Stereoregular oligomers of methyl methacrylate

Summary Isotactic (it-) and syndiotactic (st-) MMA oligomers from 19-mer to 29-mer could be isolated efficiently from it-PMMA ( = 28.6) and st-PMMA ( = 28.6) (sample load: 50 mg) by the SFC using a 10 mm i. d. x 250 mm column packed with silica gel. DP of each isolated oligomer was determined by FD mass spectroscopy, and the values agreed well with those calculated from the relative intensity of ¹H NMR signals due to CH₃O- and the terminal t-C₄H₉-groups. Glass transition temperature (T _g) of the it-28-mer measured by DSC was 34.5°C, which was higher than that of the it-PMMA by 6.5°C. T _g of both the it-and st-oligomers increased linearly with DP in the range of DP=2029. A 1: 1 mixture of the it- and st-27-mers annealed at 140°C showed an endothermic transition at 102.3°C which was attributable to melting of stereocomplex, whereas an annealed 1: 1 mixture of the it- and st-PMMAs had a much broader endotherm around 80140°C.Part 5: Ute K, Miyatake N, Hatada K (1992) J. Macromol. Sci.-Chem., A29, in press     

Silicone sampling tubes can cause drastic artifacts in measurements with aerosol instrumentation based on unipolar diffusion charging

Aerosol instrumentation based on unipolar diffusion charging has become popular in the recent years. These instruments can be made very small, making them suitable as personal monitors. In many applications, including personal monitoring, the use of flexible sampling tubes is required. We found that degassing from these sampling tubes can alter the gas composition of the aerosol, which changes the ion properties in the unipolar charger. As a result, the particle concentrations, measured with a unipolar diffusion charger are biased. The strongest effect was found with new, conductive silicone tubes, because of the degassing of siloxanes. Results obtained with one miniature diffusion size classifier unit were by a factor of approximately two too low. Partector and Nanoparticle Surface Area Monitor showed in principle the same behavior, but to a lower degree. Other tube materials were found to have even the opposite effect, i.e., the measured concentrations increased, when measuring through a tube. The largest observed increase was, however, only approximately 14%. Tygon? tubes were found to be the best compromise considering particle losses and effect on the diffusion charger.

Copyright © 2016 American Association for Aerosol Research     

Catechin and epicatechin in testa and their association with bioactive compounds in kernels of cashew nut (Anacardium occidentale L.)

Catechins in testa and bioactive compounds in testa-free and testa-containing kernels of cashew nuts were analysed. The cashew nut testa contained (+)-catechin and (−)-epicatechin with concentrations of 5.70 and 4.46 g per kg DM, respectively. Testa-containing kernels revealed significantly higher levels of β-carotene (218 vs. 89.6 μg/kg DM), lutein (525 vs. 292 μg/kg DM), and α-tocopherol (10.1 vs. 2.4 mg/kg DM), similar amounts of zeaxanthin (7.0 vs. 7.1 μg/kg DM), γ-tocopherol (10.6 vs. 10.1 mg/kg DM), stearic acid (41 vs. 43 g/kg DM), oleic acid (214 vs. 219 g/kg DM) and linoleic acid (69 vs. 62 g/kg DM), but a lower concentration of thiamine (3.0 vs. 10.7 mg/kg DM) in comparison to testa-free samples. The testa-containing kernels provide high amounts of catechins and higher concentrations of β-carotene, lutein and α-tocopherol than do testa-free cashew nut kernels. This could have potential health benefits for consumers.     

Inactivation of peroxidase, polyphenoloxidase, and lipoxygenase in paprika and chili powder after immediate thermal treatment of the plant material

Residual activities of lipoxygenase (LOX), peroxidase (POD), and polyphenoloxidase (PPO) were determined in paprika and chili powder after immediate thermal treatment of the fresh plant material. Heat treatments comprised water and steam blanching of the integral fruits and pasteurization of the comminuted tissues, respectively. PPO showed the lowest heat stability and was completely inactivated by heating at 80 °C for 10 min. Inactivation of LOX was also largely accomplished by heating at 90 °C for 5 min and at 100 °C for 5 min, whereas up to 3.5% (paprika) and 3.3% (chili) of the initial POD activities were retained even when applying rigorous time–temperature regimes. The results demonstrate that substantial inactivation of deteriorative enzymes was ensured by the recently suggested process, thus facilitating the production of high quality spice powders.     

Validation of a Duplex Real-Time PCR for the Detection of Salmonella spp. in Different Food Products

A 5′ nuclease duplex real-time polymerase chain reaction (PCR) assay was developed and validated with various food products for the specific and fast detection of Salmonella spp. in food. The assay used previously published primers in combination with a newly developed probe targeting the invA gene. An internal amplification control, which is coamplified in a duplex PCR, was included in the assay. The analysis of 1,934 natural food samples with real-time PCR and the cultural method in parallel resulted in a relative accuracy of 100% and 99.84% respectively, depending on the enrichment procedure in which buffered peptone water and selective enrichment in Rappaport–Vassiliadis (RV) broth were employed. The duplex real-time PCR assay has proven to be a specific, sensitive and fast screening method for Salmonella spp. in food. The overall analysis time of the PCR method was approximately 28 h, in contrast to 4 to 5 days with conventional Salmonella diagnostics. The developed assay has been shown to be a reliable diagnostic tool for use in routine analysis. It has been validated thoroughly and has become an official method in Germany for the detection of Salmonella spp. in food.     

Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway in vitro and in vivo

Recently, the coffee constituents 5-O-caffeoylquinic acid (CGA) and N-methylpyridinium (NMP) were identified as inducers of the Nrf2/antioxidant-response element (ARE) detoxifying pathway under cell-culture condition. To study the impact of CGA and NMP on the Nrf2-activating properties of a complex coffee beverage, two different model coffees were generated by variation of the roasting conditions: a low-roast coffee rich in CGA and a heavy-roast low in CGA but containing high levels of NMP. Activation of the Nrf2/antioxidant-response element pathway was monitored in vitro and in vivo.     

Effective Approaches for Estimating the Functionalization Pattern of Carboxymethyl Starch of Different Origin

Three types of differently prepared carboxymethyl starches were analyzed by HPLC and ¹H-NMR spectroscopy after chain degradation. In derivatives obtained in the conventional manner with values of the degree of substitution (DS) up to 0.85; glucose, mono- and di-O-carboxymethyl glucose were detected as building units. Comparison with statistic calculations revealed an even distribution of functional groups along the chain. ¹H-NMR studies confirmed a preferred substitution at the 2 position of the repeating unit. Comparable results were obtained for the carboxymethyl ether of amylose, amylopectin and β-cyclodextrin. The analysis of carboxymethylated starch samples prepared using a new synthesis concept via a reactive microstructure revealed a high DS achieved in a one-step synthesis as well as a non-statistic distribution of carboxymethyl groups along the chain. A significant amount of 2,3,4,6-tetra-O-functionalization, caused by the branched structure of starch, was found. Moreover, carboxymethylation of 6-O-triphenylmethyl starch and subsequent detritylation yields a regioselectively functionalized polymer consisting not only of the expected mono- and di-O-carboxymethylated repeating units but also containing a significant amount of 2,3,4-tri-O-functionalized anhydro-glucose units.     

Effects of processing and storage on the stability of free and esterified carotenoids of red peppers (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) and hot chilli peppers (<Emphasis Type="Italic">Capsicum frutescens</Emphasis> L.)

The stability of non-esterified carotenoids and carotenoid esters in paprika and chilli powder as affected by various processing treatments and storage conditions were studied. For this purpose, freshly harvested chilli and paprika pods were minced, immediately heated at 80, 90 and 100 °C for 5 and 10 min, respectively, and lyophilised. Alternatively, thermal treatment prior to mincing was applied. Processing resulted in a 25–34% loss of the initial carotenoid contents in chilli and 20–53% in paprika. Degradation of individual non-esterified carotenoids, mono- and diesters was monitored, generally showing an increased processing stability of mono- and diesters compared to their non-esterified counterparts. Capsanthin, capsorubin, zeaxanthin and β-cryptoxanthin mono- and diesters esterified with saturated fatty acids displayed similar stabilities, whereas susceptibility of the non-esterified pigments to degradation differed considerably. During storage over 4 months at ambient temperature pigment contents dropped by 16.7 and 9.6% in chilli and by 39.7 and 38.8% in paprika powders with and without illumination, respectively.     

Electron seed dressing of barley—aspects of its verification

Seeds (e.g. cereal grains) are treated with low energy electrons for seed dressing to inactivate phytopathogenic organisms on their surface and in the seed coat. To verify the electron treatment of barley by e-ventus^® technology, three physical detection methods were investigated: photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR). Influencing factors such as storage time and temperature, geographic origin of samples and light exposure were studied. All three detection methods proved to be suitable, with PSL being the most convenient. But also ESR by measuring the barley husks offered a simple and rapid verification. Although TL was more laborious to perform, it was highly reliable. PSL was able to classify electronically dressed seeds after storage times of at least 12–13 months independent of storage temperatures, assayed in the range of 5–23 °C. The applicability of ESR after storage was dependent on the measuring system used and on storage temperature. At room temperature the advanced E-Scan? spectrometer allowed verification of treatment for at least 7.5 months, whereas the EMS 104 spectrometer was applicable only up to 2 months of storage. Storage temperatures of 5 °C markedly prolonged the verifiability of treatment. Using TL, treated samples stored at room temperature could be easily verified for at least 13 months. Fading of the PSL signal of treated barley was observed under the influence of light, the extent of fading being influenced by illuminance but not by treatment of the samples with high or low energy electrons. Contrary to PSL, TL and ESR were found to be still applicable for the detection of treated barley exposed to light.