Showing papers in "Lwt - Food Science and Technology in 1999"

Antioxidant activity of water extract of Harng Jyur (Chrysanthemum morifolium Ramat).

Abstract: The antioxidant activity of water extracts of Harng Jyur (Chrysanthemum morifolium Ramat) from four varieties, including Huang Harng Jyur (HHJ), Bai Harng Jyur (BHJ), Gan Harng Jyur (GHJ), and Kung Harng Jyur (KHJ), was investigated. The water extracts of the four Harng Jyur varieties showed strong antioxidant activity in linoleic acid and liposome model systems. Each extract at 20 mg exhibited 65.3–71.8% inhibition on malondialdehyde formation of rat liver homogenate in vitro, greater than 20 mg of tocopherol. A correlation established between the total phenolic compounds and antioxidant activity, yielded a coefficient of r2=0.934, 0.997, 0.758 and 0.983 for HHJ, BHJ, GHJ and KHJ respectively. Each extract of the four Harng Jyur varieties had effective activities as radical scavengers, metal chelators, and active oxygen scavengers. These properties may be the major reasons for the inhibition of lipid peroxidation. Of the four varieties, BHJ was the most significant antioxidative material. No mutagenicity in the four varieties was found in Salmonella typhimurium TA 98, either with or without S9 mix.

Comparison of Dietary Fibre from By-products of Processing Fruits and Greens and from Cereals

Abstract: The dietary fibre constituents of apple, pear, orange, peach, artichoke and asparagus dietary fibre concentrates and of wheat and oat bran were measured using an enzymatic-gravimetric method. In addition, the water-holding capacity of the dietary fibre concentrates and cereals was estimated by centrifugation. Dietary fibre concentrates of fruits and greens showed a high content of total dietary fibre (35–59 g/100 g), insoluble dietary fibre (21–44 g/100 g) and soluble dietary fibre (10–14 g/100 g), referred to dry matter. The soluble fraction was found to be greater dietary fibre concentrates of fruits and greens than in wheat and oat bran (3–4 g/100 g). Measurements of water-holding capacity showed that dietary fibre concentrates of fruits and greens had a greater affinity for water than those from cereals.

Extrusion Cooking of Rice Flour and Amaranth Blends

Abstract: Response surface methodology was used to investigate the extrusion cooking and product properties of rice flour and amaranth blends in a CM45-F conical, counter-rotating twin-screw extruder. Three mixtures at a level of 20, 40 and 60 g/100 g amaranth were extrusion cooked using a central composite design with varied barrel temperature (150-190 °C), feed moisture (11-16 g/100 g wb), feed rate (15-35 kg/h), and screw speed (58-82 rpm). Pressure, torque, specific mechanical energy (SME), Brabender pasting properties, expansion of extrudate characterised by sectional (SEI) and longitudinal expansion (LEI), product density, breaking strength, and total colour change were determined. Increasing amaranth content in the blends increased die pressure, but decreased torque and SME. Increasing amaranth content caused an enormous decrease in the sectional expansion index (SEI) and increase in the breaking strength of extrudate. Well expanded rice-amaranth products with acceptable soft texture were at amaranth levels of 20-40 g/100 g. Optimal extrusion cooking conditions most likely to produce rice-amaranth products suitable for a puffed snack food were at high barrel temperature, low moisture, high screw speed, and feed rates in the range of 25-35 kg/h.

Microbial Biofilm in Food Processing

Abstract: In their natural environment microorganisms can survive massive changes even though they continually fight among themselves. In this environment the cells have to adapt to the conditions or die. Most cells survive by adhering to a surface after which they hide under a layer of polysaccharides. In time this becomes a biofilm where different kinds of microorganisms can live together. In the biofilm the microorganisms develop their own microenvironment in which their own species can live even though the conditions are not ideal. Besides protecting from the hostile environment the biofilm acts as a trap for acquiring nutrients. Biofilm formation causes problems in many branches of the food industry, where it can cause energy losses, reduce flow and heat transmission or block membrane pores. Both harmless microorganisms and humane pathogenic bacteria can form biofilms. Flow variations or cleaning can make pieces of this biofilm detach and spread in the process flow.

Properties of ultraviolet irradiated protein films

Abstract: Protein-based films were cast from film-forming solutions of wheat gluten, corn zein, egg albumin, and sodium caseinate. Control and ultraviolet (UV) irradiated (253.7 nm, 51.8 J/m 2 ) films were evaluated for tensile strength, total soluble matter, water vapor permeability, and Hunter L, a, and b color values. UV treatment increased tensile strength of gluten, zein, and albumin films suggesting the occurrence of UV radiation-induced cross-linking within film structures. For caseinate films, UV-curing did not affect tensile strength but substantially reduced total soluble matter. Small but significant decreases in total soluble matter also were noticed for UV-treated zein and albumin films. UV irradiation reduced water vapor permeability of albumin films but did not affect water vapor permeability of the other types of films. Gluten, albumin, and caseinate films had increased yellowness as a result of UV treatment. In contrast, UV treatment decreased the yellowness of zein films, possibly due to destruction of zein pigments by UV radiation.

Changes in starch microstructure on baking and staling of wheat bread

Abstract: The microstructure of starch in dough and in fresh and aged bread crumb was studied by light microscopy The samples were cryosectioned and stained with Light Green and iodine to localize protein and starch, respectively In dough a partial segregation of starch from the protein phase is observed On baking, starch was gelatinized and led to the formation of a continuous starch network The starch fraction itself was inhomogeneous and consisted of swollen and interconnected starch granules The two starch polymers, amylose and amylopectin, were found to phase separate and amylose was accumulated in the centre of starch granules Polarized-light microscopy of fresh bread crumb showed that starch gelatinization was accompanied by the loss of birefringence On ageing the bread crumb regained birefringence The combination of light microscopy in the bright-field and polarized mode allowed identification of the birefringent structures The most intense birefringence was observed in the amylose rich centre of starch granules, whereas the outer amylopectin rich zones showed slight birefringence It is concluded that the ordered structures result from the reordering of amylose and amylopectin It is hypothesized that the reorganization of the intra-granular amylose fraction enhances the rigidity of starch granules on bread staling

Properties of Peanut Protein Film: Sorption Isotherm and Plasticizer Effect

Abstract: The objectives of this study were to determine the effect of type and level of plasticizer on film properties and determine their sorption isotherms. Peanut protein films were formed by using four types of plasticizer (glycerin, sorbitol, polyethylene glycol and propylene glycol) at three levels (0.67, 1.17, 1.67 g/g of protein content). Sorption isotherms of peanut protein at pH 6.0, 7.5 and 9.0 were determined. Glycerin showed the best performance as a plasticizer compared to the others. The concentration of glycerin between 0.67 and 1.67 g/g of protein did not affect the water permeability and oxygen permeability. However, tensile strength decreased (from 5.14 to 4.10 MPa), with an increase of glycerin from 1.17 to 1.67 g/g of protein and percent elongation increased (from 105 to 164%) when glycerin increased from 0.67 to 1.67 g/g of protein. Peanut protein was very hydrophilic, the equilibrium moisture content of film increased sharply at pH 7.5 and 9.0 (0.602 and 0.939 and 0.621 to 1.083 g/g of dry matter, respectively) with an increase in relative humidity (RH) from 75 to 93% RH. Film thickness depended on the RH, and film at pH 6.0 showed the greatest change in film thickness with increasing RH.

A Low Cost Video Technique for Colour Measurement of Potato Chips

Abstract: A computer-based video image analysis system has been developed to quantify the colour of potato chips in L * a * b * colour space. This system is not sensitive to light intensity, and the light reflection effect from the undulating surface of the chips was not significant to the colour measurement. The presence of undesirable spots on the chip surface was also quantified. The sensitivity of the technique to separate ‘colours’ correlated well with the capability of the human eye. The technique shows encouraging potential for use in studying the colour and appearance of other kinds of products.

Validation of a Systematic Approach to Design Equilibrium Modified Atmosphere Packages for Fresh-Cut Produce

Abstract: A systematic approach is validated for designing equilibrium modified atmosphere (EMA) packages (1–5 mL/100 mL O2, 3–10 mL/100 mL CO2, balance N2) for fresh-cut produce (trimmed Brussels sprouts, shredded spinach, shredded chicory endives, shredded iceberg lettuce, grated carrots, complete heads of iceberg lettuce and a mixture of red, green and yellow bell peppers). The respiration rate is calculated by two mathematical methods based on measurements conducted at the same conditions (temperature, relative humidity, gas composition) as those created in the EMA packages. When the respiration rate, the fill weight and the package dimensions are known, the required transmission rate for O2and CO2of the packaging film is determined for each commodity based on steady state equations. New packaging films with high permeability for O2and CO2were tested in these experiments. A validation of the designed packages is necessary to complete this systematic approach and to determine the shelf-life of the EMA packaged fresh-cut produce.

Organic and phenolic acids in beer

Abstract: In a previous study we evaluated the effects of brewing on compounds potentially involved in the antioxidant defence system. The objectives of this paper were to determine organic acids and to characterize the quantity and quality of phenolic acids in four Italian lager beers. The data obtained on organic acids are in line with the values reported in the literature for malic, pyruvic, lactic, acetic, ketoglutaric, citric, succinic, citramalic and fumaric acid. Phenolic acid composition was determined using two different high-performance liquid chromatography (HPLC) methodologies: HPLC-ECD (amperometric electrochemical detection) and HPLC-DAD (photodiode array detection). The most common phenolic acid was found to be m-coumaric followed by ferulic, o-coumaric, p-coumaric and 3-OH-benzoic. Vanillic, chlorogenic, homovanillic, p-OH-benzoic, 2,6-dihydroxybenzoic, syringic, gallic, protocatechuic, caffeic and finally, 3,5-dihydroxybenzoic acids were present in small quantities. The amount of phenolic acids is quite low in absolute terms and in relationship to data available in the literature. Statistically significant differences were not found between the two different analytical methods utilized.

Effect of Heat Treatment and Particle Size of Different Brans on Loaf Volume of Brown Bread

Abstract: Brown bread was produced by adding bran (all of the same nominal particle size range) from 10 widely differing wheat samples to a common base white flour The different brans caused different levels of loaf volume depression In all cases, dry heat-treatment of the brans decreased total reducing substances, inactivated lipase and increased loaf volume and height However, the loaves still differed somewhat in volume A similar study was conducted with three bran fractions of different sizes (Pollard 075 mm 18 mm), from the same grist, to a common base white flour Smallest loaf volumes were obtained with Pollard and largest with Digestive Subjecting the brans to the heat-treatment, increased loaf volume However, smallest volumes were still obtained with Pollard Brans were also milled to a common maximum particle size (

Physical and Chemical Characteristics of Raspberry Pulp: Storage Effect on Composition and Color

Abstract: Raspberry pulp at different soluble solids contents was made from thawed fruit by milling, vacuum concentration (10–37°Brix), pasteurization and canning. The influence of storage at 4, 20, and 37°C was investigated. The variations in anthocyanin and ascorbic acid content and additional color indices, including Hunter parameters, were determined. Minor changes occurred when the raspberry pulp concentrate was stored at 4°C. While percent residual anthocyanin and ascorbic acid content decreased following first order reaction kinetics, increases in percent polymeric color followed near zero order kinetics and the index of polymeric color remained practically constant throughout the storage. Hunter ΔEvariation during storage was in accordance with the thermal degradation of anthocyanin as cyanidin-3-glucoside.

Postharvest browning of litchi fruit by water loss and its prevention by controlled atmosphere storage at high relative humidity

Abstract: Postharvest browning of litchi fruit caused by water loss was investigated in relation to anthocyanin content, polyphenol oxidase (PPO) activity, pH value, and membrane permeability. Total anthocyanin concentration decreased with pericarp desiccation. Fruit stored at 90% relative humidity (RH) had the lowest loss of total anthocyanins over the storage period, while total anthocyanin content of fruit stored at 60 and 70% RHs significantly declined. Polyphenol oxidase activity with 4-methylcatechol as a substrate tended to increase with reduced storage RH, but no activity towards anthocyanins was detected. Furthermore, in the presence of 4-methylcatechol, the oxidation of anthocyanins by PPO was observed. The pH value was initially low, and then increased with pericarp desiccation, which was associated with increased PPO activity. Conversely, the integrity of membrane systems, which increased with reduced storage RH and increased storage time, showed that membrane structure became more vulnerable. These results indicate that oxidation of both phenolic and anthocyanins by PPO seems to affect the response of litchi fruit to water loss in terms of browning, and suggest that substrate-enzyme contact should be emphasized as this could promote enzymatic reaction leading to browning. Storage at 1°C under controlled atmosphere (3–5% O2and 3–5% CO2) at 90% RH gave good browning control and fruit quality maintenance.

High Pressure Thawing of Fish (Whiting): Influence of the Process Parameters on Drip Losses

Abstract: Atmospheric thawing and pressure-assisted thawing were applied to frozen fish prior to heat treatment (80 °C/20 min). The influence of the pressure level (between atmospheric pressure and 200 MPa), of the freezing rate, of the pressurization rate, and of the pressure holding time was studied in comparison with a thawing process at atmospheric pressure. High freezing rate (0.77 vs.0.14 °C/min), high pressurization rate (100 vs. 42 MPa/min) reduced the thawing drip losses at a given pressure. A decrease in the drip volume for high pressure thawing compared to atmospheric thawing was obtained only by prolonging the pressure holding time. This parameter was most influential in reducing the drip loss. Electrophoresis analysis of thawing drips and of sarcoplasmic proteins of fish fillets showed a modification of the line 48 kDa proteins whose intensity decreased from 150 MPa.

Antimicrobial Food Packaging Materials from Poly(ethylene-co-methacrylic acid)

Abstract: A technique of combining poly(ethylene-co-methacrylic acid), PEMA, with benzoic acid and sorbic acid to form antimicrobial food packaging material was developed. Heat-pressed film was first modified with NaOH (1 mol/L) or HCl (1 mol/L) and then incorporated with benzoic acid and sorbic acid, respectively, by using acetone as a swelling agent. The incorporation of preservatives into fabricated antimicrobial films was confirmed by characterization of the specific vibrational stretching shown on the IR spectra of the resulting films. Sodium hydroxide and preservative-treated films exhibited dominantly antimicrobial properties in fungal growth inhibition tests, presumably due to the higher amount of preservatives released from the films (75 mg benzoic acid or 55 mg sorbic acid per g of film) than other types of films. Based on the results, we demonstrated that the combination technique with acetone as swelling agent was feasible to manufacture antimicrobial food packaging films.

Water and Fat Transfer Properties of Polysaccharide Films on Fried Pastry Mix

Abstract: This study investigated the use of edible films to reduce fat absorption in fried foods. The edible films studied were gellan gum, methyl cellulose and hydroxypropyl cellulose. All three films were found to reduce the fat absorption into the food by 50–91%; however, methyl cellulose reduced the fat more than other films. Gellan gum increased the water loss by about 100% while hydroxypropyl cellulose and methyl cellulose decreased the water loss by 30%. The fat and water diffusivities of the gellan gum film were increased with the increase in film thickness.

Heat transfer during frying of potato slices.

Abstract: The convective heat transfer coefficient during deep-fat frying of potatoes was determined at different temperatures. The temperature, 0.1 cm below the top and bottom surfaces of a 0.05×0.05×0.005 m potato sample was monitored over time. The thermal conductivity and specific heat of the sample were expressed as a function of time, and the data were analyzed using the heat transfer equation with an explicit finite difference method. Crust formation occurred primarily at the bottom surface of the potato slice. Therefore, the frying was examined at the bottom surface; before and after the crust formation. The convective heat transfer coefficient ranged between 300 to 335 W / m 2 °C for the top, and 450 to 480 W/m 2 °C for the bottom surface before crust formation. After crust formation, it varied between 70 to 150 W/m 2 °C for the bottom surface within the studied temperature range of 150 to 190 °C.

Freezing Kinetics of a Model Oil-in-Water Emulsion under High Pressure or by Pressure Release. Impact on Ice Crystals and Oil Droplets

Abstract: Oil-in-water emulsions stabilized by sodium caseinate were frozen by the following processes: (a) Cooling to −18°C at 207 MPa, followed by slow (approximately 9 min) pressure release (SPR) or fast (approximately 3 s) pressure release (FPR), then by a freezing plateau at −0.6°C; (b) Freezing under a constant pressure of 100 MPa, at −9°C (freezing under high pressure, FUP); (c) Control freezing at atmospheric pressure and −0.6°C (freezing at atmospheric pressure, FAP). In all cases, emulsion samples were frozen in a cylindrical tubing immersed in a propanediol/water mix at −29°C. Freezing kinetics, measured with T thermocouples inserted at the sample centre or the surface, indicated very slow freezing by FUP (due to a ΔT of only 20°C). Freezing by FPR produced the shortest freezing plateau. The pressure–temperature coordinates of the sample on the phase diagram of water, determined with a fast data acquisition system, revealed moderate or extensive supercooling before nucleation for SPR or FPR, respectively. Samples were fixed by freeze substitution and the imprints of ice crystals at different sample depths were examined by light microscopy. Ice crystals resulting from FPR were small, irregularly shaped and without specific orientation, while those from FUP were larger, needle-shaped, radially oriented and with a marked size gradient from sample surface to centre. Results are consistent with enhanced supercooling and uniform ice nucleation assumed to occur upon FPR. Pressure release from 300 MPa and −16.5°C gave similar results as from 207 MPa and −18°C, while FPR from 100 MPa and −8°C resulted in less nucleation, a longer freezing plateau and some needle-shaped crystals. None of the freezing processes significantly modified the size distribution of oil droplets, as determined on thawed emulsions.

Volatiles Produced by Staphylococcus xylosus and Staphylococcus carnosus during Growth in Sausage Minces Part II. The Influence of Growth Parameters

Abstract: Aseptic model minces inoculated with commercial samples of either Staphylococcus xylosus orStaphylococcus carnosus were prepared in accordance with an experimental design investigating the effect of seven parameters: fermentation temperature, pH, salt, nitrate, glucose, ascorbate, and the access of air. Volatiles produced by the cultures were collected during growth, identified and quantified. The data were analysed by partial least squares regression. The results showed that oxygen in general had more influence on the aroma producing capacity of Staphylococcus xylosus than ofStaphylococcus carnosus which was more affected by nitrate and glucose. The two strains differed mostly with regards to pH. Aroma production by both strains was strongly related to growth—either positively or negatively depending on compound. Potent aroma compounds such as methyl-branched aldehydes and acids arising from degradation of leucine, isoleucine and valine, and aromatic compounds arising from phenylalanine were produced in lower amounts when the bacteria grew well, that is, produced cell mass, whereas the opposite was the case for compounds such as sulphides and ketones.

Apple Juice Clarification Using Microfiltration and Ultrafiltration Polymeric Membranes

Abstract: The flux behavior of polyethersulfone (0.2 μ m), polyvinylidene fluoride (0.2 μ m), cellulose (0.2 μ m, 100 kDa, 30 kDa, 10 kDa), and polysulfone (0.2 μ m, 100 kDa, 30 kDa, 10 kDa) membranes was examined during dead-end filtration of apple juice. Membranes with molecular weight cut-off of 30 and 100 kDa had superior flux performance to 0.2 μ m or 10 kDa membranes. A crossflow system equipped with various tubular polymeric membranes was also used to clarify apple juice at a temperature of 50°C, a crossflow velocity of 3.3 m/s and a transmembrane pressure of 414 kPa. Steady state fluxes increased as the molecular weight cut-off increased from 9 to 200 kDa. When challenged with P. diminuta, log reduction values between 6 and 7 were obtained with the crossflow tubular polymeric system. Membranes between 20 and 200 kDa produced juices with similar initial characteristics that underwent comparable changes during storage at 4, 25 and 35°C over 4–16 wk. The impact of filtration through the 9 kDa membrane was however noticeable on the physico-chemical properties since the apple juice had a green tint, lower soluble solids, lower flavanol content, and experienced minimal changes in browning and turbidity.

Role of Selected Yeasts in Cheese Ripening: An Evaluation in Foil Wrapped Raclette Cheese

Abstract: The purpose of this study was to investigate selected yeasts (Galactomyces geotrichum, Pichia jadinii, Yarrowia lipolytica, Debaryomyces hansenii) for lactic acid utilization, lipolysis, proteolysis and flavour development in foil ripened Raclette cheeses. Foil ripening was chosen in order to exclude the influence of the surface flora. An unreplicated 24full factorial experimental design in two blocks of eight vats was used. In the mature cheeses, the lactic acid content was increased, probably as a result of increased lactic acid bacteria due to the release of yeast metabolites. Yeasts seemed to show either esterase or lipase activity. Furthermore, yeasts revealed peptidolytic activity leading to an increase in smaller peptides and free amino acids. Except for Gal. geotrichum, they also enhanced the formation of biogenic amines.Y. lipolytica was capable of improving the overall sensory characteristics of cheese, but all other species influenced the flavour rather negatively. Since hardly any viable yeasts were detectable in the mature cheeses, the action by yeasts could be attributed to enzymes released after cell lysis.

The structure of cold-set whey protein isolate gels prepared with Ca++

Abstract: The mechanism(s) of Ca2+-induced cold gelation of whey protein isolate was investigated. Kinetic data revealed that the rate constant of aggregation (20 g/L protein, 3°C) progressively increased as [CaCl2] was raised from 10 mmol/L to a maximum of 30 mmol/L, and then declined as [CaCl2] was raised to 120 mmol/L. This could be explained as the combined effect of charge dispersion and Ca2+-bridging caused by increasing [CaCl2]. Young modulus increased as protein was raised from 60–100 g/L w/v at each of the calcium levels tested (5–150 mmol/L). The calculated fractal dimension of the gels increased from 2.3 to 2.6 as a function of increasing [CaCl2]. This was also observed by scanning and transmission electron micrographs.

The Low Calorie Sweetener Stevioside: Stability and Interaction with Food Ingredients

Abstract: The stability of the low calorie sweetener stevioside during different processing and storage conditions, as well as the effects of its interaction with the water-soluble vitamins ascorbic acid, thiamin, riboflavin, pyridoxine and nicotinic acid, the organic acids acetic acid, citric acid, tartaric acid and phosphoric acid, the other common low calorie sweeteners saccharin, cyclamate, aspartame, acesulfame, neohesperidin dihydrochalcone, and caffeine in coffee and tea, were evaluated. Incubation of solid stevioside at elevated temperatures for 1 h showed good stability up to 120°C, whilst forced decomposition was noticed at temperatures exceeding 140°C. In aqueous solution stevioside was remarkably stable in a pH range of 2–10 under thermal treatment up to 80°C; however, under strong acidic conditions (pH 1), a significant decrease in the stevioside concentration was detected. Up to 4 h of incubation with individual water-soluble vitamins in aqueous solution at 80°C showed no significant changes with regard to stevioside and the B-vitamins, whereas a protective effect of stevioside on the degradation of ascorbic acid was observed, resulting in a significant delayed degradation rate. In the presence of other individual low calorie sweeteners, practically no interaction was found at room temperature after 4 months of incubation in aqueous media. Stability studies of stevioside in solutions of organic acids showed a tendency towards enhanced decomposition of the sweetener at lower pH values, depending on the acidic medium. In stevioside-sweetened coffee and tea, very few significant chances in caffeine content or in stevioside content were found.

Volatiles Produced by Staphylococcus xylosus and Staphylococcus carnosus during Growth in Sausage Minces Part I. Collection and Identification

Abstract: Aseptic model minces were inoculated with commercial samples of either Staphylococcus xylosus or Staphylococcus carnosus. Volatiles produced by the cultures were collected during growth by diffusive sampling onto adsorbent traps, identified by thermal desorption-gas chromatography-mass spectrometry and quantified by thermal desorption-gas chromatography-flame ionisation. The data were analysed by principal component analysis. The study showed that both starter cultures produced a large number of volatiles in concentrations of sensory importance. Almost all of the major volatiles resulted from amino acid degradation, suggesting that the effect of Staphylococcus starter cultures on flavour quality is much related to their ability of catabolizing amino acids. With the exception of diacetyl, acetoin and 2-methyl-1-butanol, both cultures formed the same volatiles. Diacetyl and acetoin were not produced by Staphylococcus carnosus and 2-methyl-1-butanol was not produced by Staphylococcus xylosus. The ketones, acetone, 3- and 4-methyl-2-pentanone, and the two sulphides, dimethyldisulphide and dimethyltrisulphide, were produced in higher amounts by Staphylococcus xylosus, whereas methyl-branched, short-chain aldehydes and acids were produced in higher amounts by Staphylococcus carnosus. 2-Pentanone, aromatic compounds and nitrogen-compounds were produced in similar amounts by both cultures.

Stability to Hydrolysis and Browning of Trehalose, Sucrose and Raffinose in Low-moisture Systems in Relation to Their Use as Protectants of Dry Biomaterials

Abstract: The aim of this study was to investigate the stability to hydrolysis and nonenzymatic browning at 45°C of low-moisture trehalose, sucrose and raffinose in model systems containing amino compounds in relation to their potential use as protectants of biomaterials. Sugar hydrolysis was negligible in trehalose systems and very low in raffinose. Hydrolysis was noticeable in sucrose systems, however, leading to browning development. Sucrose systems showed, by far, the fastest colour development, particularly in the presence of lysine and glycine as sources of amino groups. The results confirm the extraordinary stability of trehalose. Raffinose was also found to be quite resistant to hydrolysis, indicating that this molecule has low tendency to participate in Maillard reactions.

Fat Content and Homogenization Effects on Flavour and Texture of Mayonnaise with Added Aroma

Abstract: The influence of fat content (700 and 820 g/kg) and homogenization on the texture and flavour of mayonnaise with added citral (semi-polar) or pyroligneous acid (polar) was investigated. The quality of mayonnaise was described by sensory descriptive profiling. Mayonnaise containing 820 g fat/kg had the highest intensity of sour smell, sour taste, thickness and fattiness. Increased fat content, from 700 to 820 g/kg, did not significantly affect the perception of smoke flavour due to pyroligneous acid, or lemon flavour due to citral. Homogenization increased sweetness and whiteness, and depressed thickness and fattiness in mayonnaises with added pyroligneous acid.

Storage Stability of Freeze-dried Starter Cultures (Streptococcus thermophilus) as Related to Physical State of Freezing Matrix

Abstract: The temperature dependence for loss of acidification activity during storage of a freeze-dried skimmed milk based starter culture of Streptococcus thermophilus in a matrix of ascorbic acid, casein and sucrose or mannitol showed Arrhenius behaviour below the glass transition temperature (Tgas determined by differential scanning calorimetry), with an energy of activation depending on the sugar with 57 kJ/mol for sucrose and 40 kJ/mol for mannitol, but not on the initial concentration of sugar before freezing (60 g/kg or 120 g/kg of dry matter). For storage at or above Tg(Tgwas around 50 °C), loss of activity increased dramatically with non-Arrhenius temperature dependence. Mannitol based glasses yielded better protection for aerobic storage and this was probably due to better antioxidative properties.

The Behaviour of Starter Cultures in Concentrated Yoghurt (Labneh) Produced by Different Techniques

Abstract: Concentrated yoghurts were produced by fermenting milks concentrated by ultra-filtration and reverse osmosis, and by removing whey from batches of natural yoghurt using the same techniques. The choice of procedure influenced the chemical composition of the end-products and also, as indicated by the titratable acidities and acetaldehyde contents of the labnehs, the metabolic activity of the starter culture. Although the behaviour of the cultures varied with the total solids in the milk, the total colony counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp.bulgaricus recorded after 24 h at 4°C were similar in all samples. A taste panel assessment revealed a definite preference for labneh (230 g/kg total solids) produced at this concentration by ultra-filtration of natural yoghurt (160 g/kg total solids).

Dealcoholization of Wine. Behaviour of the Aroma Components during the Process

Abstract: The changes in the aromatic composition of a white wine during the dealcoholization process have been studied together with how the aromatic compounds accumulated in different condensers during the process. The dealcoholization was carried out in an industrial system working under vacuum continuously at 1000 L/h. Samples were taken every 10 min in two different sections of the system, where the volatile compounds were being condensed. Results show that esters and fatty acids do not need very low temperatures to condense and be recovered, whereas aliphatic alcohols need lower temperatures to condense due to their high volatility. The final product was lacking in almost all of the volatile compounds.

Identification of Compounds Contributing to Boiled Potato Off-flavour (‘POF’)

Abstract: Boiled potato off-flavour is a cardboard-like note, that develops within hours when boiled potatoes are stored Using a panel of four professional judges, it was verified that a clearly detectable off-flavour develops during the storage of boiled potatoes Two different isolation methods (direct extraction and vacuum distillation/extraction) in combination with GC-MS and GC-sniffing were applied to the same freshly boiled and stored boiled potatoes Eight compounds, (pentanal, hexanal, nonanal, (E)-2-octenal, 2,4-heptadienal, (E)-2-nonena, (E,E)-2,4-nonedienal and 2,4-decadienal) were appointed as potential contributors to the off-flavour, since these compounds could be detected during GC-sniffing, and increased in concentration during storage The eight compounds, that most probably appear as a result of lipoxygenase initiated oxidation of linoleic and linolenic acid during the boiling process, were quantified in freshly boiled and stored boiled potatoes