Application of principal component analysis to chemical characteristics of Mahon cheese

 The chemical composition of the seven existing types of Mahon cheese, manufactured under the “Mahon” cheese Appellation of Origin, were studied. Of the cheeses, four were industrial (fresh, half-ripened, ripened and old-ripened) and three were traditionally manufactured (half-ripened, ripened and old-ripened). The chemical parameters were evaluated using ANOVA, Tukey’s multiple range test and principal component (PCA) analyses. Significant differences were found between Mahon cheeses ripened for different times in terms of moisture and non-protein nitrogen (NPN) contents (p <0.001); these differences were found to be independent of the manufacturing methodology, i.e. industrial or traditional. The ash and fat contents of industrially manufactured cheeses were significantly different from those in traditionally manufactured cheeses (p <0.001). PCA reduced chemical variables to two independent components: the first principal component was high in moisture, NPN content and water activity; the second, in NaCl, ash and fat contents. These results indicate that the seven types of Mahon cheese described by the “Mahon” cheese Appellation of Origin can be differentiated by their chemical characteristics. Received: 4 April 1997 / Revised version: 4 July 1997     

Effects of controlled atmosphere storage and low-dose irradiation on potato tuber components affecting acrylamide and color formations upon frying

The effects of normal and controlled atmosphere combinations on tuber components responsible for acrylamide formation were studied during prolonged storage at 9±1 °C using the tubers of “Agria” and “Russet Burbank.” The effects of low-dose irradiation (50, 200 Gy) prior to normal atmosphere storage were also studied. There was only a limited increase in the concentrations of sugars during 6 month of storage under normal atmosphere conditions. Low-dose irradiation slightly decreased the rate of sweetening in the tubers. The potential of acrylamide formation remained almost the same; however, the loss of firmness became clearer during 6 month of storage under normal atmosphere conditions. Controlled atmosphere storage in which O₂ was deficient to a sufficient respiration increased the concentrations of sugars, and thus, the potential of acrylamide formation in potatoes upon frying at 170 °C for 10 min. The sum of glucose and fructose concentrations showed a good correlation (r ²∼0.90) with the potential of acrylamide formation for both cultivars.     

Biogenic amines in meat inoculated with Lactobacillus sake starter strains and an amine-positive lactic acid bacterium

 Formation of biogenic amines in minced meat inoculated with two Lactobacillus sake starter culture strains and an amine-positive lactic acid bacterium (G-106) was studied. The effects of these starter cultures against the formation of biogenic amines were dependent on the kind of decarboxylating microorganisms present in the raw material and the effects were different for each amine. Starter strains maintained the microbiological quality of the meat kept at 20°C for 7 days, and inhibited the formation of putrescine and cadaverine. They also inhibited the formation of phenylethylamine caused by G-106 when it was present at an initial level of 10² colony-forming units (CFU)/g. However, the formation of tyramine was not affected and the formation of histamine was increased when starters were used in samples inoculated with G-106. Received: 4 December 1996 / Revised form: 27 January 1997     

Biogenic amines in meat inoculated with Lactobacillus sake starter strains and an amine-positive lactic acid bacterium

 Formation of biogenic amines in minced meat inoculated with two Lactobacillus sake starter culture strains and an amine-positive lactic acid bacterium (G-106) was studied. The effects of these starter cultures against the formation of biogenic amines were dependent on the kind of decarboxylating microorganisms present in the raw material and the effects were different for each amine. Starter strains maintained the microbiological quality of the meat kept at 20°C for 7 days, and inhibited the formation of putrescine and cadaverine. They also inhibited the formation of phenylethylamine caused by G-106 when it was present at an initial level of 10² colony-forming units (CFU)/g. However, the formation of tyramine was not affected and the formation of histamine was increased when starters were used in samples inoculated with G-106. Received: 4 December 1996 / Revised form: 27 January 1997     

Endogenous formaldehyde level of foods and its biological significance

 Formaldehyde was measured in different food samples based on its reaction with hydralazine to form s-triazolo-(3,4-α)-phthalazine(Tri-P). Formaldehyde reacts with hydralazine under mild acidic conditions to form Tri-P. The reaction products were separated by reversed-phase, high-performance liquid chromatography. The method of sample preparation and chromatography are reviewed and the analytical method validated. Using the discussed methods we measured formaldehyde levels in 23 animals and 22 vegetable and fruit samples. Formaldehyde levels were one and a half times higher in vegetable samples compared to meat samples. Received: 23 December 1996 / Revised version: 17 March 1997     

A Validated HPLC-DAD Method for Routine Determination of Ten Phenolic Compounds in Tomato Fruits

Awareness of consumers about phenolic compounds and their positive role in human nutrition is increasing nowadays. Therefore, studies with large number of samples for determination of the effect of agronomic or processing conditions on phenolic composition of foods are arising on importance. This work describes a validated HPLC-DAD method for simultaneous quantification of ten intact phenolic compounds, including phenolic acids and flavonoids (4-caffeoylquinic acid, 5-caffeoylquinic acid, dicaffeoylquinic acids I and II, tricaffeoylquinic acid, quercetin trisaccharide, quercetin-3-O-rutinoside, kaempferol-3-O-rutinoside, naringenin, and naringenin chalcone), in tomato fruit extracts. Extraction treatment and chromatographic system were chosen with the aim of minimizing time, equipment, and disposable costs in laboratory. Method was applied for characterization, for the first time, of three Spanish tomato cultivars (“Caramba”, “Montserrat”, and “Pera de Girona”) which showed significant differences in their phenolic content. Validation parameters for the compounds with commercially available standards (91–105% accuracy; 68–97% recovery; 5–90 μg/kg LOQ; <10% RSD repeatability; >0.99 r ² for calibration curves; 5,500–115,000 N) can be considered suitable for practical purposes in high-throughput analysis.     

Bioactive components and antioxidant capacity of Chinese bayberry (<Emphasis Type="Italic">Myrica rubra</Emphasis> Sieb. and Zucc.) fruit in relation to fruit maturity and postharvest storage

Total phenolics, flavonoids, anthocyanins, cyanidin-3-O-glucoside (Cy-3-glu) and antioxidant capacity of Chinese bayberry fruit (Myrica rubra Sieb. and Zucc.) differed among the four cultivars “Baizhong” (white), “Fenhong” (pink), “Wuzhong” (red) and “Biqi” (dark red). Antioxidant capacity determined by both the ferric reducing antioxidant power (FRAP) assay and 2,2-diphenyl-2-picrylhydrazyl (DPPH^.) radical scavenging capacity was significantly correlated with the antioxidant components in the fruit, and directly related to fruit color. Cy-3-glu accounted for at least 82, 38, and 12% of the total antioxidant capacity in “Biqi”, “Wuzhong” and “Fenhong” fruits, respectively. No detectable Cy-3-glu was found in “Baizhong” fruit. Greater fruit maturity was associated with higher levels of all the bioactive components and antioxidant capacity. Significant increases were also found during postharvest storage of “Biqi” fruit held at either 20 °C for 2 days or 0 °C for 5 days. However, these levels decreased during a 2-day shelf-life at 20 °C after 5 days at 0 °C. These results show that storage and shelf-life conditions are important if health-based bioactive components of bayberry fruit are to be maintained after harvest.     

Impedance measurements to assess microbial contamination of ready-to-use vegetables

 An impedometric method for estimating the microbial load of ready-to-use vegetables, either inoculated or not inoculated with antimicrobial-producing lactic acid bacteria, was investigated. The correlation (R ²) between total mesophilic bacteria (log cfu/g) and time to detection was 0.889. A discrepancy was observed for the impedometric measurement of low coliforms counts, particularly in samples inoculated with lactic acid bacteria and stored at 8°C for 6 days. Time to detection for the two groups of microorganisms was less than 11 h. Received: 25 November 1996 / Revised version: 23 January 1997     

Impedance measurements to assess microbial contamination of ready-to-use vegetables

 An impedometric method for estimating the microbial load of ready-to-use vegetables, either inoculated or not inoculated with antimicrobial-producing lactic acid bacteria, was investigated. The correlation (R ²) between total mesophilic bacteria (log cfu/g) and time to detection was 0.889. A discrepancy was observed for the impedometric measurement of low coliforms counts, particularly in samples inoculated with lactic acid bacteria and stored at 8°C for 6 days. Time to detection for the two groups of microorganisms was less than 11 h. Received: 25 November 1996 / Revised version: 23 January 1997     

Changes in the chemical and functional properties of protein fibers by reaction with carbonyl compounds. Part II. Reaction of arginine and amido groups. Quantitative determination of reacting carbonyl groups

The arginine content of Vicia faba protein/casein(1:1)-fibers is made to decrease up to 50 per cent by reaction with glyoxal and up to 15 per cent by dialdehyde starch. Formaldehyde and glutaric dialdehyde do not influence the arginine content. The content in amido groups is not affected by the reaction with glyoxal, dialdehyde starch, formaldehyde, and glutaric dialdehyde. The reaction of the fiber protein with the quoted aldehydes increases in the following order: glyoxal < formaldehyde < dialdehyde starch < glutaric dialdehyde and is dependent on the concentration of the specific aldehyde.     

Isolation of a novel peptide from silkworm pupae protein components and interaction characteristics to angiotensin I-converting enzyme

The hydrolysate of silkworm protein produced by acid protease (Asperqiius usamii NO. 537) contains angiotensin I-converting enzyme inhibitory activity. Four kinds of protein components were identified in silkworm pupae protein, albumin, globulin, prolamin and glutelin, and the albumin was in the highest quantity. The four component proteins were then further hydrolyzed by acid protease under the same conditions, and the hydrolysate of albumin was determined with the highest ACE inhibiting effect, followed by globulin. Albumin could be easily hydrolyzed under the aqueous conditions, and the overall albumin protein content was higher than the other three protein components. The peptide sequence “APPPKK” was determined by LC–MS/MS separation and X!Tandem software identification. The peptide inhibitory activity was 0.047 mg/mL in IC₅₀. The peptide was bonded to Asp⁴¹⁵, Asp⁴⁵³, Thr²⁸², His ³⁵³, Glu¹⁶² in hydrogen bond to ACE active pocket by flexible docking calculations. This study indicates that silkworm pupae protein may be a suitable candidate to explore functional foods with anti-hypertension bioactivity.     

Evaluation of the effect of centrifugation using a barycentric method

 The effect of centrifugation of liquid polydisperse systems is determined quantitatively by measuring the resultant displacement of the centre of mass. The physical quantity “specific displacement of the centre of mass” is proposed as a new characteristic of the precipitation of this systems. A device is described which can be used to measure the displacement of the centre of mass of a suspension or emulsion after centrifugation. The advantages of the proposed method and device are pointed out. Received: 18 August 1997 / Revised version: 20 November 1997     

Stereoisomeric flavour compounds LXXVI: direct enantioseparation, structure elucidation and structure-function relationship of 4-tert-butyl-α-methyldihydrocinnamaldehyde

 Using enantioselective gas chromatography and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin (DIAC-TBDMS-β-CD) as the chiral stationary phase, the direct enantioseparation of 4-tert-butyl-α-methyldihydrocinnamaldehyde was achieved. The threshold values and odour characteristics of the enantiomers were investigated by enantioselective gas chromatography/olfactometry. In order to elucidate stereochemical features, the carbonyl-function was oxidized to the corresponding acid and diastereomeric amides were generated with (S)-2-amino-2-phenyl-ethanol [L(+)-α-phenylglycinol] as the enantiopure reagent. After separation and isolation by high-performance liquid chromatography, absolute configurations were deduced from X-ray structure elucidation of a pure stereoisomer. Amide cleavage, reduction and selective oxidation yielded the enantiomers of 4-tert-butyl-α-methyldihydrocinnamaldehyde. Received: 7 October 1996 / Revised version: 18 November 1996     

Isolation and identification of 3,4-dideoxypentosulose as specific degradation product of oligosaccharides with 1,4-glycosidic linkages

Although it is well known that arginine side chains of proteins become extensively modified in the course of the advanced Maillard reaction, to date only few possible arginine derivatives are known. Recently, N-δ-[5-(3-hydroxypropyl)-4-oxo-imidazolon-2-yl]-l-ornithine (PIO) was identified as a new arginine derivative, formed exclusively from the side-chain of peptide-bound arginine and degradation products of oligosaccharides with 1,4-glycosidic linkages. In the present paper, a previously unknown C5 dicarbonyl compound, namely 3,4-dideoxypentosulose (3,4-DDPS), was isolated by means of semi-preparative RP-HPLC as the corresponding chinoxaline after heating lactose followed by trapping the 1,2-dicarbonyl compound with o-phenylenediamine. Identification was achieved using LC–MS as well as ¹H- and ¹³C-NMR. Synthesis of 3,4-DDPS as the corresponding 2-hydroxy-dihydro-pyran-3-one proved the structure analysis. During heating of N-α-hippuryl arginine (Hip-Arg) with 2-hydroxy-dihydro-pyran-3-one, Hip-PIO was formed as the only arginine derivative. The formation of 3,4-DDPS from oligosaccharides with 1,4-glycosidic linkages follows a new and quantitatively important pathway of carbohydrate degradation in foods.     

Progress in wine authentication: GC–C/P–IRMS measurements of glycerol and GC analysis of 2,3-butanediol stereoisomers

The determination of glycerol and 2,3-butanediol by photometric or enzymatic methods is well established. This paper reports on the direct assessment of glycerol and stereoselective analysis of 2,3-butanediol isomers in wine using capillary GC without any derivatisation. A “model wine” and commercially available wines, as well as wines of definite origin were investigated. The contents of glycerol and 2,3-butanediol and the ratio of (R,R)- and meso-2,3-butanediol were determined. Capillary GC has proved to be a reliable alternative in glycerol assessment from wine, thus a GC-IRMS method for authenticity assessment of glycerol was developed.δ¹³C_V‐PDB and δ¹⁸O_V‐SMOW multi-element IRMS-analysis of glycerol, an important by-product of wine fermentation, is reported. For that reason glycerol, extracted from a self-prepared “model wine”, from wines of definite origin, as well as commercially available wines, was investigated. Furthermore, the ¹⁸O/¹⁶O and ¹³C/¹²C isotope ratios of commercial glycerols from different origins were determined. In addition fermentation experiments with beet and cane sugar, and with grape juices were carried out. In order to check the influence of water on the oxygen isotope ratios, water from different places in Germany was used in the fermentation experiments with cane and beet sugar.     

Minor Strecker degradation products of phenylalanine and phenylglycine

Phenylalanine (Phe) was oxidized with either potassium peroxodisulfate or glyoxal. Volatile reaction products were isolated and analyzed by GC/FID and GC/MS. Nonvolatile products were derivatized with diazomethane and analyzed by the same methods. Under the experimental reaction conditions (equimolar ratio of reactants, 100vv°C, 1 h), the decomposed amount of amino acid was 28% (glyoxal) and to 74% (peroxodisulfate), respectively. Sixteen volatile compounds having their origin in the amino acid molecule were detected and identified. The major compound was phenylacetaldehyde (208 mg/peroxodisulfate, 11 mg/glyoxal), followed by bibenzyl, benzaldehyde, and benzyl alcohol. Other products were present in concentrations lower then 0.1 mg. For comparison, the lower homologue of Phe, phenylglycine, was oxidized under the same conditions. Analogously, 21% (glyoxal) and 65% (peroxodisulfate) of this amino acid decomposed, predominantly to benzaldehyde (242 mg/peroxodisulfate, 95 mg/glyoxal). A minor decomposition product was benzoic acid (2.9 mg), other ten products arose at levels lower then 0.1 mg. The formation of minor oxidation products during Strecker degradation of amino acids suggests the importance of radical reactions. In systems comprising glyoxal, ten heterocyclic compounds arose as minor products (3-furancarbaldehyde, 5-methyl-2-furancarbaldehyde, 2-pyrrolcarbaldehyde, 3-phenylpyridine, pyrazine, methyl-, ethyl-, vinyl-, and 2-phenylethylpyrazine).     

Application of synchronous fluorescence spectroscopy for the determination of some chemical parameters in PDO French blue cheeses

The present study was aimed at investigating the potential of using synchronous fluorescence spectroscopy (SFS) coupled with multivariate statistical analyses for the determination of some chemical parameters (pH, fat, dry matter, protein and soluble nitrogen) of French blue-veined cheeses belonging to four brands (FA-Fourme d’Ambert, FM-Fourme de Montbrison, BA-Bleu d’Auvergne and BC-Bleu des Causses). Three partial least square regression models with leave-one-out cross-validation technique were considered in the present study. The first one including the “Fourme cheeses” (FA and FM), the second one including the “Blue cheeses” (BA and BC) and the last one including the 4 Blue-veined cheeses (FA, FM, BA and BC). The models qualities were investigated principally by the R ² (coefficient of determination) and the RPD (ratio of standard deviation to root-mean-square error of cross-validation) factors. The results showed that SFS succeeded to predict ash and protein in Blue (ash: R ² = 0.90, RPD = 3.17; protein R ² = 0.80, RPD = 2.24) or Fourme cheeses (ash: R ² = 0.81, RPD = 2.29; protein R ² = 0.81, RPD = 2.26) when considered individually, while SFS failed to predict all the physicochemical parameters when the two groups were analyzed jointly.     

The texture of low calorie grape juice jelly

 In this work the production of grape juice jellies with a low methoxyl pectin was studied. Availability of this kind of jelly will increase the range of dietetic products and is a promising alternative use for grapes surplus to the needs of the enological industry. The formulation of the jellies was optimized by response surface methodology (RSM), using as independent variables total sugar content (20 – 50°Brix), low methoxyl pectin content (0.5 – 1.5%) and processing temperature (55 – 90°C) at five levels. The dependent variable was the overall balance (B), a response obtained from sensory analysis. B was chosen from a series of sensory attributes evaluated by a test panel and the data treated by principal component analysis (PCA). The resulting polynomial equation (R ² = 0.92) showed the maximum value for B to occur for a jelly produced with 38°Brix of total sugar, 1.2% of low methoxyl pectin and a processing temperature of 69°C. The sensory-optimized jelly was objectively characterized for texture and dynamic rheological behaviour. Received: 2 October 1996 / Revised version: 7 January 1997     

Environmental pH determines citrulline and ornithine release through the arginine deiminase pathway in Lactobacillus fermentum IMDO 130101

Sourdough lactic acid bacteria (LAB) need to be adapted to a highly acidic and, therefore, challenging environment. Different mechanisms are employed to enhance competitiveness, among which conversion of arginine into ornithine through the arginine deiminase (ADI) pathway is an important one. A combined molecular and kinetic approach of the ADI pathway in Lactobacillus fermentum IMDO 130101, a highly competitive sourdough LAB strain, identified mechanisms with advantageous technological effects and quantified the impact of these effects. First, molecular analysis of the arcBCAD operon of 4.8 kb revealed the genes encoding the enzymes ornithine transcarbamoylase, carbamate kinase, arginine deiminase, and an arginine/ornithine (A/O) antiporter, respectively, with an additional A/O antiporter 702.5 kb downstream of the ADI operon. The latter could play a role in citrulline transport. Second, pH-controlled batch fermentations were carried out, generating data for the development of a mathematical model to describe the temporal evolution of the three amino acids involved in the ADI pathway (arginine, citrulline, and ornithine) as a result of the activity of these enzymes and transporter(s). Free arginine in the medium was converted completely into a mixture of citrulline and ornithine under all conditions tested. However, the ratio between these end-products and the pattern of their formation showed variation as a function of environmental pH. Under optimal pH conditions for growth, citrulline release and some further conversion into ornithine was observed. When growing under sub-optimal pH conditions, ornithine was the main product of the ADI pathway. These kinetic data suggest a role in adaptation of L. fermentum IMDO 130101 to growth under sub-optimal conditions.     

Authentication of three valuable <Emphasis Type="Italic">Dendrobium</Emphasis> species by adapter ligation-mediated allele-specific amplification

The adapter ligation-mediated allele-specific amplification (ALM-ASA) has been applied to authenticate three valuable Dendrobium species (Dendrobium aphyllum, Dendrobium devonianum and Dendrobium officinale) and their corresponding “Fengdou” foods samples. Three species-specific primers and a universal primer were designed. By using these primers, three amplification products are 198 bp (D. aphyllum), 250 bp (D. devonianum) and 310 bp (D. officinale) in length, which were clearly distinguishable on a 2.0% agarose gel. In addition, no band was observed with other 17 allied Dendrobium species of “Fengdou”. The results showed that ALM-ASA could be used to authenticate not only the three valuable Dendrobium species but related food products such as “Fengdou” foods by simultaneous detection of three-site nucleotide difference on rDNA internal transcribed spacer region.