Generation and characterization of standardized forms of trehalose dihydrate and their associated solid-state behavior

Trehalose dihydrate is a nonreducing disaccharide which has generated great interest in the food and pharmaceutical industries. However, it is well recognized that considerable batch to batch variation exists for supposedly identical samples, particularly in terms of the thermal response. In this investigation, two standardized forms of trehalose dihydrate were generated using two distinct crystallization pathways. The two batches were characterized using scanning electron microscopy, X-ray powder diffraction, and FTIR. The thermal responses of the two forms were then studied using modulated temperature differential scanning calorimetry (MTDSC) and thermogravimetric analysis (TGA). In particular, we describe the technique of quasi-isothermal MTDSC as a means of studying the change in equilibrium heat capacity as a function of temperature. Finally, variable temperature FTIR was utilized to assess the change in bonding configuration as a function of temperature. SEM revealed significant differences in the continuity and grain structure of the two batches. The TGA, MTDSC, and quasi-isothermal MTDSC studies all indicated significant differences in the thermal response and water loss profile. This was confirmed using variable temperature FTIR which indicated differences in bond reconfiguration as a function of temperature. We ascribe these differences to variations in the route by which water may leave the structure, possibly associated with grain size. The study has therefore demonstrated that chemically identical dihydrate forms may show significant differences in thermal response. We believe that this may assist in interpreting and hence controlling interbatch variation for this material

Impact of milk protein type on the viability and storage stability of microencapsulated Lactobacillus acidophilus using spray drying

Three different milk proteins — skim milk powder (SMP), sodium caseinate (SC) and whey protein concentrate (WPC) — were tested for their ability to stabilize microencapsulated L. acidophilus produced using spray drying. Maltodextrin (MD) was used as the primary wall material in all samples, milk protein as the secondary wall material (7:3 MD/milk protein ratio) and the simple sugars, d-glucose and trehalose were used as tertiary wall materials (8:2:2 MD/protein/sugar ratio) combinations of all wall materials were tested for their ability to enhance the microbial and techno-functional stability of microencapsulated powders. Of the optional secondary wall materials, WPC improved L. acidophilus viability, up to 70 % during drying; SMP enhanced stability by up to 59 % and SC up to 6 %. Lactose and whey protein content enhanced thermoprotection; this is possibly due to their ability to depress the glass transition and melting temperatures and to release antioxidants. The resultant L. acidophilus powders were stored for 90 days at 4 °C, 25 °C and 35 °C and the loss of viability calculated. The highest survival rates were obtained at 4 °C, inactivation rates for storage were dependent on the carrier wall material and the SMP/d-glucose powders had the lowest inactivation rates (0.013 day−1) whilst the highest was observed for the control containing only MD (0.041 day−1) and the SC-based system (0.030 day−1). Further increase in storage temperature (25 °C and 35 °C) was accompanied by increase of the inactivation rates of L. acidophilus that followed Arrhenius kinetics. In general, SMP-based formulations exhibited the highest temperature dependency whilst WPC the lowest. d-Glucose addition improved the storage stability of the probiotic powders although it was accompanied by an increase of the residual moisture, water activity and hygroscopicity, and a reduction of the glass transition temperature in the tested systems

Korovkin's theorem for locally compact Abelian groups

In 1953 P.P. Korovkin proved that {1,cos,sin} is a test set for each sequence (Tn) of positive linear operators on the space C of continuous real 2 π-periodic functions, in the sense that lim Tnf = f uniformly for f = 1 , cos and sin implies that lim n->∞ Tn f = f uniformly for each f ∈ C . This thesis deals with versions of Korovkin's result on LP(G), p ∈ [1,∞) , and Cu(G) (the complex vector spaces of pth-power integrable functions and of bounded uniformly continuous functions on G , respectively) where G is a locally compact abelian Hausdorff group. In Chapter One we refer to some known Korovkin results, mainly in the setting of vector lattices and using the concept of affineness, and relate these to the LP(G) and Cu(G) cases. The second chapter examines the use of sets of continuous characters as tests sets. We find that in general even the entire dual of G need not be a test set and that a restriction on the supports of the operators is necessary; though when G is compact any set of continuous characters that separates the points of G and contains the identity is a test set. From a suitable family of functions on G it is possible to define a useful modulus of continuity and to obtain quantitative Korovkin results in terms of it; this is the basis of Chapter Three. We give a general construction of such a family of functions and show that when G is compact and connected each function can be constructed from a finite set of continuous characters, so that we obtain a quantitative version of the result of Chapter Two specified in the preceding paragraph. Finally, in the appendix we consider saturation in LP(G), generalising the usual definition by introducing the notion of trivial class (those functions that are eventually perfectly approximated). We also extend a result, due to Bemd Dreseler and Walter Schempp, describing the saturation class for certain types of convolution operators on L2(G)

Transitions and Phenomenology of a,a-trehalose polymorphs inter-conversion

J. THERMAL ANAL. CALORIM