Showing papers in "Lwt - Food Science and Technology in 2003"

Determination of in vitro antioxidant activity of fennel (Foeniculum vulgare) seed extracts

Abstract: In this study, the antioxidant activity of water and ethanol extracts of fennel (Foeniculum vulgare) seed (FS) was evaluated by various antioxidant assay, including total antioxidant, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, metal chelating activities and reducing power. Those various antioxidant activities were compared to standard antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol. The water and ethanol extracts of FS seeds showed strong antioxidant activity. 100 μg of water and ethanol extracts exhibited 99.1% and 77.5% inhibition of peroxidation in linoleic acid system, respectively, and greater than the same dose of α-tocopherol (36.1%). The both extracts of FS have effective reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. This antioxidant property depends on concentration and increasing with increased amount of sample. In addition, total phenolic compounds in the water and ethanol extracts of fennel seeds were determined as gallic acid equivalents. The results obtained in the present study indicated that the fennel (F. vulgare) seed is a potential source of natural antioxidant. Although, the tests presented here show the usefulness of FS extracts as in vitro antioxidants it still needs to be that this extracts show their activity in emulsions, biological systems, health implications or dry foods.

Antimicrobial activity of essential oils on the native microflora of organic Swiss chard

Abstract: The antimicrobial activity of several essential oils on the native microflora of Swiss chard was evaluated. The agar diffusion technique (paper disc) was used to establish, in a rapid way, the susceptibility of the native microflora to the different essential oils and to choose those with the greatest antimicrobial activity. An optical method (turbidimetry) and a microdilution method (plate count) were used to determine the minimum bactericidal concentration (MBC) and the minimum inhibitory concentration (MIC). Both methods produced similar results. The essential oils of Eucalyptus globules, Melaleuca alternifolia, Pimpinella anisum and Syzygium aromaticum presented the largest antimicrobial activity. For these oils, the MBC values were in the range of 0.093–1.5 mL/100 mL.

Extending shelf-life of minimally processed apples with edible coatings and antibrowning agents

Abstract: Effect of edible coatings in combination with antibrowning agents on minimally processed apple slices was studied during storage at 3°C for 2 week. To control initial respiration rate of apple slices, edible coatings were applied to cut apples as semipermeable barriers against air. Initial respiration rate showed a decrease by 5% and 20% in carrageenan (0.5 g/100 mL)-coated and whey protein concentrate (5 g/100 mL)-coated apples, respectively, at 25°C. Edible coatings in combination with antibrowning agents effectively prolonged the shelf-life of minimally processed apple slices by 2 week when stored in packed trays at 3°C. Addition of various antibrowning agents to these coating solutions was advantageous in maintaining color during storage. Addition of CaCl 2 (1 g/100 mL) significantly inhibited the loss of firmness. These edible coatings in combination with antibrowning agents also showed positive sensory analysis results and beneficial reduction of microbial levels. WPC (5 g/100 mL) containing ascorbic acid (1 g/100 mL) plus CaCl 2 (1 g/100 mL) was the most effective preservation treatment in terms of sensory quality after 2 week.

Evaluation of drying technologies for retention of physical quality and antioxidants in asparagus (Asparagus officinalis, L.)

Abstract: The objective of this research is to evaluate drying methods that have the potential of adding value to green asparagus especially for use as ingredient in instant foods or as a nutraceutical product. Five drying methods were used: namely, tray drying (TD), spouted bed (SB) drying, combined microwave and spouted bed drying (MWSB), Refractance Window (RW) drying and freezedrying. Asparagus spears with diameters between 9 and 12 mm were blanched in 85 � C water-bath for 3 min, slicedinto 2–4 mm thickness (or pureed for RW drying), then dried to moisture content less than 0.1 db. MWSB drying produced asparagus particles with good rehydration and color characteristics, and was the fastest among the methods where heated air was used. When using MWSB drying, the power level of 2 W/g and 60 � C heatedair resultedin highest retention of total antioxidant activity (TAA). TAA of asparagus was enhanced after RW and freeze-drying, with the TAA values being significantly higher than for heated air-drying methods. In all cases, the tip portion of asparagus retained more TAA after drying than either middle or basal parts. The highest amount of ascorbic acid was retained in the product after RW drying, followed by freeze-drying, MWSB and SB drying. TD resulted in the least retention of ascorbic acid.

Effect of thermal pasteurization on Valencia orange juice color and pigments

Abstract: Changes in carotenoid pigment content and juice color due to thermal pasteurization of Valencia orange juices were studied. Total carotenoid pigment content loss was significant (P

Effect of soaking and extrusion conditions on antinutrients and protein digestibility of legume seeds.

Abstract: The effects of soaking (in water for 16 h) and extrusion conditions including barrel temperature (140°C and 180°C) and feed moisture (18% and 22%) on antinutrients, total and phytate phosphorus and protein digestibility of whole meal of four kinds of legumes (peas, chickpeas, faba and kidney beans) were investigated. The results obtained indicated that the soaking and extrusion significantly decreased antinutrients such as phytic acid, tannins, phenols, α-amylase and trypsin inhibitors. Moreover, extrusion processing decreased the percentage of phytic acid phosphorus to total phosphorus. The in vitro protein digestibility of legume extrudates was also improved. Therefore, extrusion of legumes a priori soaked in water for 16 h is recommended to improve the nutritive value of these legumes in order to increase its utilization by human and animal when consumed directly or as an ingredient of certain meals.

Influence of high pressure on the color and microbial quality of beef meat

Abstract: An experimental design was used to study the effect of various pressure values (50–600 MPa) and holding times (20–300 s) on color and microbiological quality of bovine muscle (Biceps femoris). The experiments were conducted at 10°C. The pressure intensity is more significant than holding time for redness, total color difference and metmyoglobin content. Pressure higher than 300 MPa induces modifications of meat color parameters such a decrease of the total color difference (ΔE), a decrease in the total flora and a 1 week delay before microbial growth (520 MPa, 260 s). During the first 3 days of storage (4°C), the increase in redness is maintained for the 130 MPa samples while the redness of the 520 MPa samples decreases gradually, in relation to the increase of metmyoglobin. The cooking (1 h at 65°C) done after pressurization led to the disappearance of color differences observed between the nontreated and pressurized samples.

Sensitivity of four pathogenic bacteria to Turkish thyme and oregano hydrosols

Abstract: The two thyme ( Thymus vulgaris L. and Thymus serpyllum L.) and three oregano ( Origanum vulgare L., Origanum onites L. and Origanum majorana L.) hydrosols, widely used in food products and as drinks, were tested for their inhibitory effects against four pathogenic bacteria ( Escherichia coli ATCC 25922, E. coli O157:H7 ATCC 33150, Staphylococcus aureus ATCC 2392 and Yersinia enterocolitica ATCC 1501). Two principles were used in determining the antibacterial effects of spice hydrosols: inhibition zones were determined by paper disc diffusion method, and the bacteriostatic effects, bactericidal effects and the growth inhibition levels were studied as colony forming units (cfu) in broth cultures. All tested bacteria were inhibited by all of the spice hydrosols using paper disc diffusion method. According to serial dilution method, while all spice hydrosols at 10 and 25 mL/100 mL concentrations had generally bacteriostatic activities, the same hydrosols appeared to have bactericidal effects at concentrations above 50 mL/100 mL. The most sensitive of the bacteria against the spice hydrosols was S. aureus . In addition, the most inhibitive of the spice hydrosols on the four pathogenic bacteria were O. onites L. and O. majorana L.

Kinetics of quality change associated with potatoes stored at different temperatures

Abstract: Undesirable storage conditions lead to physical and chemical quality loss in stored potatoes, which affect their consumer acceptability. Studies aimed at quantifying the extent of those changes under different storage conditions are valuable for minimizing the deleterious effect on product quality. The objective of this study was to evaluate the quality change in stored potatoes and quantify the associated kinetic parameters (rate constants) and activation energy to help model the changes in potato quality as function of storage temperature and time. Potatoes were stored at five temperatures (4°C, 8°C, 12°C, 16°C and 20°C) and, at different storage times (at least 5 time intervals) samples were removed and evaluated for different quality parameters (physical: texture and color; chemical: ascorbic acid (AA), reducing sugars (RS), starch (S), total sugars (TS), total soluble solids, pH and titrable acidity (TA) and physiological: respiration rate). The results revealed that potatoes became softer and darker by passage of time, and higher temperature resulted in more rapid changes in the different quality parameters. Chemical changes during the storage were decreased AA, pH and S, and increased TA, RS and TS. Only small changes were observed with peroxidase and polyphenoloxidase activity. Respiration rate increased with temperature and duration of storage. In general, most changes were well described by some form of first-order rate. Temperature sensitivity of rate constants was adequately described by the Arrhenius model.

Efficacy of plant essential oils as antimicrobial agents against Listeria monocytogenes in hotdogs

Abstract: The purpose of this study was to evaluate the antimicrobial activity of different plant essential oils against Listeria monocytogenes , both in vitro and in a food system. Essential oils of thyme, clove, and pimenta were found to be most effective, based on disc diffusion experiments. Thyme and clove proved to be highly effective against L. monocytogenes in peptone water (1 g/l) and reduced the bacterial population below detection limits at concentrations of 1 ml/l. Experiments were also carried out in hotdogs of different fat content (zero-, low-, and full-fat) to evaluate the antimicrobial activity of essential oils against L. monocytogenes . Thyme essential oil reduced bacterial populations significantly ( P ⩽0.05) at 1 ml/l level in zero- and low-fat hotdogs, but not in full-fat hotdogs. At 10 ml/l level it reduced the bacterial population >1.3 log 10 cfu/g in zero-fat hotdogs, but was less effective in low- and full-fat hotdogs. Clove essential oil also exhibited antimicrobial activity at 1 ml/l in all hotdogs, and was more effective than thyme at 5 ml/l. However, increasing concentration to 10 ml/l did not result in significant ( P ⩽0.05) reduction of bacterial population. It is concluded that efficacy of essential oils was reduced in a food system due to interaction with food components.

Diagnosing the cause of proteolysis in UHT milk

Abstract: Proteolysis of UHT milk during storage at room temperature is a major factor limiting its shelf-life through changes in its flavour and texture. The latter is characterised by increases in viscosity leading in some cases to gel formation. The enzymes responsible for the proteolysis are the native milk alkaline proteinase, plasmin, and heat-stable, extracellular bacterial proteinases produced by psychrotrophic bacterial contaminants in the milk prior to heat processing. These proteinases react differently with the milk proteins and produce different peptides in the UHT milk. In order to differentiate these peptide products, reversed-phase HPLC and the fluorescamine method were used to analyse the peptides soluble in 12% trichloroacetic acid (TCA) and those soluble at pH 4.6. The TCA filtrate showed substantial peptide peaks only if the milk was contaminated by bacterial proteinase, while the pH 4.6 filtrate showed peptide peaks when either or both bacterial and native milk proteinases caused the proteolysis. Results from the fluorescamine test were in accordance with the HPLC results whereby the TCA filtrate exhibited significant proteolysis values only when bacterial proteinases were present, but the pH 4.6 filtrates showed significant values when the milk contained either or both types of proteinase. A procedure based on these analyses is proposed as a diagnostic test for determining which type of proteinase-milk plasmin, bacterial proteinase, or both-is responsible for proteolysis in UHT milk. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.

Effects of chitosan coating on shelf life and quality of fresh-cut Chinese water chestnut

Abstract: Application of chitosan coating to browning control and quality maintenance of fresh-cut Chinese water chestnut (CWC) was investigated. Fresh-cut CWC were treated with aqueous solution of 0.5, 1 or 2 g chitosan/100 mL, placed into trays over-wrapped with plastic films, and then stored at 4°C. Changes in color, total phenolic content and phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) activities were measured. The effects of chitosan coating on eating quality and overgrowth of spoilage organisms were also evaluated. Application of chitosan coating delayed discoloration associated with reduced activities of PAL, PPO and POD as well as lower total phenolic content, and slowed down the loss in eating quality associated with higher contents of total soluble solids, titrratable acidity and ascorbic acid of fresh-cut CWC. Disease development of the fresh-cut CWC-treated chitosan coating was also inhibited compared to the control. Increasing the concentration of chitosan coating markedly enhanced the beneficial effects. The results showed that application of chitosan coating effectively extended shelf life and maintained quality of fresh-cut CWC.

Effect of pre-drying on kinetics of moisture loss and oil uptake during deep fat frying of chickpea flour-based snack food

Abstract: Mass transfer kinetics of moisture outflow and oil uptake during deep fat frying of snack food prepared from a blend of chickpea flour and modified starch have been investigated. The effect of frying temperature and pre-fry drying has also been studied. The results indicated that an increase in the temperature of frying (150–200°C) caused an increase in mass transfer coefficient for moisture (0.045–0.096 s −1 ) as well as for oil (0.056–0.082 s −1 ). Pre-fry drying also had a significant effect on the deep fat frying. As the pre-fry drying time was increased (0–90 min) before frying at 175°C, it resulted in a decrease in kinetic coefficient for moisture transfer (0.056–0.039 s −1 ) as well as in kinetic coefficient for oil transfer (0.063–0.035 s −1 ). Based on the kinetics and sensory data, the optimum pre-fry drying and frying times were 40 min and 45 s, respectively, which resulted in 54% reduction in the oil content of the fried product, without compromising on the sensory quality characteristics.

Stable isotope ratios, major, trace and radioactive elements in emmental cheeses of different origins

Abstract: Twenty Emmental cheeses from six European regions (Allgau (D), Bretagne (F), Finland, Savoie (F), Switzerland and Vorarlberg (A)) were analysed for stable isotope ratios such as 13C/12C, 15N/14N, 18O/16O, D/H and 87Sr/86Sr, as well as major (Ca, Mg, Na, K), trace (Cu, Mn, Mo, I) and radioactive elements (90Sr, 234U, 238U). The discriminating potential of these parameters was evaluated using difference tests of mean values and principal component analysis (PCA). “Finland”, “Bretagne” and “Savoie” cheeses were well separated using δ13C-, δ15N-, δ2H- and δ87Sr-values. Concentrations of molybdenum and sodium allowed the groups “Switzerland”, “Vorarlberg” and “Allgau” to be separated. 90Sr activity was highly correlated with the altitude of the production zone. Using this parameter, “Finland” and “Bretagne” were separated from “Vorarlberg” cheese. The results of the current screening test will help selecting the best tracers of origin for the remainder of the project.

Characteristics of soybeans as affected by soaking conditions

Abstract: The water absorption of soybeans in soaking is directly related to the changes in textural characteristics and grinding properties of soybeans for processing. In this study, we determined the characteristics of water absorption, solid loss, and moisture content, textural characteristics and grinding properties of soybeans at four different soaking temperatures, 10°C, 20°C, 30°C, and 40°C, and various soaking times up to 8 h. We found that the solid loss increased significantly when the soaking temperature increased from 30°C to 40°C. The measured moisture data of soaked soybeans fitted well with the data predicted using Peleg's equation. Rupture force and maximum tangent and secant modulus measured by the compression test decreased as the moisture increased, up to 122%. The grinding property of soaked soybeans was related only to the final moisture content and not to the soaking conditions. High soaking temperature could significantly reduce the required soaking time. Based on these results, we recommend that soybeans be soaked to minimal final moisture content of 120% before grinding.

Changes in aromatic components of banana during ripening and air-drying

Abstract: Fresh and dried bananas were extracted by solid phase micro-extraction (SPME) and analysed by gas chromatography (GC). The effect of the geographic origin of the fruit on aromatic composition was first examined. Twelve aromatic compounds (2 alcohols, 9 esters and 1 phenol) were identified by GC-MS. The aromatic changes of Cavendish banana was then studied during ripening and drying. Seven volatile compounds, four among the previous 12 (Isoamyl alcohol, Isoamyl acetate, Butyl acetate and Elemicine) and three other nonidentified compounds were selected by olfactometric analysis as characteristics of banana smell. The seven selected aromatic compounds were analysed during convective air-drying at 40°C, 60°C and 80°C. The entraining of aromatic compounds by water vapor was the main mechanism that occurred during the first 2 h of drying. It is suggested that Maillard reaction products were developed at the end of drying at 80°C. Some compounds strongly decreased during drying (Isoamyls) whereas other nonidentified compounds were partly retained. Elemicine was found to be the most thermal resistant one. Changes in aromatic components were dependent on the moisture content of the pulp (Xpl) and on the air-drying temperature (Ta).

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Abstract: Yam tubers ( Dioscorea alata ) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.

Estimation of shelf-life of concentrated yogurt by monitoring selected microbiological and physicochemical changes during storage

Abstract: Labneh, produced by blending concentrated skim milk yogurt and cultured cream, was stored at 5°C, 15°C, or 25°C and changes in selected microbiological, physicochemical and sensory parameters were monitored during storage. Counts of lactic acid bacteria exhibited relatively small changes upon storage, at 5°C and 15°C, and decreased in samples at 25°C whereas total psychrotrophs, psychrotrophic yeasts and yeast and mold counts increased irrespective of storage temperature. pH decreased and lactic acid increased with rates of change increasing in parallel with storage temperature. The degree of whey separation increased with samples stored at 15°C and 25°C exhibiting initially an increase followed by a marked decrease in syneresis towards end of storage. Yeasty taste of samples increased as aging progressed at the different storage temperatures. Changes in sensory properties and physicochemical parameters, during storage, correlated best with yeast and mold counts. Shelf-life data of samples were adequately described by Weibull distribution. The nominal shelf-life of labneh, determined using sensory changes and microbiological counts as failure criteria, ranged between 18.5–18.9, 8–9.5 and 2.7–3.1 days at 5°C, 15°C and 25°C, respectively. Q10 (shelf-life at T°C/ shelf-life at T+10°C) and Ea (activation energy) for flavor deterioration of labneh were 2.02 at 5°C and 11.2 kcal/mol, respectively.

Changes in ascorbic acid, polyphenol content and antioxidant activity in minimally processed cactus pear fruits

Abstract: Cactus pear fruits ( Opuntia ficus indica Mill, cv. ‘Gialla’) were manually peeled, then placed in plastic boxes sealed with a film with high permeability to gases, and kept at 4°C for 9 days. After 3, 6 and 9 days, chemical, physical, microbiological and sensorial parameters, total phenols, vitamin C and antioxidant capacity were determined. In-package gas concentrations were measured almost daily. Vitamin C and antioxidant capacity remained unchanged, while polyphenols decreased after 6 days in storage. Of the chemical parameters, only pH and acidity changed significantly, without however, adversely affecting sensorial properties. Microbiological growth was limited and fungal colonies were never visually detected.

In vitro digestibility and colonic fermentability of aleurone isolated from wheat bran

Abstract: Two aleurone preparations, isolated from wheat bran, with different levels of tissue purity, were compared to the wheat bran starting material. Chemical composition, in vitro digestibility and in vitro fermentability were investigated and microscopy was used to visualize morphological changes. Arabinoxylans constituted the main part of the dietary fibre fraction. However, the degree of branching was found to be lower in arabinoxylans from aleurone than in that from original bran. Due to the high fibre content, in vitro digestibility was rather low but digestible compounds were largely eliminated. In vitro fermentability using fresh human faecal material turned out to be higher in aleurone than in wheat bran. Moreover, the degree of purity of the aleurone preparations influenced the amount of fermentation products. Proportions of the main short chain fatty acids were very similar in all samples, with ratios of propionate and butyrate slightly above average compared to other dietary fibre sources. Arabinoxylans from aleurone were virtually completely degraded within 8 h, whereas with wheat bran, substantial amounts were still present after 24 h. Moreover, increasing arabinose:xylose ratios during fermentation suggested a better fermentability of arabinoxylans with a lower branching degree. Microscopic investigations confirmed the better fermentability of aleurone compared to wheat bran. In addition, a specific breakdown pattern of aleurone cell walls could be observed.

Prevention of enzymatic browning in sliced potatoes by blanching in boiling saline solutions

Abstract: The response surface methodology was applied to investigate the way in which variables, such as time of treatment, sodium or calcium chloride concentrations and lactic acid concentration, affect the blanching of potato slices in boiling solutions Two 3 factor-5 level, second order central composite designs were developed to analyse the considered variables Results showed that all the considered blanching treatments allowed polyphenoloxidase inactivation With regard to colour, the use of calcium chloride, already at low concentrations, would seem better than the use of sodium chloride Under the applied operative conditions, the best results were obtained with short times of treatment and low lactic acid concentrations

Development of a model for quality assessment of tomatoes and apricots

Abstract: The quality of tomato and apricot cultivars was assessed by sensory evaluation, consumer tests and instrumental methods. The overall sensory appreciation of tomatoes was mainly reflected by attributes such as “sweetness”, “aroma”, “juiciness” and “firmness”. Hedonic classification of samples allowed to significantly improve the correlation between instrumental data and consumer appreciation. Instrumental measurements were focused on total sugar content (°Brix) and total amount of volatile compounds and texture (firmness). For tomatoes the CAR/PDMS fibre and for apricots the PDMS fibre were used for the analysis of total volatiles. The results obtained with tomatoes and apricots confirmed the applicability of the quality assessment model developed for evaluation of the quality of strawberries.

Relationship between sensory perception and flavour-active volatile compounds of germinated, sourdough fermented and native rye following the extrusion process

Abstract: Relation between sensory profiles and flavour-active volatile compounds was explored on six rye extrudates, representing two rye cultivars (Amilo and Akusti) and three pretreatments (germination, sourdough fermentation and milling), prior to the extrusion cooking. The processing method used before the extrusion cooking was shown to be very decisive for the perception; the germinated, sourdough fermented and milled rye extrudates clustered to cultivar pairs according to their pretreatment on the regression plot including the whole sample set. Germinated, extruded rye was cereal and fresh in flavour, and hard in texture, and dimethyl sulphide and 2-methylbutanal were highly related to these sensory attributes. Sourdough fermented, extruded rye had a sour, intense flavour and aftertaste, and porous texture, the most relevant volatile compounds being furfural, ethyl acetate, 3-methylbutanol and 2-methylbutanol. The extrudates prepared from rye flour were very mild in flavour and somewhat tough in texture, and 2-ethylfuran, 2-methylfuran, hexanal and pentanal were the dominating volatile compounds. The present study clearly demonstrated the effect of processing on adjusting the flavour of rye. Sensory perception and volatile compounds of germinated, sourdough fermented, and native rye were substantially different, and they remained variable after the second treatment, i.e. the extrusion process. The pretreatment process was shown to be most dominant in the formation of the flavour of the rye extrudates. The rye cultivar had an unsubstantial effect on the sensory profiles.

Gelatinization and retrogradation of potato (Solanum tuberosum) starch in situ as assessed by differential scanning calorimetry (DSC).

Abstract: The thermal behavior of potato starch in situ has been studied and compared to properties of isolated starch. Gelatinization and retrogradation properties were studied by differential scanning calorimetry. One early and three late varieties with different degree of mealiness were examined. The early variety (Solanum tuberosum var. Rocket) had lower dry matter content and lower starch gelatinization temperature than the later varieties (var. Asterix, Bintje and King Edward). Samples from distinct parts of the potato tuber were analysed to compare the tissue zones. The starch in the water-rich pith appeared to gelatinize at a higher temperature than in samples from the outer parts of the tuber. This was seen for isolated starch as well as for starch in situ; however, the differences were more pronounced in situ. To investigate the influence of tuber size, samples were taken from stem end storage parenchyma. No influence of tuber size on the starch gelatinization properties was detected by the method used. Retrogradation properties were also studied for stem end storage parenchyma. Melting temperatures of recrystallized amylopectin did not differ between varieties, though there were small differences in rate of recrystallization as measured by changes in melting transition enthalpy with time.

Combined ultraviolet-C and modified atmosphere packaging treatments for reducing microbial growth of fresh processed lettuce

Abstract: For reducing microbial growth and keeping sensory quality of fresh processed ‘Red Oak Leaf’ lettuce, combined ultraviolet-C (UV-C) at 254 nm radiation and modified atmosphere packaging (MAP) treatments were applied. Five UV-C doses (0.4, 0.81, 2.44, 4.07, and 8.14 kJ/m2) and passive MAP throughout 10 days of storage at 5°C were evaluated. The respiration rates (RR) of unprocessed, fresh processed, and fresh processed and UV-C-treated ‘Red Oak Leaf’ lettuce were monitored. While minimal processing did not induce significant changes, UV-C radiation increased the RR. Consequently, CO2 level within bags containing radiated lettuce was higher than in control bags. Within packages of radiated product a steady state of about 2–10 kPa O2 and 5–12 kPa CO2 was established. The combination of UV-C radiation and MAP was effective for reducing the growth of psychrotrophic and coliform bacteria as well as yeast growth. However, lactic acid bacteria growth was not affected or even stimulated. Compared to control, the sensory quality of lettuce pieces was not adversely affected by this combined treatment. As main conclusion, UV-C was effective to reduce growth of most of the microbial groups without adversely affecting sensory quality of ‘Red Oak’ lettuce.

Changes in the rheology and microstructure of processed cheese during cooking

Abstract: The ‘creaming reaction’ of a processed cheese can be traced by the change in its viscosity profile. The viscosity profile can be measured by shearing the processed cheese at a low but constant shear rate using a rheometer. We showed that this change in the viscosity profile during cooking occurred in processed cheese made from a typical formulation as well as from a fat-free model system. This indicated that the ‘creaming reaction’ is primarily a protein-based interaction, which takes places with or without the presence of fat. The observed viscosity profile can be explained in terms of changes in the protein structure of the molten processed cheese during processing. A model is proposed.

Life cycle assessment (LCA) of cleaning-in-place processes in dairies

Abstract: Four Cleaning-In-Place (CIP) methods for dairies were compared using life cycle assessment (LCA) The methods were conventional alkaline/acid cleaning with hot water disinfection, one-phase alkaline cleaning with acid chemical disinfection, enzyme-based cleaning with acid chemical disinfection and the conventional method with disinfection by cold nitric acid at pH 2 Production of detergents, transport, the user phase in the dairy and waste management of containers were included The user phase was found to be the most important part of the life cycle The CIP methods with small volumes and low temperatures, such as enzyme-based cleaning and one-phase alkaline cleaning, turned out to be the best alternatives for the impact categories energy use, global warming, acidification, eutrophication and photo-oxidant formation Milk residues flushed out in the rinsing phase were the main contributor to eutrophication, but the phosphorus and nitrogen in the detergents also influenced the results Evaluation of toxic substances poses a methodological problem in LCA In this study, detergents partly composed of toxic substances were included, and the overall assessment was that the one-phase alkaline cleaning method was preferable from an environmental point of view A qualitative assessment of toxicity was performed

Sequential disinfection of Escherichia coli O157:H7 inoculated alfalfa seeds before and during sprouting using aqueous chlorine dioxide, ozonated water, and thyme essential oil

Abstract: Several outbreaks of human illness have been documented in the United States associated with alfalfa sprouts. This study was done to evaluate the efficacy of aqueous chlorine dioxide (ClO2) (10, 25, and 50 mg/L), ozonated water (4.60, 9.27, and 14.3 mg/L) and thyme oil (1.0, 2.5, and 5.0 mL/L), for 3, 5, and 10 min, respectively, alone or their sequential washing (thyme oil followed by ozonated water and aqueous ClO2) for eliminating Escherichia coli O157:H7 from alfalfa seeds prior and during sprouting. Alfalfa seeds were inoculated with a three-strain E. coli O157:H7 mixture and dried to attain approximately 106 cfu/g of seed. No single washing treatment was able to ensure complete elimination of E. coli O157:H7 from alfalfa seeds. Germination of seeds was not adversely affected by any of the treatments. A membrane-transferring surface-plating method was evaluated to recover uninjured and injured E. coli O157:H7. Direct surface-plating on selective media, Sorbitol MacConkey-cefixime-tellurite (SMac-CT) showed significantly (P⩽0.05) low populations recovered, thus indicating a large population of injured cells for each washing treatments in comparison to membrane-transferring surface-plating method tryptic soy agar/membrane/Sorbitol-MacConkey agar-cefixime-tellurite (TSA/M/SMac-CT). Regardless of different washing treatments, populations of E. coli O157:H7 increased to 7.8–8.2log10 cfu/g after sprouting (72 h). Results of this study also showed that sequential washing treatments (as irrigation water) during sprouting process have greater lethality than other sanitizer treatments alone.

Release of nisin from various heat-pressed and cast films

Abstract: Nisin-incorporated biopolymers (methylcellulose (MC), hydroxypropylmethyl cellulose (HPMC), κ-carrageenan and chitosan) films made by heat-press and casting methods were investigated. For quantitative determinations of nisin release in both categories of prepared films, the plate diffusion method was employed using Micrococcus luteus ATCC 10240 as the test microorganism. Cast films exhibited larger inhibitory zones overall when compared with that of the heat-pressed method. Among all the nisin-incorporated films assayed, the antimicrobial activity was most effective in MC films in the heat-pressed category and chitosan films in the cast films category.

Influence of yeast and vegetable shortening on physical and textural parameters of frozen part baked French bread

Abstract: The objective of this project was to study the influence of yeast and vegetable shortening on physical and textural parameters of frozen part baked French bread stored for 28 days and to produce a frozen part baked bread with physical and textural characteristics similar to those of the fresh one. Four formulations were used with different quantities of yeast and vegetable shortening. Dough was prepared by mixing all ingredients in a dough mixer at two speeds. After resting, the dough was divided into 60 g pieces, molded and proofed. The bread was partially baked for 7 min at 250°C, in a turbo oven. After cooling, it was frozen until the core temperature reached −18°C and stored at the same temperature up to 28 days. Once a week, samples were removed from the freezer to complete the baking process, without previous thawing. Mass, volume, water content, firmness, cohesiveness and springiness were measured 1 h after final baking. Resistance to extension and extensibility of dough were measured after mixing. Specific volume and chewiness were determined. Bread with higher yeast content presented a higher specific volume, whereas vegetable shortening reduced its crumb firmness and chewiness.