To prevent the adulteration of agricultural resources and provide a solution to enhance the green coffee bean supply chain, authentication using the near-infrared spectroscopy (NIRS) technique was investigated. Partial least square with discrimination analysis (PLS-DA) models combined with various preprocessing methods were built from NIR spectra of 153 Vietnamese green coffee samples. The model combined with the standard normal variate and the first order of derivative yielded excellent performance in predicting coffee species with the error cross-validation of 0.0261. PLS-DA model of mean centre and first-order derivative spectra also yielded good performance in verifying geographical indication of green coffee with the error of 0.0656. By contrast, the predicting abilities of post-harvest methods were poor. The overall results showed a high potential of the NIRS in online authentication practices. 相似文献
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose. 相似文献
Mycotoxins are secondary metabolites produced by filamentous fungi that usually contaminate food products. Coffee is a natural product susceptible to mycotoxin contamination. The present study evaluates the presence of nivalenol, deoxynivalenol, T-2 and HT-2 Toxin, diacetoxyscirpenol, aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, fumonisin B1, fumonisin B2, ochratoxin A, zearalenone, enniatin A, enniatin A1, enniatin B, enniatin B1, and beauvericin in coffee samples, using liquid chromatography tandem mass spectrometry (LC-MS/MS). The results show that zearalenone was not present in any sample. In the positive samples the contents of fumonisins ranged from 58.62 to 537.45 μg/kg, emerging mycotoxins ranged from 0.10 to 3569.92 μg/kg, aflatoxins ranged from 0.25 to 13.12 μg/kg, and trichothecenes, excepting nivalenol, ranged from 5.70 to 325.68 μg/kg. Nivalenol presented the highest concentrations, from 0.40 to 25.86 mg/kg. Ochratoxin A ranged from 1.56 to 32.40 μg/kg, and five samples exceeded the maximum limit established by the European Commission. 相似文献
Roasting coffee led to a drop in the ochratoxin A (OTA) concentration, as measured by the reference method, especially for dark type roasts. The way the beverage was prepared also affected the OTA content, which could paradoxically be higher than that of the initial roasted coffee. Assays on the thermal stability of pure OTA showed that it ought to be found in larger quantities in roasted coffee. This suggested that OTA was masked by reactions with the substrate during roasting. The absence of OTA in green coffee is therefore the best guarantee of safety. 相似文献
Experimental studies were conducted using molecular sieve zeolites to remove pungent smell components from a coffee aroma-containing gas evolved from roasted and ground coffee packed in a percolation vessel. The components such as methyl mercaptan or acetaldehyde were selectively adsorbed from coffee volatiles, and a decrease of pungent odor was recognized on sensory evaluation. The adsorption selectivity was based on pore sizes of adsorbents and molecular sizes of adsorbates. Zeolite 5Å was preferable to 4Å for separation efficiency of methyl mercaptan and recovery yield of residual volatile compounds. 相似文献
In the present study, commercial pure Ti and Ti-6Al-4V alloy specimens with and without alkali and heat treatments were implanted
in the abdominal connective tissue of mice. Conventional stainless steel 316L was also implanted for comparison. After three
months, their biocompatibility was evaluated byin vitro andin vivo experiments. Surface structural changes of specimens due to the alkali treatment and soaking in Hank’s solution were analyzed
by XRD, SEM, XPS and AES. An apatite layer, which accelerates the connection with bone, was formed more easily on the alkali
treated specimens than the non-treated specimens. The number of macrophages, which is known to increase as the inflammatory
reaction proceeds, was much lower for the alkali and heat treated specimens than for the others. The average thickness of
the fibrous capsule formed around the implant was much thinner for the alkali and heat treated specimens than for the others. 相似文献
Summary: Novel light‐sensitive hollow capsules were fabricated from the small molecule 3‐sulfopropylacrylate potassium (SPA) and poly(allylamine hydrochloride) (PAH). With UV irradiation, SPA could be photopolymerized in the wall of hollow capsules. After photopolymerization the capsule size and surfaces showed pronounced differences. The capsules became much more rigid as indicated by an increase in the modulus of more than a factor of 5.
CLSM image of SPA/PAH hollow capsule emission at 554 nm, from rhodamine B after photopolymerization. 相似文献