Development of a method for water determination in lactose

The determination of water content of lactose and the water activity, which is related to it, are important to assess its microbiological stability as well as its technical and commercial quality. Lactose is a very important product in the dairy sector, but also in the pharmaceutical domain.     

Water content of natural cyclodextrins and their essential oil complexes: A comparative study between Karl Fischer titration and thermal methods

The paper presents a comparative study regarding the water determination in natural cyclodextrins and in their essential oil complexes (Apiaceae, Liliaceae, and Cupressaceae families) by using Karl Fischer titration (KFT) and thermal methods. For the natural cyclodextrins, the influence of the solvent hydrophobicity and the preheating temperature on the water extraction process were evaluated. The water contents, estimated by KFT in both methanol and methanol–octanol solvent systems, were 10.6% and 14.4% for α- and β-cyclodextrin, respectively; the water content, estimated by KFT in a more hydrophilic solvent system, methanol–formamide, was 0.4–0.6% higher. Thermogravimetric evaluation of water conducts to lower values. For the essential oil/cyclodextrin complexes, the KFT water content were in the range of 6.4–8.1%, higher values being obtained in the case of Juniperus essential oil/β-cyclodextrin complexes (7.5–8.1%). With some exceptions, thermal analyses of complexes are in good agreement with the KFT results.     

Influence of the correction for moisture/water content on the quality of the certification of cadmium,copper and lead mass fractions in rice

The moisture/water content of rice sample was determined by means of three different methods: oven drying, Karl Fischer titration and thermogravimetry. These results were applied for the certification of the Cd, Cu and Pb mass fractions by isotope dilution mass spectrometry, IDMS, in this rice material.     

From contact angle titration to chemical force microscopy: a new route to assess the pH-dependent character of the stratum corneum

Despite of its complex multicomponent organization and its compact architecture, the Stratum corneum (SC) is not completely impermeable to substances directly applied on the skin surface. A huge number of works have been dedicated to the understanding of the mechanisms involved in substance permeation by exploring deeper layers than the SC itself. Surprisingly, there is a poor interest in studies relating to interactions which may occur in the near-surface region (i.e. approximately 1 nm depth) of the SC. In this work, equilibrium proton-transfer reactions have been used as probes to define in a fundamental point of view the nature of the SC interactions with its environment. Such titration curves are investigated on 'in vitro' SC (isolated SC from abdominal skin tissue) and on 'in vivo' volar forearm (a sebum poor area). The results are discussed in term of work of adhesion and surface pKa values. Because SC can 'reconstruct' under heating, influence of the temperature on titration curves is investigated and the role of the different components is discussed. Different sigmoidal transitions were observed. Two common pKa values (pKa(1) = 4 and pKa(2) = 11.5) were clearly identified in both cases and associated to an acid-base character. By playing with the temperature of 'in vitro' SC, the 'accessibility' of polar functions was increased, thus refining the results by revealing an amphoteric character with an acid-to-base transition at pH 3.5 and two acid transitions at pH = 6.5 and pH = 11.5. Adhesion forces between an Atomic Force Microscopy (AFM) tip and a single isolated corneocyte through buffered liquid media were also investigated to better understand the role of the individual corneocytes.     

Water retention of treated stratum corneum measured by a coupling method: thermal desorption-mass spectrometry

A thermal desorption autosampler coupled to a mass spectrometer has been used to measure the in vitro water retention of human stratum corneum as a function of treatment applied. Samples were treated with ingredients possessing good hygroscopic properties which are used in the formulation of moisturizing creams. After being treated, stratum corneum samples were dried and rehydrated and then analysed. The paper describes the method used to quantify their hygroscopic capacity in terms of the percentage of water retained. Ten humectants were examined, of which urea, glycerine, ammonium lactate and a new salt of an α-hydroxy acid were found to have the highest activities. This method can also be used to quantify the water retention capacity of various types of pathological skin such as ichthyosis and psoriasis.     

A Raman spectroscopic study of meat protein/lipid interactions at protein/oil or protein/fat interfaces

Structural changes in proteins of meat, FC (fat cream layers) and OC (soya bean oil cream layers) were studied by Raman spectroscopy. Results revealed that adsorption of proteins to the cream layers resulted in a maximum scattering change from 1657 to 1661 cm^?1, the intensity of amide I was significantly increased (P < 0.05), the percentages of secondary structures of proteins in the raw meat and meat cream layers were significantly different (P < 0.05), the bands near 540 and 475 cm^?1 were significantly (P < 0.05) higher in intensities in the soya bean oil cream layer samples compared to raw meat alone, the normalised intensity of the tryptophan band near 758 cm^?1, from 0.52 in the raw meat to 1.11 (fat cream layer) or 0.72 (soya bean oil cream layer). These results indicated that disulphide bonds, hydrophobic interactions and hydrogen bonding were of the main interactions observed in proteins and lipids at the emulsion interface.     

Raman spectroscopy a promising technique for quality assessment of meat and fish: A review

Raman spectroscopy data have been compared to different traditional methodologies such as protein solubility, apparent viscosity, water holding capacity, instrumental texture methods, dimethylamine content, peroxide values, and fatty acid composition commonly used to determine quality in fish and meat muscle treated under different conditions of handling, processing and storage through the changes of proteins, water and lipids of muscle food. It has been shown that Raman spectroscopy data are related to the results obtained with these traditional quality methods and could be used to evaluate muscle food quality. In addition, Raman spectroscopy provides structural information about the changes of proteins, water and lipids of muscle food that occur during the deterioration. Raman spectroscopy can also be used for determining muscle food identification. Besides, this spectroscopy technique has several advantages compared to traditional methods since it is a direct and non-invasive technique which requires small portions of sample.     

The effect of lens wear on refractive index of conventional hydrogel and silicone-hydrogel contact lenses: a comparative study.

PURPOSE: The purpose of this work was to evaluate the ability of four silicone-hydrogel contact lenses (galyfilcon A, balafilcon A, lotrafilcon A and lotrafilcon B) to retain their equilibrium water content before and after wear, through measurements of refractive index and compare with that of a conventional disposable hydrogel contact lens (etafilcon A). METHODS: The refractive indices of 115 contact lenses were measured using an automated refractometer (CLR 12-70, Index Instruments, Cambridge, U.K.) before and after a schedule of daily wear by 58 patients for 30 days in the case of silicone-hydrogel lenses and 15 days for the conventional contact lenses. RESULTS: In the silicone-hydrogel contact lenses the changes on the refractive indices were not statistically significant, however after being worn the refractive index of the conventional etalfilcon A hydrogel contact lens increased significantly (p<0.001). CONCLUSION: The results presented here show that after being worn the silicone-hydrogel contact lens, show more capacity to retain or to reach their initial equilibrium water content than conventional hydrogel contact lenses. This suggests that the silicone-hydrogel contact lenses are less susceptible to spoilation over time maintaining its biocompatibility and contributing to the clinical success of lens performance.     

Physico-chemical studies on a wide composition range of low-moisture glucose–fructose mixtures: rates of crystallisation

The crystallisation rates of low-moisture (from 2% to 10% w/w) glucose–fructose mixtures were investigated at a variety of storage temperatures (from 0 to 60 °C). It was found that d -fructose considerably retards the rate of crystallisation. High storage temperatures induced a decrease in the 'threshold' moisture content, which is necessary for the initial nucleation and further development of the glucose and/or fructose crystals. This knowledge of crystallisation rates can be exploited in terms of storage of confectionery products containing d -glucose, d -fructose or both of them, and honey.     

Detection of genetically modified rice: collaborative validation study of a construct-specific real-time PCR method for detection of transgenic Bt rice

A collaborative trial study has been conducted for validation of an extraction method and a subsequent real-time PCR for detection of a transgenic Bt rice line (‘Bt63’) in rice products originating from China. A total of 17 laboratories participated in the study and each laboratory received 16 coded samples comprising of rice grain flours, rice noodle flours and plasmid DNAs. Of the accepted results all Bt63-positive rice grain samples (0.1 or 0.05% w/w) and all rice noodle samples prepared from marketed rice products were detected correctly. The result demonstrates that ‘Bt63’ rice is detectable even at low relative mass concentrations of 0.05%. The absolute LOD determined with plasmid DNA samples showed to be at least five copies of the ‘Bt63’ target sequence. The data provided in this study show that the method is fit-for-purpose to inspect Chinese rice products for the presence of EU-unauthorised rice lines carrying the ‘Bt63’ construct.     

Iron complexes of dietary flavonoids: Combined spectroscopic and mechanistic study of their free radical scavenging activity

Combined spectroscopic (UV/visible, Raman, MS) and theoretical approaches were used to assess interaction of iron(III) with quercetin and baicalein in aqueous buffered solutions. Obtained results implicated formation of two iron quercetin complexes, with pH-dependent stoichiometries of 1:2 and 1:1, and one iron baicalein complex with stoichiometry of 1:1. Results of vibrational analysis and theoretical calculations implicated 3-hydroxy-4-carbonyl and the 3′-hydroxy-4′-hydroxy group of catechol as chelating sites for quercetin. For baicalein 5-hydroxy-6-hydroxy group is energetically the most favourable, although 5-hydroxy-4-carbonyl and 6-hydroxy-7-hydroxy chelating sites are energetically similar. Antiradical activity, reaction stoichiometry and number of inactivated DPPH molecules per mole of antioxidant indicated quercetin as a better antioxidant than its iron complex, baicalein and iron baicalein complex. The same structural features appeared to be important both in complexation and antioxidant activity. The equilibrium geometries, optimised using the B3LYP/6-31G (d, p) level of theory, predicted structural modifications between the ligand molecules in free state and in the complex structures. Correlation between experimental and theoretical results was very good.     

Near infrared reflectance analysis of oil concentration in an emulsion: A study of oil and water migrations in a mayonnaise-based salad

Equations were derived for estimating the oil concentration in mayonnaise containing 11–75% (w/w) oil in mayonnaise-based salads by measurements of absorption using a near infrared scanning spectrometer (Neotec 6350 Research Composition Analyzer). The precision of the predictions averaged from two or three equations was better than ±1.0% at an oil concentration of 40% (w/w). The use of the method is demonstrated by its application to a study of the migration of oil and water in coleslaw during the first 6h after production.     

Physico-chemical characteristics of M. Longissimus dorsi from three lines of free-range reared Iberian pigs slaughtered at 90 kg live-weight and commercial pigs: a comparative study

Longissimus dorsi muscles from three lines of Iberian pig and those from commercial pigs were analysed in order to evaluate their quality for fresh consumption. Iberian pigs were reared in a natural outdoor production system with access to grass, while m. Longissimus dorsi from commercial pigs were procured from a local slaughterhouse. Iberian pigs’ Longissimus dorsi showed a higher fat (P<0.05) and lower phospholipid contents (g PL/g fat; P<0.05) than Longissimus dorsi from commercial pigs. Iberian pigs’ Longissimus dorsi muscles had a higher content of haem iron (P<0.05) than those from commercial pigs and consequently m. Longissimus dorsi exhibited a redder colour (higher a*-value) that diverged less from the true red axis (lower hue value; P<0.05) than those from commercial pigs which resulted paler (higher L*-value; P<0.05). Total fat and neutral lipid fatty acid profiles showed higher percentages of palmitic, oleic, total saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) m. Longissimus dorsi of Iberian pigs than in the commercial ones (P<0.05). m. Longissimus dorsi from the commercial pigs contained higher proportions of polyunsaturated fatty acids and a higher n-6/n-3 ratio value (P<0.05).     

Application of decolourised hsian‐tsao leaf gum to low‐fat salad dressing model emulsions: a rheological study

The effects of mixed gums, including decolourised hsian‐tsao leaf gum (dHG) mixed with propylene glycol alginate (PGA) or xanthan gum (XG), and egg yolk concentration on the rheological properties of low‐fat salad dressing model emulsions were studied. All model emulsions showed pseudoplastic flow behaviour. Model emulsions with PGA addition showed the lowest pseudoplasticity, followed by those with dHG and then XG addition. Increasing the PGA level in the dHG/PGA system reduced the pseudoplasticity. Increasing the XG level in the dHG/XG system did not change the pseudoplasticity significantly but imparted a significant increase in viscosity. Dynamic viscoelasticity measurements indicated that model emulsions with dHG or XG addition could be classified as elastic gels. However, model emulsions with PGA addition essentially belonged to the class of either dilute or concentrated solutions rheologically, depending on the egg yolk concentration. The rheological characteristics of individual gums were found to be confounded in generating the rheological characteristics of model emulsions containing them. Copyright © 2004 Society of Chemical Industry     

Comparative study of colorectal health related compounds in different types of bread: Analysis of bread samples pre and post digestion in a batch fermentation model of the human intestine

Seven different types of wheat and rye bread were analysed for colorectal health related compounds, pre and post digestion, in batch fermentation model of the human intestine. Pre digestion, higher amounts of colorectal health-related dietary fibre compounds (soluble/insoluble/total dietary fibre, arabinoxylans, β-glucans) and phytochemicals (mono-/di-phenolic acids, phytic acid, hydroxymethylfurfural) were detected in wholemeal than in refined flour types of bread, as well as in rye flour types than in wheat flour types of bread. Post digestion, faecal bacterial metabolites of colorectal health promoting (acetate/propionate/butyrate, lactate, free mono-/di-phenolic acids) and impairing (amino metabolites, bile acid metabolites) activities were found in fermentation supernatants of bread samples. All types of bread positively affected faecal bacterial metabolism; among the different types of bread, the highest stimulation of organic acid production (acetate/propionate/butyrate, lactate) and the lowest detrimental bacterial enzyme activities (β-glucuronidase, urease) were detected for wheat flour bread, whereas the strongest retardation of bacterial bile acid degradation and the strongest stimulation of phenolic acid metabolite release (phenylpropionic/phenylpropenoic acid derivatives) were induced by wholemeal rye bread. This study for the first time presents a qualitative and quantitative overview over the broad spectrum of colorectal health related compounds in high- and low-fibre types of bread, pre and post in vitro digestion, and highlights the significance of bread for the preventive nutritional intervention of colorectal cancer.