Beitrag zur Kenntnis der Wechselwirkungen zwischen Proteinen und Polyphenolen der Kakaobohnen w?hrend der Fermentation

Zusammenfassung Auf Grund der Schwierigkeit, die Kakaoproteine vollständig zu extrahieren und isolieren, wurde untersucht, ob ihre beschränkte Löslichkeit in 0,2%iger KOH auf Wechselwirkungen mit Polyphenolen bei der Probenpräparation oder Fermentation beruht. Nach Vorextraktion der löslichen Polyphenole mit Aceton-Wasser-Gemischen bei tiefen Temperaturen blieben in frischen, zermahlenen Cotyledonen nur 13–15% des ursprünglichen Proteins unlöslich und nur 7–8% nach einer vorhergehenden anaeroben Wasserbehandlung, nach einer aeroben Wasserbehandlung jedoch 35 bis 40% in Abhängigkeit von den löslichen Polyphenolen.. Dieser, auf oxydativen Polyphenol-Wechselwirkungen beruhende unlösliche Rest ist im fermentierten Kakao gering. Elektrophoretisch ließen sich dementsprechend nur im ersten Falle 3 Proteinfraktionen trennen.Unter Berücksichtigung von Ergebnissen anderer Autoren wird diskutiert, ob, wie bei der Chinongerbung, Verknüpfungen zwischen chinoiden Gruppen der Polyphenole und freien Aminogruppen der Proteine angenommen werden könnten und ob eine solche Reaktion auf Grund ihrer intensiven hydrolytischen Spaltung in der anaeroben Phase der Fermentation nur an einem kleinen Teil der ursprünglichen Proteine jedoch in größerem Umfang an seinen Spaltprodukten, insbesondere Aminosäuren, erfolgt.     

Multifunctional thin film sensors based on amorphous diamond-like carbon for use in tribological applications

Amorphous diamond-like carbon films are well known for their excellent tribological properties. In this paper, we will discuss the sensoric properties of multifunctional a-C:H films with respect to force/load/pressure and temperature measurement. It turned out that nanostructured amorphous carbon films showed an impressive piezoresistive effect.Unlike well known strain gages and piezoresistive sensors, which detect a deformation of the base substrate, this novel sensor can be used in a complete stiff arrangement without any elastic joint. For film preparation, rf-plasma CVD processes were used. Besides gas pressure, a variation of the substrate power and bias potential was performed. It turned out that the tribological parameters varied slightly (hardness: 20-30 GPa, friction coefficient: 0.10 to 0.15), whereas the electrical parameters showed remarkable differences with respect to the electrical resistivity and piezoresistivity.This paper will also present different applications of amorphous carbon thin film sensors.     

Characterization of Conventional,Biodynamic, and Organic Purple Grape Juices by Chemical Markers,Antioxidant Capacity,and Instrumental Taste Profile

The objectives of this study were to characterize organic, biodynamic, and conventional purple grape juices (n = 31) produced in Europe based on instrumental taste profile, antioxidant activity, and some chemical markers and to propose a multivariate statistical model to analyze their quality and try to classify the samples from the 3 different crop systems. Results were subjected to ANOVA, correlation, and regression analysis, principal component analysis (PCA), hierarchical cluster analysis (HCA), soft independent modeling of class analogy (SIMCA), and partial least‐squares discriminant analysis (PLSDA). No statistical significant differences (P > 0.05) were observed among juices from the 3 crop systems. Using PCA and HCA, no clear separation among crop systems was observed, corroborating the ANOVA data. However, PCA showed that the producing region highly affects the chemical composition, electronic tongue parameters, and bioactivity of grape juices. In this sense, when organic and biodynamic were grouped as “nonconventional” juices, SIMCA model was able to discriminate 12 out of 13 organic/biodynamic juices and 17 out of 18 conventional juices, presenting an efficiency of 93.5%, while 11 out of 13 non‐conventional and 100% conventional grape juices were correctly classified using PLSDA. The use of electronic tongue and the determination of antioxidant properties and major phenolic compounds have shown to be a quick and accurate analytical approach to assess the quality of grape juices.     

Influence of the texture of gelatin gels and pectin gels on strawberry flavour release and perception

The release of strawberry flavour compounds from pectin gels and gelatin gels was evaluated by instrumental and sensory analysis. Three gel textures were established based on Young’s modulus of elasticity (E) for each gel. The E of the low, medium and high rigidity gelatine and pectin gels was 181, 300 and 493 N m⁻², respectively. Air/gel partition coefficients were determined by static headspace analysis. In-nose/proton transfer reaction-mass spectrometry analysis produced temporal release profiles. Sensory analysis was conducted to assess perceived odour, thickness, strawberry flavour and sweetness using magnitude estimation. The type of hydrocolloid affected static and in-nose compound concentrations significantly. The pectin gels showed lower air/gel partition coefficients than the gelatin gels, but increased flavour release. Increased gel rigidity resulted in lower air/gel partition coefficients; higher maximum concentrations of volatiles and lower release rates during in-nose analysis; decreased perception of odour, strawberry flavour and sweetness; and higher intensity ratings for thickness in sensory analysis. Consequently, both type of hydrocolloid and rigidity of the sample greatly affected flavour release and perception.     

Effect of acetic acid on subcellular structures of cocoa bean cotyledons

Characteristic post-mortem changes in subcellular structures are described which are caused by the penetration of acetic acid during incubation of cocoa seeds in aqueous media. In the storage cells lipid is agglomerated and separates from hydrophilic portions in proportion to the acetic acid concentration and pH. This effect is less pronounced at 50°C than at 40°C. In the absence of acetic acid or with very low concentration of undissociated acetic acid other substructural characteristics dominate in most of the cells. At 50°C Post-mortem changes do not induce lipid agglomeration. At 40°C the intact protein vacuole swells and its matrix structure becomes spongy as a response to in-vivo water absorption. Finally, it is shown that a concentration gradient persists in whole seeds for most of the time required for fermentation, because of the slow diffusion of acetic acid. The results are compared with temperature effects on subcellular structures and are discussed in relation to their significance for proteolysis in cocoa seeds during fermentation.     

A different perspective on conspicuity related motorcycle crashes

The most common type of conflict in which a motorcyclist is injured or killed is a collision between a motorcycle and a car, often in priority situations. Many studies on motorcycle safety focus on the question why car drivers fail to give priority and on the poor conspicuity of motorcycles. The concept of ‘looked-but-failed-to-see’ crashes is a recurring item. On the other hand, it is not entirely unexpected that motorcycles have many conflicts with cars; there simply are so many cars on the road. This paper tries to unravel whether – acknowledging the differences in exposure – car drivers indeed fail to yield for motorcycles more often than for other cars. For this purpose we compared the causes of crashes on intersections (e.g. failing to give priority, speeding, etc.) between different crash types (car–motorcycle or car–car). In addition, we compared the crash causes of dual drivers (i.e. car drivers who also have their motorcycle licence) with regular car drivers. Our crash analysis suggests that car drivers do not fail to give priority to motorcycles relatively more often than to another car when this car/motorcycle approaches from a perpendicular angle. There is only one priority situation where motorcycles seem to be at a disadvantage compared to cars. This is when a car makes a left turn, and fails to give priority to an oncoming motorcycle. This specific crash scenario occurs more often when the oncoming vehicle is a motorcycle than when it is a car. We did not find a significant difference between dual drivers and regular car drivers in how often they give priority to motorcycles compared to cars.     

Functional Screen for microRNAs Suppressing Anchorage-Independent Growth in Human Cervical Cancer Cells

The progression of anchorage-dependent epithelial cells to anchorage-independent growth represents a critical hallmark of malignant transformation. Using an in vitro model of human papillomavirus (HPV)-induced transformation, we previously showed that acquisition of anchorage-independent growth is associated with marked (epi)genetic changes, including altered expression of microRNAs. However, the laborious nature of the conventional growth method in soft agar to measure this phenotype hampers a high-throughput analysis. We developed alternative functional screening methods using 96- and 384-well ultra-low attachment plates to systematically investigate microRNAs regulating anchorage-independent growth. SiHa cervical cancer cells were transfected with a microRNA mimic library (n = 2019) and evaluated for cell viability. We identified 84 microRNAs that consistently suppressed growth in three independent experiments. Further validation in three cell lines and comparison of growth in adherent and ultra-low attachment plates yielded 40 microRNAs that specifically reduced anchorage-independent growth. In conclusion, ultra-low attachment plates are a promising alternative for soft-agar assays to study anchorage-independent growth and are suitable for high-throughput functional screening. Anchorage independence suppressing microRNAs identified through our screen were successfully validated in three cell lines. These microRNAs may provide specific biomarkers for detecting and treating HPV-induced precancerous lesions progressing to invasive cancer, the most critical stage during cervical cancer development.