| 1. |
- Wessling, C., et al.
(författare)
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Antioxidant ability of bht- and ?-tocopherolimpregnated ldpe film in packaging of oatmeal
- 2001
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Ingår i: Journal of the Science of Food and Agriculture. - 0022-5142 .- 1097-0010. ; 81:2, s. 194-201
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Tidskriftsartikel (refereegranskat)abstract
- Cereals in general, and particularly oatmeals, are considered rather sensitive to oxidation owing to their relatively high fat content. The addition of antioxidants can sometimes prolong the shelf-life of products. The aim of the present study was to investigate how the rate of lipid oxidation ora packaged oatmeal product was affected by the nature and level of antioxidants incorporated in an LDPE film structure. The stability of the product, which was determined by hexanal analysis using GC-MS and by electronic nose analysis, showed very small variations over the chosen storage period. No oxidation, as determined by hexanal levels in the oatmeal, was initiated during storage, but small variations in volatile profile were seen among the samples analysed by the electronic nose. The product stored in the BHT-impregnated LDPE film had undergone the least change during 10 weeks of storage at 20°C. ?-Tocopherol-impregnated LDPE film did not appear to prolong the shelf-life of the oatmeal at all. © 2000 Society of Chemical Industry.
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| 2. |
- Wessling, C., et al.
(författare)
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Retention of ?-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) in contact with foodstuffs and food-simulating liquids
- 1999
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Ingår i: Journal of the Science of Food and Agriculture. - 0022-5142 .- 1097-0010. ; 79:12, s. 1635-1641
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Tidskriftsartikel (refereegranskat)abstract
- Alpha-tocopherol occurs as a natural antioxidant in many foods and has also found use as a stabiliser in polymeric packaging materials. During storage of a food in contact with a plastic material, ?-tocopherol may be released from the packaging material and transferred into the food. An active packaging application with the transfer of a substance, such as an antioxidant, from a packaging material to a food may help to prolong the shelf-life of the food. In this study, the retention of ?-tocopherol in low-density polyethylene (LDPE) and polypropylene (PP) was investigated for contact with liquid foods with different fat contents and food simulants with different ethanol contents. The PP film exhibited excellent retention of ?-tocopherol when in contact with all media, whereas some losses were observed from the LDPE film. A number of factors including fat, alcohol and organic acid contents of the various foodstuffs seemed to influence the loss of ?-tocopherol from the LDPE film.
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| 3. |
- Lerceteau, Estelle, et al.
(författare)
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Evolution of cacao bean proteins during fermentation : a study by two-dimensional electrophoresis
- 1999
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Ingår i: Journal of the Science of Food and Agriculture. - : JOHN WILEY & SONS LTD. - 0022-5142 .- 1097-0010. ; 79:4, s. 619-625
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Tidskriftsartikel (refereegranskat)abstract
- The protein content of cacao (Theobroma cacao) beans was studied by quantitative two-dimensional electrophoresis (2-DE) and by measuring total and protein nitrogen by the Kjeldahl method from the unfermented stage up to the seventh day of fermentation. The major trends in evolution of protein concentration were followed by measuring the intensities of some of the most abundant bean polypeptides. During fermentation a biphasic proteolytic process was observed. Protein degradation was detected after two days of fermentation, and was most pronounced during the third day. Following the initial phase of degradation until the end of fermentation, very little further protein degradation was observed, possibly due to the release of polyphenolic compounds and their subsequent complexing with the remaining proteins. Total protein estimated by the Kjeldahl method decreased to 57% of the initial value during the fermentation period. The process of degradation is selective, with some polypeptides resisting more than others. The evolution of total protein and non-protein nitrogen content is also described. (C) 1999 Society of Chemical Industry.
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| 4. |
- Ofstad, R., et al.
(författare)
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Liquid loss as effected by post mortem ultrastructural changes in fish muscle : Cod (Gadus morhua L) and salmon (Salmo salar)
- 1996
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Ingår i: Journal of the Science of Food and Agriculture. - 0022-5142 .- 1097-0010. ; 71:3, s. 301-312
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed in order to assess the effect of early post mortem structural changes in the muscle upon the liquid-holding capacity of wild cod, net-pen-fed cod (fed cod) and farmed salmon. The liquid- holding capacity was measured by a low speed centrifugation test. Transmission electron microscopy was used to discover ultrastructural changes both in the connective tissue and in the myofibrils. Differential scanning calorimetric thermograms of the muscle proteins were recorded to elucidate whether fundamental differences did exist between the proteins of the raw material tested. Multivariate statistics were used to explicate the main tendencies of variations in the thermograms. The salmon muscle possessed much better liquid-holding properties than the cod muscle, and wild cod better than fed cod regardless of the storage time. Both fed cod and farmed salmon, underwent the most severe structural alterations, probably caused by the low muscle pH values. The higher liquid-holding capacity of the salmon muscle was related to species specific structural features and better stability of the muscle proteins. The myofibrils of the salmon muscle were denser and intra- and extracellular spaces were filled by fat and a granulated material. The differences in thermograms of muscle from wild and fed cod were largely explained by the variations in pH. The severe liquid loss of fed cod is due to a low pH induced denaturation and shrinkage of the myofibrils. Post mortem degradation of the endomysial layer and the sarcolemma may have further facilitated the release of liquid.
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| 5. |
- Ofstad, R., et al.
(författare)
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Ultramicroscopical structures and liquid loss in heated cod (Gadus morhua L) and salmon (Salmo salar) muscle
- 1996
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Ingår i: Journal of the Science of Food and Agriculture. - 0022-5142 .- 1097-0010. ; 72:3, s. 337-347
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed in order to assess the effect of heating in pre-and post-rigor muscle of fed cod, wild cod and farmed salmon harvested at different times of the year. The structural changes in muscle samples pre- heated from 5 to 60°C were qualitatively evaluated using both light and transmission electron microscopy techniques. The microstructural changes are discussed in relation to the liquid loss measured by a low-speed centrifugation test. The heat-induced structural changes varied between the fish tested, reflecting different degrees of post mortem degradation prior to heating, the muscle-pH and species-specific structural properties. The fed fish, both cod and salmon, underwent the most severe structural degradation. This reflected both the low muscle pH and the more severe post mortem degradation observed in these fish prior to heating, compared with the wild cod. Heating caused extensive shrinkage of the myofibrils and hence, widened intermyofibrillar and extracellular spaces in both the fed cod and the salmon muscle. In the sample of wild cod muscle, the extracellular spaces were narrow and the myofibrils were closely packed. The difference in heat-induced liquid loss of the fed compared with the wild cod muscle coincides with their different structural features, as observed both by LM and TEM. The better liquid-holding properties of the salmon muscle than the cod muscle are attributed to the species-specific ultrastructural features as observed with TEM. In addition to the denser appearance of the salmon myofibres, it is suggested that both fat droplets and aggregated sarcoplasmic proteins filling the intermyofibrillar and extracellular spaces are important in preventing release of liquid upon heating.
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| 6. |
- Undeland, Ingrid, et al.
(författare)
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Influence of skinning on lipid oxidation in different horizontal layers of herring (Clupea harengus) during frozen storage
- 1998
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Ingår i: Journal of the Science of Food and Agriculture. - 0022-5142 .- 1097-0010 .- 0346-718X. ; 78:3, s. 441-450
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Tidskriftsartikel (refereegranskat)abstract
- This study was conducted to evaluate the effect of skinning and of compositional differences on the oxidative stability of various horizontal layers from herring (Clupea harengus) during frozen storage. Herring fillets, with and without skin, were stored at -18°C for 0, 3, 9, 16 and 28 weeks. After each storage period, the fillets were divided horizontally into three layers: 'under skin', 'middle part' and 'inner part'. Each layer was then extracted for total lipids, in which peroxide value (PV), absorbance at 234 nm (A234) and 268 nm (A268) as well as lipid-soluble fluorescent oxidation products (FP) were measured. Prior to storage, the fat content, fatty acid pattern and ?-tocopherol were also analysed. During storage of skinless fillets, the under skin layer increased most in PV, A234, A268 and FP (P < 0.05), followed by the inner and middle parts. In fillets stored with skin, the high oxidation rate of the under skin layer lipids was suppressed, but this layer still gave rise to the highest responses. Firstly, these results point to the protective properties of the skin and, secondly, to the unfavourable composition of the under skin layer: a lot of dark muscle; the silver surface; the highest fat content and the lowest level of ?-tocopherol. Concerning the fatty acid pattern in the three layers, the amount of C20 : 5, C18 : 1 and C20 : 1 in the fat gradually decreased from the under skin layer towards the inner part of the fillet, whereas the opposite was true for C22 : 6.
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| 7. |
- Alessandrini, Laura, et al.
(författare)
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Effect of steam cooking on the residual enzymatic activity of potatoes cv. Agria
- 2011
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 91:12, s. 2140-2145
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The aim of this work was to study the influence of steam cooking on pectin methylesterase (PME) and endogenous alpha- and beta-amylase activities in different tissues (cortex and pith) of raw and heat-treated potatoes cv. Agria. Three different cooking temperatures were chosen (55, 70 and 85 degrees C). For each cooking trial, time-temperature profiles were recorded and the degree of cooking was expressed in terms of cooking factor. RESULTS: Steam cooking contributed to significantly activate PME at 55 degrees C and to reduce its activity at the final processing temperature (85 degrees C), with the highest amount in the cortex (0.3745 +/- 0.0007 mu mol galacturonic acid (GA) g(-1) fresh weight (FW) min(-1)) compared with the pith (0.2617 +/- 0.0012 mu mol GA g(-1) FW min(-1)). The presence of heat-labile and heat-stable isoforms of PME in the considered potato tissues was also assumed. Heat treatment by steam resulted in a significant decrease in endogenous alpha- and beta-amylase activities in both tissues compared with the raw potato, though without complete deactivation. Starch-degrading enzymes were also found to be differently distributed in the raw tuber. CONCLUSION: Steam cooking affected in different ways the assessed residual enzymatic activity in the considered tissues of potatoes cv. Agria. Further research is needed to confirm the results obtained. (C) 2011 Society of Chemical Industry
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| 8. |
- Alklint, Charlotte, et al.
(författare)
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Accelerated storage and isothermal microcalorimetry as methods of predicting carrot juice shelf-life
- 2005
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 85:2, s. 281-285
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of predicting the shelf-life of pasteurized carrot juice by isothermal microcalorimetry or change in pH was investigated and compared with traditional plate count results. A small increase in thermal power (2 muW), maximal increase of and acceleration of thermal power all gave rapid, well-correlated results for the shelf-life, as did pH, during accelerated storage. The effect of accelerated storage (17degreesC) on the microbial flora of pasteurized carrot juice was also compared with the flora from storage at 8degreesC, and it was found that accelerated storage is feasible for the rapid evaluation of shelf-life, but that the microbial flora in the spoilt juice will be different. (C) 2004 Society of Chemical Industry.
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| 9. |
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| 10. |
- Andersson, Staffan, et al.
(författare)
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Tocopherols in rose hips (Rosa spp.) during ripening
- 2012
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 0022-5142 .- 1097-0010. ; 92, s. 2116-2121
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Rose hips are used as a food ingredient and in health products. They are rich in various bioactive compounds such as carotenoids and vitamin C, but data on their vitamin E content (tocopherols and tocotrienols) are limited. In this study, four different species ofRosa were analysed for tocopherol and tocotrienol content during ripening in three different years. RESULTS: Only a- and ?-tocopherol were found in the fleshy parts of the rose hips, and the tocopherol content and vitamin E activity varied depending on date of harvesting, species and year. The amount of vitamin E activity differed between species of Rosa and years, whereas the changes during ripening were relatively small. CONCLUSION: The choice of species must be considered if tocopherol content is to be optimised when rose hips are used as a food ingredient. Copyright (C) 2012 Society of Chemical Industry
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