition temperatures, their membrane permeability, and their ionic and nonionic properties, on S. aureus growth were investigated. The effects of relative humidity (RH; 84 to 95%, adjusted by sucrose plus fructose, glycerol, or NaCl), initial pH (4.5 to 7.0, adjusted by HCl), and potassium sorbate concentration (0 or 1,000 ppm) on the growth of S. aureus were determined. Growth was monitored by turbidity over a 24-week period. Toxin production was determined by enterotoxin assay. The 1,792 data points generated were analyzed by LIFEREG procedures (SAS Institute, Inc., Cary, N.C.), which showed that all parameters studied significantly affected the growth responses of S. aureus. Differences were observed in the growth-no-growth boundary when different humectants were used to achieve the desired RH values in both the absence and the presence of potassium sorbate. Sucrose plus fructose was most inhibitory at neutral pH values, while NaCl was most inhibitory at low pH values. The addition of potassium sorbate greatly increased the no-growth regions, particularly when pH was <6.0. Published kinetic growth and survival models were compared with boundary models developed in this work. The effects of solutes and differences in modeling approaches are discussed.
  Applied and Environmental Microbiology 05/2002; 68(4):1864-71. · 3.83 Impact Factor