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PubMed1996

[Importance of nutritional status in digestion capacity and lactose tolerance].

The aim of this study is to determine the capacity of undernourished patients to digest and tolerate the lactose in milk administered by tube-feeding. It was a controlled double-blind crossover trial in 25 hospitalized patients who required enteral feeding due to medical reasons. They were divided in two groups differing by nutritional status: 10 patients in Group 1 were malnourished with a mean weight for height of 69% (+/-15% SD) of their ideal one; Group 2 had 15 well nourished patients (mean weight for height of 103 +/- 15%). Each patient received two dietary treatments: intact milk and hydrolyzed milk (> 90% of lactose hydrolyzed). Lactose digestion was measured by the hydrogen breath test. Hydrogen excretion with intact milk was 505 +/- 117 ppm in Group 1 versus 58 +/- 15 ppm in the control group. With hydrolyzed milk, these values were 53 +/- 27 and 14 +/- 23, respectively. The scoring of symptoms after drinking intact milk was 4.3 +/- 0.7 in Group 1 vs 1.5 +/- 0.3 in Group 2, and they were lower with hydrolyzed milk (0.5 +/- 0.2 vs 0.3 +/- 0.2 respectively). The undernourished group had a higher incidence of both lactose maldigestion (p < 0.0001) and lactose intolerance (p < 0.001) than the control group. Our results strongly suggest that undernourishment is accompanied always or almost always by lactose intolerance.

Adult↗
PubMed1999

Continuous ethanol fermentation of lactose by a recombinant flocculating Saccharomyces cerevisiae strain.

Alcohol fermentation of lactose was investigated using a recombinant flocculating Saccharomyces cerevisiae, expressing the LAC4 (coding for beta-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus. Data on yeast fermentation and growth on a medium containing lactose as the sole carbon source are presented. In the range of studied lactose concentrations, total lactose consumption was observed with a conversion yield of ethanol close to the expected theoretical value. For the continuously operating bioreactor, an ethanol productivity of 11 g L(-1) h(-1) (corresponding to a feed lactose concentration of 50 g L(-1) and a dilution rate of 0.55 h(-1)) was obtained, which is 7 times larger than the continuous conventional systems. The system stability was confirmed by keeping it in operation for 6 months.

Bioreactors↗
PubMed2001

Wedgelike glycodendrimers as inhibitors of binding of mammalian galectins to glycoproteins, lactose maxiclusters, and cell surface glycoconjugates.

Galectins are mammalian carbohydrate-binding proteins that are involved in cell-cell and cell-matrix adhesion, cell migration, and growth regulation with relevance to inflammation and tumor spread. These important functions account for the interest to design suitable low molecular weight inhibitors that match the distinct modes of presentation of the carbohydrate recognition domains of the different galectin subfamilies. Using 3,5-di-(2-aminoethoxy)benzoic acid as the branching unit, wedgelike glycodendrimers with two, four, and eight lactose moieties (G1-G3) were synthesized. They were tested in solid-phase competition assays with lactose maxiclusters and various N-glycan branching profiles (miniclusters) as the matrix and also in cell assays. Prototype galectins-1 and -7, chimera-type galectin-3, a plant (AB)(2) toxin, and a lactose-binding immunoglobulin G fraction from human serum were the carbohydrate-binding targets. Potent inhibition and remarkable cluster effects were seen for the homodimeric galectin-1, especially in combination with biantennary N-glycans as the matrix. Remarkably, for the tetravalent G2 glycodendrimer, the inhibitory potency of each lactose unit reached a maximum value of 1667 relative to free lactose. In haemagglutination experiments as a model for cell adhesion, galectin-3 was markedly sensitive to increased sugar valency and a relative potency per lactose of 150 was reached. The spatial orientation of the carbohydrate recognition domains of the endogenous lectins and the branching pattern of the carbohydrates of the glycoprotein matrices used are both important factors in the design and synthesis of glycodendrimers with galectin-selective properties.

Animals↗
PubMed2003

Novel escherichia coli strain allows efficient recombinant protein production using lactose as inducer.

An important characteristic of promoters used in recombinant protein production in Escherichi coli is their inducibility in a simple and cost-effective manner. The IPTG inducible promoters lac, tac, and trc are powerful and widely used for basic research. However, the use of IPTG in large-scale production is undesirable due to its high cost and toxicity. The promoters mentioned above can also be induced by the addition of lactose, which has the double role of inducer and carbon and energy source. Nevertheless, the use of this sugar in industrial processes has several drawbacks, which result in low volumetric yields and difficulties in process control. We have genetically engineered a BL21 strain to allow the efficient use of lactose as inducer in fed-batch cultures. Two modifications were introduced, the exchange of the wild-type lac operator by a constitutive one (lacO(c)) and the replacement of the gal alleles to recover the Gal(+) phenotype. The constitutive expression of the lac operon overcame the negative effects that the Lac nongenetic heterogeneity of wild-type E. coli introduces when lactose is used as inducer. The gal(+) genotype allowed the complete use of the lactose as carbon and energy source. The relevance of these two modifications in the efficient utilization of lactose as inducer was demonstrated in fed-batch cultures of the novel recombinant strain MP101 harboring expression vectors containing the calf prochymosin gene or the pccB gene, which encodes for the carboxyltransferase component of a propionyl-CoA carboxylase complex from Streptomyces coelicolor. Similar levels of recombinant protein production (up to 16 g/L) were obtained by using either lactose or IPTG as inducers, which confirmed the success of the genetics modifications introduced.

Bacterial Proteins↗
PubMed2006

Milk, milk products and lactose intake and ovarian cancer risk: a meta-analysis of epidemiological studies.

It has been proposed, on the basis of animal models and ecological studies, that consumption or metabolism of dairy sugar may increase the risk of ovarian cancer. Case-control and cohort studies of the association between lactose and dairy food consumption and ovarian cancer risk, however, have yielded varied findings. We summarized the available literature on this topic using a meta-analytic approach. Random-effects models were used to estimate the summary relative risks (RR(summary)). A linear regression analysis of the natural logarithm of the RR was carried out to assess a possible dose-response relationship between lactose intake and ovarian cancer risk. Eighteen case-control and 3 prospective cohort studies were eligible for inclusion in the meta-analysis. The findings of case-control studies were heterogeneous, and, except for whole milk (RR(summary) for highest vs. lowest category = 1.27, 95% confidence interval [CI] = 0.97-1.68), do not provide evidence of positive associations between dairy food and lactose intakes with risk of ovarian cancer. In contrast, the 3 cohort studies are consistent and show significant positive associations between intakes of total dairy foods, low-fat milk, and lactose and risk of ovarian cancer. The RR(summary) for a daily increase of 10 g in lactose intake (the approximate amount in 1 glass of milk) was 1.13 (95% CI = 1.05-1.22) for cohort studies. In conclusion, prospective cohort studies, but not case-control studies, support the hypothesis that high intakes of dairy foods and lactose may increase the risk of ovarian cancer.

Animals↗
PubMed1982

Regulation of lactose transport by the phosphoenolpyruvate-sugar phosphotransferase system in membrane vesicles of Escherichia coli.

Regulation of lactose uptake by the phosphoenolpyruvate-sugar phosphotransferase system (PTS) has been demonstrated in membrane vesicles of Escherichia coli strain ML 308-225. Substrates of the phosphotransferase system inhibited D-lactate energized uptake of lactose but did not inhibit uptake of either L-alanine or L-proline. This inhibition was reversed by intravesicular (but not extravesicular) phosphoenolpyruvate. Lactose uptake was also inhibited by enzyme IIIglc preparations that were shocked into the vesicles, and this inhibition was reversed by phosphoenolpyruvate. Intravesicular HPr and enzyme I stimulated methyl alpha-glycoside uptake but did not inhibit or stimulate lactose accumulation. Vesicles maintained at 0 degree C for several days partially lost 1) the ability to take up lactose, 2) the ability to accumulate PTS substrates, and 3) PTS-mediated regulation. Phosphoenolpyruvate addition restored all of these activities. These results support a mechanism in which the relative proportions of phosphorylated and nonphosphorylated forms of a phosphotransferase constituent regulate the activity of the lactose permease.

Bacterial Proteins↗
PubMed2003

Immobilization of fine particles on lactose carrier by precision coating and its effect on the performance of dry powder formulations.

The feasibility of immobilization of fine particles on a lactose carrier by precision coating and producing carrier particles of different surface roughness from the same core was explored. A relationship between the resultant surface roughness of the carrier and the in vitro deposition pattern of salbutamol sulfate was established. Lactose carrier particles in the precision coating chamber were spray coated with liquid suspensions consisting of micronized lactose dispersed in isopropyl alcohol (IPA) and/or water mixtures. The surface-modified lactose particles were fractionated and then characterized by laser diffraction for size, image analysis for shape, and scanning probe microscopy for surface roughness. The in vitro deposition pattern of salbutamol sulfate from the drug-lactose mixtures was determined with the twin-stage glass impinger and expressed as the fine particle fraction and dispersibility of the drug. Immobilization of fine particles on carrier particles was feasible by the precision coating process as shown by the scanning probe topographs and the roughness values of the carrier particles. Generally, more discrete fine particles were deposited on the carrier surface and a higher surface roughness was seen when the spray suspension consisting of a higher proportion of IPA was used. A significant correlation was found between the fine particle fraction of salbutamol sulfate with the roughness of lactose. This relationship established between the in vitro drug deposition pattern and the microscopic surface roughness of the carrier would be helpful in the optimization of drug delivery to targeted areas in the lungs.

Albuterol↗
PubMed2004

Visualization of the crystallization of lactose from the amorphous state.

The physical stability and solid-state recrystallization of spray-dried 'amorphous' lactose particles were visualized using environmentally controlled atomic force microscopy (EC-AFM) and conventional optical microscopy. The morphology and crystalline state were investigated as a function of relative humidity (RH) and were correlated with bulk gravimetric vapor sorption measurements that were run in parallel. The metastable nature of amorphous spray-dried lactose particles was apparent at low RHs (<30% RH). Visualization of the recrystallization transformation of amorphous lactose during moisture uptake at 58 and 75% RH suggested only a proportion of the collapsed particles undergoes nucleation and crystal growth. The irregular surface morphology of the recrystallized particles suggested a secondary nucleation and growth process. Primary nucleation of alpha-lactose monohydrate within the non-recrystallized particles required exposure to elevated RH (94% RH). In relation to bulk measurements of moisture-induced amorphous recrystallization of spray-dried lactose, the results suggest that recrystallization of amorphous lactose, above a critical RH, may be induced by the presence of very low levels of a seed material, which may dramatically reduce the activation energy barrier for nucleation and crystal growth.

Crystallization↗
PubMed1993

Cysteine scanning mutagenesis of putative transmembrane helices IX and X in the lactose permease of Escherichia coli.

Using a functional lactose permease mutant devoid of Cys residues (C-less permease), each amino-acid residue in putative transmembrane helices IX and X and the short intervening loop was systematically replaced with Cys (from Asn-290 to Lys-335). Thirty-four of 46 mutants accumulate lactose to high levels (70-100% or more of C-less), and an additional 7 mutants exhibit lower but highly significant lactose accumulation. As expected (see Kaback, H.R., 1992, Int. Rev. Cytol. 137A, 97-125), Cys substitution for Arg-302, His-322, or Glu-325 results in inactive permease molecules. Although Cys replacement for Lys-319 or Phe-334 also inactivates lactose accumulation, Lys-319 is not essential for active lactose transport (Sahin-Tóth, M., Dunten, R.L., Gonzalez, A., & Kaback, H.R., 1992, Proc. Natl. Acad. Sci. USA 89, 10547-10551), and replacement of Phe-334 with leucine yields permease with considerable activity. All single-Cys mutants except Gly-296 --> Cys are present in the membrane in amounts comparable to C-less permease, as judged by immunological techniques. In contrast, mutant Gly-296 --> Cys is hardly detectable when expressed at a relatively low rate from the lac promoter/operator but present in the membrane in stable form when expressed at a high rate from T7 promoter. Finally, studies with N-ethylmaleimide (NEM) show that only a few mutants are inactivated significantly. Remarkably, the rate of inactivation of Val-315 --> Cys permease is enhanced at least 10-fold in the presence of beta-galactopyranosyl 1-thio-beta-D-galactopyranoside (TDG) or an H+ electrochemical gradient (delta mu-H+). The results demonstrate that only three residues in this region of the permease -Arg-302, His-322, and Glu-325-are essential for active lactose transport. Furthermore, the enhanced reactivity of the Val-315 --> Cys mutant toward NEM in the presence of TDG or delta mu-H+ probably reflects a conformational alteration induced by either substrate binding or delta mu-H+.

Amino Acid Sequence↗
PubMed2001

A triple mutant, K319N/H322Q/E325Q, of the lactose permease cotransports H+ with thiodigalactoside.

In a previous study, we characterized a lactose permease mutant (K319N/E325Q) that can transport H+ ions with sugar. This result was surprising because other studies had suggested that Glu-325 plays an essential role in H+ binding. To determine if the lactose permease contains one or more auxiliary H+ binding sites, we began with the K319N/E325Q strain, which catalyzes a sugar-dependent H+ leak, and isolated third site suppressor mutations that blocked the H+ leak. Three types of suppressors were obtained: H322Y, H322R, and M299I. These mutations blocked the H+ leak and elevated the apparent Km value for lactose. The M299I and H322Y suppressors could still transport H+ with beta-d-thiodigalactoside (TDG), but the H322R strain appeared uncoupled for H+/sugar cotransport. Four mutant strains containing a nonionizable substitution at codon 322 (H322Q) were analyzed. None of these were able to catalyze uphill accumulation of lactose, however, all showed some level of substrate-induced proton accumulation. The level seemed to vary based on the substrate being analyzed (lactose or TDG). Most interestingly, a triple mutant, K319N/H322Q/E325Q, catalyzed robust H+ transport with TDG. These novel results suggest an alternative mechanism of lactose permease cation binding and transport, possibly involving hydronium ion (H3O+).

Amino Acid Substitution↗
PubMed2006

Determination of the surface free energy of crystalline and amorphous lactose by atomic force microscopy adhesion measurement.

PURPOSE: This study was conducted to accurately measure the dispersive surface free energy of lactose solids in ordered and disordered states. METHODS: Atomic force microscopy (AFM) was used to determine the contact adhesion force between an AFM tip and lactose under low humidity (ca. 1% RH). The geometry of the tip contacting apex was characterized by scanning a porous aluminum film with ultrasharp spikes (radius 2-3 nm). A sphere vs. flat surface model was employed to relate the adhesion force determined to the surface energy based upon the Johnson-Kendal-Roberts theory. Spray-dried amorphous lactose in a compressed-disk form and single crystals of alpha-lactose monohydrate were prepared as model samples. RESULTS: The condition of the smooth sample surface and sphere-shaped tip used was shown to be appropriate to the application of the JKR model. The surface energy of crystalline [(0,-1,-1) face] and amorphous lactose was determined to be 23.3 +/- 2.3 and 57.4 +/- 7.9 mJ m(-2), respectively. CONCLUSIONS: We have demonstrated the capability of AFM to measure the dispersive surface free energy of pharmaceutical materials directly through a blank probe at the nanometer scale. These data, although consistent with results from more traditional methods, illustrate some unique attributes of this approach, namely, surface energies are directly derived from solid-solid interactions, measurements may be made on specific crystalline faces, and the potential exists to identify the submicron heterogeneity of organic solids in terms of their molecular energy states (such as ordered and disordered lactose).

Algorithms↗
PubMed1987

The role of protons in the mechanism of galactoside transport via the lactose permease of Escherichia coli.

The kinetic mechanism of lactose transport across the cytoplasmic membrane has been investigated and the results related to standard models for the lactose-H+ symport reaction using computer simulation. It is shown that the biphasic kinetics reported for lactose uptake (Kaczorowski, G.J. and Kaback, H.R. (1979) Biochemistry 18, 3691-3697) are consistent with random binding of lactose and protons and rapid subsequent translocation of the ternary lactose-H+-permease complex. Such a model is also shown to explain the observed dependence of the kinetic parameters on the magnitude of the protonmotive force. Both sugar and protons are shown to cause product inhibition of lactose flux and the ability of standard models to account for the pattern of inhibition is discussed. Three apparent dissociation constants have been determined for the protonation reactions in the external medium: two (pKa 6.3 and 9.6) control the activity of the permease, whilst the third (pKa 8.3) controls the affinity of the permease for galactosides. A similar set of dissociation constants has been determined for the internal reactions. Again two (pKa 6 and 9.8) control activity and a third (pKa 8.8) controls the affinity for galactosides. The dissociation reactions characterised by pKa 8.3, 8.8, 9.6 and 9.8 are attributed to the dissociation of the substrate (symported) proton from the binary proton-permease complexes (pKa 8.3 and 8.8) and the ternary proton-galactoside-permease complexes (pKa 9.6 and 9.8). The third pair (pKa 6.3 and 6.0) must be interpreted as describing a separate protonation reaction which may have a regulatory or auxiliary role in transport.

Bacterial Proteins↗
PubMed1992

Counter-diffusion of lactose and lactic acid in kappa-carrageenan/locust bean gum gel beads with or without entrapped lactic acid bacteria.

The effective diffusion coefficient (De) and equilibrium partition factor (Kp) for lactose and lactic acid in k-carrageenan (2.75% w/w)/locust bean gum (0.25% w/w) (LBG) gel beads (1.5-2.0 mm diameter), with or without entrapped Lactobacillus casei subsp. casei (L. casei), were determined at 40 degrees C. Results were obtained from transient concentration changes in well-stirred solutions of finite volume in which the beads were suspended. Mathematical models of unsteady-state diffusion into and/or from a sphere and appropriate boundary conditions were used to calculate effective diffusion coefficients of lactose and lactic acid from the best fit of the experimental solute concentration changes. The effective diffusivities of lactose and lactic acid were 5.73 x 10(-10) and 9.96 x 10(-10) m2 s-1, respectively. Furthermore, lactic acid was found to modify gel structure since lactose diffusion characteristics (De and Kp) differed significantly from an earlier study and in the literature. In gel beads heavily colonized with L. casei, the effective diffusion coefficients of lactose and lactic acid were respectively 17% and 24% lower than for cell-free beads. Partition coefficients also confirmed the obstruction effect due to the cells, and decreased from 0.89 to 0.79, and from 0.98 to 0.87, for lactose and lactic acid, respectively. External mass transfer was estimated by an unsteady-state model in infinite volume using the Biot number. The effect of external mass transfer resistance on De results and the data reported in the literature are discussed.

Carrageenan↗
PubMed1995

Measurement of lactose consumption reliability and comparison of two methods.

The objective of this study was to assess the reliability of lactose consumption measured with a food-frequency questionnaire and to compare food-frequency data to prospectively recorded data. A self-administered food-frequency questionnaire (FF1) was completed by 295 women ages 38 to 49. Two months later, 75 received the same food-frequency questionnaire (FF2), and 75 received a 1-week diet diary listing 23 commonly eaten lactose-containing foods. Estimated mean intake of lactose was 16.1 g/d with FF1. Intake was slightly (but not significantly) higher at follow-up: Mean difference (95% confidence interval) was 1.4 (-0.8, 3.7) g/d for FF2 versus FF1, and 0.5 g (1.3, 2.3) g/d for the diet diary versus FF1. A moderate level of correlation was found: r = 0.57 between FF1 and FF2, and r = 0.65 between FF1 and the diet diary. Smaller subsets of items (n = 15 and n = 7) could be used to estimate lactose, with 89% and 82% agreement within tertiles, respectively. Since relatively few foods contain substantial amounts of lactose, a limited food-frequency or structured diary may be useful in research studies on the association between lactose consumption and ovarian cancer or other diseases.

Adult↗
PubMed2005

Optimization of lactose utilization in deproteinated whey by Kluyveromyces marxianus using response surface methodology (RSM).

Kluyveromyces marxianus Y-8281 yeast culture was utilized for the biological treatment of deproteinated whey wastewater in a batch system. Removal of lactose was optimized by the utilization of response surface methodology, RSM. The empirical model developed through RSM in terms of effective operational factors of medium pH, temperature, lactose and ammonia concentrations was found adequate to describe the treatment of deproteinated whey. Through the analysis, medium pH and temperature were found to be the most significant factors and an increment in both had a positive effect on lactose utilization, while lactose and ammonia concentrations had the least weight within the ranges investigated. Based on contour plots and variance analysis, optimum operational conditions for maximizing lactose removal were found to be 31 degrees C, 45 g/L whey powder concentration, 4 g/L total ammonium salt concentration and medium pH 6. Under the optimum operating conditions determined, 95% lactose removal was achieved after an 18-h fermentation.

Ammonia↗
PubMed2005

Comparative study of erythritol and lactose monohydrate as carriers for inhalation: atomic force microscopy and in vitro correlation.

The adhesion of micronised salbutamol sulphate to two carrier excipients, lactose monohydrate and erythritol, was investigated using the atomic force microscope (AFM) colloid probe technique and correlated with their respective physico-mechanical properties and aerosolisation performance. The particle size, morphology and moisture sorption properties of the carriers were similar thereby allowing direct comparison of functionality. AFM force measurements (n = 1024 force curves) were obtained between salbutamol sulphate drug probes (n = 4) and the excipients, as 63-90 microm sieve fractions and atomically smooth crystals. In general, significant differences in drug adhesion to lactose monohydrate and erythritol were observed (ANOVA, p<0.05), with erythritol exhibiting relatively greater adhesiveness. A linear relationship between drug probe adhesion to lactose monohydrate and drug probe adhesion to erythritol was established with salbutamol sulphate-lactose monohydrate adhesion being 60-70% of that of the erythritol system. In vitro analysis suggested good correlation with the adhesion measurements. The aerosolisation of salbutamol sulphate from erythritol carrier particles was significantly less (ANOVA, p<0.05) than from lactose monohydrate, with a fine particle dose (<6.4 microm) of 41.9 +/- 7.4 microg and 24.9 +/- 3.1 microg for the lactose monohydrate and erythritol carriers, respectively (n = 3).

Administration, Inhalation↗
PubMed2004

Endotoxin testing in inhalation grade lactose-a useful quality parameter?

Alpha-lactose monohydrate is the standard carrier used for dry powder inhalation drug products. The physico-chemical characteristics of this carrier material need to be monitored and specified carefully in order to guarantee functionality of the powder formulation. But also microbiological acceptance criteria need to be considered during development and routine testing. In this study, the endotoxin content of 19 batches of alpha-lactose monohydrate provided by two different manufacturers was determined with a semi-quantitative LAL assay. The endotoxin content was found to be less than 18 endotoxin units (EU)/g lactose in all cases and less than 3 EU/g in most cases. Assuming that the typical lactose has an endotoxin content of 10 EU/g and that a patient inhales six times daily 25 mg of lactose and that the total amount of lactose reaches the lung, this translates to an endotoxin exposure of 1.5 EU per day. On the other hand, the proposal for endotoxins in air limits the endotoxin concentration to 50 EU/m3 which corresponds to approximately 3333 EU inhaled endotoxins a day during normal breathing (breathing at rest conditions). The maximum endotoxin exposure by dry powder inhalations is thus two log steps lower than the recommended acceptable daily intake.

Administration, Inhalation↗
PubMed2004

Approaches to determine the enthalpy of crystallisation, and amorphous content, of lactose from isothermal calorimetric data.

Amorphous lactose will crystallise rapidly if its glass transition temperature is reduced below its storage temperature. This is readily achieved by storing samples at ambient temperature and a relative humidity (RH) of greater than 50%. If the sample is monitored in an isothermal microcalorimeter as it crystallises, the heat changes associated with the event can be measured; indeed this is one of the methods used to quantify the amorphous content of powders and formulations. However, variations in the calculation methods used to determine these heat changes have led to discrepancies in the values reported in the literature and frequently make comparison of data from different sources difficult. Data analysis and peak integration software allow the selection and integration of specific areas of complex traces with great reproducibility; this has led to the observation that previously ignored artefacts are in fact of sufficient magnitude to affect calculated enthalpies. In this work a number of integration methodologies have been applied to the analysis of amorphous spray-dried lactose, crystallised under 53 or 75% RH at 25 degrees C. The data allowed the selection of a standard methodology from which reproducible heat changes could be determined. The method was subsequently applied to the analysis of partially amorphous lactose samples (containing 1-100% (w/w) amorphous content) allowing the quantification limit of the technique to be established. It was found that the best approach for obtaining reproducible results was (i) to crystallise under an RH of 53%, because this slowed the crystallisation response allowing better experimental measurement and (ii) to integrate all the events occurring in the ampoule, rather than trying to select only that region corresponding to crystallisation, since it became clear that the processes occurring in the cell overlapped and could not be deconvoluted. The technique was able to detect amorphous contents as low as 1% (w/w), using this integration strategy, although it was observed that the calibration plot constructed showed a negative deviation from linearity. It is suggested that such non-ideal behaviour results from the formation of varying ratios of alpha-lactose monohydrate, anhydrous alpha-lactose and anhydrous beta-lactose.

Calorimetry↗