Thermal stabilisation of cocoa fruit pulp - Effects on sensory properties, colour and microbiological stability.

To improve cocoa pulp's shelf-life, preservation processes are necessary while maintaining the quality of the pulp. We applied pasteurisation and UHT-treatment and investigated different quality parameters: dry matter content, water activity, total soluble solids, colour and peroxidase activity. Both technologies inactivated peroxidase successfully. The colour of the pasteurised pulp was similar to the fresh, while UHT-treated pulp was more brownish. The sensory properties were investigated in detail by descriptive analysis and the identification of aroma-active volatile organic compounds. Fresh pulp revealed the highest aroma intensity for attribute unripe banana-like, whereas UHT-treated pulp scored highest in the intensity of attribute tropical fruit-like. Pasteurised pulp showed strong similarities to the fresh pulp. Fresh cocoa pulp exhibited 74 aroma-active regions identified by GC-MS/O. UHT-treated and pasteurised pulp accounted for 66 and 60 aroma-active regions, respectively. Five identified substances were only found in the fresh and pasteurised pulp, namely: δ-carene, 1-pentanol, 3-(methylthio)propanol, phenol and δ-undecalactone. Similarly, fresh and UHT-treated pulp shared ten exclusive odorants, such as decanal, geraniol, and δ-nonalactone. The pasteurised and UHT-treated pulp shared two compounds, δ-decalactone and 5-(hydroxymethyl)furfural. Furthermore, the thermally treated pulps could be stored at 4 °C and 23 °C for 24 weeks without observing a significant growth of microorganisms. The rate of non-enzymatic browning was higher in samples stored at 23 °C compared to those stored at 4 °C, leading to higher browning indices. We demonstrated that pasteurisation and ultra-high temperature treatment are suitable technologies for the stabilisation of cocoa fruit pulp. These resulted in prolonged shelf-lifes and minimal changes in the sensory prorperties of the treated pulps, characterised by a reduction in the aroma diversities. This work provides important insights for the thermal stabilisation of further side-streams.

Aroma-active volatiles and rheological characteristics of the plastic mass during conching of dark chocolate.

Chocolate conching is a highly complex, thermomechanical process that transforms the aroma and flow properties of a dry starting material. Different conched plastic masses of dark chocolate were characterized. Rheological characterization of plastic masses was performed for the first time using a closed cavity rheometer (CCR1). In free cocoa butter derived from the plastic masses, acetic acid, benzaldehyde, (R,S)-(±)-linalool, 2,3,5,6-tetramethylpyrazine, and 2-phenylethanol were quantified by stable isotope dilution analysis (SIDA2) and gas chromatography-mass spectrometry. During the conching process, the amount of free cocoa butter increased possibly due to de-agglomeration. The complex viscosity of the plastic mass decreased as a function of conching time. Regarding aroma refinement, the concentrations of all five aroma-active volatiles decreased with increasing conching duration, albeit to varying degrees. The level of acetic acid showed the most pronounced decrease of about 60%, whereas linalool exhibited the lowest decrease in concentration, up to 26%. Overall, a lower polarity or boiling point of the aroma-active volatiles was linked to a stronger decrease in concentration during conching. These data illustrate the influence of conching on texture and the respective aroma changes, which deepens understanding of the conching effect on the sensory quality of dark chocolate.

Influence of elongation and desaturation on chemosensory properties in acrylates and their corresponding 1-alken-3-ones.

Acrylates as well as 1-alken-3-ones are both known to be odour active substances but are generally identified in different materials. Nonetheless, butyl acrylate and 1-octen-3-one were both found to elicit a similar mushroom-like odour in previous studies. This led to the question of whether acrylates and enones with the same overall chain length generally elicited similar odours and whether they had similar odour thresholds. Overall, most of the investigated substances showed a mushroom-like, geranium-like or fruity odour. In contrast, short chained substances elicited garlic-like, lighter gas-like or glue-like, odour qualities, suggesting a correlation between the odour quality and the overall chain length. The results showed that only between the analogue structures butyl acrylate and 1-octen-3-one as well as hexyl acrylate and 1-decen-3-one could similar odour qualities be observed. All investigated substances showed low odour threshold values in air between 0.0032 ng/lair (1-hexen-3-one) and 55 ng/lair (1-dodecen-3-one). Overall, 1-alken-3-ones revealed a higher dependency on the chain length when compared to their respective acrylates. The introduction of a second terminal double bond led to a decrease of OT values in case of the acrylates and to an increase in case of the ketones that neither contained a second terminal double bond nor a double bond located close to the carbonyl group. Despite their structural similarities, the results suggest that both substance classes are perceived in a different manner and are therefore likely to be recognized by different types of receptors or are related to different activation patterns in multi-receptor stimulation processes.

Design and Evaluation of TIM-3-CD28 Checkpoint Fusion Proteins to Improve Anti-CD19 CAR T-Cell Function.

Therapeutic targeting of inhibitory checkpoint molecules in combination with chimeric antigen receptor (CAR) T cells is currently investigated in a variety of clinical studies for treatment of hematologic and solid malignancies. However, the impact of co-inhibitory axes and their therapeutic implication remains understudied for the majority of acute leukemias due to their low immunogenicity/mutational load. The inhibitory exhaustion molecule TIM-3 is an important marker for the interaction of T cells with leukemic cells. Moreover, inhibitory signals from malignant cells could be transformed into stimulatory signals by synthetic fusion molecules with extracellular inhibitory receptors fused to an intracellular stimulatory domain. Here, we designed a variety of different TIM-3-CD28 fusion proteins to turn inhibitory signals derived by TIM-3 engagement into T-cell activation through CD28. In the absence of anti-CD19 CAR, two TIM-3-CD28 fusion receptors with large parts of CD28 showed strongest responses in terms of cytokine secretion and proliferation upon stimulation with anti-CD3 antibodies compared to controls. We then combined these two novel TIM-3-CD28 fusion proteins with first- and second-generation anti-CD19 CAR T cells and found that the fusion receptor can increase proliferation, activation, and cytotoxic capacity of conventional anti-CD19 CAR T cells. These additionally armed CAR T cells showed excellent effector function. In terms of safety considerations, the fusion receptors showed exclusively increased cytokine release, when the CAR target CD19 was present. We conclude that combining checkpoint fusion proteins with anti-CD19 CARs has the potential to increase T-cell proliferation capacity with the intention to overcome inhibitory signals during the response against malignant cells.

Texture, sensory properties and functionality of extruded snacks from pulses and pseudocereal proteins.

BACKGROUND: The protein-rich fractions of pulses and pseudocereals exhibit a well-balanced amino acid profile, particularly when combined in different portions, and are therefore high-value ingredients for the production of extruded snacks. However, the impact of a combination of pulses and pseudocereals on the physical and sensory qualities of extruded snacks has not been investigated up to now. Native or preconditioned protein isolates and concentrates from pulses - as single ingredients or in combination with protein-rich flours of pseudocereals - were analyzed regarding their thermal and functional properties in relation to extrusion characteristics. Low moisture extrusion cooking was used to investigate the impact of protein source (lentil, lupin, faba bean), pseudocereal source (quinoa, amaranth, buckwheat) and protein content (30%, 50%, 70%) on sectional expansion, specific hardness, density and sensory properties of the snacks. RESULTS: With increasing protein content from 30% to 50%, the sectional expansion decreased and the density and specific hardness of the extrudates increased, which could be counteracted by preconditioning of the protein-rich ingredients. Lupin protein-based extrudates exhibited satisfactory texture and sensory properties. Extruded mixtures of pulses and pseudocereals (70% protein) exhibited a smaller sectional expansion compared to pulses as single ingredients (30%, 50%), regardless of pseudocereal type. However, the texture and sensory properties of the extruded blends were satisfactory. CONCLUSIONS: We show for the first time that protein-rich fractions of pulses and pseudocereals can be processed into expanded snacks with favorable texture and nutritional properties such as increased protein contents (70%) and balanced amino acid profiles. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Aroma Properties of Cocoa Fruit Pulp from Different Origins.

Cocoa pulp occurs as a by-product of cocoa bean production and can be repurposed to different food applications, such as jams, fruit preparations and beverages, improving the sustainability of cocoa production, as well as the livelihoods of cocoa farmers. In this work, aroma-active compounds of fresh cocoa fruit pulps from different origins were investigated by applying aroma extract dilution analyses in combination with gas chromatography-mass spectrometry/olfactometry for identification. In total, 65 aroma-active compounds were determined in four different pulps originating from Indonesia, Vietnam, Cameroon, and Nicaragua. Vietnamese pulp showed the highest number of aroma-active regions, while Cameroonian pulp accounted for the lowest. Moreover, Cameroonian cocoa pulp showed the lowest FD factors. Overall, the odorants with the highest FD factors were trans-4,5-epoxy-(E)-decenal, 2- and 3-methylbutanoic acid, 3-(methylthio)propanal, 2-isobutyl-3-methoxypyrazine, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, 4-vinyl-2-methoxyphenol, δ-decalactone, 3-hydroxy-4,5-dimethylfuran-2(5H)-one, dodecanoic acid, and linalool. This study provides insights into the aroma composition of fresh cocoa pulp from different origins for future food applications.

Aroma-Active Compounds in Robusta Coffee Pulp Puree-Evaluation of Physicochemical and Sensory Properties.

Wet coffee processing generates a large amount of coffee pulp waste that is mostly disposed of in the processing units. To reduce this waste and the associated environmental burden, an alternative strategy would be to exploit the coffee pulp to produce a durable and stable consumable product. Accordingly, a puree produced from Robusta coffee pulp was investigated in relation to its physicochemical and sensory properties. After thermal and chemical stabilization, the obtained puree (pH 3.6) was found to exhibit a multimodal particle size distribution, shear-thinning behavior, and lower discoloration, as well as an antioxidant capacity of 87.9 µmolTE/gDM. The flavor of the puree was examined by sensory evaluation and the corresponding analyses of aroma-active volatile compounds, as determined using aroma extract dilution analyses (AEDA) and gas chromatography-mass spectrometry/olfactometry (GC-MS/O). The puree was characterized by dominant fruity (4.4), floral (3.4), citrusy (3.3) and hay-like (3.3) odor impressions. The aroma-active compounds were predominantly aldehydes, acids, and lactones, whereby (E)-ß-damascenone, geraniol, 4-methylphenol, 3-hydroxy-4,5-dimethylfuran-2(5H)-one, and 4-hydroxy-3-methoxybenzaldehyde exhibited the highest flavor dilution (FD) factor (1024), thereby indicating their high impact on the overall aroma of the puree. This study demonstrates an approach to stabilize coffee pulp to produce a sweet, fruity puree with comparable physical properties to other fruit purees and that can be used as a new and versatile flavoring ingredient for various food applications.

Contribution of S. xylosus and L. sakei ssp. carnosus Fermentation to the Aroma of Lupin Protein Isolates.

Aroma-active compounds of lupin protein isolate and lupin protein isolate fermented with Staphylococcus xylosus and Lactobacillus sakei ssp. carnosus were investigated. The changes in aroma-active compounds were determined by application of aroma extract dilution analysis in combination with gas chromatography-mass spectrometry/olfactometry for identification, and by stable isotope dilution assays for quantification. A total of 30 aroma-active compounds for non-fermented and fermented samples were identified. The aroma profile of LPI fermented with Lactobacillus sakei ssp. carnosus was characterized as roasty and popcorn-like. Staphylococcus xylosus generated cheesy impressions, being in line with the fact that the main aroma compounds acetic acid, butanoic acid, and 2/3-methylbutanoic acid could be identified. Quantification of butanoic acid further confirmed these findings with the highest concentration of 140 mg/kg for LPI fermented with Staphylococcus xylosus. Our study provides insights into how fermentation utilizing different fermentative microbial strains, namely Staphylococcus xylosus and Lactobacillus sakei ssp. carnosus alters the aroma profile of lupin protein isolates. This demonstrates the potential of shaping fermented protein-based foods via targeted microbiological refinement.

Odor characterization of post-consumer and recycled automotive polypropylene by different sensory evaluation methods and instrumental analysis.

Despite the growing interest of the automotive industry in using recycled polymers, their undesired odor is limiting their application in vehicles' interior components. To get deeper insights into its causes, this study aimed at characterizing the odor of post-consumer and recycled automotive polypropylene with different contents of talc and an anti-fogging additive. Samples were evaluated by different sensory methods currently applied by the automotive industry (GMW 3205 and VDA 270), which confirmed, that they are not feasible for reuse in interior automotive applications. As these odor evaluations are usually performed by non-trained panelists and do not allow a detailed description of the samples' single odor qualities, sensory evaluation according to ISO 13299 was performed by trained panelists. Samples showed medium-high odor intensities rated from 5.1 to 5.6, and a general dislike of the odor with hedonic ratings from 1.8 to 2.6 (scale 0-10). Their odor profiles correlated well with the odorants identified by chemo-analytical characterization using gas chromatography-olfactometry (GC-O) and two-dimensional GC-O coupled with mass spectrometry (2D-GC-MS/O). An array of odorants with benzene and phenolic structures were identified as potential contributors to the samples' overall smell and are likely to originate from degradation of additives commonly used in automotive components. While the addition of talc or anti-fogging additive did not significantly improve the odor of the samples, the description of the samples' smell and the identification of odor-active compounds related to it allow the development of avoidance strategies for the manufacturing of neutral smelling products intended for vehicles' interior applications.

Structure-Odor Activity Studies on Derivatives of Aromatic and Oxygenated Monoterpenoids Synthesized by Modifying p-Cymene.

Thymoquinone was recently reported as having a unique pencil-like odor and being the impact compound for the cedar-like and cedar wood-based product smell such as pencils. The compounds thymol and carvacrol are structurally related odorants commonly found in plants and foods such as thyme and oregano, also having a significant contribution to their overall aroma. However, a systematic elucidation of the sensory properties in this class of oxygenated, aromatic monoterpenoids has not been carried out. To close this gap and gain new insights into structure-odor relationships leading to pencil-like and woody odors, 19 structurally related derivatives of p-cymene starting from thymol and carvacrol were synthesized and characterized. The compounds had odor thresholds ranging from 2.0 ng/L air to 388.8 ng/L air, being lowest for thymol and carvacrol and highest for thymohydroquinone. The compounds smelled mostly thyme-like, oregano-like, and pencil-like with phenolic, earthy, and medicinal variations in their odor character, which could be successfully linked to structural motifs.

Odorant composition of post-consumer LDPE bags originating from different collection systems.

The establishment of recycling systems aiming at high-quality recyclates from post-consumer plastic waste are essential to avoid the waste of resources. One main impediment for introducing recyclates into the market is their unwanted odor. For this reason, this study aimed at determining if the collection strategy affects the odor profile of post-consumer LDPE bags. Furthermore, the effect of hot water washing, inspired by the conventional mechanical recycling procedure, on the odor of post-consumer LDPE bags was screened. More than 60 odorants were detected in LDPE bags collected in a separate plastic fraction as well as in LDPE bags from the non-separated collection by means of gas chromatography-olfactometry, and 37 of them were unequivocally identified using two-dimensional gas chromatography-mass spectrometry/olfactometry. The sensory results revealed that the type of collection affects the overall odor intensity, the hedonic tone of the odor and the odor profile. Namely, cheesy and fecal smelling odorants were predominant in the waste that had not been separated at source, whereas odorants with earthy and moldy smells showed mostly higher intensity ratings in the waste separated at source. Short chain carboxylic acids, likely originating from microbial spoilage of organic waste, were found with higher dilution factors in the mixed fraction, and could, accordingly, contribute to the observed differences. Additionally, we could show that the hot washing procedure, applied to the LDPE sample from the separate collection system, significantly reduced the overall odor intensity from 8 to 6.3 (0-10 scale). However, the washed waste still showed high smell intensity ratings.

Nosy confirmation: reconstitution of the characteristic odor of softwood via quantitative analysis and human sensory evaluation.

The significance of wood odors beyond flavoring effects for barbecues and wine aged in barrels has recently been under discussion. Wood has an immense influence on our physical and mental condition through our palate, such as positive health and mood-stimulating effects. As a result of increased public interest, the key odorants from various natural wood species were recently decoded. To gain profound insights into the contribution of single odorants to the overall scent of distinct wood types, this study compares several softwood species (Scots pine, incense cedar, European larch, Norway spruce, and white fir) by odor profile analysis. Nine odor-active constituents, which were previously detected in those woods, were quantified using stable isotope dilution analysis (SIDA). Odor activity values (OAVs) calculated on the basis of odor thresholds (OTs) determined in cellulose revealed hexanal, octanal, (E)-non-2-enal, p-cresol, vanillin, and thymoquinone as dominant odorants for wood odor. Recombination experiments by mixing the odorants in their naturally occurring concentrations in a cellulose matrix confirmed the successful characterization of the key odorants for Scots pine and incense cedar wood.

Correlations between odour activity and the structural modifications of acrylates.

Acrylates (acrylic esters) are versatile monomers that are widely used in polymer formulations because of their highly reactive α,ß-unsaturated carboxyl structure. Commonly used acrylates such as butyl acrylate are known to emit a strong unpleasant odour, and the monomers are therefore potential off-odorants in acrylic polymers. However, up to now, the odour properties of structurally related acrylic esters have not been characterised in detail. To obtain deeper insights into the smell properties of different acrylates, we investigated the relationship between the molecular structure and odour thresholds as well as the odour qualities of 20 acrylic esters, nine of these synthesised here for the first time. The OT values of 16 acrylates fell within the range from 0.73 to 20 ng/Lair, corresponding to a high-odour activity. Moreover, sec-butyl acrylate and 2-methoxyphenyl acrylate showed even lower OT values of 0.073 and 0.068, respectively. On the other hand, the OT values of the hydroxylated acrylates 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate were 5-244 times higher than those of the other compounds, demonstrating that the presence of a hydroxyl group obviously favours odour inactivity.

Thermally Induced Generation of Desirable Aroma-Active Compounds from the Glucosinolate Sinigrin.

Glucosinolates are the most abundant secondary sulfur-containing plant metabolites in the plant family of Brassicaceae. These phytochemicals are well-known for their enzymatic degradation induced by the enzyme myrosinase, resulting in pungent odor impressions derived from their respective degradation products. However, up to now, only little attention has been paid to non-enzymatic thermal degradation and the release of additional aroma-active compounds. Thermal treatment is particularly important in the processing of Brassica vegetables, and thereby, glucosinolates as precursors can act as a natural source of odorants. Application of gas chromatography-olfactometry to the volatile fractions obtained after heat treatment of sinigrin (2-propenyl glucosinolate) in different matrices (phosphate buffer at a pH value of 5, 7, or 9, silicon oil, silica gel (7% water), sea sand, and glycerol) showed a high potential to generate aroma-active compounds, mainly revealing onion- and garlic-like odor impressions deriving from sulfur-containing odorants. A clear dependency of the formation of desired aroma-active compounds upon the respective matrix was found, indicating the need of detailed investigations to obtain knowledge for the best use of glucosinolates as a source of natural aroma compositions. For example, the distillate obtained from sinigrin heat-processed in buffer solution at pH 7 led to the identification of 17 odorants.

Elucidation of Thermally Induced Changes in Key Odorants of White Mustard Seeds (Sinapis alba L.) and Rapeseeds (Brassica napus L.) Using Molecular Sensory Science.

Heat-processing of Brassica seeds led to the formation of a characteristic pleasant popcorn-like and coffee-like aroma impression compared to the mainly pea-like aroma of the corresponding raw seeds. To analyze this phenomenon on a molecular basis, raw and roasted white mustard seeds and rapeseeds were analyzed using the sensomics approach. Application of comparative aroma extract dilution analysis (cAEDA) and identification experiments to raw and roasted (140 °C, 30 min) mustard seeds revealed 36 odorants (all identified for the first time) and 47 odorants (41 newly identified), respectively. Twenty-seven odorants in raw and 43 odorants in roasted (140 °C, 60 min) rapeseeds were found, which were all described for the first time. Among the set of volatiles, 2-isopropyl-3-methoxypyrazine (earthy, pea-like) and 4-ethenyl-2-methoxyphenol (clove-like, smoky) showed high FD factors in both raw seeds. 4-Hydroxy-2,5-dimethylfuran-3(2H)-one (caramel-like), 2,3-diethyl-5-methylpyrazine (earthy), dimethyl trisulfide (cabbage-like), and 2-acetyl-1-pyrroline (popcorn-like) were present at high flavor dilution (FD) factors in both roasted Brassica seeds. Odorants, differing in cAEDA or showing high FD factors in at least one of the seeds, were quantitated by stable isotope dilution analysis (SIDA), followed by the calculation of odor activity values (OAVs) using odor thresholds determined in refined sunflower oil. Eighteen aroma compounds in raw and 28 in roasted mustard seeds as well as 14 in raw and 25 in roasted rapeseeds revealed OAVs ≥1. All four aroma recombinates, prepared by mixing the odorants showing OAVs ≥1 in their naturally occurring concentrations, showed a very good similarity with the original seeds and, thus, proved the successful characterization of the respective key odorants.