Ellagic acid-loaded soy protein isolate self-assembled particles: Characterization, stability, and antioxidant activity.

The limited water solubility and bioactivity of lipophilic phytochemicals may be enhanced by delivery systems. Ellagic acid (EA) has antioxidant and anti-inflammatory properties, but low solubility and instability limit its use in the food industry. In this study, the pH-shift method was applied to encapsulate EA with soy protein isolate (SPI). The interaction, encapsulation, and protective potential of the EA-loaded soy SPI complexes (SPI-EA) were investigated. The fluorescence spectra results suggest that the reaction between SPI and EA is spontaneous, with hydrophobic interactions predominating. Binding of EA molecules quenches the intrinsic fluorescence of SPI, mainly static quenching, with a binding site involved in the binding process. The ultraviolet (UV)-visible spectroscopy of the SPI-EA complexes included the characteristic absorption peaks of both SPI and EA, and the scanning electron microscopy images further indicated that the EA had been successfully embedded in SPI. Fourier transform infrared spectroscopy illustrates that EA has significantly changed the secondary structure of the SPI, primarily in the form of a decreased content of α-helix structures and an increased content of ß-sheet and random coil structures. The encapsulation efficiency of EA was concentration-dependent, up to 81.08%. The addition of EA reduces the size of SPI particles (d < 155 nm). In addition, the SPI-EA complex showed up to 81.05% and 96.46% 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity. TGA showed that the degradation temperature of SPI-EA complex could be extended up to 300°C. And by encapsulation of EA, the loss of EA under the action of UV light, heat treatment, and high concentration of salt ion sensitive environment can be reduced. PRACTICAL APPLICATION: Ellagic acid (EA), a natural bioactive with low water solubility and stability, can be enhanced by forming an inclusion complex with soy protein isolate (SPI). SPI-EA complex has broad potential applications in the food, beverage, and pharmaceutical industries. Multiple spectral analyses have contributed to our understanding of the formation and interaction mechanisms of the SPI-EA complex under pH-driven conditions. Stability assays have also aided in the development of dietary resources for EA.

Predicting minty compounds binary mixtures' pleasantness by odor intensity in aqueous solutions.

The aroma of mint is well-liked by the public, and key flavor odorants in mint aroma had been found, but how these molecules interact and form a satisfying odor remains a challenge. Quality, intensity, and pleasantness are our most basic perceptions of aromas; both intensity and pleasantness can be quantified. However, compared to intensity, research on pleasantness was lacking. Pleasantness was one of the most important indicators for formulating a satisfying mint flavor, and the study of binary mixtures was fundamental to our understanding of more complex mixtures. Therefore, the purpose of this study was to explore the characteristics of pleasantness as a function of concentration and, at the same time, to investigate the relationship between intensity and pleasantness in binary mixtures. Thirty sensory evaluation volunteers participated in the evaluation of the intensity and pleasantness of six key flavor odorants of mint and five binary mixtures. The results showed that the pleasantness increased first and then decreased or stabilized with the rising of concentration; even though the interactions in binary mixtures were not the same, their pleasantness could be predicted using the intensities of the components by Response Surface Design of Experiments, and the goodness of fit was greater than 0.92, indicating that the models had the great predictive ability. PRACTICAL APPLICATION: Whether blending flavors or evaluating them, a great deal of experience is required, yet the acquisition of this experience is a long process. Performing these tasks is difficult for the novice, and it helps to quantify the feeling for the flavor and build some mathematical models.

Antimicrobial, antioxidant, anti-inflammatory, and cytotoxic activities of Cordyceps militaris spent substrate.

Cordyceps militaris is a medicinal mushroom and has been extensively used as a traditional medicine in East Asia. After the chrysalis seeds are matured and harvested, the spent substrate of C. militaris still contains active ingredients but is usually discarded as waste. This study aimed to determine the antioxidant and anti-inflammatory activities of C. militaris spent substrate extract and its inhibitory activity on the Malassezia commensal yeasts that can cause dandruff and seborrheic dermatitis. Active substances in the spent substrate of C. militaris were extracted using a hot water extraction method and were used for the determination of antioxidant activity by measuring their ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radicals, hydrogen peroxide, and superoxide anions. The ability to inhibit Malassezia was analyzed using the broth microdilution method, and the reparative effect on oxidative damage in HaCaT cells was measured using in vitro cell analysis. Respiratory burst evaluation was used to determine the anti-inflammatory capacity of extracts. Analysis of the Malassezia-inhibiting activity of the extracts showed that the minimum inhibitory concentration was 6.25 mg/mL. The half maximal inhibitory concentration (IC50) values of DPPH, O2-, H2O2 and OH- were 3.845 mg/mL, 2.673 mg/mL, 0.037 mg/mL and 0.046 mg/mL, respectively. In the concentration range of 2 to 50%, the extract was non-toxic to cells and was able to protect HaCaT cells from H2O2 damage. When the volume fraction of the extract was 20.96%, its anti-inflammatory ability reached 50%. These results demonstrated that the extract may be a safe and efficacious source for pharmaceutical or cosmetic applications, with Malassezia-inhibiting, antioxidant and anti-inflammatory activities.

Structural Characterization of a Polygonatum cyrtonema Hua Tuber Polysaccharide and Its Contribution to Moisture Retention and Moisture-Proofing of Porous Carbohydrate Material.

Porous carbohydrate materials such as tobacco shreds readily absorb moisture and become damp during processing, storage, and consumption (smoking). Traditional humectants have the ability of moisture retention but moisture-proofing is poor. Polygonatum cyrtonema Hua polysaccharide (PCP 85-1-1) was separated by fractional precipitation and was purified by anion exchange and gel permeation chromatography. The average molecular weight (Mw) of PCP 85-1-1 was 2.88 × 103 Da. The monosaccharide composition implied that PCP 85-1-1 consisted of fucose, glucose, and fructose, and the molar ratio was 22.73:33.63:43.65. When 2% PCP 85-1-1 was added to tobacco shreds, the ability of moisture retention and moisture-proofing were significantly enhanced. The moisture retention index (MRI) and moisture-proofing index (MPI) increased from 1.95 and 1.67 to 2.11 and 2.14, respectively. Additionally, the effects of PCP 85-1-1 on the aroma and taste of tobacco shreds were evaluated by electronic tongue and gas chromatography-mass spectrometry (GC-MS). These results indicated that PCP 85-1-1 had the characteristics of preventing water absorption under high relative humidity and moisturizing under dry conditions. The problem that traditional humectants are poorly moisture-proof was solved. PCP 85-1-1 can be utilized as a natural humectant on porous carbohydrates, which provides a reference for its development and utilization.

Preparation and characterization of the dimethyl sulfide-ß-cyclodextrin inclusion complex.

Dimethyl sulfide has been widely used in flavors and can also be used as a solvent and catalyst. However, dimethyl sulfide is volatile, and its lasting power is weak. Furthermore, dimethyl sulfide is insoluble in water and is unstable in some cases. This study concentrated on the encapsulation of dimethyl sulfide in ß-cyclodextrin to form an inclusion complex and to improve the durability, water solubility, and stability of dimethyl sulfide. The product was successfully produced and characterized by scanning electron microscopy, diffraction of X-rays, and thermal analysis. The dimethyl sulfide loading capacity is 6.40±0.08%. Based on the thermal release characteristics of dimethyl sulfide, the kinetic and thermodynamic parameters were obtained. The apparent activation energy, pre-exponential factor, and reaction order of the dimethyl sulfide release reaction were obtained and the values were 95.0 ± 0.1 kJ/mol, 1.03 × 1015 s-1 , and 1, respectively. The activation entropy change, activation enthalpy change, and activation Gibbs free energy change were 41.6 J/K, 95.0 kJ/mol, and 81.3 kJ/mol, respectively, during the process of dimethyl sulfide release at 56.7℃. To make it clear that the dimethyl sulfide molecule interacts with ß-cyclodextrin molecule, molecular simulation was used to investigate the formation process of the dimethyl sulfide-ß-cyclodextrin inclusion complex. The binding energy and the optimized structure were obtained. When the Z coordinate of the S atom in the dimethyl sulfide molecule is 1.1 × 10-10  m, the binding energy attained the minimum value, -51.3 kJ/mol. These basic data are helpful for understanding the dimethyl sulfide-ß-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and ß-cyclodextrin. PRACTICAL APPLICATION: By forming an inclusion complex with ß-cyclodextrin, the stability, durability, and water solubility of dimethyl sulfide can be improved. Dimethyl sulfide-ß-cyclodextrin inclusion complex can be widely used in the food, beverage, flavor, and fragrance industries. The kinetic and thermodynamic parameters, binding energy, and the results of molecular simulation are helpful to understand the dimethyl sulfide-ß-cyclodextrin inclusion complex formation mechanism and the interaction between dimethyl sulfide and ß-cyclodextrin.

Fabrication and characterization of ethyl acetate-hydroxypropyl-ß-cyclodextrin inclusion complex.

Flavors play crucial role in food industry. Ethyl acetate, as probably one of the most used of all flavor chemicals by volume, is used widely in many industries. However, ethyl acetate is not too stable and can be slowly decomposed by moisture. Furthermore, ethyl acetate is a volatile liquid insoluble in water and it does not last long enough. In order to solve these problems, hydroxypropyl-ß-cyclodextrin was used as wall material to encapsulate ethyl acetate in this work. The product was characterized by Fourier transform infrared (FTIR) spectroscopy and thermalgravimetric analysis (TGA). The results showed that the peaks at 1,744 and 1,056 cm-1 in the FTIR spectrum of ethyl acetate disappeared in the FTIR spectrum of ethyl acetate-hydroxypropyl-ß-cyclodextrin inclusion complex. After the encapsulation of ethyl acetate, the O-H and C-H stretching absorption of hydroxypropyl-ß-cyclodextrin changed. The TGA results showed that from 77°C to 292°C ethyl acetate is released from the ethyl acetate-hydroxypropyl-ß-cyclodextrin inclusion complex in temperatures far beyond ethyl acetate 77°C boiling point. This phenomenon confirmed that the lastingness and thermal stability of ethyl acetate can be improved by the formation of an inclusion complex. The loading capacity of ethyl acetate was 4.86 ± 0.08% and ethyl acetate:hydroxypropyl-ß-cyclodextrin stoichiometry is close to 1:1. The interaction of ethyl acetate and hydroxypropyl-ß-cyclodextrin was investigated using molecular mechanics calculation. The binding energy was calculated and the possible conformation of ethyl acetate-hydroxypropyl-ß-cyclodextrin inclusion complex was optimized to the minimum energy. The binding energy minimum is at the 0.44 × 10-10  m point and its value is -103.9 kJ/mol. PRACTICAL APPLICATION: Encapsulation of ethyl acetate in hydroxypropyl-ß-cyclodextrin is a possible way to protect ethyl acetate, improve its stability, water solubility, and may also enhance its lastingness.

Effects of Surface Functional Groups on the Adhesion of SiO2 Nanospheres to Bio-Based Materials.

The interactions between nanoparticles and materials must be considered when preparing functional materials. Although researchers have studied the interactions between nanoparticles and inorganic materials, little attention has been paid to those between nanoparticles and bio-based protein materials, like leather. In this study, organically modified silica nanospheres (SiO2 nanospheres) loaded with rose fragrance were prepared using (3-aminopropyl) triethoxysilane (APTES), (3-mercaptopropyl) triethoxysilane (MPTES), or 3-(2, 3-epoxypropyloxy) propyl triethoxysilane (GPTES) using the sol-gel method. To study the interactions between the modified SiO2 nanospheres and leather, a non-cross-linking adsorption experiment was conducted. According to the Dubinin-Radushkevich isotherm calculation, we found that the adsorption process of leather fiber and organically modified silica nanospheres is physical. The average adhesion energies of APTES-, MPTES-, and GPTES-modified SiO2 nanospheres on the leather are 1.34016, 0.97289, and 2.09326 kJ/mol, respectively. The weight gain, adsorption capacity, and average adhesion energy show that the modified SiO2 nanospheres can be adsorbed on leather in large quantities. The sensory evaluation confirmed that GPTES-modified SiO2 nanospheres endowed the leather with an obvious rose aroma.

Sensory evaluation of the synergism among ester odorants in light aroma-type liquor by odor threshold, aroma intensity and flash GC electronic nose.

Although esters were important odorants in light aroma-type liquor, it was still puzzling that sensory interaction between esters made the odor quality of light aroma-type liquor outstanding. The aim of the paper was to investigate perceptual interaction among esters. The odor thresholds of eighteen esters and 35 binary mixture were determined by a three-alternative forced-choice procedure. The relationship between odor threshold and carbon chain length of homologous ethyl esters was investigated. Moreover, 31 binary mixtures present either a synergistic effect or additive action. Furthermore, odor quality and odor intensity were determined by p/τ plot and σ/τ plot, respectively. From the p/τ plot, an ideal sigmoidal function for odor quality was obtained. From the σ/τ plot, for all 120 binary mixtures, just 9 mixtures were in the hyper-additivity area (σ > 1.05), and two were in the so-called perfect additivity area (0.95 < σ < 1.05). Almost one half (48%) showed compromise level. Finally, a significantly difference was observed by flash gas chromatography electronic nose (p < .05). Sensory analysis revealed that a mask effect of fruity note was occurred by adding ethyl phenylacetate at various levels (100, 2500, 58,000 ppb) to the fruit recombination and an enhancement effect of floral note was reported by adding phenylethyl acetate at low (1400 ppb) or high level (11,500 ppb). It was noticed that sweet note was significantly enhanced by adding phenylethyl acetate at peri-threshold (3200 ppb).

Production and characterization of nanocapsules encapsulated linalool by ionic gelation method using chitosan as wall material

Abstract Linalool has been extensively applied in various fields, such as flavoring agent, perfumes, cosmetics and medical science. However, linalool is unstable, volatile and readily oxidizable. A sensitive substance can be encapsulated in a capsule, so encapsulation technology can solve these problems. In this paper, linalool-loaded nanocapsules (Lin-nanocapsules) were prepared via the ionic gelation method and Lin-nanocapsules were characterized. The results of Fourier transformation infrared spectroscopy (FTIR) showed that linalool was successfully encapsulated in the wall materials. Scanning electron microscopy (SEM) results demonstrated that the shapes of Lin-nanocapsules, with smooth surfaces, were nearly spherical. Lin-nanocapsule average particle size was 352 nm and its polydispersity index (PDI) was proved to be 0.214 by the results of dynamic light scattering (DLC). Thermogravimetric results indicated that linalool loading capacity (LC) was 15.17%, and encapsulation could decrease linalool release and increase linalool retaining time under the high temperature. Oscillatory shear and steady-state shear measurements of Lin-nanocapsule emulsions were systematically investigated. The results of steady-state shear showed that Lin-nanocapsule emulsion, which was Newtonian only for high shear rate, was non-Newtonian. It was proved by oscillatory shear that when oscillation frequency changed from low to high, Lin-nanocapsules emulsion changed from viscous into elastic.

Creation and imitation of a milk flavour.

Flavour plays a crucial role in food and is the most important aspect of milk. Milk has a pleasant smell and milk flavour can be used in several products. However, how to recreate milk flavour has rarely been reported. Therefore, the creation of milk flavour is of great interest. This study focused on the creation and imitation of milk flavour. The approach to flavour creation involves identifying the attributes of the flavour and developing an impactful, authentic flavour. Accordingly, to create a milk flavour, the notes of milk flavour were identified by smelling and tasting milk. Based on the identified notes, aroma ingredients were selected to blend into a milk-flavour. After olfactory discrimination, several modifications and adjustments were made and a typical milk flavour formula was obtained. The results showed that the milk flavour has the following notes: milky, acidic, vanilla-like, caramel-like, aldehydic, fruity, beany, buttery, meaty, and vegetative. Lactones, acids, aldehydes, alcohols, ketones, esters, sulphur compounds, furans, and nitrogen compounds can provide these notes. Based on the developed formula, a harmonious flavour with typical characteristics of milk was obtained by blending the selected aroma ingredients.

Production of a transparent lavender flavour nanocapsule aqueous solution and pyrolysis characteristics of flavour nanocapsule.

Flavour plays an important role and has been widely used in many products. Usually, the components of flavour are volatile and the sensory perception can be changed as a result of volatilization, heating, oxidation and chemical interactions. Encapsulation can prevent the loss of volatile aromatic ingredients, provide protection and enhance the stability of the core materials. This work concentrated on production of a transparent lavender flavour nanocapsule aqueous solution. The results showed that a transparent lavender flavour microcapsule aqueous solution can be produced using hydroxypropyl-ß-cyclodextrin (HP-ß-CD) as wall material. The combination and interaction of flavour and wall materials were investigated by pyrolysis. Pyrolysis characteristics and kinetic parameters of the flavour nanocapsule were determined. During thermal degradation of blank HP-ß-CD and flavour-HP-ß-CD inclusion complex, three main stages can be distinguished. Due to the vaporization of lavender flavour encapsulated in HP-ß-CD, the thermogravimetric (TG) curve of blank HP-ß-CD shows a leveling-off from room temperature to 269 °C, while the TG curve of flavour-HP-ß-CD inclusion complex is downward sloping in this temperature range. The kinetic parameters are helpful in understanding the mechanism of molecular recognition between hosts and guests.

Optimization and application of headspace-solid-phase micro-extraction coupled with gas chromatography-mass spectrometry for the determination of volatile compounds in cherry wines.

A simple, rapid and solvent-free multi-residue method has been developed and applied to confirm and quantify a series of volatile compounds in five cherry wines by gas chromatography coupled with mass spectrometry (GC-MS). Four parameters (e.g., coating material of fiber, temperature and time of extraction, and addition of sodium chloride in the solution) of headspace solid-phase micro-extraction (HS-SPME) were optimized, resulting in the best extraction condition including 50/30 µm DVB/CAR/PDMS fiber, 45 min and 50 °C of SPME, and 2g of sodium chloride addition in the wine during the extraction. The SPME had LODs and LOQs ranging from 0.03 to 7.27 µg L(-1) and 0.10 to 24.24 µg L(-1) for analytic compounds, respectively. Repeatability and reproducibility values were all below 19.8%, with mean values of 12.7% and 10.5%, respectively. Regression coefficients (R(2)) of detective linearity of the standard curves was higher than 0.9852. Moreover, relative recoveries of analytical targets were achieved in a range of 60.7-125.6% with good relative standard deviation values (≤20.6%). In addition, a principal component analysis (PCA) was used to analyze the aroma profiles of the wines, which indicated that five samples were distinctly divided into two groups based on their different geographical origins and volatile compounds.

Study of production and pyrolysis characteristics of sweet orange flavor-ß-cyclodextrin inclusion complex.

Flavor plays an important role and has been widely used in foods. Encapsulation can prevent the loss of volatile aromatic ingredients, provide protection and enhance the stability of the flavor. Kinetic and thermodynamic parameters are helpful in understanding the mechanism of molecular recognition between hosts and guests. This work focused on the study of production of a sweet orange flavor-ß-cyclodextrin (CD) inclusion complex, and investigated the combination of flavor and ß-CD by thermogravimetric analysis. Pyrolysis characteristics, kinetic and thermodynamic parameters of the flavor-ß-CD inclusion complex were determined. The results showed that the flavor-ß-CD inclusion complexes can form large aggregates in water. During thermal degradation of blank ß-CD and flavor-ß-CD inclusion complex, three main stages can be distinguished. The thermogravimetric (TG) curve of blank ß-CD shows a leveling-off from room temperature to 250°C, while the TG curve of flavor-ß-CD inclusion complex is downward sloping in this temperature range.

A review of the preparation and application of flavour and essential oils microcapsules based on complex coacervation technology.

This paper briefly introduces the preparation and application of flavour and essential oils microcapsules based on complex coacervation technology. The conventional encapsulating agents of oppositely charged proteins and polysaccharides that are used for microencapsulation of flavours and essential oils are reviewed along with the recent advances in complex coacervation methods. Proteins extracted from animal-derived products (gelatin, whey proteins, silk fibroin) and from vegetables (soy proteins, pea proteins), and polysaccharides such as gum Arabic, pectin, chitosan, agar, alginate, carrageenan and sodium carboxymethyl cellulose are described in depth. In recent decades, flavour and essential oils microcapsules have found numerous potential practical applications in food, textiles, agriculturals and pharmaceuticals. In this paper, the different coating materials and their application are discussed in detail. Consequently, the information obtained allows criteria to be established for selecting a method for the preparation of microcapsules according to their advantages, limitations and behaviours as carriers of flavours and essential oils.

Characterization of aroma compounds of Chinese famous liquors by gas chromatography-mass spectrometry and flash GC electronic-nose.

Aroma composition of five Chinese premium famous liquors with different origins and liquor flavor types was characterized by gas chromatography-mass spectrometry (GC-MS) and flash gas chromatographic electronic nose system. Eighty-six aroma compounds were identified, including 5 acids, 34 esters, 10 alcohols, 9 aldehydes, 4 ketones, 4 phenols, and 10 nitrous and sulfuric compounds. To investigate possible correlation between aroma compounds identified by GC-MS and sensory attributes, multivariate ANOVA-PLSR (APLSR) was performed. It turned out that there were 30 volatile composition, ethyl acetate, ethyl propanoate, ethyl 2-methyl butanoate, ethyl 3-methyl butanoate, ethyl lactate, ethyl benzenacetate, 3-methylbutyl acetate, hexyl acetate, 3-methyl-1-butanol, 1-heptanol, phenylethyl alcohol, acetaldehyde, 1,1-diethoxy-3-methyl butane, furfural, benzaldehyde, 5-methyl-2-furanal, 2-octanone, 2-n-butyl furan, dimethyl trisulfied and 2,6-dimethyl pyrazine, ethyl nonanoate, isopentyl hexanoate, octanoic acid, ethyl 5-methyl hexanoate, 2-phenylethyl acetate,ethyl oleate, propyl hexanoate, butanoic acid and phenol, ethyl benzenepropanoate, which showed good coordination with Chinese liquor characteristics. The multivariate structure of this electronic nose responses was then processed by principal component analysis (PCA) and hierarchical cluster analysis (HCA). According to the obtained results, GC-MS and electronic nose can be used for the differentiation of the liquor origins and flavor types.

Pyrolysis characteristics of bean dregs and in situ visualization of pyrolysis transformation.

Biomass is an important renewable and sustainable source of energy. Waste products from biomass are considered as attractive feedstocks for the production of fuel. This work deals with the pyrolysis of bean dregs, a biomass waste from soybean processing industry. A technique has been developed to study bean dregs pyrolysis by in situ visualization of bean dregs transformation in a quartz capillary under a microscope using a charge-coupled device (CCD) camera monitoring system. The technique enables us to observe directly the processes and temperatures of bean dregs transformation during pyrolysis. In situ visualization of reaction revealed that how oily liquids are generated and expulsed concurrently from bean dregs during pyrolysis. Pyrolysis characteristics were investigated under a highly purified N(2) atmosphere using a thermogravimetric analyzer from room temperature to 800 °C at different heating rates of 10, 30 and 50 °C/min. The results showed that three stages appeared in this thermal degradation process. The initial decomposition temperature and the peak shifted towards higher temperature with an increase in heating rate. Kinetic parameters in terms of apparent activation energy and pre-exponential factor were determined.

Management of acquired bronchobiliary fistula: A systematic literature review of 68 cases published in 30 years.

AIM: To outline the appropriate diagnostic methods and therapeutic options for acquired bronchobiliary fistula (BBF). METHODS: Literature searches were performed in Medline, EMBASE, PHMC and LWW (January 1980-August 2010) using the following keywords: biliobronchial fistula, bronchobiliary fistula, broncho-biliary fistula, biliary-bronchial fistula, tracheobiliary fistula, hepatobronchial fistula, bronchopleural fistula, and biliptysis. Further articles were identified through cross-referencing. RESULTS: Sixty-eight cases were collected and reviewed. BBF secondary to tumors (32.3%, 22/68), including primary tumors (19.1%, 13/68) and hepatic metastases (13.2%, 9/68), shared the largest proportion of all cases. Biliptysis was found in all patients, and other symptoms were respiratory symptoms, such as irritating cough, fever (36/68) and jaundice (20/68). Half of the patients were treated by less-invasive methods such as endoscopic retrograde biliary drainage. Invasive approaches like surgery were used less frequently (41.7%, 28/67). The outcome was good at the end of the follow-up period in 28 cases (range, 2 wk to 72 mo), and the recovery rate was 87.7% (57/65). CONCLUSION: The clinical diagnosis of BBF can be established by sputum analysis. Careful assessment of this condition is needed before therapeutic procedure. Invasive approaches should be considered only when non-invasive methods failed.

Raman spectra of amino acids and their aqueous solutions.

Amino acids are the basic "building blocks" that combine to form proteins and play an important physiological role in all life-forms. Amino acids can be used as models for the examination of the importance of intermolecular bonding in life processes. Raman spectra serve to obtain information regarding molecular conformation, giving valuable insights into the topology of more complex molecules (peptides and proteins). In this paper, amino acids and their aqueous solution have been studied by Raman spectroscopy. Comparisons of certain values for these frequencies in amino acids and their aqueous solutions are given. Spectra of solids when compared to those of the solute in solution are invariably much more complex and almost always sharper. We present a collection of Raman spectra of 18 kinds of amino acids (L-alanine, L-arginine, L-aspartic acid, cystine, L-glutamic acid, L-glycine, L-histidine, L-isoluecine, L-leucine, L-lysine, L-phenylalanine, L-methionone, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine, L-valine) and their aqueous solutions that can serve as references for the interpretation of Raman spectra of proteins and biological materials.

Kinetics of amino acid production from bean dregs by hydrolysis in sub-critical water.

Amino acids play an important physiological role in all life-forms and can be recovered from bean dregs waste using sub-critical water hydrolysis. This work deals with the hydrolysis kinetics of bean dregs. Kinetics was conducted in a temperature range of 200-240°C using a 300-ml stainless steel batch reactor. Since the reaction kinetics in sub-critical water is very complicated, a simplified kinetic model to describe the hydrolysis of bean dregs is proposed: a single consecutive reaction. The differential equations resulting from the model were fit to experimental data to obtain kinetic rate constants. By means of the Arrhenius plot, the activation energy as well as the pre-exponential factor was determined. A good agreement between the simplified model and the experimental data was obtained. The kinetic parameters provided useful information for understanding the hydrolysis reaction of bean dregs. The experimental results show that the best hydrolysis technology is: reaction temperature 200°C, reaction time 20 min. Under this condition, the total amino acid yield reaches 52.9%. Based on the results, this method could become an efficient method for bean dregs liquefaction, producing valuable amino acid.