圆容栅角位移传感器设计

介绍了一种用发射电极和标尺电极来设计圆容栅角位移传感器的方法.通过分析电容传感器测量角位移的原理,将输出电压信号转换成脉冲信号,每一个脉冲信号代表一个确定的角位移,在一个固定角度内输出的脉冲数越多表示传感器的分辨率越高.在动栅盘上粘贴一些发射电极,在定栅盘上粘贴一些标尺电极.为了确保不在同一时间输出多个脉冲,发射电极和标尺电极的安装数目必须互质.同时为了保证脉冲间隔是均等的,还需要更多地考虑发射电极和标尺电极的安装数目,提供了一种设计圆容栅的新方法,有效地提高了角位移传感器的精度和分辨率.     

2‐Furoylmethyl amino acids,hydroxymethylfurfural, carbohydrates and β‐carotene as quality markers of dehydrated carrots

BACKGROUND: Processing of vegetables in the food industry usually includes dehydration as a preservation process. Industrial convective air drying of carrot can involve steam blanching of the raw product after peeling and cutting, and different stages of dehydration (first space, second space and final drying). Although the shelf‐life of carrot is significantly extended, important changes in its chemical composition can take place during dehydration since high temperatures and long times are used. This research is a preliminary study to evaluate the usefulness of β‐carotene, carbohydrates, hydroxymethylfurfural (HMF) and 2‐furoylmethyl amino acids (2‐FM‐AA) as quality markers of dehydrated carrots. RESULTS: A considerable decrease in β‐carotene and reducing carbohydrates was observed during dehydration. HMF, absent in raw carrots, increased during the whole drying process and the highest formation was found during the steam blanching stage. 2‐FM‐AA of lysine, arginine, γ‐aminobutyric acid and alanine were progressively originated up to the second space and decreased during the final drying. CONCLUSION: The combined use of HMF and 2‐FM‐AA seems to be advantageous for the assessment of the optimal processing conditions to obtain high‐quality dehydrated carrots. Copyright © 2008 Society of Chemical Industry     

Changes in vitamin content of powder enteral formulas as a consequence of storage

The thiamine, vitamin E (α-, γ- and δ-tocopherol) and vitamin A (all-trans and 13-cis-retinol) contents of four commercial powder enteral formulas (A, B, C and D) have been determined. The vitamin intake provided by the studied formulas was always above the US daily recommendations. Powder enteral formulas A and D were stored at 30 °C for up to 6 months with a water activity of 0.44 (A_w = 0.44), and formula A was also stored under atmospheric conditions for 3, 4 and 6 months. Formulas A and D kept at 30 °C and A_w = 0.44 suffered a gradual loss in vitamin content (from 3% to 4% after 1 month to 58–60% after 6 months). Formula A, stored at 30 °C under atmospheric conditions, underwent a slight reduction in vitamin content after 3 months, similar to that found after 1 month with A_w = 0.44, and from that time onward, this decreased steadily (to 30% after 6 months). The RDA of thiamine, vitamin E and vitamin A for women and men were met only when the powder enteral formulas were stored at 30 °C with A_w = 0.44 up to 1 month and without A_w up to 3 months. These results show that A_w and storage period have a marked effect on the stability of thiamine, vitamin E and A during the storage of powder enteral formulas and should be taken into consideration for the shelf-life of the product.     

Aroma profile and physico‐chemical properties of artisanal honey from Tabasco,Mexico

The aim of this work was to characterise, physico‐chemically, sugar composition and aroma profile of ten honey samples collected by small producers during two seasons and produced in different agricultural ecosystems from Tabasco State (Mexico). The mean values obtained for the physico‐chemical parameters were: pH 3.63; 19.25% moisture; 78.8°Brix sugar; 0.64% ash; 0.25 mS cm^?1 electrical conductivity and 0.58 water activity. Based on colour parameters, Tabasco honeys can be placed in the group of dark honeys. In the analysed samples; fructose was the major sugar (39.45%), followed by glucose (35.74%) while sucrose only represented 2.93%. The volatile profiles of the ten honey samples were obtained by gas chromatography‐mass spectrometry. All the honeys were characterised by their high contents of benzene and furan‐related compounds. As a result, artisanal honeys from Tabasco (Mexico) can be considered to present a good level of quality.