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61.
The effects of exposure of slices of Havarti cheeses to monochromatic light of wavelengths 366 nm, 405 nm, and 436 nm, respectively, were studied by tristimulus colorimetry, solid-phase microextraction gas chromatographic analysis of volatiles, and open-end fluorescence spectroscopy. Having determined the photon fluxes of the three wavelengths by ferrioxalate actinometry, it was possible to quantify the effects of light exposure in an absolute manner. For all analyses, the most severe effects were caused by visible light, leading to colour bleaching, change in hue, riboflavin degradation, and formation of the secondary oxidation products hexanal, 1-pentanol, and 1-hexanol. Apparent quantum yields for formation of hexanal and 1-pentanol were found to be insignificantly different for 405 nm and 436 nm exposures, having values of (3-5) x 10(-5) mol x einstein(-1) and (9-13) x 10(-5) mol x einstein(-1), respectively. These compounds were not formed when exposed to 366 nm light. In contrast, 1-hexanol was formed when exposing cheese to all three wavelengths, resulting in apparent quantum yields of (2-6) x 10(-5) mol x einstein(-1). The results obtained are discussed in relation to the interplay between inherent product colorants, light sources, and transmission characteristics of the packaging materials. 相似文献
62.
Zhigang Zhu Lise Kristensen Gareth F. Difford Morten Poulsen Samantha J. Noel Waleed Abu Al-Soud Søren J. Sørensen Jan Lassen Peter Løvendahl Ole Højberg 《Journal of dairy science》2018,101(11):9847-9862
In the present study, we hypothesized that the rumen bacterial and archaeal communities would change significantly over the transition period of dairy cows, mainly as an adaptation to the classical use of low-grain prepartum and high-grain postpartum diets. Bacterial 16S rRNA gene amplicon sequencing of rumen samples from 10 primiparous Holstein dairy cows revealed no changes over the transition period in relative abundance of genera such as Ruminococcus, Butyrivibrio, Clostridium, Coprococcus, and Pseudobutyrivibrio. However, other dominant genus-level taxa, such as Prevotella, unclassified Ruminococcaceae, and unclassified Succinivibrionaceae, showed distinct changes in relative abundance from the prepartum to the postpartum period. Overall, we observed individual fluctuation patterns over the transition period for a range of bacterial taxa that, in some cases, were correlated with observed changes in the rumen short-chain fatty acids profile. Combined results from clone library and terminal-restriction fragment length polymorphism (T-RFLP) analyses, targeting the methyl-coenzyme M reductase α-subunit (mcrA) gene, revealed a methanogenic archaeal community dominated by the Methanobacteriales and Methanomassiliicoccales orders, particularly the genera Methanobrevibacter, Methanosphaera, and Methanomassiliicoccus. As observed for the bacterial community, the T-RFLP patterns showed significant shifts in methanogenic community composition over the transition period. Together, the composition of the rumen bacterial and archaeal communities exhibited changes in response to particularly the dietary changes of dairy cows over the transition period. 相似文献
63.
This work was performed to evaluate the effect of electrical stimulation (ES) on pH fall and meat quality of LD and BF in Danish halothane free pigs stunned with CO(2). ES resulted in a significant drop in pH of 0.3 units in both LD and BF and 3 h lairage resulted in 0.1 units lower pH at 20 min post mortem. Lairage time did not affect and did not interact with the effect of ES on any of the measured meat quality parameters. ES did not affect the ultimate pH in LD, BF, SM and SC or internal reflection value in LD. However, ES caused higher internal reflection and drip loss in BF and increased the PSE frequency in LD (2 to 7%) and in BF (2 to 49%). The frequency of PSE areas in the centre of SM was 70% for ES pigs compared to 9% for control pigs. ES and ageing improved the tenderness and reduced the hardness in LD as well as shear force of unaged BF. The effect of ES on tenderness and hardness was approximately half the effect of ageing, but the effect of ES and ageing were additive. ES significantly increased the activities of cathepsin B+L in the myofibrillar fraction, but there were no differences in proteolytic activity in the other fractions. It is concluded that ES improves tenderness in LD and BF, but has a negative effect on the quality of BF and SM. Therefore ES is not an economically attractive alternative for improvement of tenderness in LD compared to ageing in Danish pigs. ? 相似文献
64.
The development of PSE (pale, soft and exudative) meat is characterized by a rapid decrease in pH post-mortem and/or a low ultimate pH. We investigated some physiological properties of the live muscle (the glycogen content, the non-bicarbonate buffering capacity and 'resting pH'), which could influence both the decrease in pH and the ultimate pH. Measurements were performed on three halothane genotypes, hal(N)hal(N), hal(N)hal(n) and hal(n)hal(n), with their known predispositions for PSE meat. It was demonstrated that the glycogen content in both the groups of double recessive and heterozygous individuals was higher than the levels in the group of homozygous dominant pigs. No difference was found in non-bicarbonate buffering capacity between the groups. The groups with the highest glycogen levels also had the lowest 'resting pH' values. The results indicate that measurement of glycogen content in vivo may be superior to the halothane test in detecting PSE-prone individuals. The lower pH values of carriers of the hal(n) gene further indicate that the characteristic rapid decrease after slaughter may not be as fast as generally accepted, as even very low pH values can be observed in the muscles of live pigs. 相似文献
65.
Lei Yuan Mads Frederik Hansen Henriette Lyng Røder Ni Wang 《Critical reviews in food science and nutrition》2020,60(13):2277-2293
AbstractAttachment of microorganisms to food contact surfaces and the subsequent formation of biofilms may cause equipment damage, food spoilage and even diseases. Mixed-species biofilms are ubiquitous in the food industry and they generally exhibit higher resistance to disinfectants and antimicrobials compared to single-species biofilms. The physiology and metabolic activity of microorganisms in mixed-species biofilms are however rather complicated to study, and despite targeted research efforts, the potential role of mixed-species biofilms in food industry is still rather unexplored. In this review, we summarize recent studies in the context of bacterial social interactions in mixed-species biofilms, resistance to disinfectants, detection methods, and potential novel strategies to control the formation of mixed-species biofilms for enhanced food safety and food quality. 相似文献
66.
Diana Brumini Camilla Bø Furlund Irene Comi Tove Gulbrandsen Devold Donata Marletta Gerd E. Vegarud Christine Monceyron Jonassen 《International Dairy Journal》2013,28(2):109-111
Antiviral activity of Ragusano donkeys' milk proteins was investigated for the effect on echovirus type 5, known to infect the gastrointestinal tract of humans. Three protein fractions were tested; casein (CN), whey protein (WP) and a low molecular whey protein fraction (LWP; <30,000 Da). The antiviral activity of WP and LWP was tested on echovirus type 5 at three concentrations (1, 5 and 10 mg mL?1); CN was assessed only at the lower concentration. All donkey milk protein fractions showed significant inhibition on virus replication at the concentration of 1 mg mL?1, and both WP and LWP fractions showed significant inhibition on the virus replication at all concentrations tested. The strongest antiviral effect was observed for the WP fraction. These findings show that the different whey proteins in donkey milk, probably acting in synergy, exert antiviral activity on echovirus 5 and might contribute to prevent gastrointestinal virus infections in humans. 相似文献
67.
Alejandra Castro Galya Céspedes Sergio Carballo Björn Bergenståhl Eva Tornberg 《Food research international (Ottawa, Ont.)》2013,50(1):392-400
Yacon roots are a promising source of inulintype fructans (35 g/100 g dry matter) with a total amount of dietary fiber of about 45 g/100 g dry matter. The polydispersity of the particle size distribution of yacon aqueous suspension was reduced with increasing the degree of homogenization due to two phenomena: aggregation of particles, and disruption of large particles. Nonhomogenized yacon suspensions exhibited large cell clusters that were disrupted into small cell clusters, single cells, and aggregates. The most concentrated suspension exhibited mainly aggregates.The volume fraction of the suspensions decreased significantly with increasing the degree of homogenization. This was attributed to a denser packing of small particles and aggregates in between large particles thus allowing the water within the structure to be released.Yacon suspensions exhibited high elastic modulus (750 Pa) at low water insoluble solids content (0.9% WIS). Additional results suggested that inulintype fructans contributed to the elastic properties of yacon suspensions.The yacon suspensions studied in this work can be considered as semiconcentrated suspensions, i.e. the plot elastic modulus of the suspensions versus concentration exhibited a region immediately after the transition region. Particle interactions seem to be of great importance in this region in the particular case of yacon suspension since the elastic modulus (G′) reached 750 Pa at low water insoluble solids content (< 1%). 相似文献
68.
Setareh Amiri Laurent Duroux Jeppe Lund Nielsen Asbjørn Haaning Nielsen Donghong Yu 《纺织学会志》2013,104(3):327-336
In this study, a temperature-sensitive fabric with antibacterial properties was prepared by the formation of silver nanoparticles (AgNPs) on nonwoven poly (propylene) (PP) grafted with poly (N-iso-propylacrylamide) (PNIPAAm-PP). First, PNIPAAm was grafted onto corona-treated nonwoven PP. Afterwards, silver nanoparticles were synthesized on the temperature-sensitive hydrogel layer grafted to the surface of nonwoven PP by the reduction of silver ions (Ag+). Fourier transform infra-red spectroscopy confirmed the presence of PNIPAAm on the nonwoven PP. scanning electron microscopy-energy dispersive X-ray spectroscopy was used to investigate surface morphology and the presence of silver particles in the samples. Inductively coupled-plasma atomic emission spectroscopy revealed that the Ag content in Ag-functionalized PNIPAAm-PP was significantly higher than Ag-functionalized corona-treated PP with the same concentration of silver solution. Moreover, the results of the swelling rate experiment confirmed that PNIPAAm-PP maintained temperature-sensitive properties after functionalizing with Ag. The results showed that the formation of AgNPs with enhancement in antibacterial property was possible onto PNIPAAm-PP. 相似文献
69.
Fredriksson-Ahomaa M Murros-Kontiainen A Säde E Puolanne E Björkroth J 《International journal of food microbiology》2012,155(1-2):69-72
Yersinia enterocolitica is a psychrotrophic, facultative anaerobic zoonotic bacterium belonging to family Enterobacteriaceae and it can be transmitted from pigs to humans through pork. The growth of bacteria belonging to Enterobacteriaceae and aerobic spoilage bacteria is usually effectively restricted by 20% or more CO(2) enriched atmosphere at refrigerated temperatures. In this study, 40 samples of meat strips from pig cheek (musculus masseter) and 40 samples from hind leg (m. semimembranosus) muscles were packaged in modified atmosphere (MA) (30% CO(2)/70% O(2)) and stored at 6°C for 12d. Twenty naturally contaminated samples per muscle type were studied on days 1 and 13. Violet red bile glucose (VRBG) and de Man Rogosa Sharpe (MRS) agar plates were used for enumeration of Enterobacteriaceae including Y. enterocolitica and lactic acid bacteria, respectively. During the 12-d storage at 6°C in MA, the mean number of bacteria on pork strips of cheek meat was increasing from 1.6 to 4.5 log cfu/g and from 3.1 to 7.2 log cfu/g on VRBG and MRS agar plates, respectively. Most of the oxidase-negative isolates on VRBG plates, which were isolated from the cheek meat samples after 12-d cold storage in MA, were identified as Y. enterocolitica 4/O:3. The mean number of this pathogen was 4.1 log cfu/g varying between 2.3 and 5.4 log cfu/g. The pH of the cheek meat and leg meat was measured on days 1 and 13, and it remained high (pH>6) in most cheek meat samples during the storage. No Y. enterocolitica 4/O:3 was isolated from meat strips of hind leg. This study shows that cheek meat of slaughter pigs is contaminated with Y. enterocolitica 4/O:3 and that this pathogen can grow well on raw pork packaged in MA at 6°C even in the presence of high number of lactic acid bacteria. 相似文献
70.
Fat supplements are used in diets for dairy cows to increase energy intake and milk production and the fatty acid composition of the feed affects milk fatty acid composition. A total of 74 Danish Holstein and 41 Danish Jersey cows were divided into 4 groups and the cows within each group were fed a mixed ration supplemented with 0, 3.5, 6.8, or 10.2% of dry matter of a linseed:rapeseed (1:3) mixture during lactation wk 6 to 30. Milk yield, fat, and lactose contents were not affected by treatments for Danish Holsteins, whereas these parameters increased when increased amounts of oilseeds were fed to Danish Jerseys. For both breeds, milk protein content decreased when increased amounts of oilseeds were fed. The milk fatty acid composition showed higher concentrations of saturated fatty acids and lower concentrations of unsaturated fatty acids in milk fat from Danish Jerseys compared with Danish Holsteins. Increased amounts of oilseeds in feed increased milk fat concentration of all C18 fatty acids except C18:2 n-6, whereas the content of C6 to C14, C11 to C17, and in particular, C16, decreased. This effect was more pronounced for Danish Holsteins than for Danish Jerseys. The apparent recovery of C18:2 n-6 and C18:3 n-3 decreased when increased amounts of oilseeds were fed; however, this was most likely due to increased amounts of fatty acid from feed used for other energy demands than milk production. It was concluded that up to 6.8% of oilseed supplementation can be fed without production problems and, in many cases, with positive production responses, including an improved milk fatty acid profile. 相似文献