Jens Adler-Nissen

Production of specific-structured lipids by enzymatic interesterification: Elucidation of Acyl migration by response surface design

Production of specific-structured lipids (SSL) by lipase-catalyzed interesterification has been attracting more and more attention recently. However, it was found that acyl migration occurs during the reaction and causes the production of byproducts. In this paper, the elucidation of acyl migration by response surface design was carried out in the Lipozyme IM (Rhizomucor miehei)-catalyzed interesterification between rapeseed oil and capric acid in solvent-free media. A five-factor response surface design was used to evaluate the influence of five major factors and their relationships. The five factors, water content, reaction temperature, enzyme load, reaction time and substrate ratio, were varied at three levels together with two star points. All parameters besides substrate ratio had strong positive influences on acyl migration, and reaction temperature was most significant. The contour plots clearly show the interactions between the parameters. The migration rates of different fatty acids were also compared from three different sets of experiments during the lipase-catalyzed reaction. The best-fitting quadratic response surface model was determined by regression and backward elimination. The coefficients of determination (R2) of the model were 0.996 and 0.981 for Q2 value. The results show that the fitted quadratic model satisfactorily expresses acyl migration for the enzymatic interesterification in the batch reactor used.

Antimicrobial enzymes: Applications and future potential in the food industry

Antimicrobial enzymes are ubiquitous in nature, playing a significant role in the defense mechanisms of living organisms against infection by bacteria and fungi. Hydrolytic antimicrobial enzymes function by degrading key structural components of the cell walls of bacteria and/or fungi, whereas antimicrobial oxidoreductases exert their effects by the generation in situ of reactive molecules. The potential of these enzymes in food preservation is still far from realized at present.

Rheological properties of biscuit dough from different cultivars, and relationship to baking characteristics

Abstract Rheological properties of semi-sweet biscuit doughs from eight wheat cultivars were studied, and related to the dimensional changes of biscuits after cutting and baking. The tested cultivars were selected in order to represent a wide diversity in biscuit baking performance, and were grown with low use of N-fertiliser in three successive years. A standard recipe for semi-sweet biscuit dough was used, and the amount of water added was adjusted to the water absorption capacity. The rheological properties of the dough were characterised by creep recovery and oscillation. The fundamental methods showed that maximum strain at creep, recovery, storage modulus G ′, and phase angle δ were significantly influenced by the tested cultivars. The ranking of the cultivars according to phase angle δ was identical in each of the years investigated 3 which indicates that phase angle δ reflects differences in structural properties with genetic control. Multivariate regression of flour physiochemical, dough rheological, and biscuit baking characteristics showed that a decrease in biscuit length was correlated under several rheological parameters, including phase angle δ , Farinograph and creep recovery parameters. Sedimentation value was the only physiochemical flour characteristic with considerable influence on the model. Validation of the partial least squares-model including all samples from the 3 years gave only a weak correlation ( r =0.58), whereas when each single year was evaluated separately, the correlation increased considerably ( r =0.71 and 0.87).

Salt distribution in dry-cured ham measured by computed tomography and image analysis.

Forty-seven hams were scanned four times by computed tomography (CT) while being manufactured into dry-cured hams. An image-processing algorithm measured CT values in the lean part of the hams and provided line profiles reflecting the magnitude and spatial location of salt gradients. At the end of manufacturing, seven entire hams were dissected and the salt content of the lean part determined. Likewise, in the remaining 40 hams, the lean meat of the slices corresponding to the CT images was dissected, analyzed chemically for NaCl and compared to the CT value. The salt content of entire dry-cured hams correlated well (r(2)=0.94) to the CT value of a 10 mm section located at the center of femur bone, perpendicular to the length axis of the hams. In the same position, significant correlations between the CT values before (r(2)=0.71) and after (r(2)=0.80) the ageing period and actual chemical analysis of the same section were demonstrated. Line profiles illustrating the combined salt distribution and dehydration within a ham related to the physical characteristics of the ham as well as to the manufacturing process. These findings reveal that the effects of altered manufacturing practices can be followed non-invasively, while hams are still in production. Computed tomography combined with appropriate image analysis offers advantages as a non-invasive tool in both research and product development.

23Na-MRI quantification of sodium and water mobility in pork during brine curing

A model study on movements of sodium ions in pork loin during brining was carried out using (23)Na-magnetic resonance imaging ((23)Na-MRI). Samples of different pH and post-mortem age were mounted in Plexiglas(®) cylinders with built-in phantoms and cured in 18.9% and 18.1% NaCl (w/v), respectively. One-dimensional (23)Na-MRI and apparent diffusion coefficient (ADC) profiles were obtained over 5 days with intervals of 24 h. On day 5 the meat was cut into 1 cm slices and analyzed for chloride content. (23)Na-MRI and ADC profiles of meat provided detailed non-destructive information about salt and water movements during brine curing. Quantification of salt concentration in meat by one-dimensional (23)Na-MRI profiling proved successful at values above 0.9 g NaCl/100 g sample in the meat. (23)Na measurements were calibrated against chemically determined chloride, yielding a linear relationship. (23)Na-MRI profiles suggested that the diffusion of salt into whole meat cuts cannot be described by simple ordinary Fickian diffusion with a constant diffusion coefficient. The diffusion coefficient is suggested to be affected by changes in NaCl concentration, swelling and degree of dehydration.

Production of specific structured lipids by enzymatic interesterification: optimization of the reaction by response surface design

Rapeseed oil and capric acid were interesterified in solvent-free media catalyzed by Lipozyme IM from Rhizomucor miehei to produce specific-structured lipids (SSLs), The process was optimized by response surface design concerning the effects of acyl migration and the byproducts of diacylglycerols (DAGs). A five-factor response surface design was used to evaluate the influences of five major factors and their relationships. The five factors were water content (W e , wt-% based on enzyme used), reaction temperature (T e ,° C), enzyme load (E 1 , wt-% based on substrates), reaction time (T r , h) and substrate ratio (S r , rapeseed oil/capric acid, mol/mol). varied at three levels together with two star point levels. The net incorporation [Δ(I f -M f )], in which I f represents incorporation (1,3-positions) and M f acyl migration (2-position), and the contents of DAGs were analyzed and calculated. All parameters had strong influence on the net incorporation, and the experimental and predicted values were close. The best fitting quadratic model was determined hy regression and backward climination. The coefficients of determination (R 2 ) of the models were 0.971 for net incorporation and 0.938 for DAG content. Thus, e conclude that the quadratic response models adequately expressed the reaction. Based on the models, the reaction was optimized for the maximum net incorporation and minimum DAG content. The reaction and the control of water content or water activity (Aw) was also discussed.

Release of peppermint flavour compounds from chewing gum: effect of oral functions

During chewing, the oral cavity functions like a bellow, forcing volatile flavour compounds into the exhaling air to the nasal compartment. Accordingly, we hypothesised that flavour release from chewing gum is predominantly governed by chewing frequency (CF), although other oral functions, like masseter muscle activity (MMA), chewing force (CFO), and saliva flow rate (SFR), may also play a role. In 10 healthy young males, the retronasal expired air of menthol and menthone from peppermint-flavoured (2%) chewing gum was determined as functions of CF, SFR, MMA, and CFO. The experimental setup comprised three separate series of a 4-min chewing period. These series differed only with respect to CF, i.e., habitual frequency, and 60 and 88 strokes/min. Results showed that more than 50% of the released menthol and menthone could be retrieved in the expired air and saliva. After 2-min of chewing, the concentration of flavour compounds in the expired air depended primarily on MMA and CF, becoming higher with increased MMA and CF. The concentration of flavour compounds in saliva depended primarily on SFR and the duration of the chewing task, becoming lower with high SFR and prolonged chewing duration. An increased volume of saliva in the mouth seemed to keep more flavour compounds in the aqueous phase, thereby diminishing the release via the retronasal route. In conclusion, flavour release to the retronasal compartment was dependent on MMA and CF and influenced by the volume of saliva present in the mouth.

Quantification of salt concentrations in cured pork by computed tomography.

Eight pork loin samples were mounted in Plexiglas cylinders and cured for five days. Samples were scanned by computed tomography (CT) once every 24 h. At the end of the experiment, the cylinders were cut in 1 cm sections and analyzed for chloride. From image analysis of the CT images, concentration profiles were extracted and fitted to a diffusion model which included a term to account for a non-negligible mass transfer coefficient. It was found that CT provides accurate estimates of salt gradients in meat and it was suggested that this analytical method could be valuable in scientific research and product development.

Production of specifically structured lipids by enzymatic interesterification in a pilot enzyme bed reactor: process optimization by response surface methodology

Pilot production of specifically structured lipids by Lipozyme IM-catalyzed interesterification was carried out in a continuous enzyme bed reactor without the use of solvent. Medium-chain triacylglycerols and oleic acid were used as model substrates. Response-surface methodology was applied to optimize the reaction system with four process para-meters, these being volume flow rate, water content in the substrates, reaction temperature, and substrate ratio. The incorporation of acyl donors, product yields, and the content of diacylglycerols were measured as model responses. Enzyme activity was not identical for the sequential experiments in the same enzyme bed due to the deactivation of the Lipozyme IM. Therefore, the results were normalized based on enzyme deactivation models. Well-fitting quadratic models were obtained after normalizing the data for the incorporation of oleic acid and the production of mono-incorporated and di-incorporated structured lipids with multiple regression and backward elimination. The coefficient of determination (R2) for the incorporation was 0.93 and that for the diincorporated products was 0.94. The optimal conditions were flow rate, 2 ml/min; temperature, 65 °C; substrate ratio, 5.5; and water content, 0.1%. The production of diacylglycerols was not well correlated with any of the parameters, and the yield generally decreased with the experimental sequence. This was due to the stoichiometric water in the substrate mixture in the packed enzyme bed being complicated by the water binding and absorption of the immobilized lipase. The main effects of parameters were also examined, and conclusions in agreement with our previous results were made. Produktion von spezifisch strukturierten Lipiden durch enzymatische Interesterifizierung in einem Versuchs-Emzymbettreaktor: Prozesoptimierung mit der Response Surface Methodik.Die Produktion spezifisch strukturierter Lipide durch Lipozyme IM-katalysierte Interesterifizierung wurde als Versuch in einem kontinuierlichen Enzymbettreaktor ohne Verwendung von Losungsmitteln durchgefuhrt. Triacylglycerole mittlerer Kettenlange und Olsaure wurden als Modellsubstrate verwendet. Die Response Surface Methode wurde zur Optimierung des Reaktionssystems mit den vier Prozesparametern angewendet, und zwar mit der volumetrischen Fliesgeschwindigkeit, dem Wassergehalt der Substrate, der Reaktionstemperatur und dem Substratverhaltnis. Die Integration von Acyldonoren, die gewonnene Produktmenge und der Gehalt von Diacylglycerolen wurden als Modellantwort gemessen. Die Enzymaktivitat war bei aufeinanderfolgenden Versuchen im selben Enzymbett aufgrund der Deaktivierung von Lipozyme IM nicht gleichbleibend. Daher wurden die Ergebnisse basierend auf Enzym-Deaktivierungsmodellen normalisiert. Es wurden gut angepaste quadratische Modelle erhalten, nachdem die Daten uber die Integration der Olsaure und die Bildung von monoinkorporierten und diinkorporierten strukturierten Lipiden mit multipler Regression und ruckwartiger Elimination normalisiert wurden. Der Determinationskoeffizient (R2) fur die Integration war 0,93 und der fur die diinkorporierten Produkte 0,94. Die optimalen Bedingungen lagen bei folgenden Werten: Fliesgeschwindigkeit 2ml/min, Temperatur 65 °C, Substratverhaltnis 5,5 und Wassergehalt 0,1 %. Die Produktion von Diacylglycerolen war nicht gut mit den anderen Parametern korreliert, und die Ausbeute sank generell mit fortschreitender experimenteller Sequenz. Dieses lag an dem stochiometrischen Wasser in der Substratmischung im gepackten Enzymbett und wurde weiterhin kompliziert durch die Wasserbindung und -absorption der immobilisierten Lipase. Die Hauptauswirkungen der Parameter wurden ebenfalls untersucht und Schlusfolgerungen gezogen, die mit unseren fruheren Ergebnissen ubereinstimmen.

3D modelling of coupled mass and heat transfer of a convection-oven roasting process

A 3D mathematical model of coupled heat and mass transfer describing oven roasting of meat has been developed from first principles. The proposed mechanism for the mass transfer of water is modified and based on a critical literature review of the effect of heat on meat. The model equations are based on a conservation of mass and energy, coupled through Darcys equations of porous media - the water flow is mainly pressure-driven. The developed model together with theoretical and experimental assessments were used to explain the heat and water transport and the effect of the change in microstructure (permeability, water binding capacity and elastic modulus) that occur during the meat roasting process. The developed coupled partial differential equations were solved by using COMSOL Multiphysics®3.5 and state variables are predicted as functions of both position and time. The proposed mechanism was partially validated by experiments in a convection oven where temperatures were measured online.