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.     

The impact of high-temperature, short-time thermal treatment on texture and weight loss of green asparagus

 The kinetics of the degradation of texture and loss of weight of green asparagus heated to between 100 and 130 °C was studied. The texture of the asparagus was evaluated with two types of cells fitted to a universal texturometer: one cell measured resistance to cutting with a wire and the other was a Kramer cell. The two methods enabled distinction between the different thermal treatments, although the Kramer cell gave information about the behaviour of parts of the spear further away from the tip. The thermally induced degradation of the texture and loss of weight followed first-order kinetics. With respect to the texture, the parameters obtained with the wire cell 2.5, 5 and 7.5 cm from the tip were activation energy (E _a)=19, 20 and 23 kcal/mol, respectively, and those obtained with the Kramer cell were E _a=18.3, 20.9 and 24 kcal/mol, depending on the section of asparagus investigated. For loss of weight an E _a of 8.9 kcal/mol was obtained; thus, it is an important quality factor to be taken into account when optimizing the process of canning green asparagus. Received: 7 November 1996     

The impact of high-temperature, short-time thermal treatment on texture and weight loss of green asparagus

 The kinetics of the degradation of texture and loss of weight of green asparagus heated to between 100 and 130 °C was studied. The texture of the asparagus was evaluated with two types of cells fitted to a universal texturometer: one cell measured resistance to cutting with a wire and the other was a Kramer cell. The two methods enabled distinction between the different thermal treatments, although the Kramer cell gave information about the behaviour of parts of the spear further away from the tip. The thermally induced degradation of the texture and loss of weight followed first-order kinetics. With respect to the texture, the parameters obtained with the wire cell 2.5, 5 and 7.5 cm from the tip were activation energy (E _a)=19, 20 and 23 kcal/mol, respectively, and those obtained with the Kramer cell were E _a=18.3, 20.9 and 24 kcal/mol, depending on the section of asparagus investigated. For loss of weight an E _a of 8.9 kcal/mol was obtained; thus, it is an important quality factor to be taken into account when optimizing the process of canning green asparagus. Received: 7 November 1996     

Shelf life of ready‐to‐cook cauliflower mixtures as affected by packaging film mass transport properties

In this work, the influence of packaging mass transport properties on quality loss of fresh‐cut cauliflower mixtures was addressed. The study was organised in two subsequent experimental steps; first, the selection of micro‐perforated packaging films was carried out by monitoring the package headspace gas concentrations of fresh‐cut white, green cauliflower and roman cabbage. Then, the effects of the barrier properties of the selected micro‐perforated film on shelf life of two different fresh‐cut cauliflower mixtures, stored at 4 ± 1 °C, were addressed. Results suggested that, among the investigated films, the micro‐perforated polymeric matrix with the lowest oxygen transmission rate value showed the best performance as it created the optimum headspace gas composition for each cauliflower variety, as well as, for the product mixtures. The appearance of visible moulds was the factor limiting product shelf life that accounted for about 18 days for both the investigated cauliflower mixtures.     

Firming of starch gels and amylopectin retrogradation as related to dextrin production by α-amylase

 The effect of dextrins produced by α-amylase on the firming and amylopectin retrogradation of wheat starch gels was studied. Different gel samples were prepared and included several ingredients, for example, α-amylase, vital gluten and glucoamylase. Amylopectin retrogradation, gel firming and the dextrin profile were analysed throughout a 5-day storage period. Both processes, i.e. firming and starch retrogradation, increased with time, and were not affected by the incorporation of gluten into the mixture. The well-known effect of α-amylase to retard bread crumb firming was also found to be relevant to starch gels. From the results obtained in this work, it seems that this anti-firming effect is not due to modifications of the starch but to dextrins produced by starch hydrolysis, since the effect did not occur when dextrins were removed by glucoamylase. Received: 30 December 1996     

Changes in chemical composition during storage of peaches (Prunus persica)

 Effects of storage time have been studied through 21 physical and chemical parameters in different batches of peaches stored at a controlled temperature (10–12  °C). The parameters were analyzed in order to assess possible differences between nutritional composition and consumer acceptability. The parameters studied were: weight, pH, titratable acidity, soluble solids (°Brix), moisture, vitamin C, soluble sugars, protein, dietary fiber (NDF, ADF, pectic substances), ashes, and mineral content (macroelements: Na, K, Ca, Mg, and P; microelements: Fe, Cu, Mg, and Zn). Analysis of variance revealed significant differences based on storage time and batch. Received: 22 June 1998 / Revised version: 25 September 1998     

Nutrients and antinutritional factors in faba beans as affected by processing

 The influence on the nutrients content (soluble sugars, starch, dietary fibre and calcium) and antinutritional factors (α-galactosides and phytic acid) of faba beans (Vicia faba, L. major) of soaking in different solutions (distilled water, citric acid, and sodium bicarbonate solutions), cooking the presoaked seeds, dry-heating and germination have been studied. Soaking brought about a decrease in starch, sucrose, fructose, α-galactoside, dietary fibre and calcium content. Glucose was detected in soaked faba beans and soaking did not modify the phytic acid content. Cooking the presoaked faba beans produced a slight decrease in starch, and caused a general drop in α-galactosides, dietary fibre, calcium and phytic acid, with the exception of seeds presoaked in sodium bicarbonate in which cooking did not cause any appreciable changes in comparison with the unprocessed faba beans. Germination caused a sharp reduction in α-galactoside and phytic acid content after 6 days, whilst starch and dietary fibre decreased slightly. Calcium, however, enjoyed a slight increment during germination which was related to the decrease in the content of hemicellulose and phytic acid. Dry-heating caused a noticeable reduction in all the nutrients and antinutritional factors investigated. Of all the treatments studied, germination appears to be the best processing method to obtain nutritive faba bean flour, since it caused a minor decrease in starch content (15% loss), the largest α-galactoside and phytic acid removal (94% and 45%, respectively) and provided an appreciable amount of dietary fibre. Received: 21 December 1997 / Revised version: 19 February 1998     

Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

 The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test. Received: 27 May 1998 / Revised version: 15 July 1998     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Influence of traditional smoking on the triglyceride composition during the ripening of Idiazabal cheese

 The influence of traditional smoking on the triglyceride (TG) composition of Idiazabal cheese during ripening was studied using HPLC. The partition numbers (PNs) of the TGs ranged between 22 and 53, the groupings of TG peaks with PN values of 36, 34, and 38 being the main contributors. Statistically significant differences between the smoked and the unsmoked cheeses were recorded during the ripening period. Smoking had a significant effect on certain groups of TGs at different ripening times and no effect on others. The differences in the TG profiles of the cheeses were the result of differing levels of lipolytic activity, which was heightened by smoking. Received: 29 December 1997 / Revised version: 9 March 1998     

Formation of aliphatic acids by carbohydrate degradation during roasting of coffee

 A major fraction of the acidity generated on coffee roasting can be attributed to formation of the four aliphatic acids formic, acetic, glycolic and lactic. Addition of sucrose, glucose or fructose to green coffee beans gave, compared to untreated beans, significant increases in the yields of the four acids on subsequent roasting. In addition, model studies using these three carbohydrates confirmed sucrose as the principal green bean precursor of the acids. Arabinose, erythrose and 1,6-anhydroglucose were identified as reaction products of sucrose thermal degradation and also subsequently served as precursors for acid formation. Isotopic labelling experiments indicated that known degradation pathways could be used to explain the formation of the four aliphatic acids from sucrose. Received: 7 January 2000     

Colour changes during manufacture of Galician chorizo sausage

 Galician chorizo sausage is a smoked-meat product containing chilli pepper. This study investigated changes in its colour (CIE colour coordinates L*, a* and b*, together with redness index, hue, chroma and perceived colour) during the curing process. Samples were obtained from three manufacturers (A, B and C) whose smoking and curing procedures differ markedly. Most of the colour measurement showed clear changes during curing. All measurement except external L* varied significantly among samples obtained from the different manufacturers. Pairwise comparisons indicated that in most cases there were significant differences between samples from manufacturer A (who smokes the product for only 6 h) and manufacturers B and C (who smoke the product for a longer period), but not between samples from manufacturers B and C. The pH, water activity and moisture content were also monitored; again, these variables differed significantly between A and B and between A and C, but not between B and C. Received: 8 October 1997 / Revised version: 19 January 1998     

Quality control charts for storage of raisins and dried figs

 Shewhart control charts are constructed by using the Hunter Lab color scale parameters to assure maintenance of the color of raisins and dried figs during storage in modified atmosphere packages, vacuum packages, or nylon bags. These control charts may be used to maintain the quality within acceptable limits and make it possible to readjust storage conditions if the acceptable limits should be violated. Received: 11 March 1996     

Colour changes during manufacture of Galician chorizo sausage

 Galician chorizo sausage is a smoked-meat product containing chilli pepper. This study investigated changes in its colour (CIE colour coordinates L*, a* and b*, together with redness index, hue, chroma and perceived colour) during the curing process. Samples were obtained from three manufacturers (A, B and C) whose smoking and curing procedures differ markedly. Most of the colour measurement showed clear changes during curing. All measurement except external L* varied significantly among samples obtained from the different manufacturers. Pairwise comparisons indicated that in most cases there were significant differences between samples from manufacturer A (who smokes the product for only 6 h) and manufacturers B and C (who smoke the product for a longer period), but not between samples from manufacturers B and C. The pH, water activity and moisture content were also monitored; again, these variables differed significantly between A and B and between A and C, but not between B and C. Received: 8 October 1997 / Revised version: 19 January 1998     

Aggregation of minced hake during frozen storage

 Aggregation in minced hake muscle (Merluccius merluccius) during storage at –20  °C was studied in conditions where there is progressive deterioration of functionality and texture as measured by apparent viscosity and shear resistance. Natural actomyosin was extracted with 0.6 M NaCl over a period of 49 weeks. Insoluble residue was extracted successively with 2% sodium dodecyl sulphate (SDS) and 2% SDS plus 5% β-mercaptoethanol (ME) solutions. SDS–polyacrylamide gel electrophoresis was performed on the extracted fractions. The results showed a 75% decrease in 0.6 M NaCl extractability by the end of the storage period. Initially the remaining precipitate was all extracted in 2% SDS and although the amount extracted in this solution increased as storage time progressed, its proportion decreased, accounting for as little as 40–50% of the protein aggregate by the end of storage. The proteins most involved in formation of the aggregate not extracted in 0.6 M NaCl were myosin and actin. Neither of these proteins was fully recovered in the fractions extracted with 0.6 M NaCl, 2% SDS, or 2% SDS plus 5% ME, and therefore it was inferred that they were forming part of the aggregates, bound by covalent bonds. Received: 17 November 1998     

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     

Nonvolatile reaction products of heat-induced degradation of α-glucans Part II: Analysis of short-chain α-glucans by gas chromatography/mass spectrometry

 By means of model systems, the thermal behaviour of short-chain α-glucans (degree of polymerization, 1–4) as well as that of 1,6-anhydro-β-d-glucopyranose at 180  °C in quasi-waterfree systems was investigated. The main aim was to identify anhydrosugars, isomeric products and other products which cannot be degraded by amylolysis. Using the techniques described it was possible to detect 1,6-anhydrodisaccharides with different linkages, as well as glucobioses and their homologues. Maltulopyranose and its homologues were detected for the first time during thermolysis of the α-glucans, but free fructose has yet to be detected during their thermolysis. A possible mechanism for the formation of maltulopyranose is proposed. Besides these results, the formation of 1,2-anhydrosaccharides as reactive intermediates of thermolysis of α-glucans is reported. Received: 21 November 1997/Revised version: 12 January 1998     

Nonvolatile reaction products of heat-induced degradation of α-glucans Part II: Analysis of short-chain α-glucans by gas chromatography/mass spectrometry

 By means of model systems, the thermal behaviour of short-chain α-glucans (degree of polymerization, 1–4) as well as that of 1,6-anhydro-β-d-glucopyranose at 180  °C in quasi-waterfree systems was investigated. The main aim was to identify anhydrosugars, isomeric products and other products which cannot be degraded by amylolysis. Using the techniques described it was possible to detect 1,6-anhydrodisaccharides with different linkages, as well as glucobioses and their homologues. Maltulopyranose and its homologues were detected for the first time during thermolysis of the α-glucans, but free fructose has yet to be detected during their thermolysis. A possible mechanism for the formation of maltulopyranose is proposed. Besides these results, the formation of 1,2-anhydrosaccharides as reactive intermediates of thermolysis of α-glucans is reported. Received: 21 November 1997/Revised version: 12 January 1998     

Hygienic quality of commercial minced meat as indicated by aerobic micro-organisms and Coliform bacteria

 The hygienic quality of commercial beef and beef-pork minced meat was examined using aerobic micro-organisms and Coliform bacteria as indicator organisms. About 70% of the samples examined were of good quality and about 30% of tolerable quality. Aerobic micro-organisms can be recommended as an initial means of monitoring the hygienic quality of minced meat, being better for this purpose than Coliform bacteria. In about 7% of the samples the pH was more than 6.0 or below 5.3, and thus the meat was not suitable for consumption. Recommended amounts of micro-organisms for classification of commercially available minced meat as being of good, tolerable and bad hygienic quality are suggested as well as the associated pH values. Received: 25 October 1995/Revised version: 31 January 1996     

Amyl alcohols as compounds indicative of raw cocoa bean quality

 Amyl alcohols were isolated from raw cocoa beans by steam distillation and quantified by means of gas chromatography. Concentration ratios between primary and secondary amyl alcohols and between alcohols, aldehydes and acetates were calculated. These ratios indicate the fermentation degree and possible staling of cocoa beans. Hence, flavour quality of raw cocoa beans may be measured and the method used for industrial quality control. Received: 27 October 1995/Revised version: 25 March 1996