| 1. |
- Undeland, Ingrid, 1968, et al.
(författare)
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Lipid oxidation in fillets of herring (Clupea harengus) during frozen storage. Influence of pre-freezing storage.
- 1999
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:5, s. 2075-2081
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Tidskriftsartikel (refereegranskat)abstract
- Fillets of herring (Clupea harengus) were kept on ice for 0, 3, 6, and 9 days prior to storage at −18 °C for 0, 21, 42, 63, and 84 days. At each storage point, peroxide value (PV), absorbance at 268 nm (A268), fluorescent products (FP), α-tocopherol, glutathione peroxidase (GSH-px) activity, and ascorbic acid were measured. As shown by regression analyses, samples held for 6 days on ice formed oxidation products at the highest rate during frozen storage, followed by, for PV and FP, the 9-day samples. These data indicate that severe changes that negatively affect the oxidation process took place in the herring muscle between 3 and 6 days after catch. Both the initial antioxidant levels and the rate of antioxidant loss at −18 °C decreased with increased prefreezing holding time, the latter being most obvious for GSH-px activity and ascorbic acid. α-Tocopherol showed the largest losses and had disappeared entirely from the 6- and 9-day samples at the end of the frozen storage. Partial least-squares regression analysis of the data showed that ice storage had a greater effect than frozen storage on changes in PV, A268, FP, α-tocopherol, and ascorbic acid. For GSH-px activity, frozen storage had the greatest effect.
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| 2. |
- Undeland, Ingrid, 1968, et al.
(författare)
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Lipid Oxidation in Fillets of Herring (Clupea harengus) during Ice Storage
- 1999
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 47:2, s. 524-532
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Tidskriftsartikel (refereegranskat)abstract
- The influence of ice storage on lipid oxidation, odor, antioxidants, water-soluble catalysts, and microorganisms was investigated in fillets of herring (Clupea harengus) during 15 days. Based on linear regression analyses of the data, significant rises (p ≤ 0.05) in lipid oxidation products were seen after 2−3 days and in “rancid” odor after 2.5 days. Peroxide value (PV), fluorescent product (FP), and ascorbic acid analyses were the chemical measures most strongly correlated to “rancid” odor (r = 0.97). Antioxidants decreased in the following order: α-tocopherol > ascorbic acid > glutathione peroxidase (GSH-px); however, GSH-px correlated best to the development of lipid oxidation products (rmean = −0.96). The activity of aqueous pro-oxidants, which were enzymatic in nature to a great extent, had decreased by 75% at day 15. No significant increase in total bacteria was seen until after 7 days. There were major local differences in both composition and stability throughout the fillet. Oxidation proceeded most rapidly in the tissue right under the skin, probably explained by its high initial pro-oxidative activity.
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| 3. |
- Undeland, Ingrid, 1968, et al.
(författare)
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Lipid Oxidation in Minced Herring (Clupea harengus) during Frozen Storage. Effect of Washing and Precooking
- 1998
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Ingår i: Journal of Agricultural and Food Chemistry. - 0021-8561 .- 1520-5118. ; 46, s. 2319-2328
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Tidskriftsartikel (refereegranskat)abstract
- A 23 factorial experimental design was used to investigate the effect of washing in combination with precooking on the oxidative stability of lipids in minced herring (Clupea harengus) at −18 °C. The following variables were studied: washing (no, yes), cooking time (38, 54 min), and cooking temperature (55, 100 °C).The responses monitored were peroxide value (PV), absorbance at 234 nm (A234), absorbance at 268 nm (A268), and lipid soluble fluorescent products (FP). A partial least-squares regression analysis (PLS) revealed that the best lipid stability was obtained at minimum cooking time and at lower temperature. On the basis of compositional analyses and in vitro experiments, this finding was proposed to be due to heat inactivation of catalytic enzymes, without simultaneous activation, for example, of hemoproteins. Washing reduced these benefits from precooking by removal of pro-oxidative enzymes and also through a reduction in the amount of antioxidants as well as a relative increase in phospholipids and free fatty acids in the fat.
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| 4. |
- Börjesson, Thomas S., et al.
(författare)
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Off-odorous compounds produced by molds on oatmeal agar : Identification and relation to other growth characteristics
- 1993
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Ingår i: Journal of Agricultural and Food Chemistry. - Washington : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 41:11, s. 2104-2111
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Tidskriftsartikel (refereegranskat)abstract
- Ten Penicillium and Aspergillus species, four with a strong musty off-odor and six reference fungi without any characteristic odor, were cultivated on oatmeal agar for 5 days in cultivation vessels provided with an inlet and an outlet for air. Samples of volatile metabolites were collected on a porous polymer adsorbent attached to the outlet from day 2 through day 5 after inoculation. Adsorbed compounds were desorbed thermally and analyzed with GC/MS and a combined GC and sensory analysis, the GC sniff technique. Multivariate analysis of GC/MS and fungal odor data revealed strong associations between 6 of 65 volatile compounds and musty off-odor. The GC sniff technique showed that five of these, dimethyl disulfide, 1-octen-3-ol, 2-methylisoborneol, and two C11H18 compounds, had prominent off-odors. In addition, geosmin, 1-methoxy-3-methylbenzene, and methylphenol were produced in large amounts by some off-odorous fungi and contributed to their unpleasant odor. 3-Methylfuran, 2-methyl-1-propanol, and 3-methyl-1-butanol were much more commonly produced than the off-odorous compounds. Both odorous and other volatile metabolites could be detected after 2 days of fungal growth. The production of odorous metabolites was enhanced at the time of sporulation.
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| 5. |
- Petersson, Stina, et al.
(författare)
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Growth of Penicillium roqueforti, P-carneum, and P-paneum during malfunctioning airtight storage of high-moisture grain cultivars
- 1999
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Ingår i: Postharvest biology and technology. - : Elsevier. - 0925-5214 .- 1873-2356. ; 17:1, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Penicillium roqueforti is an important spoilage fungus in high-moisture grain stored under airtight conditions where a malfunctioning storage system allows air leakage. It has recently been proposed that P. roqueforti be divided into three different species: P. roqueforti, P. carneum, and P. paneum (Boysen, M., Skouboe, P., Frisvad, J., Rossen, L., 1996. Reclassification of the Penicillium roqueforti group into three species on the basis of molecular genetic and biochemical profiles. Microbiology 142, 541-549). Differences in susceptibility to infection with the three mold species among winter wheat, spring wheat, rye, and barley during airtight storage of high-moisture grain were evaluated using a variety of grain cultivars. To simulate air leakage into such a storage system, grain (0.96 water activity) was inoculated, packed in glass tubes with a restricted air supply and incubated at 25 degrees C for 14 days. Molds and yeasts were quantified as colony forming units (CFU) on selective media. Generally, there was no difference in infection ability between P. roqueforti, P. carneum and P. paneum. All of them reached about 10(6) CFU/g in barley and winter wheat. However, rye appeared to be resistant to infection. A comparison of different barley and spring wheat cultivars revealed that P. roqueforti, P. carneum and P. paneum grew less vigorously on the malt cultivars Maud and Mentor and the spring wheat cv. Dragon than on other cultivars. In addition, batch-related differences in resistance to mold growth were found for spring wheat cv. Dragon.
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| 6. |
- Petersson, Stina, et al.
(författare)
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Pichia anomala as a biocontrol agent during storage of high-moisture feed grain under airtight conditions
- 1999
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Ingår i: Postharvest biology and technology. - : Elsevier. - 0925-5214 .- 1873-2356. ; 15:2, s. 175-184
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Tidskriftsartikel (refereegranskat)abstract
- Pichia anomala is antagonistic against a range of spoilage molds in vitro as well as against Penicillium roqueforti in high-moisture wheat during malfunctioning airtight storage in laboratory experiments. The use of Pichia anomala to improve the postharvest control of Penicillium roqueforti during airtight storage of feed grain was evaluated in outdoor silos. Inoculated and control winter wheat (cultivar Kosack) in 160-kg portions were stored at a water activity of 0.93 for 12 months in silos that were opened twice a week. During the first 2 months, inoculated Pichia anomala increased to about 10(7) colony-forming units (CFU)/g, while naturally occurring Pichia anomala in the treatments without inoculated yeast increased from 10(4) to 10(6) CFU/g. During the same period, CO2 concentrations increased to almost 70% and stabilized at 50-60%. During the coldest period, O-2 concentrations of <1% could be detected between samplings, whereas during the rest of the storage detectable O-2 levels were only found immediately after sampling. There were no clear differences in CO2 or O-2 levels between treatments. The inoculated Penicillium roqueforti did not grow during the storage period, probably owing to high numbers of Pichia anomala in combination with the high CO2 and low O-2 concentrations in the silos. In laboratory experiments, it was found that Pichia anomala survived long-term storage in airtight sealed test tubes better at 15 degrees C than at - 20 degrees C. The aerobic stability of moist wheat after 10 and 12 months of silo storage was clearly enhanced by an initial inoculation with Pichia anomala.
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