Enzymatic production of alkyl esters through alcoholysis: A critical evaluation of lipases and alcohols

This paper focuses on a detailed evaluation of commercially available immobilized lipases and simple monohydric alcohols for the production of alkyl esters from sunflower oil by enzymatic alcoholysis. Six lipases were tested with seven alcohols, including straight and branched-chain primary and secondary alcohols. The reactions were conducted in a batch stirred reaction vessel using stoichiometric amounts of substrates under solvent-free conditions. Dramatic differences in alcoholysis performance were observed among the different lipases. For most of the alcohols, Novozym 435 produced the highest yield of FA alkyl esters, with yields well over 90% for methanol, absolute ethanol, and 1-propanol. Overall, 96% ethanol was the preferred alcohol for all lipases except Novozym 435, and ethanolysis reactions reached the maximal conversion efficiency. Increasing the water content in the system resulted in an increased degree of conversion for all lipases except Novozym 435. The secondary alcohol 2-propanol significantly reduced the alcoholysis reaction with all lipases; however, the branch-chain isobutanol was more advantageous than linear 1-butanol for Novozym 435, Lipozyme RMIM, and Lipase PS-C. Many commercial immobilized lipases are highly efficient and promising for the production of alkyl esters, offering high reaction yields and a simple operation process.     

A silicon potentiometer for hearing aids

An angledetector with a digital output is described. The component is meant as an alternative to the traditional slide potentiometer used as volume control in many hearing aid applications. The component is based on the use of magnetic field sensitive MOSFET's (MAGFET's) detecting the position of a tiny bar magnet placed above a silicon chip. Because of the galvanic separation between the anglesetting bar magnet and the electrical circuit, this component is insensitive to the rather hostile environment hearing aids are exposed to. The lifetime of the component is thereby increased significantly. The electrical circuit contains a switched current A/D-D/A conversion system for offset compensating the MAGFET's and for converting the MAGFET signal currents into a digital output proportional to the input angle. The system can operate with a supply voltage down to 2.3 V. The average current consumption is 1.5 A. The peak current is close to 160 A. The system operates correctly within the clock frequency range of 5 Hz to 25 kHz. It is implemented using a commercially available 1.5 m CMOS process.     

Random parameter models of interstate crash frequencies by severity,number of vehicles involved,collision and location type

A nine-year (1999–2007) continuous panel of crash histories on interstates in Washington State, USA, was used to estimate random parameter negative binomial (RPNB) models for various aggregations of crashes.     

Enzyme-enhanced extraction of antioxidant ingredients from red algae Palmaria palmata

The effect of various protease and carbohydrase treatments on the extraction of polyphenols and other antioxidant ingredients from the red algae Palmaria palmata (dulse) was investigated. In addition, the relative contribution of different fractions to the overall antioxidant capacity of the hydrolysate was evaluated. Considerable differences were observed both in total phenolic content (TPC) and antioxidant activities of the hydrolysates evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorbance capacity (ORAC) and ferrous ion-chelating ability assays. All the proteases tested had significant enhancing effect on the extraction of polyphenols and other active components compared to carbohydrases and cold water extraction (control). The Umamizyme extract had the highest TPC and consequently exhibited the strongest scavenging capacity against DPPH and peroxyl radicals. Further fractionation of the Umamizyme extract revealed that the crude polyphenol fraction possessed the highest peroxyl radical scavenging activity, whereas the crude polysaccharide fraction was more effective for chelating ferrous ions. The data from this study suggest the potential of protease treatment to improve value-added utilization of dulse extracts as antioxidants in functional foods and nutraceuticals.     

Fatty acid selectivity of microbial lipase and lipolytic enzymes from salmonid fish intestines toward astaxanthin diesters

The objective of the work described in this paper was to study a possible FA selectivity of digestive lipolytic enzymes isolated from salmon and trout intestines toward astaxanthin diesters of various FA composition and compare it with the FA selectivity of microbial lipase. Astaxanthin diesters of varying FA composition were prepared in excellent yields (>90%) by chemical esterification using a carbodiimide coupling aget. The astaxanthin diesters were screened in a hydrolysis reaction by various commercially available lipases. The highest conversion rates were observed with the Candida rugosa lipase, which discriminated against n−3 PUFA. The rate of hydrolysis was determined by HPLC. Digestive lipolytic enzymes isolated from salmon and rainbow trout intestines displayed reversed FA selectivity. Thus, astaxanthin diesters highly enriched with n−3 PUFA including EPA and DHA were observed to be hydrolyzed at a considerably higher rate than the more saturated esters. Similar trends in FA selectivity were observed in the hydrolysis of fish oil TAG by the digestive lipolytic enzyme mixtures.     

Frozen herring as raw material for spice‐salting

One batch of herring (Clupea harengus) was spice‐salted fresh and as thawed after 32 days of frozen storage at −24 °C. After salting, samples of both groups were sent to participating laboratories in Iceland, Denmark, Norway, Germany and England. The herring was kept at 5 ± 1 °C and sampled three times during a 26 week storage period. The development of taste and texture characteristics (determined by sensory evaluation and instrumental texture measurements), formation of low‐molecular‐weight nitrogen compounds and changes in proteolytic activity were followed in both groups. The sensory evaluation results showed that thawed salted herring ripened in a similar manner to herring salted fresh, but at a faster rate. Instrumental texture analysis showed a faster rate of tenderising in thawed salted herring. Proteolytic activity measured as general activity and with specific synthetic substrates was higher in the thawed salted herring. The formation of trichloroacetic acid‐soluble nitrogen and free amino acids was faster in the previously frozen herring. The results show an accelerated but similar rate of ripening in thawed spice‐salted herring in comparison with fresh salted herring. © 2000 Society of Chemical Industry     

The effects of various salt concentrations during brine curing of cod (Gadus morhua)

The method used for salting of cod (Gadus morhua) is believed to influence the quality and characteristics of the final product. In recent years an initial brine salting for 1–4 days has preceded dry salting; this increases both the weight yield and quality of the final product. After removal from the brine, dry salting is followed by packaging and storage. The effect of the salt concentration in the brine has been a matter of controversy, with some indication that higher weight yield and quality may be obtained by using lower salt concentrations than by using a fully saturated brine solution. Therefore to test this hypothesis, the effect of different brine salting methods was studied; traditional brine salting, maintaining a constant brine concentration and increasing the salt concentration gradually during brining. The results indicated that the effect on weight yield, chemical composition and water holding capacity of the salted or rehydrated cod were not significant. Altering salt concentration of the brine, by adding salt during brining, did not result in any significant improvements in weight yield, either after the salting process or after the rehydration. The overall quality was increased by using a lower salt concentration of 16° Bau compared with 20 and 24° Bau.     

Coupled reservoir-wellbore simulation of geothermal reservoir behavior

The reservoir simulator TOUGH and the wellbore simulator WFSA have been coupled to model flow of geothermal brine in the reservoir as well as in the wellbore. An outline of the structure of the two computer codes is given, together with the relevant equations. A new module, COUPLE, has been written to serve as an interface between TOUGH and WFSA. Two sample problems are given to illustrate the use of the coupled codes. One of these problems compares the results of the new simulation method to those obtained by using the deliverability option in TOUGH. The coupled computing procedure is shown to simulate more accurately the behavior of a geothermal reservoir under exploitation.     

Age and pedestrian injury severity in motor-vehicle crashes: a heteroskedastic logit analysis

This research explores the injury severity of pedestrians in motor-vehicle crashes. It is hypothesized that the variance of unobserved pedestrian characteristics increases with age. In response, a heteroskedastic generalized extreme value model is used. The analysis links explanatory factors with four injury outcomes: fatal, incapacitating, non-incapacitating, and possible or no injury. Police-reported crash data between 1997 and 2000 from North Carolina, USA, are used. The results show that pedestrian age induces heteroskedasticity which affects the probability of fatal injury. The effect grows more pronounced with increasing age past 65. The heteroskedastic model provides a better fit than the multinomial logit model. Notable factors increasing the probability of fatal pedestrian injury: increasing pedestrian age, male driver, intoxicated driver (2.7 times greater probability of fatality), traffic sign, commercial area, darkness with or without streetlights (2-4 times greater probability of fatality), sport-utility vehicle, truck, freeway, two-way divided roadway, speeding-involved, off roadway, motorist turning or backing, both driver and pedestrian at fault, and pedestrian only at fault. Conversely, the probability of a fatal injury decreased: with increasing driver age, during the PM traffic peak, with traffic signal control, in inclement weather, on a curved roadway, at a crosswalk, and when walking along roadway.     

Performance of a photochromic time–temperature indicator under simulated fresh fish supply chain conditions

The objective of this study was to investigate the performance of a photochromic time–temperature indicator (TTI) under dynamic temperature conditions simulating real fresh fish distribution chain scenarios. The work aimed at testing the possibility of extending the application of the TTI kinetic model, developed for specific temperature range of isothermal conditions, at low temperatures. The results showed that the TTI presented reproducible responses after being charged and during the discolouration process under different conditions, which revealed the reliability of the indicator. The TTI reflected well the temperature conditions of the studied scenarios, which indicates its potential application to continuously monitor the temperature history of the fresh fish supply chain. The kinetic model gave good fits in non‐abused scenarios at temperatures below 2 °C, presenting the potential for application of the model in determining the right charging level to suit a product’s shelf life at low temperatures.