Vibeke Orlien

The Effects of Conventional and Non-conventional Processing on Glucosinolates and Its Derived Forms, Isothiocyanates: Extraction, Degradation, and Applications

Abstract In recent decades, glucosinolates and isothiocyanates have attracted the interest of scientific community due to healthy properties of these bioactive compounds and their role as natural antimicrobials and anticarcinogenic agents. However, these compounds can lose their properties and transform into antinutrients depending on processing conditions. At this stage of investigation, there is a need in evaluation of the commonly accepted and new emerging methods in order to establish the optimum conditions for preserving healthy glucosinolates and isothiocyanates. This paper reviews the conventional and new promising technologies that can be useful for extraction of appropriate glucosinolates and isothiocyanates from natural sources (i.e., Brassica vegetables). The impact of different preservation processes on degradation of glucosinolates and isothiocyanates is also discussed.

Hydroperoxide formation in rapeseed oil encapsulated in a glassy food model as influenced by hydrophilic and lipophilic radicals

Abstract A glassy food model based on emulsions of sucrose, maltodextrin 10, gelatine and stripped rapeseed oil was established by freeze-drying. The glassy food model had a glass transition temperature of 61±2°C determined by Differential Scanning Calorimetry, and encapsulated oil as confirmed by Optical and Scanning Electron Microscopy. Radicals were generated thermally with either the hydrophilic radical generator 2,2′-azobis(2-amidinopropane)dihydrochloride, or with the lipophilic radical generator 2,2′-azobis(2,4-dimethyl-pentanenitrile), as confirmed by Electron Spin Resonance spectroscopy. Early events in lipid oxidation were monitored by analyses of conjugated dienes and peroxides during dry storage at 25°C for up to 7 weeks. Formation of lipid peroxides followed 0th order kinetics. The oxidation of the encapsulated oil was enhanced by radicals generated in the oil, and oxygen was able to diffuse through the glassy matrix in a rate determining process. The hydrophilic radicals were found not to enhance oxidation and were concluded to be immobilized in the glassy matrix.

Kinetics of the formation of radicals in meat during high pressure processing

The kinetics of the formation of radicals in meat by high pressure processing (HPP) has been described for the first time. A threshold for the radicals to form at 400 MPa at 25 °C and at 500 MPa at 5 °C has been found. Above this threshold, an increased formation of radicals was observed with increasing pressure (400-800 MPa), temperature (5-40 °C) and time (0-60 min). The volume of activation (ΔV(#)) was found to have the value -17 ml mol(-1). The energy of activation (E(a)) was calculated to be 25-29 kJ mol(-1) within the pressure range (500-800 MPa) indicating high independence on the temperature at high pressures whereas the reaction was strongly dependent at atmospheric pressure (E(a)=181 kJ mol(-1)). According to the effect of the processing conditions on the reaction rate, three groups of increasing order of radical formation were established: (1) 55 °C at 0.1 MPa, (2) 500 and 600 MPa at 25 °C and 65 °C at 0.1 MPa, and (3) 700 MPa at 25 °C and 75 °C at 0.1 MPa. The implication of the formation of radicals as initiators of lipid oxidation under HPP is discussed.

Casein micelle dissociation in skim milk during high-pressure treatment: Effects of pressure, pH, and temperature

The effect of pH (from 5.5 to 7.5) and temperature (from 5 to 40 degrees C) on the turbidity of reconstituted skim milk powder was investigated at ambient pressure and in situ under pressure (up to 500MPa) by measurement of light scattering. High-pressure treatment reduced the turbidity of milk for all combinations of pH and temperature due to micelle dissociation. The turbidity profiles had a characteristic sigmoidal shape in which almost no effect on turbidity was observed at low pressures (100MPa), followed by a stronger pressure dependency over a pressure range of 150MPa during which turbidity decreased extremely. From the turbidity profiles, the threshold pressure for disruption of micelle integrity was determined and ranged from 150MPa at low pH to 350-400MPa at high pH. The threshold pressure diagram clearly showed a relationship between the barostability of casein micelles and pH, whereas almost no effect of temperature was shown. This remarkable pH effect was a consequence of pressure-induced changes in the electrostatic interactions between colloidal calcium phosphate and the caseins responsible for maintaining micellar structure and was explained by a shift in the calcium phosphate balance in the micelle-serum system. Accordingly, a mechanism for high pressure-induced disruption of micelle integrity is suggested in which the state of calcium plays a crucial role in the micelle dissociation process.

Synergistic cooperation of high pressure and carrot dietary fibre on texture and colour of pork sausages.

In order to investigate the synergistic cooperation between high pressure treatment (HP) and carrot dietary fibre, two formulations of pork sausages containing different percentage of carrot dietary fibre were pressurized at 500 and 600 MPa, for 1 second, 3, 6, and 9 min at 40, 50, and 60 °C. HP treatments significantly increase Youngs Modulus and affect Hencky strain values. We conclude that HP processing and carrot dietary fibre markedly improved emulsion strength resulting in firm sausages. Colour changes were investigated and significant increase in L* value and decrease in a* value were found, indicating that HP, temperature, and dietary fibre can affect physico-chemical properties of the meat matrix altering the intrinsic ability to absorb or reflect light. The sensory evaluation showed that HP treatment synergistically cooperate with carrot dietary fibre improving sensorial attributes like homogeneity, creaminess, fattiness, and firmness as detected by Napping in combination with Ultra-Flash Profile.

Reduction of salt in pork sausages by the addition of carrot fibre or potato starch and high pressure treatment

The combined effect of high pressure processing (HPP) (400, 600 and 800 MPa) and carrot fibre (CF) and potato starch (PS) on low salt (1.2%) pork sausages was investigated and compared with high (1.8%) salt sausages. Sausages had a marked increase in whitening with increasing content of fibre or starch, pressure level, and process temperature. The degree of redness was mainly affected by pressure level and heat treatment. An important finding regarding salt reduction was that the use of starch or fibre had more impact on textural properties than the level of salt since Youngs modulus and strain at fracture were mainly affected by formulation and HPP. Water binding capacity of low salt sausages was improved to the same level as high salt sausages with HPP and addition of CF or PS particularly by the addition of PS which produced sausages with better sensory properties than CF. The sensory analysis showed that this approach is promising for producing low salt sausages.

Effect of high pressure, temperature, and storage on the color of porcine longissimus dorsi

The color of pork longissimus dorsi high pressure (HP) treated at 200 to 800 MPa at 5 and 20 °C for 10 min was determined to a high degree by pressure level and to a lesser degree by temperature. Severe color changes appeared up to a threshold pressure at 400 MPa. HP treatment at 20 °C compared to 5 °C resulted in meat, which was less red and slightly lighter. Storage at 2 °C for 6 days had no effect on lightness due to no further protein denaturation, but meat HP treated above 300 MPa became significantly less red and more yellow within the first day of storage. Reflectance spectra showed that a short-lived ferrohemochrome myoglobin species was formed during HP treatment at 300 to 800, but transformed into a brown, ferric form of the pigment within the first day of storage. This explains the observed changes in the redness and yellowness after one day of storage.

Aroma development in high pressure treated beef and chicken meat compared to raw and heat treated.

Chicken breast and beef muscle were treated at 400 and 600 MPa for 15 min at 5 degrees C and compared to raw meat and a heated sample (100 degrees C for 15 min). Vacuum-packed beef meat with a smaller fraction of unsaturated fatty acids showed better oxidative stability during 14 days of cold storage, as shown by a low steady-state level of hydroperoxide values, than vacuum-packed chicken meat. Accordingly, the critical pressures of 400 MPa and 600 MPa for chicken breast and beef sirloin, respectively, were established. Volatiles released after opening of the meat bags or during storage of open meat bags, simulating consumer behaviour, were measured under conditions mimicking eating. Quantitative and olfactory analysis of pressurised meat gave a total of 46 flavour volatiles, mainly alcohols (11), aldehydes (15), and ketones (11), but all in low abundance after 14 days of storage. Overall, beef meat contained less volatiles and in lower abundance (factor of 5) compared to chicken meat. The most important odour active volatiles (GC-O) were well below the detection thresholds necessary to impart a perceivable off-flavour. Lipid oxidation was significantly accelerated during 24h of cold storage in both cooked chicken and beef when exposed to oxygen, while the pressurised and oxygen-exposed chicken and beef meat remained stable. Pressure treatment of beef and chicken did not induce severe changes of their raw aroma profiles.

High pressure effect on the color of minced cured restructured ham at different levels of drying, pH, and NaCl.

Color changes of minced cured restructured ham was studied considering the effects of high pressure (HP) treatment (600MPa, 13°C, 5min), raw meat pH(24) (low, normal, high), salt content (15, 30g/kg), and drying (20%, 50% weight loss). Raw hams were selected based on pH(24) in Semimembranosus, mixed with additives, frozen, sliced, and dried using the Quick-Dry-Slice® process. Meat color (CIE 1976 L*a*b*) and reflectance spectra were measured before and after HP treatment. HP significantly increased L*, decreased a*, and decreased b* for restructured ham dried to 20% weight loss, regardless of salt content and pH(24). L* and a* were best preserved in high pH/high salt restructured ham. HP had no effect on the color of restructured ham dried to 50% weight loss. HP had no effect on the shape of reflectance curves, indicating that the pigment responsible for minced cured restructured ham color did not change due to HP.

Water properties and structure of pork sausages as affected by high-pressure processing and addition of carrot fibre.

The effects of high-pressure processing (HPP) and addition of carrot fibre on pork sausages have been studied using NMR T₂ relaxometry and measurements of water-binding capacity (WBC) by centrifugation. Significant effects of temperature (raw, 40, 50, or 60 °C), holding time (1s, 3, 6, or 9 min), and addition of carrot fibre on the distribution and mobility of water were found. However, the effect of carrot fibre could not be explained by structural changes in the sausages when examined by confocal laser scanning microscopy (CLSM). Correlations between T₂ relaxation measurements and WBC determined by centrifugation revealed that T₂ relaxation times were able to explain more than 90% of the variation in WBC for both non-pressure and pressure-treated sausages. However, only 49% of the variation was explained for pressure-treated sausages with carrot fibre, indicating that combining addition of fibre and high pressure treatment causes non-coherent changes in T₂ NMR relaxation times.