Reduction of off-flavor generation in soybean homogenates: a mathematical model

The generation of off-flavors in soybean homogenates such as n-hexanal via the lipoxygenase (LOX) pathway can be a problem in the processed food industry. Previous studies have examined the effect of using soybean varieties missing one or more of the 3 LOX isozymes on n-hexanal generation. A dynamic mathematical model of the soybean LOX pathway using ordinary differential equations was constructed using parameters estimated from existing data with the aim of predicting how n-hexanal generation could be reduced. Time-course simulations of LOX-null beans were run and compared with experimental results. Model L(2), L(3), and L(12) beans were within the range relative to the wild type found experimentally, with L(13) and L(23) beans close to the experimental range. Model L(1) beans produced much more n-hexanal relative to the wild type than those in experiments. Sensitivity analysis indicates that reducing the estimated K(m) parameter for LOX isozyme 3 (L-3) would improve the fit between model predictions and experimental results found in the literature. The model also predicts that increasing L-3 or reducing L-2 levels within beans may reduce n-hexanal generation. PRACTICAL APPLICATION: This work describes the use of mathematics to attempt to quantify the enzyme-catalyzed conversions of compounds in soybean homogenates into undesirable flavors, primarily from the compound n-hexanal. The effect of different soybean genotypes and enzyme kinetic constants was also studied, leading to recommendations on which combinations might minimize off-flavor levels and what further work might be carried out to substantiate these conclusions.     

Performance of identical rockbolts tested on four dynamic testing rigs employing the direct impact method

Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each laboratory has developed testing procedures;thus,the results are often reported in different ways by various laboratories.The inconsistency in testing procedures and reporting fo rmats presents a challenge when comparing re sults from different labo ratories.A series of impact tests of identical rockbolts was carried out using the direct impact method(i.e.the mass free-fall method) on the rigs in four laboratories in different countries.The purpose of these tests was to investigate the level of consistency in the results from the four rigs.Each rig demonstrated a high level of repeatability,but differences existed between the various rigs.The differences would suggest that there is noticeable equipment-dependent bias when test results obtained from different laboratories are compared.It was also observed that the energy dissipated for the plastic displacement of the bolt was smaller than the impact energy in the tests.The average impact load(AIL) and the ultimate plastic displacement(D) of the bolt describe the ultimate dynamic performance of the bolt.In the case where the bolt does not rupture,the specific plastic energy(SPE) is an appropriate parameter in describing the impact performance of the bolt.Two other relevant parameters are the first peak load(FPL) and the initial stiffness(K) of the bolt sample.The information from this test series will guide the formulation of standardised testing procedures for dynamic impact tests of rockbolts.     

高度灵活的编解码器是电信公司IPTV计划的重中之重

中信公司正全力以赴与有线电视运营商角力,这场竞争将决定今后十年电视、高速因特网以及电话服务的发展蓝图。在通过使用光纤同轴混合有线电视基础设施和专用线路向客户提供三重业务整合(视频、基于线缆调制解调器的数据服务以及语音服务)方面,有线多服务运营商(MSO)已取得了巨大成功。现在,电信公司正加强其DSL局端设备,并利用带宽效率极高的视频编解     

Enhanced Mechanical Properties and Thermal Stability of Accumulative Roll-Bonded Cu/Nb Multilayer Composites via Cryorolling

Metallurgical and Materials Transactions A - Accumulative roll-bonded(ARB) Cu/Nb multilayer composites were cryorolled and room-temperature rolled. The ultimate tensile stress of ARB composite...