Effect of thermal and high pressure processes on structural and health-related properties of carrots (Daucus carota)

In the present study, the effect of thermal and equivalent high pressure processes on structural (texture and microstructure) and health-related (total β-carotene concentration, β-carotene isomerisation and β-carotene bio-accessibility) properties of carrots was investigated. Both a mild and strong pasteurisation process and a sterilisation process were considered.     

Precipitation of β-carotene microparticles from SEDS technique using supercritical CO2

This work investigates the application of the Solution-Enhanced Dispersion by supercritical fluids technique for the precipitation of β-carotene. The effect of pressure (8.0–12.0 MPa), temperature (293–313 K) anti-solvent flow rate (20–40 mL/min), solution flow rate (1–4 mL/min) and concentration of β-carotene in the dichloromethane solution (4 and 8 mg/mL) on the precipitation yield, particle morphology and particle size and size distribution was examined. Precipitated powders presented mean particle size varying from 3.2 μm to 96.8 μm with morphology of β-carotene microparticles changing from plate-like to leaf-like particles. The statistical analysis of the experimental results revealed that pressure, organic solution concentration and CO₂ flow rate had a significant effect on particle size. The precipitation yield was observed to be within the range of 71–94% and was statistically influenced by system temperature and pressure, and anti-solvent flow rate.     

Supercritical fluid extraction of β-carotene from crude palm oil using CO2

The aim of this study was to ascertain the influence of pressure, temperature and time on the supercritical fluid extraction of β-carotene from the crude palm oil. The operating conditions were shown as follows: pressures of 75, 125 and 175 bar, temperatures of 80, 100 and 120 °C and extraction time of 1, 3 and 5 h. The extracts were analyzed using UV spectroscopy at a wavelength of 450 nm. Then the experimental data was compared with the data obtained using a statistical method. The results from the model showed a good agreement with the experimental data. The results (obtained from the statistical model) demonstrate that a pressure of 140 bar, temperature of 102 °C and extraction time of 3.14 h are required to obtain optimum yield of β-carotene (1.028 × 10⁻²%) from the extraction process, however the maximum yield of the β-carotene (1.741 × 10⁻²%) was experimentally obtained at a pressure of 75 bar, temperature of 120 °C and extraction time of 1 h.     

Release and absorption of carotenes from processed carrots (Daucus carota) using in vitro digestion coupled with a Caco-2 cell trans-well culture model

The release and absorption (bioavailability) of carotenoids is a prerequisite for their nutritional impact. This can be strongly affected by the processing conditions used to prepare the food matrix that contains them. To determine the effect of processing on carotenoid bioavailability, homogenized, raw, blanched and cooked carrots were exposed to an in vitro gastric and intestinal digestion model. Final digest samples were placed onto a Caco-2 cell trans-well monolayer culture to mimic intestinal absorption. The results show that the cooked carrot puree consisting of primarily single plant cell particles had the highest release of carotenes, followed by blanched consisting primarily of plant cell clusters and raw carrot puree consisting of larger plant cell clusters. Absorption through the Caco-2 cell layer was the highest from the digesta of cooked carrot puree followed by the digesta of blanched carrot puree. This study demonstrates that thermal processing and/or mechanical homogenization to disrupt plant cell wall matrix enhances the in vitro bioavailability of carotenes from carrots.     

Heat-induced aggregation of β-lactoglobulin A and B with α-lactalbumin

β-Lactoglobulin A and β-lactoglobulin B were heated at 75°C in the absence and presence of α-lactalbumin, and the aggregation products were characterized by size exclusion chromatography in combination with multi-angle laser light scattering and electrophoretic techniques. α-Lactalbumin did not form aggregates when heated alone, but in admixture with β-lactoglobulin it was incorporated into both the disulphide-bonded and the hydrophobically associated aggregates as well as forming α-lactalbumin dimers and other oligomers. The presence of α-lactalbumin diminished the proportion of smaller aggregates and increased the number of very large aggregates within both variant protein mixtures. In the presence of α-lactalbumin, β-lactoglobulin A was converted into a series of disulphide-bonded and the hydrophobically associated aggregates more slowly, but with a greater proportion of hydrophobically associated aggregates, than β-lactoglobulin B. These patterns are similar to that when β-lactoglobulin A or B are heated on their own. These and other results indicate that the mechanism of aggregation of α-lactalbumin/β-lactoglobulin mixtures is governed by β-lactoglobulin.     

β-carotene content in sweet potato varieties from China and the effect of preparation on β-carotene retention in the Yanshu No. 5

To compare the β-carotene contents in different Chinese sweet potato (SP) varieties and to choose a variety of SP rich in β-carotene for the study of the effect of processing methods on β-carotene retention, β-carotene in thirteen varieties of sweet potato from China was measured by HPLC. The results showed that β-carotene contents were significantly correlated with SP flesh colours, with the orange-red fleshed SP varieties being higher in β-carotene.β-carotene contents in SP were affected by many factors, and this was demonstrated using the variety of Yanshu No.5, showing that the β-carotene contents in SP grown in different farming sites in the same area ranged from 53.2 to 84.3 mg kg^− 1 fresh weight. Moreover, β-carotene distributes unevenly in one SP root, with highest concentrations in the core. The β-carotene content was positively related to the root size.Five processing methods including boiling, steaming, microwave cooking, frying, and post steam-drying were simulated in the study to check their effects on the true retention of β-carotene in SP. Compared to boiling, steaming resulted in much more loss of β-carotene and microwave cooking resulted in the biggest loss of β-carotene among the five processing methods.

Industrial relevance

Orange-fleshed sweet potato can be prepared for sale and consumption, using methods that protect the β-carotene content. This can aid in promoting sweet potato as a staple food as well as a snack food for supplying vitamin A for both rural and urban populations. Prepared orange-fleshed sweet potato can contribute to alleviating vitamin A deficiency in China as well as other low-income countries.     

DETERMINATION OF α- AND β-AMYLASE IN MALT

The Analysis Committee of the European Brewery Convention carried out a collaborative trial on malts using the specific analysis methods for α- and β-amylase activities based on dyed substrates supplied by MegaZyme (Aust.) Pty. Ltd. The repeatability and reproducibility values for the methods were judged to be unsatisfactory and consequently the methods were not recommended for Analytica-EBC.     

Effects of Processing on the Reduction of β-ODAP (β-N-Oxalyl-L-2,3-diaminopropionic acid) and Anti-Nutrients of Khesari Dhal,Lathyrus sativus

Effects of different processing techniques on the neurotoxin, β-ODAP (β- N -oxalyl-L-2,3-diaminopropionic acid), and the anti-nutritional compounds (phytate, polyphenols, trypsin and amylase inhibitors, and lectins) within four lines of Lathyrus sativus (high-, medium- and low-ODAP, and so-called ODAP-free) were investigated. Soaking of seeds in various media reduced the contents of these compounds to a varying and significant extent; losses were higher in freshly boiled water, alkaline and tamarind solutions than after soaking in drinking water. The highest losses in boiled water (65–70%) were observed for β-ODAP, followed by trypsin inhibitors (42–48%) and polyphenols (30–37%). Ordinary cooking and pressure cooking of pre-soaked seeds were found to be most effective in reducing the levels of all the natural toxicants examined, whilst fermentation and germination were more effective in destroying both of the enzyme inhibitors (amylase inhibitors by 69–71%; trypsin inhibitors by 65–66%) than either phytates or polyphenols. Lectins were not affected by most of these processes except by pressure cooking and fermentation. Dehusking of pre-soaked seeds significantly reduced β-ODAP levels, but this reduction was lower for the anti-nutrients. These findings and the high water solubility suggest that a simple and effective means of detoxifying Lathyrus by removing this neurotoxic amino acid may be practicable.     

Fractionation and identification of ACE-inhibitory peptides from α-lactalbumin and β-casein produced by thermolysin-catalysed hydrolysis

The thermolysin catalysed hydrolysates of α-lactalbumin and β-casein were fractionated by size-exclusion chromatography (SEC) and reversed-phase high performance liquid chromatography (RP-HPLC) in order to identify the peptides responsible for the high ACE-inhibitory activity of these hydrolysates. The SEC fractionation separated many co-eluting peptides into different fractions allowing individual peptides to be isolated in one or two subsequent semi-preparative RP-HPLC fractionation steps. Five potent ACE-inhibitory peptides from α-lactalbumin were isolated. They all contained the C-terminal sequence -PEW, corresponding to amino acid residues 24–26 in α-lactalbumin, and had IC₅₀ values of 1–5 μm. From one SEC fraction of the β-casein hydrolysate two potent ACE-inhibitory peptides were isolated and identified as f58-76 and f59-76 of β-casein A2. They both contained IPP as the C-terminal sequence and had IC₅₀ values of 4 and 5 μm. From another SEC fraction a new but less ACE-inhibitory peptide from β-casein was identified (f192–196; LYQQP).     

ENZYMIC QUANTIFICATION OF (1→3) (1→4)-β-D-GLUCAN IN BARLEY AND MALT

A simple and quantitative method for the determination of (1→3) (1→4)-β-D-glucan in barley flour and malt is described. The method allows direct analysis of β-glucan in flour and malt slurries. Mixed-linkage β-glucan is specifically depolymerized with a highly purified (1→3) (1→4)-β-D-glucanase (lichenase), from Bacillus subtilis, to tri-, tetra- and higher degree of polymerization (d.p.) oligosaccharides. These oligosaccharides are then specifically and quantitatively hydrolysed to glucose using purified β-D-glucosidase. The glucose is then specifically determined using glucose oxidase/peroxidase reagent. Since barley flours contain only low levels of glucose, and maltosaccharides do not interfere with the assay, removal of low d.p. sugars is not necessary. Blank values are determined for each sample allowing the direct measurement of β-glucan in maltsamples.α-Amylasedoes not interfere with the assay. The method issuitable for the routineanalysis of β-glucan in barley samples derived from breeding programs; 50 samples can be analysed by a single operator in a day. Evaluation of the technique on different days has indicated a mean standard error of 0–1 for barley flour samples containing 3–8 and 4–6% (w/w) β-glucan content.     

Factors influencing the production of o/w emulsions stabilized by β-lactoglobulin–pectin membranes

A primary emulsion was prepared by homogenizing 10 wt% corn oil with 90 wt% aqueous β-lactoglobulin solution (0.5 wt% β-lg, pH 3 or 7) using a two-stage high-pressure valve homogenizer. This emulsion was mixed with aqueous pectin (citrus, 59% DE) stock solution (2 wt%, pH 3 or 7) and NaCl solution to yield secondary emulsions with 5 wt% corn oil, 0.225 wt% β-lactoglobulin, 0.2 wt% pectin and 0 or 100 mM NaCl. The final pH of the emulsions was then adjusted (3–8). Primary and secondary emulsions were ultrasonically treated (30 s, 20 kHz, 40% amplitude) to disrupt any flocculated droplets. Secondary emulsions were more stable than primary emulsions at intermediate pHs. Secondary emulsions prepared at pH 7 had smaller particle diameters (0.35 to 6 μm) than those prepared at pH 3 (0.42 to 18 μm) across the whole pH range studied, and also had smaller diameters than the primary emulsions (0.35 to 14 μm). Ultrasound treatment reduced the particle diameter of both primary and secondary emulsions and lowered the rate of creaming. The presence of NaCl screened the charges and thus the electrostatic interaction between biopolymer molecules and primary emulsion droplets. Secondary emulsions were more stable to the presence of 100 mM NaCl at low pHs (3–4) than primary emulsions. This study shows that stable emulsions can be prepared by engineering their interfacial membranes using the electrostatic interaction of natural biopolymers, especially at intermediate pHs where proteins normally fail to function.     

2‐Furoylmethyl amino acids,hydroxymethylfurfural, carbohydrates and β‐carotene as quality markers of dehydrated carrots

BACKGROUND: Processing of vegetables in the food industry usually includes dehydration as a preservation process. Industrial convective air drying of carrot can involve steam blanching of the raw product after peeling and cutting, and different stages of dehydration (first space, second space and final drying). Although the shelf‐life of carrot is significantly extended, important changes in its chemical composition can take place during dehydration since high temperatures and long times are used. This research is a preliminary study to evaluate the usefulness of β‐carotene, carbohydrates, hydroxymethylfurfural (HMF) and 2‐furoylmethyl amino acids (2‐FM‐AA) as quality markers of dehydrated carrots. RESULTS: A considerable decrease in β‐carotene and reducing carbohydrates was observed during dehydration. HMF, absent in raw carrots, increased during the whole drying process and the highest formation was found during the steam blanching stage. 2‐FM‐AA of lysine, arginine, γ‐aminobutyric acid and alanine were progressively originated up to the second space and decreased during the final drying. CONCLUSION: The combined use of HMF and 2‐FM‐AA seems to be advantageous for the assessment of the optimal processing conditions to obtain high‐quality dehydrated carrots. Copyright © 2008 Society of Chemical Industry     

Characterization of the Supermolecular Structure of Polydatin/6‐O‐α‐Maltosyl‐β‐cyclodextrin Inclusion Complex

Polydatin is the main bioactive ingredient in many medicinal plants, such as Hu‐zhang (Polygonum cuspidatum), with many bioactivities. However, its poor aqueous solubility restricts its application in functional food. In this work, 6‐O‐α‐Maltosyl‐β‐cyclodextrin (Malt‐β‐CD), a new kind of β‐CD derivative was used to enhance the aqueous solubility and stability of polydatin by forming the inclusion complex. The phase solubility study showed that polydatin and Malt‐β‐CD could form the complex with the stoichiometric ratio of 1:1. The supermolecular structure of the polydatin/Malt‐β‐CD complex was characterized by ultraviolet–visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffractometry (XRD), thermogravimetric/differential scanning calorimetry (TG/DSC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. The changes of the characteristic spectral and thermal properties of polydatin suggested that polydatin could entrap inside the cavity of Malt‐β‐CD. Furthermore, to reasonably understand the complexation mode, the supermolecular structure of polydatin/Malt‐β‐CD inclusion complex was postulated by a molecular docking method based on Autodock 4.2.3. It was clearly observed that the ring B of polydatin oriented toward the narrow rim of Malt‐β‐CD with ring A and glucosyl group practically exposed to the wide rim by hydrogen bonding, which was in a good agreement with the spectral data.     

Hydrolysis of β-glucosyl ester linkage of p-hydroxybenzoyl β- -glucose, a chemically synthesized glucoside, by β-glucosidases

To investigate the hydrolysis of glucosyl esters by β-glucosidase, p-hydroxybenzoyl β- -glucose (pHBG) was chemically synthesized. The hydrolytic activity of some β-glucosidases for pHBG was compared to that for p-nitrophenyl β-glucoside (pNPG). The Clavibacter michiganense and Flavobacterium johnsonae enzymes could hydrolyze pHBG and steviol glycosides which are natural glucosyl esters. The commercial β-glucosidase originating from Caldocellum saccharolyticum also hydrolyzes pHBG despite having no activity for steviol glycosides. The β-glucosidase from Aspergillus niger cleaved the glucosyl ester linkage much more weakly than the glucosidic linkage. The pH-activity profile for the hydrolysis of pHBG was similar to that of pNPG by the C. saccharolyticum β-glucosidase. The similar profiles for these substrates suggested that the active site for the glucosyl ester chemically resembles that for glucoside with respect to catalysis. Kinetic analysis of the C. saccharolyticum β-glucosidase for mixed substrates of pHBG and pNPG showed that the hydrolysis of pHBG competed with that of pNPG. This result indicated that there is only one active site for both the glucosyl ester and glucoside. Mass spectroscopic analysis of the hydrolysates of pHBG in H₂¹⁸O suggested that β-glucosidase hydrolyzes glucosyl esters between the anomeric carbon of glucose and the carbonyl oxygen, not between the carbonyl carbon and the carbonyl oxygen.     

Emulsifying properties and structural characteristics of β‐conglycinin and dextran conjugates synthesised in a pressurised liquid system

The purpose of this study was to characterise the Maillard reaction in a pressurised liquid system containing β‐conglycinin and dextran. The rate of browning and the free amino content in this liquid system, with an initial pH of 7.2, were measured after reaction under atmospheric pressure and at 10 MPa. The secondary and tertiary structures of the conjugates were analysed by circular dichroism, showing that the increased pressure accelerated the reaction rate of the free amino groups and reduced the rate of browning. Significant structural changes occurred in the tertiary structure of the conjugates. Additionally, the emulsifying properties of the β‐conglycinin–dextran conjugates produced were studied. The emulsifying properties of the conjugates produced at 10 MPa were higher than those made at atmospheric pressure.     

Cloning and Sequence Analysis of the estA gene encoding enzyme for producing (R)-β-acetylmercaptoisobutyric acid from Pseudomonas aeruginosa 1001

The estA gene encoding the enzyme that catalyzes the production of (R)-β-acetylmercaptoisobutyric acid from (R,S)-ester from Pseudomonas aeruginosa 1001, was cloned in Escherichia coli and its nucleotide sequence was determined, revealing the presumed open reading frame encoding a polypeptide of 316 amino acid residues (948 nucleotides). The overall A+T and C+G compositions were 32.59% and 67.41%, respectively. The amino acid sequence of the estA gene product showed a significant similarity with that of the triacylglycerol lipase from Psychrobacter immobilis (38% identity), triacylglycerol lipase from Moraxella sp. (36% identity), and two forms of carboxyl esterases from Acinetobacter calcoaceticus (17% and 17% identities). The deduced amino acid sequences have a pentapeptide consensus sequence, G-X-S-X-G, having an active serine residue, and another active site, dipeptides H-G, located at 70–100 amino acids upstream of the G-X-S-X-G consensus sequence.