Quality of broccoli as influenced by film wrapping during shipment

'Shogun' broccoli florets were film-wrapped and stored for 7 days at 1 °C to simulate a maximum period of commercial shipment. After cold storage, florets were kept for 2.5 days at 20 °C to simulate a retail sale period. For wrapping, polyvinyl chloride (PVC) 9 µm thickness and low-density polyethylene (LDPE) 11, 15, and 20 µm thickness were used. Soluble solids content, pH, titratable acidity, weight loss, physiological disorders, visual quality, and gas composition within packages were monitored. Gas composition (about 18% O₂ and 1% CO₂ during cold storage and about 16% O₂ and 2-3% CO₂ during shelf life), overall quality, and yellowing and browning of the florets were at similar levels among the films studied. However, weight loss was about sixty times lower for all LDPE films than for PVC film. After shelf life the best results were obtained by using 15 µm LDPE. This polymeric film could be a good alternative to PVC for wrapping broccoli for commercial shipment purposes, particularly to those countries where use of PVC has been forbidden.     

Influence of ultrasound on mass transport during cheese brining

 The effect of ultrasound on mass transfer during cheese brining has been investigated. The rate of water removal and NaCl gain increased when ultrasound was applied in comparison with brining performed under static or dynamic conditions, suggesting that ultrasound improves both external and internal mass transfer. A simple diffusional model was developed to simulate mass transport during acoustic brining. Model parameters were estimated using experimental data from acoustic brining experiments carried out on cheese cylinders of 1.7×10^–2m radius and 3×10^–2 m height at different temperatures (5, 15 and 20  °C). Effective water (D _W) and NaCl (D _S) diffusivities estimated using the proposed model ranged from 5.0×10^–10m²/s and 8.0×10^–10 m²/s at 5  °C to 1.3×10^–9m²/s and 1.2×10^–9 m²/s at 20  °C. Both D _W and D _S varied with temperature according to the Arrhenius equation. Through the proposed model, water losses and NaCl gains of the experiments used in the parameter identification were accurately simulated (average %var=98.2%) and also of two additional acoustic experiments carried out under different conditions of temperature (10  °C) and sample size and geometry [parallelepiped of (6×2.5×1.25)×10^–2 m] to those used in the parameter identification (average %var=98.4%). Received: 22 September 1998 / Revised version: 20 November 1998     

Maintaining quality of wild vegetables (Aster glehni and Aruncus dioicus var. kamtschaticus) from Ulleungdo(Island), Korea by modified atmosphere packaging

Wild vegetables, Aster glehni and Aruncus dioicus var. kamtschaticus, produced from Ulleungdo (Island), Korea were packaged with 30 μm polypropylene (PP), 30 μm antifogging oriented polypropylene (A-OPP), 30 μm microperforated antifogging oriented polypropylene (MiA-OPP), 30 μm macroperforated low density polyethylene (Ma-LDPE), and 20 μm macroperforated high density polyethylene (Ma-HDPE), stored at 4, 10, and 20°C. Concentrations of O₂ and CO₂ in the packages were not modified by Ma-LDPE and Ma-HDPE. Weight loss was retarded by PP, A-OPP, MiA-OPP, especially as storage temperature decreased. Soluble solids were not affected by packaging materials. pH slightly decreased in LDPE and Ma-HDPE. Appearance, color, and overall acceptability of both vegetables stored at 4°C in PP or MiA-OPP showed the highest sensory score. These results suggest that packaging with PP or MiA-OPP films and storage at 4°C could be a useful method to maintain quality of the wild vegetables.     

Aflatoxins in nuts assayed by immunological methods

 Different kinds of raw and processed nuts available in the local retail market were investigated for aflatoxin content. Total aflatoxins and aflatoxin B₁ content were determined by immunoaffinity chromatography with fluorescence detection after reaction with bromine solution and by immunoenzymatic test kits. Of 29 investigated samples, 38% were contaminated. The total aflatoxin content in contaminated samples was between 1.20 μg/kg for peanuts and 5.50 μg/kg for walnuts. The concentration of aflatoxin B₁ found in contaminated samples was between 0.35 μg/kg for cashew nuts and 4.04 μg/kg for walnuts. The mean recovery of total aflatoxins was 95% for the Ridascreen test and 92% for immunoaffinity chromatography with fluorescence detection. For aflatoxin B₁ the mean recovery was 84%. Received: 4 March 1999 / Revised version: 17 May 1999     

Kinetics of green asparagus ascorbic acid heated in a high-temperature thermoresistometer

 Thermal degradation of green asparagus ascorbic acid in high-temperature short-time conditions was studied by heating in a five-channel computer-controlled thermoresistometer. Ascorbic acid was heated to between 110  °C and 140  °C and the degradation kinetics were analyzed assuming that two different inactivation mechanisms were occurring, one aerobic and the other anaerobic. The two reactions followed first-order kinetics, with E _a=12.3(2.0) kcal/mol and k _125  °C=47.0(3.0)×10^–3 s^–1 for the aerobic oxidation, and E _a=6.1(1.4) kcal/mol and k _125  °C=4.1(0.2)×10^–3 s^–1 for the anaerobic degradation. Received: 30 January 1998 / Revised version: 11 June 1998     

Application of multivariate statistical methods to extend the authenticity control of flavour constituents of apple juice

 The distribution of 15 aroma constituents, including the (R)- and (S)-enantiomers of ethyl 2-methylbutanoate, in 30 commercially available and laboratory prepared apple juices was evaluated by multivariate statistical methods. Principal component analysis and cluster analysis revealed ethyl 3-methylbutanoate, 3-methylbutyl acetate and (R)-ethyl 2-methylbutanoate as key components for the differentiation of apple juices. In freshly pressed and some commercial juices ethyl 3-methylbutanoate and 3-methylbutyl acetate were not present, and the (S):(R) ratio of ethyl 2-methylbutanoate was found to be >99 : 1%. Another group of commercial products was separated in which the amounts of ethyl 3-methylbutanoate and 3-methylbutyl acetate exceeded 1 μg/l and 180 μg/l, respectively, and in which the (S):(R) ratio of ethyl 2-methylbutanoate was <97 : 3%. The statistical data confirmed the high selectivity of apple fruit tissue in biosynthesizing 2-methylbutyl and 2-methylbutanoate esters, and could also be used to extend the results of enantio-multidimensional gas chromatography and other authenticity analyses. Received: 20 April 1998 / Revised version: 23 June 1998     

Multielement analysis of Chinese tea (Camellia sinensis) by total-reflection X-ray fluorescence

 Total-reflection X–ray fluorescence (TXRF) was used for the simultaneous determination of 15 elements in tea samples which were produced either by acid digestion or acidified infusion of tea leaves (Camellia sinensis). The accuracy and precision of the method were checked by its application to a certified reference material (GBW 08505 : tea). A variety of 39 tea samples of different kinds and/or qualities produced in different regions of China were analysed. The range and mean of the concentrations of elements in the tea leaves (0.1–30.000 μg g^–1) and their solubility in infusions (0.5–85%) were determined and the influence of the origin, type and quality of the tea samples was studied. In some tea leaves produced in a Se-rich region, the content of Se was found to be very high (up to 7.5 μg g^–1), in contrast to a concentration of only about 0.1 μg g^–1 Se in most of the tea leaves examined. Received: 27 January 1998     

Optimization of stepwise blanching of frozen-thawed potato tissues (cv. Monalisa)

 Response surface methodology was used to compare the effect of temperature and time of the first step of blanching on compression, shear, tension and stress-relaxation parameters of frozen-thawed potato tissues. A central, composite rotatable design was used to study the effects of variation in levels of temperature (52.93–67.07  °C) and time (15.86–44.14 min) on rheological parameters. Blanching temperature was the most important factor affecting the mechanical properties tested. The models fitted for the apparent modulus of elasticity in compression, maximum tension force, and relaxed force in the first cycle (F _r1); all had R ²>0.85 (P≤0.01) and were used for doing predictions. Optimum conditions were with in the ranges of temperature (60–65  °C) and time (25–35 min) used for each factor. In the experimental verification of the models at 65  °C during 30 min, the lowest percentage residual between experimental and predicted values was obtained for F _r1 (0.644), which was therefore the most appropiate parameter for detecting the firming effect that the pectinesterase activity produced on frozen potato tissues as a consequence of stepwise blanching under these conditions. Received: 3 February 1999 / Revised version: 12 April 1999     

Response surfaces for solubility of crude soylecithin lipid in super critical carbon dioxide

 The solubility of soy lecithin lipids in supercritical CO₂ was measured at pressures of 120, 200 and 280 bar and at temperatures of 40, 50 and 60  °C. The effects of temperature and pressure on the solubility of total lipids were studied by response surface methodology. The response surface equation to predict the solubility of total lipids in the above range of pressure and temperature is: Y=–3.237+0.0431* P–7.3×10^–5 P ²–0.00011 P*T where Y is the total lipid solubility in g/kg CO₂, P is the pressure in bar and T is the temperature in   °C. The total lipids solubility increased with pressure at constant temperature, but decreased with increasing temperature. The total lipids consisted of a very small phospholipid content compared to neutral lipids and glycolipids at all the pressures and temperatures studied. Optimum search indicated a maximum solubility of total lipids of 1.829 g/kg CO₂ at 263 bar and 40  °C. Received: 1 April 1999     

Effect of Pretreatments on Quality Characteristics of Dehydrated Ivy Gourd (Coccinia indica L.)

Ivy gourd (Coccinia indica L.) is an important tropical vegetable cultivated in India. It belongs to the Cucurbitaceae family and is attributed with neutraceutical properties such as hypoglycemic effect and contained a fair amount of ascorbic acid. The effect of blanching and different pretreatments on the quality characteristics of dehydrated ivy gourd slices was optimized. The treated ivy gourd slices were dehydrated in a cross flow hot air drier at 50 ± 1 °C to a final moisture content of 4.6%. The dehydration ratio of dried ivy gourd slices ranged from 17.1:1 to 18.7:1. Ivy gourd slices blanched at 98 °C in water, dipped in 0.2% potassium metabisulphite (K₂S₂O₅) solution and dried at 50 ± 1 °C for 5–6 h resulted in best product. Dehydrated ivy gourd slices obtained from the optimized treatment had good color, texture with rehydration ratio of 1:8.6. Equilibrium relative humidity of dehydrated slices was 34.18% with an initial moisture content of 4.6% at 28 ± 1 °C. Dehydrated slices were packed in low density polyethylene (LDPE) and metallized polyester polyethylene (MPP) pouches and stored at room temperature (27–35 °C) for 6 months. The dehydrated slices were analyzed for changes in physicochemical composition and sensory quality characteristic such as color and appearance, texture and overall quality during storage. Dehydrated ivy gourd slices remained acceptable during storage of 4 and 6 months in LDPE and MPP pouches, respectively, at room temperature.     

Optimization analysis by capillary electrophoresis of thiamine in meat: comparison with high perfomance liquid chromatography

 A new capillary electrophoresis (CE) method for the analysis of thiamine in meat is proposed. Samples were submitted to acidic and enzymatic hydrolysis and the extracts were purified using ethanol and an ion exchange column. The thiamine content was determined by CE using 100 mM sodium tetraborate, 50 mM sodium phosphate (pH 7.6), 50 mM sodium dodecyl sulphate and 10% isopropyl alcohol as a separation buffer solution. The analysis was carried out at 15 kV and 50  °C in a 70 cm effective length× 75 μm i.d. fused-silica capillary using on-column UV detection at 254 nm and 7 s injection time (27 nl injection volume). The results obtained by CE for thiamine contents in meat were compared to those obtained by HPLC using an ion-pair reverse phase column with post-column derivatization and fluorescence detection. Received: 24 August 1998 / Revised version: 21 January 1999     

Lipids classes, fatty acids and carotenes of the leaves of six edible wild plants

 α-Linolenic acid and unusual fatty acids of the ω3 and ω6 series play an important role in the modulation of human metabolism. The presence of these acids in the leaves of several edible wild plants has recently been reported. In this study, six edible wild species were selected in order to establish the fatty acid compositions in their leaf lipids. Thus, young leaves from Amaranthus viridis L.(blet), Chenopodium album L. (goosefoot), Crithmum maritimum L. (rock samphire), Plantago major L. (plantain), Portulaca oleracea L. (purslane) and Verbena officinalis L. (vervain) yielded 1.50, 2.20, 3.02, 1.46, 3.81, and 2.28 g of lipids per 100 g dry plant material. Silica gel chromatography yielded 0.64 g (Plantago major) to 2.19 g (Crithmum maritimum) neutral lipids, 0.37 g (Plantago major) to 1.60 g (Portulaca oleracea) glycolipids, and 0.26 g (Crithmum maritimum) to 0.57 g (Verbena officinalis) phospholipids per 100 g (dry weight). Gas chromatography (GC) showed the major fatty acids to be 18 : 3ω3, 18 : 2ω6 and 16 : 0 in all fractions, with high concentrations of 18 : 3ω3 in the glycolipid fraction. GC-mass spectrometric analyses did not reveal the presence of unusual fatty acids. Carotenes were found in high concentrations, ranging from 30.5 mg/100 g (Chenopodium album) to 89.2 mg/100 g (Portulaca oleracea). The analyzed plants are rich sources of essential fatty acids (18 : 2ω6 and 18 : 3ω3) and also of carotenes. Received: 29 October 1998     

Pulse Duration and Efficiency of Soft Cellular Tissue Disintegration by Pulsed Electric Fields

The effect of pulse duration on efficiency of disintegration of apple tissue by pulsed electric fields (PEF) was studied. The samples (26-mm diameter, 10-mm height) were treated by PEF at electric field strength E between 100 and 400 V/cm, pulse duration t _i of 10, 100, 1,000 μs, inter-pulse duration Δt of 100 μs and different number of pulses n. Both the degree and the time evolution of tissue damage were quantified by electrical conductivity disintegration index Z and characteristic damage time τ, respectively. The samples exposed to the same PEF treatment time nt _i showed noticeably higher disintegration efficiency for larger pulse duration. The synergism of PEF and thermal treatment with temperature T (20–50 °C) was demonstrated. The Arrhenius dependence of τ(T) for PEF treatment at E = 100 V/cm gave the decreasing activation energy W as a function of t _i, (Q ≈ 164 kJ/mol at t _i = 10 μs, Q ≈ 109 kJ/mol at t _i = 100 μs and Q ≈ 66 kJ/mol at t _i = 1,000 μs). Textural relaxation data supported the higher damage efficiency for longer pulse duration.     

Starch radicals Part III: Semiartificial complexes

 Nine starch varieties were blended and kneaded with d-fructose, d-glucose, sucrose, egg albumin and/or ethyl stearate to form semiartificial complexes. They were then thermolyzed and the numbers of unpaired spins in the solid residues were determined. Individual starch varieties began to generate unpaired spin states within 2 h of heating at 285  °C but some starch blends, particularly those of four-component starch (10 : 1 : 1 : 1) mixtures, generated free radicals within 2 h of heating at 160  °C. However, the free radical counts were minimized by the mutual complexation of the blend components and, to a certain extent, by the free radical scavenging in the blends. Received: 21 October 1997 / Revised version: 15 April 1998     

Effect of the addition of nitrate to milk on the formation of volatile N-nitrosamines and apparent total N-nitroso compounds

 Saint-Paulin, a French semihard cheese, was manufactured from milk with and without added NO₃ ^–. Reference and experimental cheeses were analysed at different stages of ripening for the presence of apparent total N-nitroso compounds (ATNC) by chemical denitrosation and chemiluminescence detection (thermal energy analyser). The fate of NO₃ ^– and NO₂ ^–was also scrutinized. The levels of ATNC and of volatile N-nitrosamines were followed during ripening. After 60 days of ripening, ATNC were detected at concentrations of 27 μg NO-N/kg and 64 μg NO-N/kg in the cheeses obtained from milk with and without added NO₃ ^–, respectively. The NO₃ ^– contents of both cheeses were nearly the same, and below 5 mg/kg. The occurrence of NO₂ ^–was not observed. No relationship was found between the NO₃ ^– contents and the contamination of the cheeses by volatile N-nitrosamines. At the beginning of ripening, the cheeses manufactured with added NO₃ ^- showed high levels of ATNC (mean value 5800 μg N-NO/kg with large variations of 570–15210 μg NO-N/kg). These ATNC contents rapidly decreased during the first days of ripening (96%), but decreased much more slowly during the following days. An hypothetical mechanism, attempting to explain the disappearance of ATNC, involving the formation of alkylated species in the cheese was proposed. Received: 30 March 1998 / Revised version: 7 October 1998     

Decomposition of sinigrin by methanol/ammonia/water treatment in model systems and mustard (Brassica nigra L.) seed meal

 Sinigrin (allylglucosinolate) was stored at 20  °C, 40  °C, and 60  °C in solutions containing 10% ammonia in 95% methanol (CH₃OH/NH₃/H₂O). The individual samples were analyzed for their contents of sinigrin, its decomposition product allyl isothiocyanate (AITC) and other reaction products. The major reaction products were allyl thiourea, methyl ester of N-allyl thiocarbamoyl acid and allyl cyanide. A newly identified decomposition product of sinigrin was ethylcyanide. Defatted Brassica nigra seed meal was treated by the CH₃OH/NH₃/H₂O mixture to simulate the procedure used for rape and mustard seed meal detoxification. suspensions of the meal in the above mixture of solvents were heated at 20  °C, 40  °C and 60  °C, respectively. The major reaction products were the same as those arising from sinigrin. Minor products identified were 4-hydroxybenzyl isothiocyanate formed from sinalbin and 2-hydroxy-butenyl cyanide which arises from progoitrin. In all cases, AITC was very rapidly decomposed. Mechanisms explaining sinigrin decomposition are presented and discussed. Received: 3 May 1999     

Effects of type of packaging material on shelf-life of fresh broccoli by means of changes in weight,colour and texture

Five polymeric films were studied to determine their ability to retain the colour, weight and texture of broccoli (Brassica oleracea L. var. Italica Monterey). The materials were oriented polypropylene (OPP), polyvinyl chloride (PVC) and two different low-density polyethylenes (LDPE), one of which contained a sachet reported to absorb ethylene. The broccoli was packaged and stored at 4 and 10 °C for 4 weeks. The weight, colour, chlorophyll content and texture were monitored during storage as well as O₂ and CO₂ concentrations inside the packages. Packaging prolonged the broccoli shelf-life by up to 14 days. The shelf-life varied depending on the packaging material and quality parameter considered. The atmosphere was modified inside the packages; however, no package provided the recommended atmosphere (O₂ 1–2% and CO₂ 5–10%) for broccoli. Packaging in OPP resulted in the highest CO₂ concentration, 6%, while the lowest O₂ concentration, 9%, was created in the LDPE package without a sachet for ethylene absorption. Storage in LDPE without ethylene absorber resulted in the overall longest shelf-life. Broccoli stored in PVC deteriorated faster than broccoli packaged in the other materials. The influence of packaging material was greater at the higher temperature.     

Ripening and ethylene biosynthesis in controlled atmosphere stored apricots

 Ethylene synthesis and metabolism were studied in apricot fruits (Prunus armeniaca L. cv. Búlida, under controlled atmosphere (CA) conditions (20% CO₂ and 20% O₂; 20% CO₂ and 1% O₂; 0.03% CO₂ and 1% O₂) and at a temperature of 2  °C. In control apricots stored outdoors in air containing 20% O₂ and 0.03% CO₂, the evolution of the physical and chemical parameters characteristic of ripening (loss of texture, decrease in acidity and increase in soluble solids) was slow during the storage period. However, for apricots stored in CAs containing 1% O₂ and 20% or 0.03% CO₂, these parameters did not show significant changes during the storage period. Ethylene production was completely inhibited in apricots stored in the three CAs, while control fruits showed a maximum ethylene level after 2 weeks of storage. This inhibition was accompanied by lower levels of 1-aminocyclopropane-1-carboxylic acid, free and total, which were more pronounced in apricots stored in the CAs containing 20% CO₂. In apricots stored in the CAs containing 1% O₂, the ethanol content increased after 1 week of storage, and this caused a smell and taste that made the fruits unsuitable for consumption. Received: 16 October 1998     

Nano Zinc Oxide-Loaded Calcium Alginate Films with Potential Antibacterial Properties

In this work, zinc oxide nanoparticles-loaded calcium alginate films were investigated for their moisture uptake behavior at different temperatures. The equilibrium uptake data was interpreted quantitatively by GAB isotherm models. The monolayer moisture contents were 0.301 ± 0.003, 0.0214 ± 0.092, and 0.171 ± 0.102 at 20, 30, and 37°C, respectively. The water vapor transmission rate was found to be 0.816 ± 0.143, 1.42 ± 0.045, and 1.632 ± 0.064 g s⁻¹ m⁻² respectively. For the moisture content range of 0.2 to 0.6, the net ∆H and ∆S values were found to be 22.73 to 11.14 KJ/mol and 0.064 to 0.034 KJ/mol/K, respectively. The moisture uptake of films increased with water activity but showed negative temperature dependence. The enthalpy of sorption (∆H) and differential entropy (∆S) were determined at different moisture content values, ranging from 0.2 to 0.6 g/g db. The two parameters showed a higher degree of correlation. The equilibrium moisture content data was used to evaluate harmonic mean temperature T _hm. Finally, the biocidal action of films was tested against model bacteria Escherichia coli.     

Effect of curing and pre-storage dip treatments on the control of storage mould of kola nuts

 The effect of curing kola nuts at 30  °C was evaluated at the Cocoa Research Institute of Nigeria, Ibadan, to determine the effect of curing time and delay between inoculation and initiation of curing on storage rot. For nuts inoculated 24 h prior to curing, 48–72 h curing at 30  °C gave optimal disease control. The incidence of rot was higher when the treatment was delayed for 48 h after inoculation. When artificially wounded and inoculated kola nuts were dipped in a solution of 1.0 g l^–1 of sodium bicarbonate for 2 mins, disease development was significantly reduced compared to the 0.5% sodium hypochorite treatment. Sodium metabisulphite also reduced disease development but the level of disease control achieved was not significantly different from that of the water-dipped controls. The in vivo results were consistent with the in vitro results. Received: 15 April 1998