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1.
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  相似文献   

2.
Mungbeans (Vigna radiata), control and γ‐irradiated at insect disinfestation dose levels (0.25 and 0.75 kGy) were germinated (0–6 days) and the qualitative and quantitative changes in soluble carbohydrates were studied in detail. The key flatulence‐producing raffinose family oligosaccharides in mungbeans were degraded in the irradiated samples at the onset of the germination (0–2 days) compared to the control where it occurred much later (>4 days). However, the reducing sugars, mainly glucose, fructose and galactose, which are metabolised easily, were enhanced in the irradiated samples. At low dose (0.25 kGy), irradiation had no effect on germination and sprout length, indicating that irradiated beans are suitable for use as sprouted beans. These observations clearly indicate that γ‐irradiation at insect disinfestation dose levels improved the digestibility and nutritional quality of mung beans by reducing the content of oligosaccharides responsible for intestinal gas production. © 1999 Society of Chemical Industry  相似文献   

3.
A combination of Fourier transform infrared (FTIR) spectroscopy and multivariate statistics as a screening tool for the determination of beet medium invert sugar adulteration in three different varieties of honey is discussed. Honey samples with different concentrations of beet invert sugar were scanned using the attenuated total reflectance (ATR) accessory of the Bio‐Rad FTS‐6000 Fourier transform spectrometer. The spectral wavenumber region between 950 and 1500 cm?1 was selected for partial least squares (PLS) regression to develop calibration models for beet invert sugar determination in honey samples. Results from the PLS (first derivative) models were slightly better than those obtained with other calibration models. Predictive models were also developed to classify beet sugar invert in three different varieties of honey samples using discriminant analysis. Spectral data were compressed using the principal component method, and linear discriminant and canonical variate analyses were used to detect the level of beet invert sugar in honey samples. The best predictive model for adulterated honey samples was achieved with canonical variate analysis, which successfully classified 88–94 per cent of the validation set. The present study demonstrated that Fourier transform infrared spectroscopy could be used for rapid detection of beet invert sugar adulteration in different varieties of honey. © 2001 Society of Chemical Industry  相似文献   

4.
Three plantain cultivars, Agbagba, Obino L'ewai and Cardaba, harvested at two stages of maturity, were irradiated at 0.1–1.0 kGy prior to storage under tropical ambient conditions. Post‐irradiation storage behaviour showed that plantain fruits at full three‐quarter grade were more responsive to irradiation treatment than at full grade maturity, while Cardaba, a type of cooking banana, showed the least response. Irrespective of varietal differences, irradiation to 0.5 kGy or higher caused severe tissue damage, softening and skin discolouration; however, γ‐irradiation at optimum dose range of 0.15–0.30 kGy effectively delayed ripening for 10–12 days in Agbagba and Obino L'ewai, respectively, without affecting respiratory pattern or fruit quality. © 1999 Society of Chemical Industry  相似文献   

5.
BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose‐dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low‐dose re‐irradiation (200‐600 Gy), medium‐dose re‐irradiation (1‐3 kGy) and high‐dose re‐irradiation (2‐6 kGy) were performed and compared using an additive dose method. An electronic‐nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One‐kGy‐irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose‐dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1‐3 kGy re‐irradiation technique gave most promising results. An E‐nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy‐irradiated mushrooms. © 2012 Society of Chemical Industry  相似文献   

6.
Effect of γ‐irradiation (2–30 kGy) on physical, proximate, functional and pasting properties of four bambara groundnut cultivars was investigated. Packed (0.74–0.75 g mL?1) and loose (0.71–0.76 g mL?1) density varied significantly among cultivars. Generally, CIE L and hue angle decreased, while CIE a, b, deltachroma and colour intensity increased with increased dose. Protein (21.23–23.77 g/100 g), fat (6.38–7.69 g/100 g), crude fibre (1.28–3.54 g/100 g), ash (1.50–4.50 g/100 g) and moisture (10.67–12.92 g/100 g) of non‐ and γ‐irradiated bambara varied with cultivars and dose. Loose (0.41–0.49 g mL?1) and packed (0.54–0.74 g mL?1) densities, water absorption (1.62–2.38 g/g) and swelling (10.50–18.00 g/g) increased marginally, while oil absorption (1.93–2.82 g/g), alkaline water retention (0.66–1.23 g/g), emulsion capacity (40.31–58.23%) and stability (31.67–46.49%) decreased with increased dose. Foam capacity (6.85–22.37%) and stability (1.80–22.37%) of γ‐irradiated flours were higher than their nonirradiated (2.03–18.26%) counterparts. Nonirradiated flours showed significantly higher viscosities than their γ‐irradiated counterparts. Flours showed slightly shear‐thinning behaviours.  相似文献   

7.
Experimental work was carried out in order to determine the usefulness of the 2‐alkylcyclobutanones as markers for irradiated Camembert cheese, salmon meat, mango and papaya. Both 2‐dodecylcyclobutanone (2‐DCB) and 2‐tetradecylcyclobutanone (2‐TCB) were readily detected in Camembert cheese even after storage for 26 days at 10 °C. A linear relationship was observed between irradiation dose (0.5–5 kGy) and the amount of cyclobutanone produced in the cheese. 2‐DCB and 2‐TCB were both identified in salmon meat irradiated in either the chilled (4 °C) or frozen state (−40 °C), although it was noted that less 2‐DCB was measured in the frozen samples. A linear response to increasing irradiation dose was demonstrated for salmon over the experimental range of 1–10 kGy. 2‐TCB was identified as the main marker for irradiated mango and could be detected in samples following storage for 14 days at 10 °C at doses as low as 0.1 kGy. As for the other products investigated, the concentration of this cyclobutanone increased linearly with increasing dose (0.1–2 kGy). With regard to papaya, 2‐DCB was identified as the principal irradiation marker. However, the concentration of this cyclobutanone decreased significantly with time, so that by day 21 of storage at 10 °C it could only be detected at the 2 kGy dose level. 2‐Tetradecenylcyclobutanone (2‐TDCB) was also detected in irradiated mango and papaya. © 2000 Society of Chemical Industry  相似文献   

8.
ABSTRACT: Quantitative analysis of glucose, fructose, sucrose, and maltose in different geographic origin honey samples in the world using the Fourier transform infrared (FTIR) spectroscopy and chemometrics such as partial least squares (PLS) and principal component regression was studied. The calibration series consisted of 45 standard mixtures, which were made up of glucose, fructose, sucrose, and maltose. There were distinct peak variations of all sugar mixtures in the spectral “fingerprint” region between 1500 and 800 cm−1. The calibration model was successfully validated using 7 synthetic blend sets of sugars. The PLS 2nd-derivative model showed the highest degree of prediction accuracy with a highest R2 value of 0.999. Along with the canonical variate analysis, the calibration model further validated by high-performance liquid chromatography measurements for commercial honey samples demonstrates that FTIR can qualitatively and quantitatively determine the presence of glucose, fructose, sucrose, and maltose in multiple regional honey samples.  相似文献   

9.
In this work, the effect of pulsed electric fields (PEF) treatment on the interactions between amino acids (using L‐Phenylalanine: L‐Phe) and sugar (using β‐Cyclodextrin: β‐CD) complex was analysed by fluorescence spectroscopy, Raman spectroscopy and simultaneous thermal analyzer. Moreover, the molecular dynamics of β‐CD–L‐Phe inclusion complex treated by PEF was calculated by molecular modelling. The results indicated that β‐CD–L‐Phe complexes are formed by a molar ratio of 1:1, and the stability constant of such complexes increased from 147 to 614 M?1 by PEF treatment. Thermal characterisations of β‐CD–L‐Phe complexes indicated that the PEF treatment could increase the yield of complexes. The PEF treatment resulted in an increase in the reaction enthalpy of β‐CD–L‐Phe inclusion complexes by DSC curve. These results show that PEF treatment has the potential to promote the chemical processing, especially the small organic molecules participate in inclusion or cross‐linking reaction.  相似文献   

10.
This study investigated the feasibility of mid-infrared (MIR) and Raman spectroscopy for (i) discrimination of three dried dairy ingredients, namely skim milk powder (SMP), whey protein concentrate (WPC) and demineralised whey protein (DWP) powder, and (ii) discrimination of preheat treatments of dried dairy ingredients using partial least squares discriminant analysis (PLS-DA). PLS1-DA models developed using MIR ranges of 800–1800 and 1200–1800 cm?1 yielded the best discrimination (correct identification of 97.2% for SMP discrimination and 100% for WPC and DWP discrimination). The best PLS2-DA model using MIR spectroscopy was developed over the spectral range of 800–1800 cm?1 and produced correct identification of 100% for dairy ingredient discrimination. Models developed using Raman 800–1800 and 1200–1800 cm?1 spectral ranges correctly discriminated (100% correctly identified) each dairy ingredient. Although all PLS1-DA and PLS2-DA models developed using both spectral technologies for preheat treatment discrimination had good discrimination accuracy (86–100%), they employed a high number of factors (8–9 for the best model). The use of the Martens uncertainty test successfully reduced the number of factors employed (3–4 for the best models) and improved the performance of PLS1-DA models for preheat treatment discrimination (all 100% correctly identified). This feasibility study demonstrates the potential of both MIR and Raman spectroscopy for rapid characterisation of dried dairy ingredients.  相似文献   

11.
The aim of this work was to characterise, physico‐chemically, sugar composition and aroma profile of ten honey samples collected by small producers during two seasons and produced in different agricultural ecosystems from Tabasco State (Mexico). The mean values obtained for the physico‐chemical parameters were: pH 3.63; 19.25% moisture; 78.8°Brix sugar; 0.64% ash; 0.25 mS cm?1 electrical conductivity and 0.58 water activity. Based on colour parameters, Tabasco honeys can be placed in the group of dark honeys. In the analysed samples; fructose was the major sugar (39.45%), followed by glucose (35.74%) while sucrose only represented 2.93%. The volatile profiles of the ten honey samples were obtained by gas chromatography‐mass spectrometry. All the honeys were characterised by their high contents of benzene and furan‐related compounds. As a result, artisanal honeys from Tabasco (Mexico) can be considered to present a good level of quality.  相似文献   

12.
This study was conducted to investigate the structural characterisation of β‐cyclodextrin (β‐CD) crosslinked by adipic acid. β‐CD was treated with different concentrations (0%, 5%, 10% and 15%, w/v) of adipic acid. Different instruments, such as scanning electron microsope (SEM), Fourier‐transform infrared (FT‐IR) spectroscopy and 1H and 13C nuclear magnetic resonance (NMR) spectra were used to find out chemical structure in the crosslinked β‐CD. SEM analysis suggested that crosslinking β‐CD with 15% adipic acid changed the original morphology and considerably increased the particle size of the raw material. FT‐IR spectroscopy data showed that an intensive absorption band at 1706 cm?1 was present in the β‐CD samples treated with 10% and 15% adipic acid, indicating a crosslinking between hydroxyl groups of β‐CD and carboxyl groups of adipic acid. NMR spectra revealed that the ester linkages between hydroxyl groups of β‐CD and carboxyl groups of adipic acid were formed after crosslinking of β‐CD with adipic acid.  相似文献   

13.
BACKGROUND: Perilla and sesame seeds, a rich source of energy, are commonly utilized in different forms in many countries. During the post‐harvest period, they are contaminated with insects as well as microbes that may have importance for keeping quality and quarantine, and thus they can be treated with ionizing radiation for insect disinfestation and microbial decontamination. Reliable and routine methods to identify whether or not a food has been irradiated are needed to help consumers' understanding of irradiated food and promote international trade. In the present study, fat‐derived hydrocarbons from irradiated perilla seeds and sesame seeds of Korean and Chinese origin were analyzed in order to identify irradiation treatment by comparing their properties during the post‐irradiation period. RESULTS: Gas chromatographic–mass spectrometric analysis showed that several saturated hydrocarbons, such as tetradecane, pentadecane, hexadecane and heptadecane, were found in the non‐irradiated control samples, while four radiation‐induced unsaturated hydrocarbons (R2 = 0.647–0.997), such as 1,7,10‐hexadecatriene (C16:3), 1,7‐hexadecadiene (C16:2), 6,9‐heptadecadiene (C17:2) and 8‐heptadecene (C17:1), were detected in all irradiated samples at 0.5 kGy or higher, with variations according to sample and origin. Concentrations of all hydrocarbons were reduced during storage and could not be detected in 0.5 kGy irradiated Chinese sample of either seed after 8 months. CONCLUSION: Radiation‐induced hydrocarbons (C16:3, 16:2, 17:2, 17:1) could be used as markers to identify irradiated perilla and sesame seeds of both Korean and Chinese origin at 1 kGy or higher for 8 months' storage at room temperature. Copyright © 2009 Society of Chemical Industry  相似文献   

14.
Changes in cumin and chili powder from India resulting from electron‐beam irradiation were investigated using 3 analytical methods: electronic nose (E‐nose), Fourier transform infrared (FTIR) spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The spices had been exposed to 6 to 14 kGy doses recommended for microbial decontamination. E‐nose measured a clear difference in flavor patterns of the irradiated spices in comparison with the nonirradiated samples. Principal component analysis further showed a dose‐dependent variation. FTIR spectra of the samples showed strong absorption bands at 3425, 3007 to 2854, and 1746 cm?1. However, both nonirradiated and irradiated spice samples had comparable patterns without any noteworthy changes in functional groups. EPR spectroscopy of the irradiated samples showed a radiation‐specific triplet signal at g = 2.006 with a hyper‐fine coupling constant of 3 mT confirming the results obtained with the E‐nose technique. Thus, E‐nose was found to be a potential tool to identify irradiated spices.  相似文献   

15.
Three phytosterols were isolated from Musa spp. flowers for evaluating their capabilities in inhibiting glucosidase and amylase activities and glycation of protein and sugar. The three phytosterols were identified as β‐sitosterol (PS1), 31‐norcyclolaudenone (PS2) and (24R)‐4α, 14α, 4‐trimethyl‐5α‐cholesta‐8, 25(27)‐dien‐3β‐ol (PS3). IC50 values (the concentration of inhibiting 50% of enzyme activity) of PS1, PS2 and PS3 against α‐glucosidase were 283.67, 11.33 and 43.10 μg mL?1, respectively. For inhibition of α‐amylase, the IC50 values of PS1, PS2 and PS3 were 52.55, 76.25 and 532.02 μg mL?1, respectively. PS1 was an uncompetitive inhibitor against α‐amylase with Km at 5.51 μg mL?1, while PS2 and PS3 exhibited a mixed‐type inhibition with Km at 52.36 and 2.49 μg mL?1, respectively. PS1 and PS2 also significantly inhibited the formation of advanced glycation end products (AGEs) in a BSA–fructose model. The results suggest that banana flower could possess the capability in prevention of the diseases associated with abnormal blood sugar and AGEs levels, such as diabetes.  相似文献   

16.
The aim of this study was to quantify glucose, fructose, sucrose and maltose contents of honey samples using Raman spectroscopy as a rapid method. By performing a single measurement, quantifications of sugar contents have been said to be unaffordable according to the molecular similarities between sugar molecules in honey matrix. This bottleneck was overcome by coupling Raman spectroscopy with chemometric methods (principal component analysis (PCA) and partial least squares (PLS)) and an artificial neural network (ANN). Model solutions of four sugars were processed with PCA and significant separation was observed. This operation, done with the spectral features by using PLS and ANN methods, led to the discriminant analysis of sugar contents. Models/trained networks were created using a calibration data set and evaluated using a validation data set. The correlation coefficient values between actual and predicted values of glucose, fructose, sucrose and maltose were determined as 0.964, 0.965, 0.968 and 0.949 for PLS and 0.965, 0.965, 0.978 and 0.956 for ANN, respectively. The requirement of rapid analysis of sugar contents of commercial honeys has been met by the data processed within this article.  相似文献   

17.
Rapid aroma profiling of food products is a potential technique for at‐line food quality evaluation. In this work the potential of zNose?, a surface acoustic wave‐based sensor, was tested for honey quality assessment. Buckwheat honey was purposely adulterated with different levels of beet and cane invert sugar, and its aroma profile was measured after different periods of headspace equilibration. PCA using the relative peak areas as well as the full zNose? spectra resulted in a clear separation between honey, and beet and cane invert sugar adulterants in the mixtures. PLS models were developed for quantitative estimation of adulterants using the entire spectra as well as the relative peak areas. Better predictions were obtained with the PLS models based on spectra than with those based on relative peak areas. A correlation of validation of 0.98 was obtained between predicted and measured percentage of adulteration. This model was also successfully validated with an external set of honey mixtures, resulting in an average deviation of 3% adulteration between the predicted and reference values. Copyright © 2004 Society of Chemical Industry  相似文献   

18.
β‐Glucans were isolated from six Greek barley cultivars (Persefoni, Kos, Thessaloniki, Athinaida, Dimitra and Triptolemos) by water extraction at 47 °C, enzymatic removal of starch and protein and subsequent precipitation of the water‐soluble β‐glucans with 37% (w/v) ammonium sulfate saturation. The purity of barley β‐glucans was high (>93% dry basis) with some small contamination by protein (<3.84%). The molecular size of the β‐glucan isolates was determined by high‐performance size‐exclusion chromatography (HPSEC); the weight‐average molecular weights and the intrinsic viscosities ranged between 0.45 × 106 and 1.32 × 106 and 2.77 and 4.11 dl g?1, respectively. Structural features of barley β‐glucans were revealed by 13C NMR spectroscopy and high‐performance anion‐exchange chromatography (HPAEC) of the oligomers released by the hydrolytic action of lichenase. Lichenase degradation showed that β‐glucans from all barley cultivars consisted of blocks of cellotriosyl and cellotetraosyl units, accounting for 90.6–92.3% of the total oligomers released, with a molar proportion of these units between 2.31 and 2.77. Rheological measurements of aqueous solutions/dispersions of β‐glucans showed the behaviour of non‐interacting polysaccharides and a transition from the typical viscoelastic response to gel‐like properties after a time period that depended on the molecular size of the polysaccharide. The lowest molecular size β‐glucans from the Triptolemos cultivar showed shorter gelation times than their higher molecular weight counterparts. The effect of sugar incorporation (glucose, fructose, sucrose, xylose and ribose), at a concentration of 30% (w/v), to the β‐glucans gels (6% w/v) on compression parameters seemed to be related to the type of sugar used; the pentose sugars substantially reduced gel firming. Copyright © 2004 Society of Chemical Industry  相似文献   

19.
BACKGROUND: As radiation‐induced alterations of the lipid fraction of foods are related to their initial fat content, concentrations of fat degradation products used as irradiation markers are expected to be lower when irradiating low‐fat‐containing foods. Thus the sensitivity required when applying analytical methods for identifying irradiation markers in foods eventually depends on their respective amounts of fat. The aim of this study was to perform the qualitative analysis of characteristic hydrocarbons resulting from irradiation of samples with a fat content as low as 25 g kg?1. RESULTS: A rapid extraction using a small amount of ethyl acetate was the unique sample pretreatment required to accomplish the analysis of radiolytic markers by using on‐line coupling of reverse phase liquid chromatography and gas chromatography with mass spectrometry detection (RPLC/GC/MS). Efficient elimination of the large volumes (up to 2170 µL) directly transferred from LC to GC was achieved by optimising the operation mode of the through‐oven transfer adsorption/desorption system used as interface. CONCLUSION: The reported procedure allowed confirmation, in less than 65 min, of the occurrence of up to five irradiation markers, namely n‐pentadecane, 1‐hexadecene, 1,7‐hexadecadiene, n‐heptadecane and 8‐heptadecene, in cooked ham irradiated at doses as low as 2 kGy. © 2012 Society of Chemical Industry  相似文献   

20.
Food adulteration is a profit‐making business for some unscrupulous manufacturers. Maple syrup is a soft target of adulterators owing to its simplicity of chemical composition. In this study the use of Fourier transform infrared (FTIR) spectroscopy and near‐infrared (NIR) spectroscopy to detect adulterants such as cane and beet invert syrups as well as cane and beet sugar solutions in maple syrup was investigated. The FTIR spectrum of adulterated samples was characterised and the regions 800–1200 cm?1 (carbohydrates) and 1200–1800 and 2800–3200 cm?1 (carbohydrates, carboxylic acids and amino acids) were used for detection. The region between 1100 and 1660 nm in the NIR spectrum was used for analysis. Linear discriminant analysis (LDA) and canonical variate analysis (CVA) were used for discriminant analysis, while partial least squares (PLS) and principal component regression (PCR) were used for quantitative analysis. FTIR was more accurate in predicting adulteration using two different regions (R2 > 0.93 and >0.98) compared with NIR (R2 > 0.93). Classification and quantification of adulterants in maple syrup show that NIR and FTIR can be used for detecting adulterants such as pure beet and cane sugar solutions, but FTIR was superior to NIR in detecting invert syrups. © 2003 Society of Chemical Industry  相似文献   

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