Functionalisation of pea protein by tryptic hydrolysis – Characterisation of interfacial and functional properties

With regard to applications in dispersed systems (i.e. emulsions), improving the poor solubility of pea protein in the pH-range applicable to foods (pH 3 to pH 7) is a prerequisite. To achieve this, a pea protein concentrate was produced on a lab scale using alkaline extraction and subsequent enzymatic hydrolysis to degrees of 2 and 4%. Solubility was improved and interfacial properties were influenced. All samples led to the formation of emulsions but displayed a tendency towards wider oil-droplet size distributions at pH close to the isoelectric point. Using microscopy, this increase could be attributed to the formation of aggregates, which in turn can be ascribed to lack of repulsion caused by the low absolute values of ζ-potentials. The same lack of repulsion led to stronger and more elastic interfacial films at pH 4 and 5 than at pH 7. Moreover, film strength increased significantly with increasing degree of hydrolysis. Dilatational experiments imply that hydrolysis enhances in-plane structural rearrangements. Thus, it is concluded that tryptic hydrolysis has the potential to improve the overall stability of emulsions.BMBF, 01EA1408C, Kompetenzcluster Ernährungsforschung: NutriAct - Ernährungsintervention für gesundes Altern, Technische Universität Berli

Thermally induced degradation of citrus pectins during storage – Alterations in molecular structure, colour and thermal analysis

Commercial citrus pectins (17 samples from 3 different suppliers) were stored at 60 °C and 80% humidity for two weeks. Molecular parameters (galacturonan content, degree of methoxylation, intrinsic viscosity), colour and behaviour in thermal analysis (DSC and TG) were tested and the results were compared with those of model pectins prepared under laboratory conditions from a previous study. Whereas the molecular parameters and colour of both groups changed similarly, considerable differences in the thermal analysis were found not only between model pectins and commercial pectins but also between commercial samples from different suppliers. It seems that varying processing conditions between laboratory preparations and industrial processing as well as differences in industrial scale processing influence the pectin properties and their degradation during storage. All commercial citrus pectin samples were strongly demethoxylated and depolymerised, former high-methoxylated pectins with degree of methoxylation (DM) > 50% became low-methoxylated with DM < 50% and some low-methoxylated samples afterwards had a DM close to pectic acid. As a result, also their gelation properties changed markedly. For pectin producing and applying companies it might be essential to check the properties of pectins after longer storage under unfavourable conditions. As a consequence, a variation of the gelation conditions for pectins after storage might be necessary

Influence of enzymatic and acidic demethoxylation on structure formation in sugar containing citrus pectin gels

Aim of the present study was to investigate the impact of different demethoxylation methods and the co-occuring side effects on the molecular properties and structure formation in pectin gels. A high-methoxylated citrus pectin (HMP) was demethoxylated using either hydrochloric acid or pectin methylesterases of plant (pPME) or fungal (fPME) origin. pPME treatment causes a more block-wise distribution of free carboxyl groups, fPME or acidic treatment a random distribution. Twelve pectin samples with four different degrees of methoxylation (DM) between 62% and 41% were prepared. The gelation process was studied by oscillatory measurements. In pectin samples from pPME treatment structure formation started at higher temperature and the final gels were more elastic in comparison to pectin from the two other modifications. The impact of the block-wise distribution of the free carboxyl groups became more evident with decreasing DM. The gelling process of pectin samples with random distribution was similar independent of DM.Side effects of all demethoxylation reactions were an altered sodium ion content (high in enzymatically treated pectin, close to zero in acidic treated) and a decrease of the molecular weight with increasing degree of demethoxylation. These side effects additionally altered the gelation process and the final gel properties in different ways

Structure formation in sugar containing pectin gels - Influence of gel composition and cooling rate on the gelation of non-amidated and amidated low-methoxylated pectin

Gel structure formation and gel properties of low-methoxyl pectin (LMP) and low-methoxyl amidated pectin (LMAP) with similar degree of methoxylation have been investigated by oscillatory rheological measurements. The gelling process was examined in a sugar-acid environment matching the conditions in jams and jellies. Factors studied included cooling rate, calcium content and pH. Parameters derived from the rheological measurements comprised the gel point, structuring velocity, initial and critical structuring temperature, average structuring developing rate and loss factor (tanδend). The influence of the cooling rate on the gelling process of LMP was moderate and the influence on the final gel properties was significant, tanδend decreased with increasing cooling rate. The calcium content significantly affected the structuring process of LMAP and the final gel properties. At high calcium content, the gelling process started at a higher temperature but the resulting gels were less strong. The pH had a significant but partly opposite effect on the gelation of LMP as well as LMAP. The differences in gelation behavior between LMP and LMAP can be explained by the lower number of available blocks of free carboxyl groups in LMAP as well as by the formation of additional hydrogen bonds through the amide groups

The Early Identification of Autism Spectrum Disorder in Preschool Settings

Caregivers often recognize the signs of Autism Spectrum Disorder (ASD) in their child before age two, yet, they often do not receive a diagnosis until after the child is four years old. Preschool teachers have high levels of exposure to the developing child and so are in an ideal position to identify children who may have ASD and refer them for assessments which may lead to access to early intervention services. This research sought to better understand whether or not preschool teachers are familiar with signs of ASD in young children, comfortable discussing concerns with parents, and knowledgeable about services to which young children with ASD may benefit. This research is important to the social work field because it is imperative to ensure public agencies are working to help families gain access to services which will aid their children in reaching their full potential. The sample in this study consisted of 84 preschool teachers, many of whom were Caucasian (78%), female (90.6%), and held a college degree (80%). The results of this study found preschool teachers to have a moderate level of knowledge regarding ASD symptoms regardless of experience. In general teachers held positive perceptions about mainstreaming and those who have had training specific to inclusion had more positive perceptions about mainstreaming than those who did not (p = .026). Teachers responded with high levels of comfort voicing their concerns about child development to parents, and teachers with greater experience reported feeling more comfortable addressing their concerns with parents. Teachers in this study reported having knowledge of services available to families with children with ASD and there was no association between teachers experience or education level and their familiarity with these services

The Early Identification of Autism Spectrum Disorder in Preschool Settings

Caregivers often recognize the signs of Autism Spectrum Disorder (ASD) in their child before age two, yet, they often do not receive a diagnosis until after the child is four years old. Preschool teachers have high levels of exposure to the developing child and so are in an ideal position to identify children who may have ASD and refer them for assessments which may lead to access to early intervention services. This research sought to better understand whether or not preschool teachers are familiar with signs of ASD in young children, comfortable discussing concerns with parents, and knowledgeable about services to which young children with ASD may beneift. This research is important to the social work field because it is imperative to ensure public agencies are working to help families gain access to services which will aid their children in reaching their full potential. The sample in this study consisted of 84 preschool teachers, many of whom were Caucasian (78%), female (90.6%), and held a college degree (80%). The results of this study found preschool teachers to have a moderate level of knowledge regarding ASD symptoms regardless of experience. In general teachers held positive perceptions about mainstreaming and those who have had training specific to inclusion had more positive perceptions about mainstreaming than those who did not (p = .026). Teachers responded with high levels of comfort voicing their concerns about child development to parents, and teachers with greater experience reported feeling more comfortable addressing their concerns with parents. Teachers in this study reported having knowledge of services available to families with children with ASD and there was no association between teachers experience or education level and their familiarity with these services

Modification and physico-chemical properties of citrus pectin – Influence of enzymatic and acidic demethoxylation

Aim of the present study was to investigate the effect of the method of demethoxylation on the particle structure and techno-functional properties of pectins with different degree of methoxylation and distribution of free carboxyl groups. Two groups of model pectins, one with 57% and one with 42% degree of methoxylation have been prepared from one single commercial pectin. Modifications were performed by an acidic and two enzymatic methods using fungal and plant-derived pectin methyl esterases. Thermal stability was investigated by thermal analysis and water uptake was determined by a sorption and a capillary sucking method. The enzyme-treated pectins were thermally less stable than the acid-treated. The water uptake of enzyme-treated pectins was higher than in acid-treated samples in the sorption method and lower in the capillary sucking tests. The different behaviour is explained by differences in pH during demethoxylation and a co-occurring variation in sodium content. Both parameters affected intermolecular interactions of the pectin macromolecules in solution, which resulted in differences in the particle morphology. The effect of the distribution of free carboxyl groups (statistical or block-wise) on the techno-functional properties was more pronounced in high-methoxylated pectins than in low-methoxylated pectins

Structure formation and rheological properties of pea protein-based gels

Nutritional recommendations for the elderly, but also the general public, include incorporation of plant proteins in the diet, an increase in the intake of Ω-3 fatty acids and an increase in intake of dietary fibre. Protein structure and structuring behaviour of plant proteins differ from that of milk proteins. Therefore, the aim of the presented study was to characterise the structuring process and resulting structure of yoghurt-style gels containing 10% pea protein with and without addition of nutritionally recommended ingredients like rapeseed-oil and/or commercial oat fibre. Rheological measurements were combined with microscopy for sample characterisation. Generally, all studied formulations were able to form acid induced gels via fermentation. The acidification led to a two-phase gelation process resulting in thick gels that showed mainly weak rheological behaviour. Supplementation with oil and/or fibre resulted in an increase of the relative concentration of pea protein in the aqueous phase and led to a strong increase in the complex shear modulus |G*| as well as the maximum structuring velocity d|G*|/dt. These effects need to be considered when tailoring yoghurt-style gels with high consumer acceptance.BMBF, 01EA1408C, Kompetenzcluster Ernährungsforschung: NutriAct - Ernährungsintervention für gesundes Altern, Technische Universität Berli

Thermal degradation of citrus pectin in low-moisture environment - Influence of acidic and alkaline pre-treatment

Pectin powder is degraded during storage and transport by demethoxylation and depolymerisation. The degradation mechanisms and especially the influence of pre-treatments on the degradation reactions are not completely understood. In this study, commercial citrus pectin was modified by either acidic or alkaline demethoxylation. The modified pectins, as well as the commercial pectin, were thermally degraded during four weeks of storage at 60 °C and 80% relative humidity. Demethoxylation and depolymerisation as well as colour alterations were examined during degradation, and the course of the reactions was monitored. It was found that the type of pre-treatment during modification determined the material properties and, thus, the water uptake of the modified pectin powders. The resulting water availability in the samples was crucial to the extent of demethoxylation and to the type and intensity of depolymerisation since some of these reactions competed for the water in the climate chamber. The pre-treatment also determined the content of neutral sugars and sodium ions of the modified pectins. High contents of these components limited the extent of degradation in different ways. A previously assumed third depolymerisation mechanism of pectins, beside backbone hydrolysis and β-elimination, was confirmed.DFG, 268547215, Strukturabhängige Abbaureaktionen von Pektinen und deren Auswirkungen auf nicht-enzymatische Bräunung und technologische Funktionalitä

Structure formation in sugar containing pectin gels – Influence of tartaric acid content (pH) and cooling rate on the gelation of high-methoxylated pectin

The aim of the study was the application of a recently published method, using structuring parameters calculated from dG′/dt, for the characterisation of the pectin sugar acid gelation process. The influence of cooling rate and pH on structure formation of HM pectin gels containing 65 wt.% sucrose were investigated. The results show that the structure formation process as well as the properties of the final gels strongly depended on both parameters. With increasing cooling rates from 0.5 to 1.0 K/min the initial structuring temperature slightly decreased and the maximum structuring velocity increased. The lower the cooling rates, the firmer and more elastic were the final gels. With increasing acid content (decreasing pH from 2.5–2.0) the initial structuring temperatures were nearly constant. The final gel properties varied visibly but not systematically. Gels with the lowest and highest pH were less elastic and weaker compared to those with medium acid concentrations