Kirsi Jouppila

Storage stability of microencapsulated cloudberry ( Rubus chamaemorus ) phenolics.

Cloudberries ( Rubus chamaemorus ) contain phenolics (mainly ellagitannins), which have recently been related to many valuable bioactivity properties. In general, phenolics are known to react readily with various components, which may create an obstacle in producing stable functional components for food and pharmaceutical purposes. In this study, the aim was to improve the storage stability of cloudberry phenolic extract by microencapsulation. The phenolic-rich cloudberry extract was encapsulated in maltodextrins DE5-8 and DE18.5 by freeze-drying. Water sorption properties and glass transition temperatures (T(g)) of microcapsules and maltodextrins were determined. Microcapsules together with unencapsulated cloudberry extract were stored at different relative vapor pressures (0, 33, and 66% RVP) at 25 degrees C for 64 days, and storage stability was evaluated by analyzing phenolic content and antioxidant activity. Compared to maltodextrin DE18.5, maltodextrin DE5-8 had not only higher encapsulation yield and efficiency but also offered better protection for phenolics during storage. Without encapsulation the storage stability of cloudberry phenolics was weaker with higher storage RVP. Microencapsulation improved the storage stability of cloudberry phenolics. The physical state of microcapsules did not have a significant role in the stability of cloudberry phenolics because phenolic losses were observed also in amorphous glassy materials. The antioxidant activity of the microencapsulated cloudberry extract remained the same or even improved slightly during storage, which may be related to the changes in phenolic profiles.

The physical state of amorphous corn starch and its impact on crystallization

Abstract Crystallization of amorphous polymers is affected by their physical state and molecular mobility. In the present study, crystallization behaviour of amorphous corn starch was related to its physical state and glass transition. Amorphous corn starch was produced by freeze-drying a gelatinized 5% (w/w) starch suspension. State diagram and sorption properties were determined to characterize the material. Amorphous corn starch samples containing 60, 70, and 80% solids were stored at various temperatures that gave various temperature differences between storage temperature and glass transition temperature ( T − T g ). The melting behaviour of crystallites formed was determined using differential scanning calorimetry. Crystallization in starch samples occurred with a rate that was dependent on storage temperature, water content, and T − T g . In addition, the melting temperature and the extent of crystallization were affected by storage temperature, water content, and T − T g . The data reported allow the prediction of crystallization in starch, as a physical state-dependent phenomenon and, therefore, stability of starch-containing products during storage.

Factors affecting crystallization and crystallization kinetics in amorphous corn starch

Abstract The levelling-off extent of crystallization and crystallization behaviour in corn starch were studied using an X-ray diffraction technique, taking into account the glass transition temperature range of amorphous corn starch. Amorphous corn starch samples at 60, 70, or 80% solids were stored at various temperatures giving various temperature differences between storage temperature and glass transition temperature ( T − T g ). Corn starch was observed to crystallize into the same crystal form, independent of water content and storage temperature and, therefore, of the T − T g . The Avrami equation was found to be useful in modelling of crystallization kinetics in starch. The data obtained can be used in prediction of stability during storage of starch-containing products with various water contents.

Crystallization and X-ray Diffraction of Crystals Formed in Water-Plasticized Amorphous Lactose

Effects of storage time and relative humidity on crystallization and crystal forms produced from amorphous lactose were investigated. Crystallization was observed from time‐dependent loss of sorbed water and increasing intensities of peaks in X‐ray diffraction patterns. The rate of crystallization increased with increasing storage relative humidity. Lactose crystallized mainly as α‐lactose monohydrate and anhydrous crystals with α‐ and β‐lactose in a molar ratio of 5:3. The results suggested that the crystal form was defined by the early nucleation process. The crystallization data are important in modeling of crystallization phenomena and prediction of stability of lactose‐containing food and pharmaceutical materials.

Glass transition and water plasticization effects on crispness of a snack food extrudate

Abstract A crispy snack model, composed of maltodextrin, wheat flour, salt, and water, with a clearly measurable glass transition was designed and produced by extrusion. The material was used to investigate effects of glass transition and water plasticization on mechanical properties and sensory crispness. Water sorption and the glass transition temperature range were determined gravimetrically and using differential scanning calorimetry (DSC) for samples stored at 0 to 85% relative humidity (RH), respectively. Mechanical properties were determined for extradates rehumidified at 0 to 76% RH. Three sensory panels evaluated crispness intensities of extrudates rehumidified at 33 to 76% RH by either breaking samples with fingers (Finger Task), biting using the incisor teeth (Bite Task), or biting and chewing (Bite‐and‐Chew Task). The extrudate was plasticized by water, as observed from a typical decrease of Tg with increasing water content. Changes in mechanical properties and loss of crispness occurred at an...

NON-ENZYMATIC BROWNING-INDUCED WATER PLASTICIZATION Glass transition temperature depression and reaction kinetics determination using DSC

An exotherm, observed in differential scanning calorimetry (DSC) scans of amorphous food materials above their glass transition temperature,Tg, may occur due to sugar crystallization, nonenzymatic browning, or both. In the present study, this exothermal phenomenon in initially anhydrous skim milk and lactose-hydrolyzed skim milk was considered to occur due to browning during isothermal holding at various temperatures above the initialTg. The nonenzymatic, Maillard browning reaction produces water that in amorphous foods, may plasticize the material and reduceTg. The assumption was that quantification of formation of water from theTg depression, which should not be observed as a result of crystallization under anhydrous conditions, can be used to determine kinetics of the nonenzymatic browning reaction. The formation of water was found to be substantial, and the amount formed could be quantified from theTg measured after isothermal treatment at various temperatures using DSC. The rate of water formation followed zero-order kinetics, and its temperature dependence well aboveTg was Arrhenius-type. Although water plasticization of the material occurred during the reaction, and there was a dynamic change in the temperature differenceT−Tg, the browning reaction was probably diffusioncontrolled in anhydrous skim milk in the vicinity of theTg of lactose. This could be observed from a significant increase in activation energy. The kinetics and temperature dependence of the Maillard reaction in skim milk and lactose-hydrolyzed skim milk were of similar type well above the initialTg. The difference in temperature dependence in theTg region of lactose, but above that of lactose-hydrolyzed skim milk, became significant, as the rate in skim milk, but not in lactose-hydrolyzed skim milk, became diffusion-controlled. The results showed that rates of diffusion-controlled reactions may follow the Williams-Landel-Ferry (WLF) equation, as kinetic restrictions become apparent within amorphous materials in reactions exhibiting high rates at the same temperature under non-diffusion-controlled conditions.

Determination of amorphous content in the pharmaceutical process environment.

The amorphous state has different chemical and physical properties compared with a crystalline one. Amorphous regions in an otherwise crystalline material can affect the bioavailability and the processability. On the other hand, crystalline material can function as nuclei and decrease the stability of an amorphous system. The aim of this study was to determine amorphous content in a pharmaceutical process environment using near infrared (NIR) and Raman spectroscopic techniques together with multivariate modelling tools. Milling was used as a model system for process‐induced amorphization of a crystalline starting material, α‐lactose monohydrate. In addition, the crystallization of amorphous material was studied by storing amorphous material, either amorphous lactose or trehalose, at high relative humidity conditions. The results show that both of the spectroscopic techniques combined with multivariate methods could be applied for quantitation. Preprocessing, as well as the sampling area, was found to affect the performance of the models. Standard normal variate (SNV) transformation was the best preprocessing approach and increasing the sampling area was found to improve the models. The root mean square error of prediction (RMSEP) for quantitation of amorphous lactose using NIR spectroscopy was 2.7%, when a measuring setup with a larger sampling area was used. When the sampling area was smaller, the RMSEPs for lactose and trehalose were 4.3% and 4.2%, respectively. For Raman spectroscopy, the RMSEPs were 2.3% and 2.5% for lactose and trehalose, respectively. However, for the optimal performance of a multivariate model, all the physical forms present, as well as the process environment itself, have to be taken into consideration.

Effect of amylose content on physical and mechanical properties of potato-starch-based edible films.

The present study investigated the amylose content and the gelatinization properties of various potato starches extracted from different potato cultivars. These potato starches were used to prepare edible films. Physical and mechanical properties of the films were investigated. The crystallinity of selected native starches and edible films made of the same starches were determined by X-ray diffraction. The amylose content of potato starches varied between 11.9 and 20.1%. Gelatinization of potato starches in excess water occurred at temperatures ranging from 58 to 69 degrees C independently of the amylose content. The relative crystallinity was found to be around 10-13% in selected native potato starches with low, medium, and high amylose content. Instead, films prepared from the same potato starches were found to be practically amorphous having the relative crystallinity of 0-4%. The mechanical properties and the water vapor permeability of the films were found to be independent of the amylose content.

Characterisation of blends of paracetamol and citric acid

The purpose of this study was to characterise physically stable amorphous blends that were sticky (low glass transition temperature) in ambient conditions. The effects of composition, melting time and melting temperature were evaluated with respect to physical and chemical property. Citric acid anhydrate and paracetamol were melt‐quenched as binary mixtures and as pure materials. Bulk samples were characterised by differential scanning calorimetry, X‐ray powder diffractometry, and Raman and Fourier transform infrared spectroscopy. The composition and the sample exposure to moisture affected significantly the physical stability of samples. The extreme melting conditions, coupled with long exposure to heat and a high melting temperature, lowered the overall crystallisation rate. Paracetamol had a stronger tendency to crystallise from the blends than did citric acid. The 50:50% (w/w) blend was physically stable for at least 27 weeks in dry conditions and was partly crystalline after 4 weeks of storage at a relative humidity of 43%. The result of the physical stability of blends is discussed in terms of hydrogen bonding interaction between paracetamol and citric acid and in relation to degradation products formed in a mixing state.

Differential Scanning Calorimetry Glass Transition Temperatures of White Bread and Mold Growth in the Putative Glassy State

ABSTRACT Differential scanning calorimetry (DSC) was used to determine the onset and end temperatures of the glass transition (Tg) for white bread equilibrated between 53 and 84% rh. Calorimetric Tg end values were ≈20°C higher than onset values, indicating that it is probably more correct to refer to a “glass transition range” rather than a glass transition temperature. Slices of white bread inoculated with a mixture of xerophilic molds were equilibrated to 75% rh (equilibrium moisture content of 14.5 g of water/100 g of dry material) and stored at 26°C. In a parallel experiment, some of the equilibrated bread samples were stored without mold inoculation and subjected to spontaneous contamination from the immediate surroundings. As suggested by measured Tg, bread stored at 75% rh and 26°C appeared to be glassy. After storage, samples of bread (inoculated or not) were spoiled by xerophilic molds, suggesting that Tg, as measured by DSC, cannot be considered as an absolute threshold for mold growth inhibition.