Electron spin resonance studies on γ-irradiated coffee bean parts

Summary Using electron spin resonance (ESR) free radicals, present naturally or formed after γ‐irradiation of parts of coffee bean, were examined by entrapping the sample in potassium chloride powder in ESR quartz tubes. The ESR signal at g=2.002 was more prominent in the spermoderm than in the whole seed portion of the coffee beans. The γ‐irradiation of coffee beans with doses of 5 or 10 kGy, normally used for decontamination, resulted in a dose‐dependent increase of a signal at g=2.002 which was accompanied by a weak triplet (a_H c. 3.0 mT), and which was also more prominent in the spermoderm. While short‐term storage (24 h at 25 ± 0.5 °C) of irradiated beans resulted in a substantial loss of signal at g=2.002, annealing at 50 ± 0.5 °C for 16 h increased this signal intensity in greater proportion than caused by irradiation alone, suggesting that generation of free radicals in the two varieties of coffee beans is not unique to the irradiation processing alone.     

Electron spin resonance spectroscopy of some irradiated foodstuffs

Electron spin resonance (ESR) spectroscopy has been used to examine components from γ-irradiated fish, meat and fruit produce in order to identify areas in which the technique may be of use in detecting an irradiation history. Results show that, in the studied samples of the flesh of meat, fish and fruit, stable radical species are not formed on irradiation, thus indicating that ESR will have no applications for determining a radiation history of such specimens. However, stable ESR signals are obtained in components where radical centres can be stabilised within a crystalline or protein matrix. Thus bone from meat or fish yields a characteristic ESR signal at levels likely to be used commercially, although signal intensity appears to be related to the degree of crystallinity of the hydroxyapatite. This would be a complicating factor in determining quantitative radiation exposure measurements. Similarly a radiation-induced ESR signal can be observed in scampi shell. The signal appears to be associated with the chitin component and thus cooking, either before or after irradiation, can result in a major decrease in signal intensity as a result of chitin degradation. Several radical species were observed in irradiated animal fat, one of which had spectral parameters similar to those obtained from organic peroxy radicals. These species were of limited stability restricting any practical ESR determination to within a few days of treatment. Stable free radical centres are produced in the seeds of fruit, but their spectra generally resemble those of the naturally occurring melanin-type pigments. Since the concentrations of the latter may vary considerably as a result of natural factors such as exposure to sunlight, ESR has limited applications in the diagnosis of an irradiation history in such materials. With irradiated grapes a weak spectral component that was not present in unirradiated specimens was observed in the seeds. It is possible, therefore, that the ESR method could be useful for detecting irradiated grapes.     

Electron spin resonance technique identification and dosimetry of irradiated chicken eggs

The electron spin resonance (ESR) technique was tested for the identification and dosimetry of irradiated chicken eggs by ESR measurements of the shell. the spectrum of powdered egg shells was interpreted as the superposition of three signals due to long-lived CO₃, ^- CO₃^3- and CO₂^- ions of the calcium carbonate matrix. Taking the amplitude of the central peak as the dose-dependent parameter, a linear dose-effect relationship was obtained up to 10kGy. the results obtained suggest the use of EPR for qualitative and quantitative analysis of irradiated fresh eggs.     

Effect of y‐radiation on chives safety and quality

The effect of γ‐irradiation on the quality of chives was evaluated. The samples were irradiated at 1.0 and 2.0 kGy, stored at 4 °C for 10 days and used for microbiological (aerobic mesophilic, moulds and yeasts, E. coli and Salmonella sp), biochemical (vitamin C and lipoperoxide (MDA) contents and superoxide dismutase (SOD) and guaiacol peroxidase (POX) activity) and sensorial evaluation. For irradiated samples, the total counts of aerobic mesophilic and moulds and yeasts showed a reduction of 6 log cycles during storage, and colour analysis showed no significant difference (P > 0.05) for the b*‐value. The contents of vitamin C were not significantly affected by irradiation and storage time. The MDA contents and SOD activity changed insignificantly at both γ‐irradiation levels after storage, while POX was significantly increased (P ≤ 0.05) at 1 kGy. Samples irradiated at 2.0 kGy presented sensorial acceptance after the storage. These results show that γ‐irradiation increases the shelf life of chives without significant changes in their quality.     

The Efficiency of TBHQ, β-carotene, Citric Acid, and Tinuvin 234® on the Sensory Stability of Soybean Oil Packaged in PET Bottles

ABSTRACT: The use of plastic packaging for oils permits exposure to light, increasing oxidation. The goal of this work was to maximize sensory stability of soybean oil packaged in PET bottles. A central composite design was used to combine different levels of TBHQ, β‐carotene, and citric acid, added to oil, and Tinuvin 234®, added to bottles. After 6 mo of storage, the oxidation degree was assessed by sensory and peroxide tests. TBHQ and Tinuvin 234 were the most effective antioxidants, and the minimum concentrations required to keep a reasonable stability during storage were: 120 ppm of TBHQ; 7 ppm of β‐carotene; 15 ppm of citric acid and 0.1% of Tinuvin 234.     

Storage stability of a tropical fruit (cashew apple,acerola, papaya,guava and passion fruit) mixed nectar added caffeine

Nectars are formulated beverages with a fruit juice or pulp as its main component. A blend of fruits can also be used, with the advantage of combining sensory and nutritional properties of different fruits. The beverages may be added with some energetic component, as caffeine, known by its stimulating effect on central nervous system. The objective of this study was to develop mixed nectar of cashew apple, papaya, guava, acerola fruit and passion fruit added caffeine. The beverage was prepared with 35% juice blend and 10% sugar, added with 100 mg of caffeine L^?1 and 60 mg of sodium metabisulfite (SO₂) L^?1 and 500 mg of sodium benzoate L^?1 as preservatives, packed in cleaned pasteurised bottles and heat processed at 90 °C for 30 s. Physicochemical, microbiological and sensory analyses of the beverage were performed initially (time zero) and during 6 months of storage at room temperature (about 25 °C). The products were microbiologically stable during storage. The vitamin C content decreased significantly throughout storage time, although it has remained relatively high. The product presented good sensory acceptance, which suggests its potential for market.     

Singlet Oxygen Oxidation Rates of ∝-, γ-, and δ-Tocopherols

ABSTRACT:  The reaction rate constants of 5 × 10⁻⁴ M, 10 × 10⁻⁴ M, and 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols with singlet oxygen in methylene chloride containing 1 × 10⁻⁵ M chlorophyll under light at 25 °C for 60 min were studied. The oxidation of tocopherols determined by a spectrophotometric method showed that the losses of 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols after 60 min under light were 21%, 16%, and 9%, respectively. The degradation of α-, γ-, and δ-tocopherols was undetectable in the absence of chlorophyll under light or in the presence of chlorophyll in dark. The losses of tocopherols under light were mainly due to singlet oxygen oxidation. The degradation rates of 20 × 10⁻⁴ M α-, γ-, and δ-tocopherols were 6.6 ×10⁻⁶ M/min, 5.0 × 10⁻⁶ M/min, and 2.9 × 10⁻⁶ M/min, respectively. The reaction rates between α-, γ-, or δ-tocopherol and singlet oxygen were 4.1 ×10⁶/M s, 3.3 × 10⁶/M s, and 1.4 × 10⁶/M s, respectively. The singlet oxygen oxidation rate of δ-tocopherol was significantly lower than α- or γ-tocopherol at α= 0.05. As the electron density in the chromanol ring of tocopherol increased, the singlet oxygen oxidation was increased.     

Shelf‐life extension of vacuum‐packaged sea bream (Sparus aurata) fillets by combined γ‐irradiation and refrigeration: microbiological,chemical and sensory changes

The combined effect of γ‐irradiation and refrigeration on the shelf‐life of vacuum‐packaged sea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensory changes of non‐irradiated and irradiated fish samples using low‐dose irradiation doses of 1 and 3 kGy. Fish species such as sea bream and sea bass are very popular in the Mediterranean countries due to their high quality characteristics, and their preservation is a constant challenge given their extreme perishability. Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 log cfu g^?1) for the non‐irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfu g^?1), H₂S‐producing bacteria typical of Shewanella putrefaciens (<2 vs 5.9 log cfu g^?1), Enterobacteriaceae (<2 vs 6.0 log cfu g^?1) and lactic acid bacteria (<2 vs 3.5 log cfu g^?1) after 10 days of storage. The effect was more pronounced at the higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H₂S‐producing bacteria typical of Shewanella putrefaciens showed higher sensitivity to γ‐radiation than did the rest of the microbial species. Of the chemical indicators of spoilage, Trimethylamine (TMA) values of non‐irradiated sea bream increased very slowly, whereas for irradiated samples significantly lower values were obtained reaching a final value of 7.9 and 6.3 mg N per 100 g muscle at 1 and 3 kGy respectively (day 42). Total volatile basic nitrogen (TVB‐N) values increased slowly attaining a value of 67.3 mg N per 100 g for non‐irradiated sea bream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per 100 g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream samples were higher than respective non‐irradiated fish and increased slowly until day 21 of storage, reaching final values of 1.1 (non‐irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg^?1 muscle (3 kGy), respectively (day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis of overall acceptability scores (sensory evaluation) a shelf‐life of 28 days (3 kGy) was obtained for vacuum‐packaged sea bream, compared with a shelf‐life of 9–10 days for the non‐irradiated sample. Copyright © 2004 Society of Chemical Industry     

Effect of Edible Coating Process and Irradiation Treatment of Strawberry fragaria spp. on Storage-keeping Quality

ABSTRACT: Gamma-irradiation and various edible coatings were tested on fresh strawberries ( Fragaria spp. ) for keeping fruit quality and extending shelf life. Four coatings based on milk protein were evaluated. In 1 experiment, coating formulation based on caseinate and/or strawberries were irradiated using a ⁶⁰Co source. Both gamma-irradiation treatment and edible coating process significantly delayed (p ≤ 0.05) molds growth. Edible coating based on irradiated caseinate was more effective than that of unirradiated caseinate. In a 2nd experiment, 3 irradiated coatings based on calcium caseinate and whey proteins were evaluated. The coating formulation based on 1:1 caseinate-whey was found to be more effective than those based on calcium caseinate. Addition of calcium chloride or a mixture of pectin and agar increased the effectiveness of the coating by delaying molds' apparition.     

The effect of γ-ray irradiation on the drying characteristics and final quality of dried potato slices

γ irradiation is known to be effective when used to reduce post‐harvest losses and control micro‐organisms and insects in stored products. It has been commonly used for processing dehydrated vegetables and fruits. However, few studies have been reported on the use of a γ irradiation treatment combined with a drying process. This study focuses on improving current technology as well as introducing a new technology by which bioproducts, dried by hot‐air, are pretreated with γ irradiation. Experiments were done to study the influence of irradiation dose air temperature and slice thickness on the dehydration rate and internal temperature of irradiated potato. These three factors were found to affect the dehydration rate and internal temperature of the potato, with an increase in irradiation dose, increasing the rate of dehydration and the internal temperature. The greater the dose, the lower the vitamin C content and the lower the rehydration ratio. The L‐colour values of the dried‐product under low dose irradiation were greater than for non‐irradiation, and at >6 kGy, the higher the dose, the lower the L‐value.     

Microbial Safety and Shelf Life of UV‐C Treated Freshly Squeezed White Grape Juice

The effects of UV‐C irradiation on the inactivation of Escherichia coli K‐12 (ATCC 25253), a surrogate of E. coli O157:H7, and on the shelf life of freshly squeezed turbid white grape juice (FSWGJ) were investigated. FSWGJ samples were processed at 0.90 mL/s for 32 min by circulating 8 times in an annular flow UV system. The UV exposure time was 244 s per cycle. The population of E. coli K‐12 was reduced by 5.34 log cycles after exposure to a total UV dosage of 9.92 J/cm² (1.24 J/cm² per cycle) at 0.90 mL/s flow rate. The microbial shelf life of UV‐C treated FSWGJ was extended up to 14 d at 4 °C. UV exposure was not found to alter pH, total soluble solid, and titratable acidity of juice. There was a significant effect (P < 0.05) on turbidity, absorbance coefficient, color, and ascorbic acid content. Furthermore, all physicochemical properties were altered during refrigerated storage. The microbial shelf life of FSWGJ was doubled after UV‐C treatment, whereas the quality of juice was adversely affected similarly observed in the control samples.     

Effect of storage time on the microbial,physicochemical and sensory characteristics of ovine whey-based fruit beverages

The aim of this study was to establish the physicochemical, sensory and microbiological quality of ovine whey-based fruit beverages produced from pasteurised ovine whey (mango flavoured–sugar sweetened [M-Su], pineapple flavoured–extra sugar sweetened [P-ESu], and tropical fruit flavoured–stevia sweetened [T-St]), and the changes in quality of these beverage types during the 15-day storage. The beverages were evaluated for their pH, colour, sediment and particle size distribution, microbiological count and sensory quality. No significant differences in the pH and the microbial counts among the beverages were noted during the storage period; however, the particle size distribution reflected the sediment formation that significantly decreased during the same period in all beverage types. The beverages were getting lighter during storage, which was evident by increasing L* and decreasing a* values for colour. All three beverage types had very high scores for taste and odour after 9 days, and colour and sediment after 5 days of storage. Beverage-type T-St was most preferred by consumers, with the highest scores for taste, odour and sensory appearance. These results can assist in the better determination of the deteriorative changes in a variety of ovine whey-based beverages, necessary changes in product composition that might result in improved product quality, and yet reducing losses incurred during ovine milk processing. In this sense, this research's findings contribute to the utilisation of whey beverages by the dairy industry to the development of functional products.     

Characterisation of zein–oleic acid films and applications in fruit coating

Pure zein films are known to be very hydrophobic, but are inappropriate for edible coating applications because of their brittle nature. In an attempt to improve the flexibility of these coatings, the influence of low concentrations of oleic acid (OA) as a plasticiser on mechanical, topographical and wetting properties of zein thin films was evaluated. Films were first obtained by casting from aqueous ethanol solutions with 4.0% in mass of zein and additions of 0%; 0.25%; 0.50%; and 1.0% (w/w) of OA. The results indicate an improvement in mechanical properties with increasing plasticiser leading to a reduction in the elastic modulus. An increase in the elongation at break has been observed, but with minor influence on tensile strength. All plasticised zein films have similar initial contact angle (approximately 69°) with a time‐dependent receding drop behaviour. An increase in plasticiser concentration increases film’s affinity towards water. As measured by atomic force microscopy, a consistent linear relation (R² = 0.991) was estimated between film composition and surface adhesion and consequently on the hydrophilicity. Surface topography also varied with plasticiser addition, becoming smoother as the OA concentration increases. When tested as an edible coating on pears (Pyrus communis L.), a formulation with 0.25% wt of plasticiser achieved the best results in preserving the pear mass as measured during the evaluated storage time (12 days) at room temperature. A 0.5% concentration of plasticiser had no influence and higher amounts resulted in a reduction in fruit protection.     

Co-trial on ESR identification and estimates of γ-ray and electron absorbed doses given to meat and bones

A multinational co-trial was organized to determine if electron spin resonance (ESR) spectroscopy could be used to monitor foods exposed to ionizing radiation. The bones of chicken legs, frog legs and pork rib bones were prepared and distributed as unknowns to the participating laboratories. In every instance, non-irradiated bones were correctly identified as such. Moreover, irradiated bones were not only correctly identified, but relatively good estimates of the absorbed dose were obtained. An intercomparison of the different approaches used by each laboratory is discussed, and recommendations for future trials are presented.     

Quality Properties,Fatty Acids,and Biogenic Amines Profile of Fresh Tilapia Stored in Ice

This work determines quality properties and fatty acids content of Nile tilapia (Oreochromis niloticus) stored in ice for 21 d. The quality properties consist of thiobarbituic acid (TBA), total volatile basic nitrogen (TVB‐N), trimethylamine (TMA), and microbiological analysis (total viable count (TVC), total coliform, Salmonella and Staphylococcus aureus) and determination of biogenic amines content (histamine, cadaverine, putrescine, spermine, spermidine, 2‐phenylethylamine, agmatine, tyramine, and ammonia). Moreover, the fat, moisture, and ash composition as well as fatty acids profile have also been analyzed. The TBA, TVB‐N, and biogenic amines analysis showed rather low levels of spoilage even after 21 d of storage. The microbiological analysis, however, showed that tilapia was unsuitable for consumption after just 10 d. The fat, ash, moisture, and fatty acids profile analysis showed that tilapia is not a good source of n?3 fatty acids. The research indicated that the microbiological analysis was the best method to establish spoilage of tilapia stored in ice, of all analytical methods performed in this study.     

Microbiological,physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified‐atmosphere packaging

This study evaluated the influence of packaging atmosphere (air versus 50% N₂/50% CO₂) on microbiological (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB‐N], NH₃, H₂S and biogenic amines) parameters in freshwater prawns during storage at 0 ± 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analysed. Both the packaging permeability and the combination of gases affected the shelf life, but the modified‐atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB‐N showed no statistical difference between the two atmosphere conditions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue.