Available lysine and fluorescence in heated milk proteins/dextrinomaltose or lactose solutions

In order to predict and compare the effects of dextrinomaltose and lactose on available lysine loss by the Maillard reaction, six model systems were prepared by mixing casein, laboratory whey protein or commercial whey protein with dextrinomaltose or lactose. The solutions were prepared at concentrations similar to those used in enteral and infant formula processing and were heated at 100, 120 or 140 °C for 0–30 min. The progress of the Maillard reaction in these model systems was followed by monitoring free fluorescence intermediary compounds. Model systems with lactose showed higher available lysine less than the model systems with dextrinomaltose; linear lysine losses were obtained between 0 and 20 min at 100 and 120 °C. At sterilization temperature and time (120 °C/10 min), lysine losses of milk proteins with dextrinomaltose as reducing sugar were 6.1% for casein, 4.1% for laboratory whey protein and 13.4% for commercial whey protein. Available lysine showed correlation with furosine in model systems prepared with lactose and casein or laboratory but not commercial whey protein at 100 and 120 °C. The initial fluorescence value obtained by mixing casein or laboratory whey protein with lactose or dextrinomaltose was low (between 3.8 and 5.7), whereas the value obtained when commercial whey proteins were used was close to 9. At 120 °C/10 min, there was only a small increase of fluorescence in casein and laboratory whey protein but a large increase in commercial whey protein (threefold the initial value). Fluorescence measurement is useful for finding the extent of the Maillard reaction in commercial whey protein (thermally damaged protein). An absolute value greater than 10 may indicate that products were prepared with thermally damaged proteins.     

Extraction yield of isoflavones from soybean cake as affected by solvent and supercritical carbon dioxide

Soybean cake has been shown to be a rich source of isoflavone and can be produced during processing of soybean oil as byproduct. The objectives of this study were to compare the extraction yield of isoflavone from soybean cake by solvent and supercritical carbon dioxide, and study the conversion of isoflavone glucosides to the biologically active aglycone by employing β-glucosidase. Results showed that with supercritical carbon dioxide extraction, a maximum yield of malonylglucoside and glucoside was generated at 60 °C and 350 bar, while a high level of acetylglucoside and aglycone was produced at 80 °C and 350 bar. Supercritical carbon dioxide extraction resulted in a lower yield of total isoflavone than solvent extraction, but the former was more applicable to extraction of acetylglucoside and aglycone, and the latter to malonylglucoside and glucoside. A peak level of aglycone was attained from conversion of isoflavone glucoside by β-glucosidase at 55 °C, pH 5, concentration 50 U/ml and incubation time of 2 h.     

Phenolic content and antioxidant capacity of supercritical carbon dioxide-treated and air-classified oat bran concentrate microwave-irradiated in water or ethanol at varying temperatures

Oat bran concentrate (OBC) was defatted with supercritical carbon dioxide (SCD), then microwave-irradiated (MI) at 50, 100 or 150 °C for 10 min in water, 50% or 100% ethanol, and extract pH, soluble solids, phenolic content (PC) and antioxidant capacity (AC) were analysed. OBC was air-classified into five fractions and MI in water at 150 °C. OBC without SCD and microwave irradiation was extracted at 22 °C. Most effective temperature during microwave irradiation for maximising extraction of PC and AC was 150 °C. Defatted OBC in 50% ethanol and MI at 150 °C extracted greatest PC and AC. SCD treatment slightly reduced PC and AC. OBC extracted in water or 50% ethanol at 22 °C without microwave irradiation had similar PC and AC than OBC MI at 150 °C, but much higher levels were observed for latter heat treatment using absolute ethanol. Air-classification shows potential to enhance PC and AC.     

Shelf-life of fresh noodles as affected by chitosan and its Maillard reaction products

The effects of Maillard reaction products (MRPs) prepared from chitosan and xylose on the shelf-life of fresh noodles were studied. A model system consisting of chitosan and xylose (1:1.5, w/w) dispersed in distilled water with pH values of 5, 6, 7, 9 was used. The systems were heated to 95 °C for up to 60 h. The development of brown color was more pronounced in the model system with a higher initial pH of the water. The antibacterial activity of chitosan increased at the beginning of the Maillard reaction, and the minimum inhibition concentration (MIC) of chitosan against Bacillus subtilis CCRC 10258 decreased to 50 μg/ml of medium from 250 μg as a result of the Maillard reaction. Gram-positive bacteria were more sensitive to chitosan or its MRPs than Gram-negative bacteria. MRP of chitosan/xylose showed a bactericidal effect against Bacillus subtilis CCRC 10258, while chitosan showed a bacteriostatic effect prior to the occurrence of the Maillard reaction. Addition of 0.05 g/100 ml chitosan (in 0.5 ml/100 ml acetic acid) to fresh noodle formulation resulted in an extension of its shelf-life for 6 more days when stored at 4 °C. However, addition of MRP resulted in the longer shelf-life lasting 14 days when stored at 4 °C.     

Optimization of conditions for galactooligosaccharide synthesis during lactose hydrolysis by β-galactosidase from Kluyveromyces lactis (Lactozym 3000 L HP G)

A study on optimisation of the conditions for galactooligosaccharide (GOS) formation during lactose hydrolysis, produced by Lactozym 3000 L HP G, was carried out. The synthesis was performed during times up to 300 min at 40, 50 and 60 °C, pH 5.5, 6.5 and 7.5, lactose concentration 150, 250 and 350 mg/mL and enzyme concentration 3, 6 and 9 U/mL. The product mixtures were analysed by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). During the hydrolysis of lactose, besides glucose and galactose, galactobiose, allolactose and 6′ galactosyl lactose were also formed as a result of transgalactosylation catalysed by the enzyme. The effect of the reaction conditions was different in the formation of di- and the trisaccharide. Thus, the optimal conditions for galactobiose and allolactose synthesis were 50 °C, pH 6.5, 250 mg/mL of lactose, 3 U/mL of enzyme and 300 min, whereas the best reaction conditions for 6′ galactosyl lactose production were 40 °C, pH 7.5, 250 mg/mL of lactose, 3 U/mL of enzyme and 120 min. These results show the possibility to obtain reaction mixtures with Lactozym 3000 L HP G, with different composition, depending on the assayed conditions.     

Citric acid as pretreatment in drying of Pacific Lion’s Paw Scallop (Nodipecten subnodosus) meats

Pacific Lion’s Paw Scallop meats were dried at 50, 60, and 70 °C after pretreatment in citric acid at pH 3 during zero (control), one, and three hours. Immersion in the acid solution reduced the scallop pH from 6.20 to 5.99 (1 h) and 5.88 (3 h) and directly affected the drying times. At 50 °C drying times were 22, 10 and 8.5 h, at 60 °C they were 15, 9.5 and 8 h, and at 70 °C they were 13, 8 and 6 h for control, 1 h, and 3 h of acid treatment. Drying times were considerably reduced as acid immersion time increased. The drying temperature had no significant effect (p ? 0.05) on colour and texture, whereas the acid treatment had a significant effect (p < 0.05), with the control scallops having greater hardness and a more intense dark colouration than those treated with acid (p < 0.05). The citric acid treatment in drying meats of scallops is a good option to decrease the drying times and therefore the process cost. Moreover, the final product has a better colour because the acid treatment reduces Maillard reaction.     

Temperature effect on the non-volatile compounds of Maillard reaction products derived from xylose–soybean peptide system: Further insights into thermal degradation and cross-linking

Solutions of soybean peptide with or without xylose were heated over a range of temperatures (80–130 °C) for 2 h to investigate the characteristics of Maillard reaction and the effect of temperature on amino acids and peptides. It was found that both peptide degradation and peptide cross-linking occurred in the Maillard reaction. The critical temperature for peptide degradation was 100 °C, and above it, peptides degraded quickly in thermal degradation system. However, in Maillard reaction system, peptides cross-linked rapidly when the temperature reached 110 °C. Bitter amino acids and peptides below 1000 Da decreased 18.44% and 28.49%, respectively, after Maillard reaction at 120 °C. On the other hand, peptides between 1000 and 5000 Da were increased significantly, nearly doubled compared to its initial hydrolysates after Maillard reaction at 120 °C. Moreover, the increase of macromolecule products was also accompanied with severe browning and pH decrement.     

Effects of supercritical carbon dioxide treatment for sterilization purpose on meat quality of porcine longissimus dorsi muscle

The objective of this study was to investigate the effect of supercritical carbon dioxide (SC-CO₂) treatment for the sterilization purpose on meat quality and protein denaturation of the porcine longissimus dorsi muscle. The conditions of SC-CO₂ treatment were 7.4 and 15.2 MPa at 31.1 °C for 10 min. SC-CO₂ treatment had no effect on muscle pH, tenderness, and water-holding capacity (WHC). However, the samples treated at 7.4 MPa had a higher lightness value (52.97 vs. 46.94, P<0.001) and a more pronounced extent of sarcoplasmic protein denaturation (73.80 vs. 80.73, P<0.01) than the control samples. These results suggest that the paler color of samples treated with SC-CO₂ was associated with the sarcoplasmic protein denaturation, and the major denaturated proteins were determined to be phosphorylase b (PH), creatine kinase (CK), triosephophate isomerase (TPI), and one unknown protein. On the other hand, other quality traits were generally unaffected by the SC-CO₂ treatments at 7.4 or 15.2 MPa.     

Short communication: Presence of galactose and glucose promotes browning of sweet whey powder

This research examined the role of sugar type on the browning of sweet whey powder during accelerated storage. Two model systems, a lactose-lysine system and a sweet whey powder system, were selected. Within each model system experiment were samples containing equimolar concentrations of lactose, galactose, and glucose, and model systems were studied at 3 pH values: 6.5, 6.0, and 5.5. Samples were analyzed for changes in color after accelerated browning at 80°C for 24 h. The results showed that the samples containing galactose and glucose browned to a greater degree than those containing lactose. Browning in the control and lactose-enriched samples was more susceptible to changes in pH. This study indicates that the processing conditions of liquid whey in which the lactose monomers glucose and galactose accumulate may predispose SWP to brown more readily.     

Functional properties of the Maillard reaction products of rice protein with sugar

The glycation of rice proteins with reducing sugars was investigated in an attempt to improve their solubility and functionality. Rice proteins isolated from a Chinese milled medium-grain rice were glycated with glucose, lactose, maltodextrin, or dextran in 2% aqueous dispersions. The sugar that provided the most improvement of the solubility, emulsification activity (EA) and emulsification stability (ES) of the Maillard reaction products was glucose. The optimum reaction conditions were at pH 11, 100 °C, and reaction time 15 min, which increased the solubility, EA and ES of rice protein from 20%, 0.46 and 11.1 to 92%, 0.64 and 18.2, respectively. Extending the reaction time beyond 15 min continued the development of latter-stage Maillard browning products without improvements in the functional properties of the Maillard reaction products. SEC–HPLC analysis with light scattering detection showed a decrease of the weight-averaged molecular weight from 500 to 100 K during the initial 15 min.     

Supercritical carbon dioxide extraction of the residual oil from palm kernel cake

Palm kernel cake contains residual oil that has never been retrieved and it is treated as wastes. In this study, supercritical carbon dioxide was used to separate the oil from the palm kernel matrix. The studied extraction parameters were at the set pressures 27.57, 34.47 and 41.36 MPa, temperatures 40-70 °C and carbon dioxide flow rate between 1 and 3 ml/min. The effect of the particle size on the oil yield was examined using different particle size that separated by sieving from ?106, ?150, ?180, ?250 and ?450 μm. The results showed that the highest oil removed was 9.26 g oil/100 g sample (p < 0.05) for the particle ?150 μm, and under extraction temperature of 70 °C, pressure 41.36 MPa, and carbon dioxide flow rate of 2 ml/min. The experimental results indicate that supercritical carbon dioxide extraction could be a viable technique to remove the remaining oil and to produce defatted palm kernel cake.     

The kinetics of Maillard reaction in lactose-hydrolysed milk powder and related systems containing carbohydrate mixtures

The kinetics of Maillard reaction in lactose-hydrolysed skim milk powder and related systems containing carbohydrate mixtures were analysed. The effect of the increase of water activity and temperature during storage of the commercial product was also evaluated. In systems with two and three carbohydrates, a marked decrease of the reaction rate was observed when monosaccharides were partially replaced by lactose, notwithstanding the fact that the former still remained in a higher proportion than lysine. The rate of available lysine loss in lactose-hydrolysed milk was mostly affected by the presence of galactose. The reaction rate constants at a_w 0.52 and at 37 and 50 °C were higher than at a_w 0.33. However, no significant differences were observed at 60 °C. Temperature is the most important factor to be controlled in order to minimise nutritional deterioration during storage.     

Influence of technological processes on phenolic compounds,organic acids,furanic derivatives,and antioxidant activity of whole-lemon powder

The healthy properties of citrus fruits have been attributed to ascorbic acid and phenolic compounds, mainly to flavonoids. Flavonoids are important phytonutrients because they have a wide range of biological effects that provide health-related properties. In this context, this study seeks to characterise the phenolic compounds in lemon and their stability in different drying processes (freeze-drying and vacuum-drying) and storage conditions (−18 and 50 °C for 1 and 3 months). A powerful high-performance liquid chromatography coupled to DAD and electrospray-ionization time-of-flight mass spectrometry (HPLC–ESI-TOF-MS) method has been applied for the separation, identification, and quantification of 19 phenolic compounds and 4 organic acids. To our knowledge, two hydroxycinnamic acids have been identified for the first time in lemon. Folin–Ciocalteu was applied to determine total phenolic compounds and TEAC, FRAP, and ORAC were applied to determine the antioxidant capacity of lemon. Total phenolic content significantly differed in the samples analysed, vacuum-dried lemon showing the highest phenolic content, followed by freeze-dried lemon and, finally, vacuum-dried lemon stored at 50 °C for 1 and 3 months. The content in furanic compounds was determined to evaluate the heat damage in lemon and it was showed an increase with the thermal treatment because of the triggering of Maillard reaction. As exception of ORAC, antioxidant-capacity assays were not correlated to phenolic content by HPLC due to the formation of antioxidant compounds during Maillard reaction.     

Optimisation of supercritical fluid extraction of flavonoids from Pueraria lobata

Supercritical carbon dioxide extraction was employed to extract flavonoids from Pueraria lobata. The optimal conditions for flavonoid extraction were determined by response surface methodology. Box–Behnken design was applied to evaluate the effects of three independent variables (pressure, temperature and co-solvent amount) on the flavonoid yield of P. lobata. Correlation analysis of the mathematical-regression model indicated that a quadratic polynomial model could be employed to optimise the supercritical carbon dioxide extraction of flavonoids. From response surface plots, pressure, temperature and co-solvent amount exhibited independent and interactive effects on the extraction of flavonoids. The optimal conditions to obtain the highest flavonoid yield of P. lobata were a pressure of 20.04 MPa, a temperature of 50.24 °C and a co-solvent amount of 181.24 ml. Under these optimal conditions, the experimental values agreed with the predicted values, using analysis of variance, indicating a high goodness of fit of the model used and the success of response surface methodology for optimising supercritical carbon dioxide extraction of flavonoids from P. lobata.     

Extraction of canola seed (Brassica napus) oil using compressed propane and supercritical carbon dioxide

This study aimed to investigate the extraction of canola seed (Brassica napus) oil using supercritical carbon dioxide and compressed propane as solvents. The extractions were performed in a laboratory scale unit at temperatures and pressures of 40, 50 and 60 °C and 20, 22.5 and 25 MPa for carbon dioxide and 30, 45 and 60 °C and 8, 10 and 12 MPa for propane extractions, respectively. The results indicated that pressure and temperature were important variables for the CO₂ extraction, while temperature is the most important variable for the extraction yield with propane. The extraction with propane was much faster than that with carbon dioxide. The characteristics of the extracted oil, that is, the oxidative stability determined by DSC and the chemical profile of fatty acids determined by gas chromatography, were similar for the two solvents. The overall extraction curves were well described by the Sovová model.     

Effect of drying methods on the reactivity of chitosan towards Maillard reaction

The effect of drying methods on chitosan reactivity towards Maillard reaction during storage of dried chitosan–lactose systems was investigated. Two different structural forms of chitosan, scaffold and microspheres, were prepared. Then they were dried by lyophilization or using supercritical fluid technology (SF-CO₂) and stored with lactose under controlled temperature conditions (60 °C) and water activity (a_w = 0.65). The drying method produced slight modifications on the chitosan structure especially in samples submitted to SF-CO₂ treatment. Differences were more evident in the reactivity of chitosan–lactose systems during storage. Maillard reaction development was assessed by quantification of a new compound which originated from the acid hydrolysis of Amadori compounds (NFMD) resulting from chitosan–lactose interactions, and not detected in the acid hydrolysates of freshly prepared chitosan-lactose systems. Maillard reaction was influenced by different factors such as the manner of lactose addition, structure of chitosan (microspheres and scaffolds) and drying method. Lyophilized chitosan in the form of microspheres with lactose, presented the highest values of NFMD (428.45 mg/100 g of sample). The determination of this compound could be used as an index of the progress of Maillard reaction.     

Direct application of supercritical carbon dioxide for the reduction of Cronobacter spp. (Enterobacter sakazakii) in end products of dehydrated powdered infant formula

The objective of this study was to develop a viable new method for inactivation of Cronobacter spp. that could be applied directly to dehydrated powdered infant formula (PIF) using supercritical carbon dioxide (SC-CO₂). Samples inoculated with Cronobacter spp. were subjected to SC-CO₂ treatment under various conditions (temperature: 63, 68, and 73°C; pressure: 15, 20, and 25 MPa; time: 10, 20, and 30 min). The survival of Cronobacter spp. was assayed, as were any changes in the quality of the treated PIF. Inactivation of Cronobacter spp. by SC-CO₂ was enhanced as temperature and pressure conditions increased (>6.32 log₁₀ cfu/g). In a validation assay using low-level inoculation (3.21 log₁₀ cfu/g), treatment at 73°C and 15 MPa for 30 min, 20 MPa for 20 and 30 min, or 25 MPa for 20 and 30 min reduced Cronobacter spp. to undetectable levels, with no recovery of cell viability. There was no significant change in water activity, pH, and color of the treated PIF. Overall, the optimum conditions for elimination of Cronobacter spp. were determined to be 73°C and 20 MPa for 20 min. These parameters for effective SC-CO₂ treatment are feasibly applicable to end product of dehydrated PIF. The results of our study may contribute to the development of an efficient method for improving the microbiological safety of PIF.     

Simultaneous analysis of Nε-(carboxymethyl)lysine,reducing sugars,and lysine during the dairy thermal process

A new analytical method allowing the simultaneous quantification of Nε-(carboxymethyl)lysine (CML), lysine, and reducing sugars (glucose, lactose, and galactose) is described. It is based on high performance anion-exchange chromatography with pulsed amperometric electrochemical detection. This method demonstrated a low limit of quantification (0.385 to 0.866 mg/L), excellent linear correlation (R² > 0.997), and desired calibration range (3.125 to 25 mg/L). In addition, lactose-lysine solutions containing sulfite (4 to 400 mmol/L) were heated at 110°C for 2 h. The results showed that sulfite inhibited the formation of CML and promoted the consumption of reducing sugars and lysine in the Maillard reaction model. The method proved to be useful for simultaneous analysis of CML, lysine, and reducing sugars (glucose, galactose, and lactose) in the Maillard reaction system. Moreover, sulfite was an effective inhibitor of CML formation.     

Inhibition of polyphenoloxidase from apple by Maillard reaction products prepared from glucose or fructose with l-cysteine under various conditions of pH and temperature

The effects of Maillard reaction products (MRPs), synthesized from equimolar glucose or fructose with l-cysteine (1 mol l⁻¹) aqueous model mixtures, by modulating pH and temperature of heating, according to a two-factor and five-level experimental design, were investigated on polyphenoloxidase (PPO) activity from apple. Final pH and absorbance measurements at 350 nm were also selected as indicators of the Maillard reaction development and checked. In general, inhibitory potency (IP) of the mixtures increased with the increase in temperature (80-120°C) and the decrease in pH (pH 2.0-12.0) of the reaction medium. A linear relationship between the IP and heating time (0-48 h) or Abs.350 nm (0-70 AU) was demonstrated for glucose/cysteine system heated from 80°C to 120°C. Polarographic and spectrophotometric data were used to calculate kinetic constants and activation energy (Ea) values of inhibitory MRPs formation versus PPO activity and of those compounds absorbing at 350 nm. Ea values for these reactions were close, being 191 and 124 kJ mol⁻¹, respectively. The experimental design allowed to conclude that linear effects of both factors as well as a quadratic effect of pH were significant, leading to optimum conditions for the production of glucose-derived MRPs inhibitors. In most cases, glucose produced MRPs with higher IP compared to counterpart fructose-cysteine MRPs.     

Lycopene extraction from tomato peel by-product containing tomato seed using supercritical carbon dioxide

This work discusses the extraction of lycopene from tomato peel by-product containing tomato seed using supercritical carbon dioxide. The presence of tomato seed in the peel by-product improved the yield of extracted lycopene. Extraction was carried out at temperatures of 70-90 °C, pressures of 20-40 MPa, a particle size of 1.05 ± 0.10 mm and flow rates of 2-4 mL/min of CO₂ for 180 min extraction time. Oil from tomato seed was extracted under similar operating conditions and analyzed using GC-MS and GC-FID, while carotenoids extracted were analyzed by HPLC. The optimum operating condition to extract lycopene, under which 56% of lycopene was extracted, was found to be 90 °C, 40 MPa, and a ratio of tomato peel to seed of 37/63. The presence of tomato seed oil helped to improve the recovery of lycopene from 18% to 56%. The concentration of lycopene in supercritical carbon dioxide as a function of density at various temperatures was determined.