Davy Van de Walle

Optimisation of enzymatic synthesis of cocoa butter equivalent from high oleic sunflower oil

BACKGROUND High oleic sunflower oil (HOSO) and a fatty acid (FA) mixture were inter-esterified in a solvent-free system catalysed by Lipozyme RM IM to produce a cocoa butter equivalent (CBE). The effects of reaction conditions on the percentage of saturate-oleoyl-saturate (SOS) and saturate-saturate-oleoyl (SSO) triacylglycerols (TAGs) were studied. The process was further optimised by response surface methodology. A five-factor response surface design was used to investigate the influences of the five major factors and their mutual relationships. The five factors were substrate ratio (A, FA/HOSO, mol mol⁻¹), enzyme load (B, wt% based on substrates), water content (C, wt% based on substrates), reaction temperature (D,°C) and reaction time (E, in hours) varying at three levels together with two star point levels. RESULTS The highest yield (59.1% SOS) and lowest acyl migration (2.9% SSO) was obtained at 10% enzyme load, 1% water content, 1:7 substrate mole ratio, 65°C reaction temperature and 6 h reaction time. All the investigated factors except substrate ratio had significant effect on acyl migration. CONCLUSION The quadratic response models sufficiently described the acidolysis reaction. All parameters had significant effect on the percentage of SOS TAGs. Based on the models, the reaction was optimised to obtain a maximum yield of SOS TAGs.

Quality attributes of dark chocolates formulated with palm sap-based sugar as nutritious and natural alternative sweetener

Consumer demand for healthier alternative sweeteners and attempts to replace the most common sweetener used in chocolate, namely sucrose, continue to increase in recent times. One sucrose alternative that has not been fully explored in chocolate is palm sap-based sugar. This work investigated the impact of sucrose replacement by coconut sugar (CCS1 and CCS2) and palm sugar (CPS1, CPS2 and CPS3) on the quality attributes of dark chocolate, more particularly colour, hardness, flow behaviour and aroma profile. The results showed that chocolates formulated with palm sap-based sugar were lighter in colour and harder than the reference chocolate made with sucrose, which could be attributed to a lower particle density and a higher moisture of palm sap-based sugar than that of sucrose. Analysis of the major volatile compounds recorded the presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP) and high concentration of pyrazine-based compounds in the palm sap-based sugar-sweetened chocolates. The former compound (DDMP) was, however, absent in the sucrose-sweetened dark chocolate. The physicochemical properties of the sugars also had a significant effect on the rheological behaviour of the final chocolates with chocolates formulated with coconut sugar recording the highest Casson viscosity. With regard to fat melting, chocolates sweetened with palm sap-based sugar and sucrose exhibited similar melting range temperature. Palm sap-based sugar nevertheless seems to have great potential for dark chocolate applications with additional health benefits.

Feasibility of a small-scale production system approach for palm sugar sweetened dark chocolate

Palm sugar is highly produced and patronised in the south-eastern part of Asia, e.g. Indonesia which is also the world’s third largest cocoa producer. Recently, interest in palm sugar sweetened chocolate and better approaches for production methods that can be easily applied in developing countries are rising. This work investigated the influence of palm sugar on the quality attributes of dark chocolate in terms of fineness, rheological behaviour and aroma profile compared to that of sucrose. Furthermore, a small-scale processing approach using the combination of Stephan mixer and ball mill compared to the conventional method was investigated. The results showed that palm sugar sweetened chocolate exhibited a higher viscosity, a higher particle volume fraction and a higher degree of particle agglomeration due to its relatively high moisture and presence of glucose and fructose. Furthermore, chocolates sweetened with palm sugar displayed a distinctive aroma profile with the abundant presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one and pyrazine-based compounds. Applying the alternative processing method leaded to the production of chocolate with rather high degree of agglomeration and viscosity as compared to chocolate produced by means of conventional processing. Moreover, the alternative processing method resulted in the presence of myrcene, β-trans-ocimene and isoamyl acetate which were not observed in the conventionally produced chocolates. The alternative processing method, however, seems to have potential for small-scale production of dark chocolate sweetened with palm sugar.

Mixed surfactant systems of sucrose esters and lecithin as a synergistic approach for oil structuring

In order to modify the self-assembly of sucrose esters (SEs) in sunflower oil, we added sunflower lecithin (SFL) as co-surfactant. It is hypothesized that SFL modifies the self-assembly of SEs by interrupting the extensive hydrogen bonding between SEs monomers. The addition of SFL into SEs induced gelation of the mixed surfactant system oleogels at all studied ratios. The 7:3 SEs:SFL combination showed enhanced rheological properties compared to the other studied ratios, which suggests better molecular ordering induced by SFL. The modifications might have been caused by interference in the hydrogen bonding, connecting the polar heads of SEs molecules in the presence of SFL. This effect was confirmed by thermal behavior and small angle X-ray diffraction (SAXD) analysis. From the crystallization and melting analyses, it was shown that the peak temperature, shape and enthalpy decreased as the SFL ratio increases. Meanwhile, the bi-component oleogels exhibited new peaks in the SAXD profile, which imply a self-assembly modification. The microscopic study through polarized and electrons revealed a change in the structure. Therefore, it can be concluded that a synergistic effect between SEs and SFL, more particularly at 7:3 ratio, towards sunflower oil structuring could be obtained. These findings shed light for greater applications of SEs as structuring and carrier agent in foods and pharmaceutical.

KIRA1 and ORESARA1 terminate flower receptivity by promoting cell death in the stigma of Arabidopsis

Flowers have a species-specific functional life span that determines the time window in which pollination, fertilization and seed set can occur. The stigma tissue plays a key role in flower receptivity by intercepting pollen and initiating pollen tube growth toward the ovary. In this article, we show that a developmentally controlled cell death programme terminates the functional life span of stigma cells in Arabidopsis. We identified the leaf senescence regulator ORESARA1 (also known as ANAC092) and the previously uncharacterized KIRA1 (also known as ANAC074) as partially redundant transcription factors that modulate stigma longevity by controlling the expression of programmed cell death–associated genes. KIRA1 expression is sufficient to induce cell death and terminate floral receptivity, whereas lack of both KIRA1 and ORESARA1 substantially increases stigma life span. Surprisingly, the extension of stigma longevity is accompanied by only a moderate extension of flower receptivity, suggesting that additional processes participate in the control of the flower’s receptive life span.All flowers eventually die. Stigma in Arabidopsis flowers can only be pollinated for a limited amount of time. Two NAC transcription factors named KIRA1 and ORESARA1 control cell death in papilla cells, as well as the stigma life span.

Biocatalytic synthesis of the rare sugar kojibiose: process scale-up and application testing

Cost-efficient (bio)chemical production processes are essential to evaluate the commercial and industrial applications of promising carbohydrates and also are essential to ensure economically viable production processes. Here, the synthesis of the naturally occurring disaccharide kojibiose (2-O-α-d-glucopyranosyl-d-glucopyranoside) was evaluated using different Bifidobacterium adolescentis sucrose phosphorylase variants. Variant L341I_Q345S was found to efficiently synthesize kojibiose while remaining fully active after 1 week of incubation at 55 °C. Process optimization allowed kojibiose production at the kilogram scale, and simple but efficient downstream processing, using a yeast treatment and crystallization, resulted in more than 3 kg of highly pure crystalline kojibiose (99.8%). These amounts allowed a deeper characterization of its potential in food applications. It was found to have possible beneficial health effects, including delayed glucose release and potential to trigger SCFA production. Finally, we compared the bulk functionality of highly pure kojibiose to that of sucrose, hereby mapping its potential as a new sweetener in confectionery products.

Investigating the rheological, microstructural and textural properties of chocolates sweetened with palm sap-based sugar by partial replacement

Palm sugar, a natural alternative sweetener which can be made from the nectar of several species of palm tree flowers, recently gains more interest. Due to its physicochemical characteristics, utilisation of palm sugar as chocolate sweetener results in different quality attributes of chocolate. In this work, a thorough investigation about the influence of palm sugar on the rheological, microstructural and textural characteristics of chocolate was carried out through partial replacement of sucrose as chocolate sweetener. Accordingly, five sucrose–palm sugar blends with different palm sugar (PS) proportion, namely PS0, PS25, PS50, PS75, and PS100 were used as chocolate sweetener. The results showed that the Casson yield value of chocolate containing palm sugar was lower than the Casson yield value of chocolate sweetened with pure sucrose which could be attributed to the presence of agglomerates in the chocolate suspension. However, palm sugar-sweetened chocolate exhibited a higher Casson viscosity and thixotropy which could be mainly attributed to the presence of glucose and fructose and the relatively high moisture content. These factors also influenced the hardness of the chocolate to some extent. A lower melting temperature and enthalpy value of the sugar phase in chocolate were observed by DSC, whereas visualisation using SEM, polarised and normal light microscopy indicated increased agglomeration due to the presence of moisture, amorphous sugar and chemical “impurities”. Rheological behaviour of molten chocolate, hardness and polarised–normalised light microscopy were evaluated at a constant temperature of 40, 20, and 50 °C, respectively, while the melting profile was measured from 20 to 200 °C at a rate of 5 °C/min.

Glucansucrase (mutant) enzymes from Lactobacillus reuteri 180 efficiently transglucosylate Stevia component rebaudioside A, resulting in a superior taste

Steviol glycosides from the leaves of the plant Stevia rebaudiana are high-potency natural sweeteners but suffer from a lingering bitterness. The Lactobacillus reuteri 180 wild-type glucansucrase Gtf180-ΔN, and in particular its Q1140E-mutant, efficiently α-glucosylated rebaudioside A (RebA), using sucrose as donor substrate. Structural analysis of the products by MALDI-TOF mass spectrometry, methylation analysis and NMR spectroscopy showed that both enzymes exclusively glucosylate the Glc(β1→C-19 residue of RebA, with the initial formation of an (α1→6) linkage. Docking of RebA in the active site of the enzyme revealed that only the steviol C-19 β-D-glucosyl moiety is available for glucosylation. Response surface methodology was applied to optimize the Gtf180-ΔN-Q1140E-catalyzed α-glucosylation of RebA, resulting in a highly productive process with a RebA conversion of 95% and a production of 115 g/L α-glucosylated products within 3 h. Development of a fed-batch reaction allowed further suppression of α-glucan synthesis which improved the product yield to 270 g/L. Sensory analysis by a trained panel revealed that glucosylated RebA products show a significant reduction in bitterness, resulting in a superior taste profile compared to RebA. The Gtf180-ΔN-Q1140E glucansucrase mutant enzyme thus is an efficient biocatalyst for generating α-glucosylated RebA variants with improved edulcorant/organoleptic properties.

Physicochemical properties and antioxidant activities of chocolates enriched with engineered cinnamon nanoparticles

The use of nanocapsules to overcome incompatibility between bioactive compounds and food matrices targeting fortification has been widely acknowledged. This study provides a novel method to enhance the nutritional properties of chocolate by employing lyophilised colloidal nanoparticles made of a combination of shellac, xanthan gum and cinnamon extract. Lyophilised colloidal nanoparticles containing cinnamon extract (LCNP-CE) were prepared by an anti-solvent precipitation method followed by freeze drying. Cinnamon extract was loaded into nanoparticle to entrap the aroma of the cinnamon extract; thereby, the cinnamon extract can be incorporated in the chocolate to expand its bioactive profile without altering its sensorial characteristic. LCNP-CE was formulated into white and milk chocolate in multilevel ratios (0–2% w/w). The results show that the fortification of milk and white chocolates by LCNP-CE significantly improved the total phenolic content and antioxidant activity of the chocolates without remarkable changes in the fineness and melting profile properties. Even though slight changes in the hardness, flow behaviour and colour have been observed, the enriched chocolates are likely in the range of acceptable values. Encapsulation has a positive impact on preventing flavour alteration on the cinnamon enriched chocolates; however, a drawback in the release behaviour of the cinnamon extract from the chocolate was observed.

Trans-α-glucosylation of stevioside by the mutant glucansucrase enzyme Gtf180-ΔN-Q1140E improves its taste profile

The adverse health effects of sucrose overconsumption, typical for diets in developed countries, necessitate use of low-calorie sweeteners. Following approval by the European Commission (2011), steviol glycosides are increasingly used as high-intensity sweeteners in food. Stevioside is the most prevalent steviol glycoside in Stevia rebaudiana plant leaves, but it has found limited applications in food products due to its lingering bitterness. Enzymatic glucosylation is a strategy to reduce stevioside bitterness, but reported glucosylation reactions suffer from low productivities. Here we present the optimized and efficient α-glucosylation of stevioside using the mutant glucansucrase Gtf180-ΔN-Q1140E and sucrose as donor substrate. Structures of novel products were elucidated by NMR spectroscopy, mass spectrometry and methylation analysis; stevioside was mainly glucosylated at the steviol C-19 glucosyl moiety. Sensory analysis of the α-glucosylated stevioside products by a trained panel revealed a significant reduction in bitterness compared to stevioside, resulting in significant improvement of edulcorant/organoleptic properties.