Showing papers in "Food Technology and Biotechnology in 2008"

Antibiotic resistance mechanisms in bacteria: biochemical and genetic aspects.

Abstract: Summary Since the discovery and subsequent widespread use of antibiotics, a variety of bacterial species of human and animal origin have developed numerous mechanisms that render bacteria resistant to some, and in certain cases to nearly all antibiotics. There are many important pathogens that are resistant to multiple antibiotic classes, and infections caused by multidrug resistant (MDR) organisms are limiting treatment options and compromising effective therapy. So the emergence of antibiotic-resistant pathogens in bacterial populations is a relevant field of study in molecular and evolutionary biology, and in medical practice. There are two main aspects to the biology of antimicrobial resistance. One is concerned with the development, acquisition and spread of the resistance gene itself. The other is the specific biochemical mechanism conveyed by this resistance gene. In this review we present some recent data on molecular mechanisms of antibiotic resistance.

Xylanases and Their Applications in Baking Industry

Abstract: Summary Xylan is the second most abundant polysaccharide and a major component of plant cell wall. Cereal xylans contain large quantities of L-arabinose and are therefore, often referred to as arabinoxylans. Xylanases are hydrolytic enzymes, which randomly cleave the b-1,4 backbone of this complex plant cell wall polysaccharide. Different species of Aspergillus and Trichoderma produce these enzymes. Xylanases are of great value in baking as they have been found to improve the bread volume, crumb structure and reduce stickiness. When xylanases are used at optimum levels, they play a significant role in increasing shelf life of bread and reduce bread staling. There is an increasing trend in baking industry towards the application of xylanases in bread production. This review discusses the application of xylanase in the bakery industry, alone and in combination with other enzymes when it shows synergism in the action with them.

Physicochemical Properties of Edible and Preservative Films from Chitosan/Cassava Starch/Gelatin Blend Plasticized with Glycerol

Abstract: Summary Edible films from chitosan, cassava starch, and gelatin plasticized with glycerol have been developed by casting method, and the effects of cassava starch (50, 100 and 150 g per 100 g of chitosan), gelatin (0, 25 and 50 g per 100 g of chitosan) and glycerol (21, 42 and 63 g per 100 g of chitosan) from the film solution on various properties of chitosan-based films have been studied using response surface methodology (RSM). The possible interactions between the major components were evaluated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The properties of the resulting chitosan-based blends for films were greatly influenced by the incorporation of cassava starch, gelatin and glycerol. The introduction of gelatin and gelatinized cassava starch suppressed the semicrystalline peaks of chitosan films. The amino peak of gelatin shifted from 1542 to 1559 cm –1 , and the NH and/or OH peak of gelatin, cassava starch and chitosan films shifted from 3384, 3414 and 3421, respectively, to 3422 cm –1 in the composite film. These results indicate that there was an interaction and molecular miscibility among the major components. The growth inhibition of phytopathogen on mango fruit surface indicated the efficiency of these coatings and they can be applied for the conservation of fresh or minimally processed fruits and vegetables.

Microbiological Production of Citric and Isocitric Acids from Sunflower Oil

Abstract: Summary The growth of wild type strain Yarrowia lipolytica VKM Y-2373 and its mutant Yarrowia lipolytica N 15 as well the biosynthesis of citric and isocitric acids on sunflower oil were studied. It was indicated that cell growth was associated with the simultaneous utilization of glycerol and free fatty acids produced during oil hydrolysis. The activities of enzymes of glycerol metabolism (glycerol kinase), fatty acid assimilation enzymes of glyoxylate cycle (isocitrate lyase and malate synthase) and citric acid cycle were comparatively assayed in Y. lipolytica grown on sunflower oil, glycerol and oleic acid. Glycerol kinase and enzymes of glyoxylate cycle were active during the whole period of cell cultivation on sunflower oil. Citric acid production and a ratio between citric and isocitric acids depended on both the strain used and the medium composition. It was revealed that wild type strain Y. lipolytica VKM Y-2373 produced almost equal amounts of citric and isocitric acids at pH=4.5 and predominantly accumulated isocitric acid at pH=6.0. The mutant Y. lipolytica N1 5 produced only citric acid (150 g/L with mass yield (YCA) of 1.32 g/g). Biochemical characteristics of mutant strain Y. lipolytica N 15 were discussed.

Production of Antioxidant Nutraceuticals by Solid-State Cultures of Pomegranate (Punica granatum) Peel and Creosote Bush (Larrea tridentata) Leaves

Abstract: Summary In this work, creosote bush (Larrea tridentata) leaves and pomegranate (Punica granatum) peels were characterized for their use as a source of antioxidants and a support in solid-state fermentation. This work focuses on the kinetic evaluation of physicochemical changes during the fungal fermentation of two tannin-rich plant materials, mainly on the polyphenolic content. Aspergillus niger GH1 was used in the fermentation processes, the cultures were monitored for 96 h. The content of proteins, crude fibres, lipids, reducing and total sugars was evaluated following the AOAC methods. Tannins were analyzed using a spectrophometric method. Biodegradation of ellagitannins was monitored kinetically and the accumulation of gallic and ellagic acids was determined by HPLC. Results demonstrated that pomegranate peel and creosote bush leaves are excellent supports for solid-state fermentation and sources of antioxidants.

Natural antioxidant constituents from selected aromatic plants and their antimicrobial activity against selected pathogenic microorganisms

Abstract: Summary Aromatic plants contain natural antioxidant constituents such as phenolic compounds, which have attracted a great deal of public and scientific interest because of their health-promoting effects as antioxidants Five plants, Filipendula ulmaria (meadow sweet), Crataegus monogyna (hawthorn), Polygonum aviculare (polygonum), Potentilla anserina (silverweed), and Pelargonium purpureum (little robin), have been examined in order to determine their phenolic composition Reversed-phase high performance liquid chromatography (RP-HPLC) was employed for the identification and quantification of phenolic compounds of the aforementioned plants Gas chromatography–mass spectrometry method (GC-MS) was also used for identification of phenolic compounds after silylation Analysis of the non-volatile and thermolabile phenolic compounds by GC-MS presupposes their conversion into volatile and thermotolerant derivatives The derivatization process was optimized against reagents, temperature and reaction time The antioxidant capacity was determined in dried plants and in their methanol extracts with the Rancimat test using sunflower oil as substrate Both pulverized plants and extracts showed antioxidant capacity Total phenolic content in the extracts was determined spectrometrically applying the Folin-Ciocalteu assay and it ranged from 72 to 282 gallic acid equivalents (GAE)/(mg/mL) Antimicrobial activity of the extracts against selected microorganisms was performed using the disk diffusion method Gram-(+) bacteria were more sensitive to the plant extracts than Gram-(–) bacteria

Investigation of Lipase Production by Milk Isolate Serratia rubidaea

Abstract: Summary Production of extracellular lipase in submerged culture of Serratia rubidaea has beeninvestigated. The lipase production was optimized in shake flask experiments. The obser-ved pH and temperature range optimum for maximum lipase production were 7–8 and30–40 °C, respectively. With a selected nitrogen source, casein ((6.5±0.015) U/mL) and soy-tone ((9.4±0.02) U/mL) were suitable substrates for accelerating lipase production. Theoptimized concentration of casein and soytone was 24 g/L ((9.95±0.02) U/mL) and 5 g/L((14.8±0.03) U/mL), respectively. The effect of carbon source on lipase production indi-cated that starch was suitable substrate to maximize lipase production ((15.60±0.20) U/mL)and the optimum concentration registered was 4 g/L ((17.46±0.20) U/mL). Investigatingthe effect of lipids and surfactants showed that the gingily oil ((20.52±0.20) U/mL) andTween 20 ((27.10±0.01) U/mL) were suitable substrates for maximizing lipase production,and the optimum concentrations registered were 15 mL/L ((23.15 ±0.24) U/mL) and 6 mL/L((34.20±0.01) U/mL), respectively. Partial purification of lipase indicated that the molecularmass of partially purified enzyme was 54 kDa.

Xylanase Production by Aspergillus niger LPB 326 in Solid-State Fermentation Using Statistical Experimental Designs

Abstract: Summary Xylanase was produced by Aspergillus niger LPB 326 cultivated on lignocellulosic substrate composed by sugarcane bagasse and soybean meal in solid-state fermentation. The effects of various variables were observed and optimized by applying statistical experimental designs. The best xylanase activity was obtained in a medium containing 10 g of sugarcane bagasse and soybean meal in the ratio of 65 and 35 %, respectively, moistened to 85 % of initial water content with a nutrient salt solution composed of (in g/L): CuSO4 0.4, KH2PO4 1.5 and CoSO4 0.0012, and incubated for 4 days at 30 °C. Under these optimized conditions, a xylanase activity of 3099 IU/g of dry matter was obtained.

Effect of medium composition on commercially important alkaline protease production by Bacillus licheniformis N-2.

Abstract: Summary Protease production by alkalophilic B. licheniformis N-2 was investigated in 50 mL of the growth medium consisting of (in g/L): glucose 10.0, soybean meal 10.0, K2HPO4 3.0, MgSO4·7H2O 0.5, NaCl 0.5 and CaCl2·2H2O 0.5 at pH=10. Different carbon and nitrogen sources in the form of fine powder of organic, inorganic and defatted meals were studied to select the suitable substrate for alkaline protease production. The highest level of alkaline protease (677.64 U/mL) was obtained in the medium containing glucose followed by soluble starch and wheat bran. Among various nitrogen sources, defatted soybean meal was found to be the best inducer of alkaline protease, while inorganic nitrogen sources in the form of ammonium salts repressed the enzyme activity up to 96 %. Thermostability studies showed that the enzyme in the presence of 10 mM Ca 2+ ions retained its residual activity up to 80 % even after incubation at 40 °C for 12 h. The enzyme was found stable over a broad range of pH (8–11) and lost 52 % of its residual activity at pH=12. After the treatment with Tween 20, Tween 45, Tween 65, Triton X-405, H2O2 and sodium perborate, each at 1.0 % concentration, the enzyme showed residual activity of 105, 82, 116, 109, 135 and 126 %, respectively. The application of alkaline protease for removal of blood stains from cotton fabric also indicates its potential use in detergent formulations.

Fungal Biodegradation of Tannins from Creosote Bush (Larrea tridentata) and Tar Bush (Fluorensia cernua) for Gallic and Ellagic Acid Production

Abstract: Summary In the present work, the production of two potent antioxidants, gallic and ellagic acids, has been studied using solid-state fermentation (SSF) of tannin-rich aqueous plant extracts impregnated in polyurethane foam. Extracts from creosote and tar bush were inoculated with Aspergillus niger PSH spores and impregnated in the polyurethane support. The kinetics of the fermentation was monitored every 24 h. The maximum biodegradation of hydrolysable and condensed tannins was, respectively, 16 and 42 % in creosote bush, and 40 and 83 % in tar bush. The maximal productions of gallic and ellagic acid (152 and 177 %, respectively) were reached with aqueous extracts of creosote bush. Tar bush extracts inoculated with A. niger PSH spores produced only gallic acid (92 %), while ellagic acid was not recovered after the fermentation process. Results demonstrated the potential use of these plants as a source for the production of antioxidants.

Optimization of the culture medium for the production of β-galactosidase from Kluyveromyces marxianus CCT 7082.

Abstract: Summary Seven strains of the genus Kluyveromyces were screened for b-galactosidase activity in a synthetic medium. Kluyveromyces marxianus CCT 7082 was selected as the best enzyme producer for optimization of the culture medium. A fractional factorial design 2 4–1 was used to determine the most relevant variables of the culture medium composition for the enzyme production. The parameters studied were the concentrations of lactose, yeast extract and (NH4)2SO4 as well as pH, and all were shown to have significant effects on the production of the enzyme. Based on the results from the first factorial design, lactose, yeast extract and (NH4)2SO4 concentrations were selected to be utilized in a 2 3 central composite rotatable design (CCRD). This led to a further optimization of the fermentation conditions to achieve higher enzyme activities, which reached 10.6 U/mL.

Investigation of microbial association of traditionally fermented sausages

Abstract: Summary The investigation included fermented sausages produced in the countries of west and south-east Europe, Greece, Bosnia and Herzegovina, Croatia, Hungary, Italy and Serbia. The sausages were produced in local meat industries in a traditional way without the use of starter cultures. Samples were collected from three production batches on day 0 and again after 2, 4, 7, 14 and 28 days. Microbiological analyses included the principal ingredients (meat, fat tissue), casings and additives (sugar, mixture of spices, salt), and the finished products. From all three production batches of fermented sausages from each individual country, 150 strains of lactic acid bacteria and 150 strains of coagulase-negative cocci were isolated. Biochemical characteristics of the isolated microorganisms were determined by API system (bioMerieux), i.e. by API 50 CHL and API ® Staph. Identification of all strains was made using the computer program APILAB Plus. From the hygienic standpoint, it is highly important that Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus were not found in the finished product. During all stages of investigation, lactobacilli and staphylococci prevailed.

Fruit Quality of New Early Ripening Strawberry Cultivars in Croatia

Abstract: Summary In this research fruit quality of seven early ripening strawberry cultivars (Clerry, Maya, Alba, Miss, Camarosa, Queen Elisa and Elsanta) during successive harvesting periods has been investigated. The following quality parameters were determined in the harvested fruits: dry matter, total soluble solids (TSS), pH, total acidity (TA), TSS/TA ratio, reducing sugars, sucrose, vitamin C, total anthocyanins, total phenolics (TP), nonflavonoids, flavonoids, antioxidant activity, and colour. Investigated cultivars differ significantly according to the basic chemical composition. The highest, statistically significant values of dry matter, soluble solids, TSS/TA ratio, vitamin C, total phenolics, nonflavonoids and antioxidant activity were determined for cultivar Elsanta. Among the other early ripening cultivars involved in the research, Alba and Maya had the lowest contents of dry matter, total soluble solids, total phenolics and nonflavonoids, reducing sugars and sucrose. The anthocyanin content was the highest in cultivars Camarosa, Miss and Maya; consequently, the most intensive colour was noted in the same cultivars. Parameters that determine fruit quality had lower values in all the investigated early ripening cultivars than in cultivar Elsanta; however, their quality was satisfactory.

Phytase Production Using Citric Pulp and Other Residues of the Agroindustry in SSF by Fungal Isolates

Abstract: Summary Phytases have important applications in human and animal nutrition because they hydrolyze the phytate present in legumes, cereal grains and oil seeds. This results in an increased availability of minerals, trace elements and amino acids as well as phosphate. Fifty potential phytase-producing fungal strains were isolated from a fertile soil obtained from the northern part of Parana State in Brazil and other alternative sources using a selective media. Thereafter phytase production was evaluated in solid-state fermentation using different residues from the agroindustry supplemented with a nitrogen source at 60 % of moisture after 96 hours at 30 °C. The highest phytase activity (51.53 units per gram of dry substrate, U/g) was achieved with citric pulp and the soil isolate FS3 in solid-state fermentation. Furthermore, treatment of the substrates prior to fermentation in order to reduce microbial contamination was shown to affect phytase production during solid-state fermentation. Heat treatment resulted in an increase of the concentration of inorganic phosphate, a well known repressor of microbial phytase production, and therefore in a reduction of phytase production. UV exposure of the substrate was shown to reduce microbial contamination without affecting phytase production.

Characterization of Volatile Compounds from Ethnic Agave Alcoholic Beverages by Gas Chromatography-Mass Spectrometry

Abstract: Summary Ethnic Agave alcoholic beverages such as raicilla, sisal, tequila, mezcal, bacanora, sotol and pulque have been analyzed by gas chromatography and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). There were 105 compounds identified, eleven were classified as major compounds and the others were classified as minor compounds. Seventeen minor compounds could be used as authenticity markers since they were beverage specific. Cluster analysis (CA) showed that Agave alcoholic beverages could be distinguished by multivariate analysis of major compounds; however, the analysis of minor compounds provided a better fingerprinting.

Maximization of Intracellular Lipase Production in a Lipase-Overproducing Mutant Derivative of Rhizopus oligosporus DGM 31: A Kinetic Study

Abstract: Summary Regulation and maximization of lipase production in a mutant derivative of R. oligosporus has been investigated using different substrates, inoculum sizes, pH of the medium, temperature, and nitrogen sources in shake flask experiments and batch fermentation in a fermentor. The production of intracellular lipase was improved 3 times following medium optimization involving one-at-a-time approach and aeration in the fermentor. Interestingly, intracellular lipase was poorly induced by oils, instead its production was induced by sugars, mainly starch, lactose, sucrose, xylose, glucose and glycerol. Dependent variables studied were cell mass, lipase activity, lipase yield, lipase specific and volumetric rate of formation. It was confirmed that lipase production in the derepressed mutant is sufficiently uncoupled from catabolite repression. The results of average specific productivities at various temperatures worked out according to the Arrhenius equation revealed that mutation decreased the magnitude of enthalpy and entropy demand in the inactivation equilibrium during product formation, suggesting that mutation made the metabolic network of the organism thermally more stable. The highest magnitudes of volumetric productivity (QP=490 IU/(L·h)) and other product attributes of lipase formation occurring on optimized medium in the fermentor are greater than the values reported by other workers. The purified enzyme is monomeric in nature and exhibits stability up to 80 °C and pH=6.0–8.0. Activation energy, enthalpy and entropy of catalysis at 50 °C, and magnitudes of Gibbs free energy for substrate binding, transition state stabilization and melting point indicated that this lipase is highly thermostable.

Characterisation and Classification of Croatian Honey by Physicochemical Parameters

Abstract: The aim of this study was to characterise 8 different monofloral/multifloral types of Croatian honey (a total of 254 samples – 2003, 2004, and 2005 harvesting seasons) based on 11 common physicochemical parameters (water content, total reducing sugar content, sucrose content, ash content, electrical conductivity, acidity, diastase and invertase activity, HMF content, proline content and optical rotation). Differences in the abovementioned parameters, established between the honey samples, are influenced by different factors, such as botanical origin, climate and regional circumstances. The results obtained within the frame of our study are as follows: 13.9 – 20.6 % for water content ; 61.0 – 77.0 % for total reducing sugars ; 0.0 – 10.7 % for sucrose content ; 0.01 – 1.13 % for ash content ; 0.11 – 1.62 mS/cm for electrical conductivity ; 5.0 – 37.7 mmol/kg for acidity ; 0.1 – 34.7 IN for invertase activity ; 6.2 – 42.3 DN for diastase activity ; 24.0 – 1020.8 mg/kg for proline content ; 0.4 – 99.8 mg/kg for hydroxymethyl-furfural (HMF) content, and -3.6 – 3.9 ˚ for optical rotation. Subsequent to the sample characterisation, results obtained with 2 monofloral [acacia (Robinia pseudoacacia) and chestnut (Aesculus hippocastanum)], and 2 multifloral (flower and meadow) honey types were subjected to the pattern recognition procedures. In this regard, unsupervised methods such as cluster and principal component analysis were employed, to the goal of evaluating the possibility of differentiation of Croatian honey stemming from different botanical origins, based on their physicochemical profile. Cluster analysis (CA) revealed the existence of two clusters, out of which the first correspondent to the best-grouped acacia honey, and the second correspondent to the dispersed group constituted of the remaining three honey types under investigation (chestnut, flower, and meadow). Principal component analysis (PCA), i.e. its first two components, stood for the average of 50.5 % of the data variance. PCA and cluster analysis had shown that physicochemical parameters are able to provide enough information to allow for the classification and distinction of the honey originating from four botanical origins under investigation (acacia, chestnut, flower, meadow).

A New Aroma Index to Determine the Aroma Quality of Roasted and Ground Coffee During Storage

Abstract: Summary The staling of ground roasted coffee blend was studied over one year of storage. Solid phase microextraction-gas chromatography-mass spectrometry analysis was carried out to identify and semi-quantify 40 volatile compounds. We focused on volatile compounds related to the ageing of coffee: methanethiol, propanal, 2-methylfuran, 2-butanone, 2,3-butanedione, 2-furfurylthiol and hexanal. Changes in sensory properties of coffee beverage prepared from the ground roasted coffee samples during storage in laminate packages (PET/ aluminium foil/PE) under air atmosphere, under nitrogen or in punctured packages were determined. Samples were stored at (23±2) °C and (40±10) % relative humidity. The reference coffee was packed similarly in laminate packages under nitrogen and stored at (–20±1) °C. Applying a statistical assessment of the results, we found the loss of most volatile compounds from all stored coffee samples, including even those stored under freezing conditions. The ratios of 2-methylfuran/2-butanone and methanethiol/hexanal proved useful indicators of staling. Our new proposed aroma index, the ratio of 2-furfurylthiol/ hexanal, proved to be the most effective, giving high correlation coefficients (R³0.80) with aroma freshness for coffee brews prepared from the ground roasted coffee stored under different conditions at room temperature.

Effect of different maceration treatments on free and bound varietal aroma compounds in wine of Vitis vinifera L. cv. Malvazija istarska bijela.

Abstract: Summary During a two-year study, the effect of different grape mash maceration treatments (skin contact at 20 °C for 10, 20 and 30 h) and cryomaceration (skin contact at 7 °C for 10, 20 and 30 h) on the concentration of free and bound monoterpenes and total phenols in Malvazija istarska wine (the most spread white wine variety in Istria) was monitored. Monoterpenic alcohols linalool, a-terpineol, citronellol, nerol and geraniol were determined by gas chromatography after isolation on octadecylsilica (C18) sorbent and elution with pentane/dichlorometane ratio of 2:1, while total phenols were determined spectrophotometrically with Folin-Ciocalteau reagent. Sensory evaluation of wines was performed using the Buxbaum method. The obtained results showed that linalool and geraniol are the most abundant monoterpenes in Malvazija istarska, and that grape mash maceration treatments cause significant increase of free and bound monoterpene concentrations compared to those in control treatment wine obtained without maceration. The content of phenols, which are subject to oxidation, was found to be significantly lower in wines produced by cryo-maceration treatments, while in those produced by maceration at 20 °C the concentration of total phenols increased proportionally with the duration of maceration, negatively influencing wine quality by causing higher colour intensity and bitter taste.

Antioxidant and acetylcholinesterase inhibiting activity of several aqueous tea infusions in vitro.

Abstract: Summary A study of antioxidant activity and acetylcholinesterase (AChE) inhibitory activity of aqueous tea infusions prepared from walnut (Juglans regia L.), peppermint (Menthapiperita L.), strawberry (Fragariaananassa L.), lemon balm (Melissa officinalis L.), sage (Salvia offici- nalis L.), and immortelle (Helichrysum arenarium (L.) Moench.) is presented here. Chemical composition of selected aqueous tea infusions was determined by high-performance liquid chromatography with photodiode-array method (HPLC-PDA), and the following phenolic compounds were identified as dominant: rosmarinic acid, gallic acid (not identified in walnut and sage), caffeic acid (in sage and peppermint), neochlorogenic acid, 3-p-couma- roylquinic acid and quercetin 3-galactoside (in walnut) and luteolin 7-O-glucoside (in sage). Antioxidant activity of the selected aqueous tea infusions was measured using low-density lipoprotein (LDL) oxidation method, 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging test, b-carotene bleaching method, and Rancimat method (induction pe- riod of lard oxidation). Strawberry and lemon balm aqueous infusions completely inhibi- ted LDL oxidation at the concentration of 0.005 g/L in the reacting system. Very long pro- longation of the lag phase was achieved with peppermint and sage aqueous infusions. All tested infusions in the concentration range of 0.05-2.85 g/L showed very pronounced ef- fect of DPPH scavenging activity (90-100 %) as well as the inhibition of b-carotene blea- ching (89-100 %). In pure lipid medium, used in Rancimat method, sage and immortelle at the concentration of 0.16 % (by mass) had the highest ability to inhibit lipid peroxidation process. Screening of the AChE inhibitory activity by Ellmans method showed that the strongest inhibition was obtained with walnut and strawberry aqueous infusions at the concentration of 1.36 g/L in the reacting system. The presented results suggest that natural antioxidants could be useful and merit further investigations in the treatment and preven- tion of Alzheimer's disease.

Evaluation of the effect of high pressure on naringin hydrolysis in grapefruit juice with naringinase immobilised in calcium alginate beads.

Abstract: Summary The reduction of bitterness in citrus juices would increase their acceptance by the consumer This reduction in grapefruit juices can be achieved as a result of an enzymatic process, with improved commercial value and maintenance of health properties The use of a cheap, simple and effective immobilisation method combined with high pressure can be a key asset in the debittering of citrus juices The aim of this study is the debittering of grapefruit juice under high pressure, with naringinase immobilized in calcium alginate beads Naringinase, an a-rhamnopyranosidase, hydrolyzes naringin (a flavanone glycoside and primary bitter component in grapefruit juice) to naringenin, which is tasteless High pressure can activate or inhibit enzymatic activities depending on the proteins and conditions The hydrolysis of naringin was first evaluated in model solution (acetate buffer 002 M, pH=40) and then in grapefruit juice In model solution, at 160 MPa and 37 °C, a 50 % increase in the concentration of reducing sugars was obtained when compared to the reaction at atmospheric pressure The higher naringenin concentration (33 mg/L) was obtained at 54 °C under high pressure of 200 MPa, which corresponds to a naringin reduction of 72 % in model solution, while at atmospheric pressure (01 MPa), the naringin reduction was only 35 % The decrease in naringin content can be directly correlated with the reduction in bitterness From the concentration of residual naringin, the percentage of reduction in bitterness was evaluated In grapefruit juice, a debittering of 75 % occurred with a pressure of 160 MPa at 37 °C for 20 minutes

A Multidisciplinary Approach to the Characterisation of Autochthonous Istrian Olive (Olea europaea L.) Varieties

Abstract: Summary The Istrian region (Croatia) has a long olive growing and oil producing tradition as well as evident biological diversity in local olive (Olea europaea L.) germplasm. The olive oil is one of the most important typical food products in Istria. Considering the current tendency of consumers to select typical regional products, there is a need to define Istrian autochthonous olive varieties and to characterize the specificity of related oils. The aim of this study is to apply a multidisciplinary approach for that purpose. Morphological and

Effect of the Addition of Blueberries on Selected Physicochemical and Sensory Properties of Yoghurts

Abstract: In this research, physicochemical and sensory properties of blueberries and sugar added to yoghurts have been investigated on the first, 10th and 20th day of storage in refrigerator. Samples were analyzed for pH, total solids, protein, fat, ash, viscosity, syneresis, Hunter's L, a, and b values, flavour, body, texture, appearance and colour. Blueberry and sugar mass fractions and storage time had a significant effect on the physicochemical and sensory properties of yoghurts. The addition of blueberries to yoghurt formula resulted in an increase in the syneresis and a decrease in the pH, fat, protein, ash, viscosity and whiteness values. The addition of sugar improved only the flavour of yoghurts. Panelists favoured samples with 25 % blueberries and 4 % sugar in terms of flavour, body, texture, appearance and colour.

Improvements in the Flavour of Soy Cheese

Abstract: Summary A review of biochemical and technological similarities and dissimilarities between soy cheese and Cheddar cheese is presented to provide guidelines for the improvements in the flavour of soy cheese. Processing technology as well as the final product of soy cheese have many similarities with Cheddar in terms of appearance, texture, mouth feel, chemical nature, biochemical processes, etc. Soy protein has many useful amino acids like Asp, Ile, Leu, Met, Phe, Trp, Tyr, Val, etc., which are precursors of flavouring compounds and the right choice of microbial cultures is necessary to benefit from them. Using low levels of sodium chloride, without the use of ethanol, and introducing new milk cheese starter and non-starter cultures like Lactococcus lactis ssp. lactis (formerly L. lactis ssp. lactis biovar. diacetylactis), Lactobacillus helveticus, Lactobacillus casei, Streptococcus lactis var. maltigenes and Lactococcus lactis ssp. cremoris that enhance flavour will be helpful to improve the flavour of soy cheese.

Amperometric Biosensor for D-Lactate Assay

Abstract: A carbon paste electrode biosensor for D-lactic acid analysis in biological samples was developed. D-lactate cytochrome c oxidoreductase from baker's yeast (EC 1.1.2.4) was used as biorecognition element of the electrode in combination with phenazine methosulphate (PMS)-Reinecke's salt precipitate as mediator. The enzyme was bound on paste due to Enzacryl using glutardialdehyde. The electrode response to D-lactate addition was linear in the concentration range of 0.015-100 mM. Limit of detection was equal to 56 mu M when signal vs. noise criterium (S/N=3) is considered. Specificity for only D-lactate was proven. Relative standard deviation of 6.6 % for 12 mM D-lactate was found. The biosensor exerts long-term stability and also good stability during repeated measuring cycles. The electrode has a good potential for use in practical samples.

Cysteine protease (Capparin) from capsules of caper (Capparis spinosa).

Abstract: Summary Proteases are enzymes that perform very important functions in organisms and are used for a variety of objectives in vitro. In recent years, proteases have been used for clinical, pharmaceutical (alimentary digestion, anti-inflammatory, etc.) and industrial applications (cheese production, meat tenderizing, leather tanning). In this research, a protease has been purified from capsules of caper (Capparis spinosa) and characterized. Caper plants have been used for food and medicine since ancient times. The plant grows abundantly in certain regions of Turkey. Ammonium sulphate fractionation and a CM Sephadex column were used for purification of the enzyme. The purification enzyme has an optimum pH=5.0 and its optimum temperature was 60 °C. The vmax and Km values determined by Lineweaver-Burk graphics were 1.38 mg/(L·min) and 0.88 mg/L, respectively. The purification degree and the molecular mass of the enzyme (46 kDa) were determined by SDS-PAGE and gel filtration chromatography. It was investigated whether the purified and characterized protease could cause milk to congeal or digest chicken and cow meat. The results show that protease can be used for industrial production.

Improvement of xylanase production by Cochliobolus sativus in submerged culture.

Abstract: The xylanase production by a new Cochliobolus sativus Cs5 strain was improved under submerged fermentation. The xylanase was induced by xylan and repressed by glucose, sucrose, maltose, xylose, starch and cellulose. Highest enzyme production (98.25 IU/mL) was recorded when wheat straw (4 % by mass per volume) was used as a carbon source after 120 h of incubation. NaNO3 increased xylanase production 5.4-fold as compared to the control. Optimum initial pH was found to be 4.5 to 5. The C. sativus Cs5 strain grown under submerged culture in a simple medium proved to be a promising microorganism for xylanase production.

Yeast Tolerance to Chromium Depends on Extracellular Chromate Reduction and Cr(III) Chelation

Abstract: Summary The sensitivity of the yeast Pichia guilliermondii ATCC 201911 (L2) to Cr(VI) and Cr(III) has been investigated. This yeast was demonstrated to have much higher resistance to Cr(III), compared to Cr(VI). At chromate level of 2.0 mM, an expanded lag phase in growth was observed, followed by the active phase of cell proliferation. During the growth arrest, a residual external chromate concentration decreased gradually to the nontoxic level, and the duration of this period was directly dependent on the initial Cr(VI) concentration in the medium, i.e. the higher the Cr(VI) level, the longer the growth delay. Thus, the tolerance of P. guilliermondii to chromate depends on its capacity for extracellular reduction of Cr(VI). As a product of chromate reduction, Cr(III) forms complexes with the components of culture liquid, which are not effectively adsorbed by the cells and do not repress the growth of P. guilliermondii. When urea is used as a nitrogen source, not only chromate reduction, but also Cr(III) chelation were shown to decrease, compared to the medium supplemented with ammonium sulphate. The experimental data confirm this concept of extracellular reduction of Cr(VI) as an important mechanism, which provides the resistance of yeast cells to chromate.

Expression of Aspergillus oryzae tannase in Pichia pastoris and its application in the synthesis of propyl gallate in organic solvent.

Abstract: Summary Gallic acid esters could be synthesized biologically by tannase in organic media, among which is propyl gallate, an antioxidant widely used as a food additive. Efficient intracellular expression of Aspergillus oryzae tannase was achieved in Pichia pastoris under the control of the AOX1 promoter, and the productivity of recombinant tannase was 960 U/L or 64 U/g dry mass. The recombinant P. pastoris was used to synthesize propyl gallate in organic solvent and the yield of propyl gallate was 53 %.