Effect of UV-C irradiation on inactivation of Aspergillus flavus and Aspergillus parasiticus and quality parameters of roasted coffee bean (Coffea arabica L.)

ABSTRACT

This study investigated the antifungal effect of ultraviolet-C (UV-C) against Aspergillus flavus and Aspergillus parasiticus on roasted coffee beans. Also, any changes in the quality of the roasted coffee beans were measured after UV-C irradiation. As UV-C irradiation time increased (0–2 h), the number of surviving A. flavus and A. parasiticus spores significantly (P < .05) decreased. The reduction values of A. flavus in round part, crack part, and whole roasted coffee beans were 2.16, 0.71, and 1.58 log₁₀ CFU g^?1, respectively, and the reduction values of A. parasiticus in round part, crack part, and whole roasted coffee beans were 1.03, 0.37, and 0.72 log₁₀ CFU g^?1, respectively, after 2 h of UV-C irradiation. Field emission scanning electron microscopy showed that the morphology of A. flavus and A. parasiticus spores included expanded wrinkles that were deformed by UV-C irradiation. The Hunter colours were significantly reduced (P < .05). There was no significant change (P > .05) in moisture content, but the pH was significantly decreased (P < .05). Most of the sensory parameters did not change, but there was a significant difference (P < .05) in flavour. Based on this study, 2 h of UV-C irradiation was effective in reducing 90% of A. flavus, but it was not effective against A. parasiticus present on roasted coffee beans. Also, Hunter colour, pH, and sensory parameters (flavour) were changed by UV-C irradiation.     

2-Hydroxy-4-methoxybenzaldehyde inhibits the growth of Aspergillus flavus via damaging cell wall,cell membrane,manipulating respiration thus creating a promising antifungal effect on corn kernels

This study investigated the antifungal activity and the potential antifungal mechanisms of 2-hydroxy-4-methoxybenzaldehyde (HMB) against Aspergillus flavus (A. flavus). The minimum inhibitory concentration (MIC) of HMB in preventing spore germination was 70 μg mL⁻¹. HMB at MIC disrupted cell wall integrity by reducing the number of septa by 86.66% (P < 0.05) in mycelia and increased cell membrane permeability by about 14-fold (P < 0.05) evidenced by propidium iodide (PI) staining. Furthermore, HMB at MIC inhibited respiration by 33.33%. These results revealed that the antifungal activity of HMB against A. flavus could be attributed to the damaged cell wall integrity, cell membrane permeability and respiration metabolism. What’s more, A. flavus was completely restrained in corn kernels due to HMB. Therefore, HMB could be applied as an effective antifungal agent.     

Effects of Tropical Citrus Essential Oils on Growth, Aflatoxin Production, and Ultrastructure Alterations of Aspergillus flavus and Aspergillus parasiticus

Ethyl acetate extracts and hydrodistillated essential oils from five cultivars of tropical citrus epicarps were evaluated for their inhibitory activities against Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Aspergillus parasiticus, and Penicillium sp. using disk diffusion and broth microdilution assays. Essential oils prepared from kaffir lime (Citrus hystrix DC) and acid lime (Citrus aurantifolia Swingle) epicarps exhibited stronger antifungal activity to all fungi than their ethyl acetate extracts with minimum inhibitory concentration and minimum fungicidal concentration values of 0.56 and 1.13 mg/ml (dry matter), respectively, against aflatoxin-producing A. flavus and A. parasiticus. The dominant components of the essential oil from kaffir lime were limonene, citronellol, linalool, o-cymene, and camphene, whereas limonene and p-cymene were major components of acid lime essential oil. Pure limonene, citronellal, and citronellol were five to six times less fungicidal than the natural essential oils, indicating the synergistic activity of many active compounds present in the oils. Kaffir and acid lime essential oils significantly reduced aflatoxin production of A. flavus and A. parasiticus, particularly lime essential oil, which completely inhibited growth and aflatoxin production of A. flavus at the concentration of 2.25 mg/ml. Target cell damage caused by acid lime essential oil was investigated under transmission electron microscopy. Destructive alterations of plasma and nucleus membrane, loss of cytoplasm, vacuole fusion, and detachment of fibrillar layer were clearly exhibited in essential-oil-treated cells.     

Natural Control of Corn Postharvest Fungi Aspergillus flavus and Penicillium sp. Using Essential Oils from Plants Grown in Argentina

The objective in this study was to evaluate the antifungal activity of essential oils from native and commercial aromatic plants grown in Argentina against corn postharvest fungi and to link the essential oil bioactivity with lipid oxidation and morphological changes in fungus cell membrane. Essential oil (EO) of oregano variety Mendocino (OMen), Cordobes (OCor), and Compacto (OCom), mint variety Inglesa (Mi), and Pehaujo (Mp), Suico (Sui); rosemary (Ro), and Aguaribay (Ag) were tested in vitro against 4 corn fungi: A. flavus (CCC116–83 and BXC01), P. oxalicum (083296), and P. minioluteum (BXC03). The minimum fungicidal concentration (MFC) and the minimum inhibitory concentration (MIC) were determined. The chemical profiles of the EOs were analyzed by GC‐MS. Lipid oxidation in cell membrane of fungi was determined by hydroperoxides and related with essential oil antifungal activity. The major compounds were Thymol in OCor (18.66%), Omen (12.18%), and OCom (9.44%); menthol in Mi and Mp; verbenone in Sui; dehydroxy‐isocalamendiol in Ag; and eucaliptol in Ro. OCor, Omen, and OCom showed the best antifungal activity. No antifungal activity was observed in Ag and Ro EO. The hydroperoxide value depended on the fungi (P < 0.001) and the antimicrobial agent (P < 0.001).Membrane lipids were oxidized by Sui EO in A. flavus BXC01 and A. flavus CCC116–83 (0.021 and 0.027 meqO₂/kg, respectively). The results suggest that the EOs of OCor, OMen, OCom, Mi, Mp, and Sui grown in Argentina can be used as natural alternatives to control fungi that produce mycotoxin in maize.     

Inhibition of Mold Growth by Butylated Hydroxyanisole

Direct addition of 200 ppm of butylated hydroxyanisole (BHA) inhibited growth of some species of Penicillium, Aspergillus, or Geotrichum in a Glucose Salts Broth (GSB) and of A. flavus and P. expansum in Potato Dextrose Agar (PDA) or applesauce. In processed cheese spread direct addition of 400 ppm BHA was required to inhibit growth of A. flavus or P. expansum, whereas the concentration necessary for inhibition of A. flavus by a BHA emulsion sprayed on the surface was decreased to 150–200 ppm. BHA was effective in GSB over a wide range of pH values and incubation temperatures against A. flavus at a concentration of 200 ppm. The antimicrobial activity against A. flavus was slightly decreased by autoclaving and A. flavus slightly overcame BHA inhibition on extended incubation. Lipid depressed the antimicrobial activity of BHA against A. flavus in GSB or PDA. A combination of 150 ppm BHA plus 0.2% potasssium sorbate gave total inhibition of growth of A. flavus in GSB.     

Characterization of Thermal Denaturation Structure and Morphology of Soy Glycinin by FTIR and SEM

The conformation and microstructure of soy glycinin were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy after dry heating and autoclaving thermal treatments. The changes in frequency and signal intensity of infrared bands revealed the thermal denaturation on the solid-state structure of glycinin. The Fourier transform infrared spectral changes were subsequently assessed using the second derivative spectroscopy in the amide I region (1700–1600 cm^?1). The bands at 1618 cm^?1 and 1682 cm^?1 were considered to reflect the formation of intermolecular and intramolecular aggregates (A1 and A2), and the contents of β -sheet indicated the degree of denaturation. In autoclaved samples, the contents of the glycinin α -helix, turn, random coil, and A2 significantly increased (P < 0.05), while the contents of the glycinin β -sheet and A1 significantly decreased (P < 0.05). The dry heating slightly affected the secondary structures of glycinin. The scanning electron microscopy results showed that the autoclaving treatment glycinin had denser and more uniform gel with homogeneous pores and heterogeneous granular structure, and the dry heating glycinin had crumbled multi-layered sheet like structure. The data suggested that the conformations of the autoclaved glycinins had more changes than dry thermally treated glycinins. While both dry thermally treated and autoclaved treated samples showed a high content in β -sheet structures which may adversely affect protein utilization.     

CuO nanoparticles/Indonesian cedarwood essential oil-loaded chitosan coating film: characterisation and antifungal improvement against Penicillium spp.

A novel formulation of composite coating comprising 0.8% chitosan (Chi) incorporating 0.025% CuO nanoparticles (CuO) and 0.5% Indonesian cedarwood essential oil (CEO) was fabricated by casting method. Fourier transform infrared, confocal laser scanning microscopy and scanning electron microscopy analyses were employed to characterise the biocompatibility of each formulation. Additionally, the physico-chemically properties of the composite coatings were characterised. The colour (L*), light transmission, zeta potential and roughness of Chi were significantly (P < 0.05) altered negatively by the presence of CuO or CEO; the colour (a*, b* and ∆E), apparent viscosity and transparency also changed positively as a consequence of CuO and CEO incorporation. The antifungal features of a pure Chi coating against Penicillium italicum and Penicillium digitatum were improved synergistically by CuO and CEO, confirmed by in vitro and in vivo assays. Composite coatings obtained in this work may have potential applications for active primary food packaging, particularly for fresh postharvest commodities.     

Effects of electron beam irradiation on storability of brown and milled rice

The effects of electron beam irradiation (EBI) treatment on the freshness and quality of brown and milled rice at different irradiation doses were investigated. The colors of brown rice (P > 0.05) and milled rice (P < 0.05) slightly changed after 5 kGy irradiation. After irradiation, the viscosities and amylose contents of the samples decreased (P < 0.05), crystal forms remained unchanged, but crystallinities decreased (P < 0.05). The microstructures of the samples did not change according to the results of the scanning electron microscopy. During the 120-day storage process, the free fatty acids of the irradiated samples increased at a slower rate than the non-irradiated samples did. Lipase activity was inhibited effectively, and the total viable bacterial count was significantly reduced (P < 0.05). Results indicated the potential of EBI to improve the quality and extend the shelf lives of brown and milled rice during storage.     

Evaluation of some essential oils as botanical fungitoxicants for the protection of stored food commodities from fungal infestation

Essential oils from different parts of 18 plants belonging to 11 families were extracted and tested against two toxigenic strains of Aspergillus flavus Link through the poisoned food technique. The oil of Mentha arvensis was found to be effective against both strains of A. flavus and completely stopped the radial mycelial growth of A. flavus at 0.10 mg mL^?1. It was found to be superior over the synthetic fungicides tested and showed a broad fungitoxic spectrum against A. niger, A. fumigatus, Botryodiplodia theobromae, Cladosporium cladosporioides, Fusarium oxysporum, Helminthosporium oryzae, Macrophomina phaseolina and Sclerotium rolfsii at 0.10 mg mL^?1. The oil completely inhibited the aflatoxin B1 production by the toxigenic strain of A. flavus at 0.05 mg mL^?1. Moreover, the Mentha oil also exhibited potent antioxidant activity in 2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulphuric acid (ABTS) bioassay. Keeping in mind the side effects of synthetic pesticides and the global interest in botanical pesticides for plant protection due to their biodegradable nature, M. arvensis oil may be used as a botanical fungitoxicant against fungal attack to stored food commodities. The antiaflatoxigenic and antioxidant nature of the oil suggest the possibility of its exploitation for enhancing the shelf life of stored food commodities. Copyright © 2007 Society of Chemical Industry     

Effects of extracts of spices on rumen methanogenesis,enzyme activities and fermentation of feeds in vitro

BACKGROUND: An experiment was conducted to study the effects of boiling water, methanol and ethanol extracts (0, 0.25 and 0.50 mL) of seeds of Foeniculum vulgare (fennel), flower buds of Syzygium aromaticum (clove), bulbs of Allium sativum (garlic), bulbs of Allium cepa (onion) and roots of Zingiber officinalis (ginger) on rumen methanogenesis, fibrolytic enzyme activities and fermentation characteristics in vitro. RESULTS: Ethanol and methanol extracts of fennel, clove and garlic at 0.50 mL and clove at 0.25 mL inhibited (P < 0.05) methane production. Carboxymethylcellulase activity was reduced (P < 0.05) by ethanol and methanol extracts (0.50 mL) of fennel and clove (0.25 and 0.50 mL). The extracts of clove reduced (0.25 and 0.50 mL) xylanase and acetylesterase activities, and the fennel extract (0.50 mL) reduced (P < 0.05) xylanase activity. However, the extracts of garlic (0.50 mL) increased (P < 0.05) acetylesterase activity. Concentrations of volatile fatty acids were reduced (P < 0.05) by the extracts of garlic and onion. The extracts of garlic caused a decrease (P < 0.05) in acetate:propionate ratio (A:P) at 0.50 mL, whereas A:P was increased (P < 0.05) by the inclusion of 0.50 mL extracts of clove. Methanol and ethanol extracts of clove decreased (P < 0.05) in vitro organic matter degradability. Extracts (0.50 mL) of clove decreased (P < 0.05) the numbers of total protozoa, small entodiniomorphs and holotrichs, whereas extracts of onion, ginger and garlic enhanced (P < 0.05) protozoal numbers (both entodiniomorphs and holotrichs). CONCLUSION: Ethanol and methanol extracts of fennel and garlic have potential to inhibit rumen methanogenesis without adversely affecting rumen fermentation. Copyright © 2009 Society of Chemical Industry     

Effects of exogenous fibrolytic enzymes on epiphytic microbial populations and in vitro digestion of silage

Epiphytic microbial populations, reducing sugar (RS) concentrations and in vitro fermentation were measured in unsterilised and sterilised barley silage and corn silage treated with an exogenous enzyme preparation. Enzyme treatments comprised spraying silages (10 ml kg^?1 DM) with a xylanase/β‐glucanase enzyme preparation or with water or autoclaved enzyme (controls). In Experiment 1, autoclaving the silages increased (P < 0.05) concentrations of RS present 24 h after treatment. Enzymes increased (P < 0.05) RS in both fresh and autoclaved silages, more so (P < 0.05) with autoclaving than without. Autoclaved enzymes did not affect RS concentrations relative to the (water) controls. Aerobic exposure of corn silage numerically increased microbial numbers; no microbial viability was detected in autoclaved silages. Enzymes increased (P < 0.05) total bacterial counts in all silage types, and this effect was more pronounced on aerobically exposed silage. In Experiment 2, RS concentrations were determined 0 and 24 h after enzyme treatment of silages unsterilised or sterilised with ethylene oxide (EO). Irrespective of EO or silage type, RS concentrations were higher (P < 0.05) 24 h after enzyme treatment than immediately after (0 h). In enzyme‐treated silages, 24 h RS concentrations were higher (P < 0.05) with EO than without. Reducing epiphytic microbiota by sterilisation conserved enzyme‐liberated RS in the silages. Aerobic exposure before applying enzymes enhanced RS‐associated increases in microbial numbers. Enzymes effectively released RS from silages, but utilisation of the RS by inherent epiphytic micro‐organisms may limit their availability to the ruminant. By releasing RS, exogenous enzymes may encourage silage deterioration if the interval between treatment and feeding is excessive. During in vitro incubation of freeze‐dried silages (Experiment 3), incorporation of ¹⁵N into microbial N was decreased by enzyme applied to fresh silage (before drying), but increased by enzyme applied after the silage had been dried. Moisture level of feeds and epiphytic microbial populations may influence the effectiveness of enzyme treatment for enhancing utilisation of feeds by ruminants. For the Department of Agriculture and Agri‐Food, Government of Canada. © Minister of Public Works and Government Services Canada 2002. Published for SCI by John Wiley & Sons, Ltd     

Influence of the cropping pattern on aflatoxin contamination in preharvest Kharif (monsoon) maize crop (Zea mays)

Aflatoxin contamination in three varieties of maize (Zea mays L), viz Diara composite, M₉ and Suwan composite, under various cultivation rates and planting densities was examined during the 1987 and 1989 Kharif (monsoon) crops. Cultivation rates comprising single line weeding (SLW) with one spading, SLW with two spadings and SLW with three spadings did not have significant effects on aflatoxin production in the preharvest standing crop. Of the three planting populations, the toxin level was highest under 56000 plants ha^?1 followed by 83000 plants ha^?1, and 67000 plants ha^?1 in Aspergillus flavus inoculated plots (I₁) and uninoculated plots (I₀), respectively. The variety M₉ was most susceptible to A flavus infection and supported higher aflatoxin production under I₁ condition. Aflatoxin concentration was lowest in Diara composite. Correlation analysis showed a positive and highly significant relation between A flavus incidence and aflatoxin contamination (r = +0.73, P < 0.01).     

Effects of nitric oxide on the alleviation of postharvest disease induced by Penicillium italicum in navel orange fruits

The present study evaluated the effects of 15 μL L^-1 nitric oxide (NO) on the fruit defence response of ‘Newhall’ navel orange. The decay rate of NO-treated navel orange fruits was significantly lower than that of control fruits during storage at 20 °C storage (P < 0.05). Treatment with NO suppressed the increase in disease incidence and lesion area in orange fruits inoculated with Penicillium italicum (P. italicum); significantly increased the activities of phenolic metabolism-associated enzymes and pathogenesis-related (PR) proteins, including polyphenoloxidase (PPO), phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU) and chitinase (CHT); and enhanced the activities of key enzymes, including 4-coumarate: CoA ligase (4CL), cinnamate-4-hydroxylase (C4H) and chalcone isomerase (CHI) in the phenylpropanoid pathway. The contents of total phenolics, flavonoids and lignin were also higher in NO-treated fruits than in control fruits. The findings suggest that exogenous NO could induce disease resistance against P. italicum in navel orange fruits.     

Structure characterization and its antiobesity of ball-milled konjac flour

Effect of ball-milled treatment done by high-frequency oscillatory-type mill for different time on structure and antiobesity of konjac flour was investigated. Konjac flour granules became smoother and remained its original shape in the first 1.5 h treatment, however its grain size changed from 657.3 (d₅₀) to 23.7 μm (d₅₀) after 4 h treatment, which meant that the pulverized model of konjac flour was a mixture of surface pulverized model and volume pulverized model, and mainly showed by the latter. The morphology and structural change of ball-milled konjac flour was characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electron spectroscopy for chemical analysis (ESCA). The results indicated that the crystallinity decreased while free energy increased obviously. However, thermal stability and the atomic building changed little or no. Compared with native konjac flour, the 4 h milled konjac flour could significantly decrease the body weight and total wet weight of fat of nutritional obese rats (P<0.05), and also decreased the content of triglyceride, glucose and high-density lipoprotein in blood of nutritional obese rat significantly (P<0.05). So the antiobesity effect of the 4 h milled konjac flour was significantly higher than that of the native konjac flour.     

Evaluation of Protective Effect of Freeze‐Dried Strawberry,Grape, and Blueberry Powder on Acrylamide Toxicity in Mice

Berries are dietary plants with high antioxidant activity. The aim of this study is to investigate the protective effect of berries (strawberry, grape, and blueberry) against the acrylamide (AA)‐induced general toxicity, genotoxicity, and reproductive toxicity in mice model, respectively. Mice were treated with 50 mg/kg b.w./day AA intraperitoneal injection for 5 d after feeding control diet or diet containing freeze‐dried strawberry, grape, and blueberry powder. The results showed that AA induced a significant general toxicity, genotoxicity, and reproductive toxicity in mice. Compared with the control diet, the diets containing berries could reverse the AA‐induced alterations in liver antioxidant enzymes activities (P < 0.05). Moreover, the AA‐induced genotoxicity could be prevented by the diet containing berries. The DNA damage in the lymphocyte and liver cells and the micronucleus formation in bone marrow cell were significantly alleviated (P < 0.05). Meanwhile, the mice fed with diets containing berries showed a recovery in the sperm count, the sperm activity rate, sperm motility parameters, and the abnormal sperm rate (P < 0.05). Berry powders have remarkable intervention against the AA‐induced general toxicity, genotoxicity, reproductive toxicity. Abundant phenolics, especially anthocyanins, may contribute to the intervention.     

The impact of fullerenol nanoparticles on the growth of toxigenic Aspergillus flavus and aflatoxins production in vitro and in corn flour

Antifungal and antimycotoxigenic activity of fullerenol nanoparticles (FNPs) were investigated on Aspergillus flavus growth isolated from a real food sample and aflatoxins (AFs) (AFB₁ and AFB₂) production. The final FNPs concentrations in in vitro and in commercial corn flour after the stationary incubation period of 7 and 14 days were in the range 0.16–80 µg/mL and 0.16–80 µg/g, respectively. Nanocharacterization of FNPs revealed an average size of 5–20 nm and a zeta potential of −35 mV. The highest degree of A. flavus mycelium growth inhibition (28%) after 7 days was observed for applied FNP concentration of 8.0 µg/mL, while after 14 days FNP concentration of 0.32 µg/mL led to the maximal inhibition of A. flavus mycelium growth (36%). Spearman's correlations analysis revealed a strong positive correlation between AFB₁ and AFB₂ concentrations in YES broth after 7 (R = 0.994, p < 0.05) and 14 days (R = 0.976), as well as between AFs concentrations and A. flavus mycelium mass after 7 (R = 0.786 for AFB₁ and R = 0.766 for AFB₂) and 14 days (R = 0.810 for AFB₁ and R = 0.833 for AFB₂). Paired samples t-test showed the existence of a statistically significant difference (p < 0.05) between the produced AFs concentrations after the incubation of 7 and 14 days. Regarding the artificially inoculated corn flour the lower applied FNP concentrations (0.16–0.8 µg/g) achieved a reduction of AFB₁ up to 42% and 60% after 7 and 14 days, respectively.     

Extrusion modifies some physicochemical properties of milk protein concentrate for improved performance in high‐protein nutrition bars

BACKGROUND

Extruded and ground milk protein concentrate powders, specifically those with 800 g kg^–1 protein (i.e. MPC80), imparted softness, cohesion and textural stability to high‐protein nutrition (HPN) bars. The present study evaluated some physicochemical properties of extruded and conventionally produced (i.e. spray‐dried) MPC80 to explain these improvements. Protein chemical changes and aggregations within MPC80‐formulated HPN bars during storage were characterized.

RESULTS

Extruded MPC80 powders had broader particle size distribution (P < 0.05) and smaller volume‐weighted mean diameter (P < 0.05) than the spray‐dried control. Loose, tapped and particle densities increased (P < 0.05) and correspondingly occluded and interstitial air volumes decreased (P < 0.05) after extruding and milling MPC80. Extrusion decreased water holding capacity (P < 0.05) and solubility (P < 0.05), yet improved the wettability (P < 0.05) of MPC80. MPC80 free sulfhydryl (P < 0.05) and free amine (P < 0.05) concentrations decreased after extrusion. Sulfhydryl and amine concentrations changed (P < 0.05) and disulfide‐linked and, more prominently, Maillard‐induced aggregates developed during HPN bar storage.

CONCLUSION

Extrusion and milling together changed the physicochemical properties of MPC80. Chemical changes and protein aggregations occurred in HPN bars prepared with either type of MPC80. Thus, the physicochemical properties of the formulating powder require consideration for desired HPN bar texture and stability. © 2017 Society of Chemical Industry     

Histological comparison of the dorsal ordinary muscles of wild and full‐cycle cultured Pacific bluefin tuna (Thunnus orientalis)

The histological properties of the cephalad parts of the dorsal ordinary muscles (CD‐OMs) of wild (body weight 33.3 ± 0.9 kg, n = 3) and full‐cycle cultured (body weights 13.1 ± 2.6 (FC 1), 20.2 ± 1.0 (FC 2) and 28.5 ± 3.6 (FC 3) kg, n = 3 respectively) Pacific bluefin tuna were investigated. The CD‐OMs of FC 1–3 tuna showed low moisture content (P < 0.05) and high fat content (about six times more, P < 0.05) in comparison with wild fish. A large quantity of adipose tissue was observed in the wide spaces between muscle fibres in the CD‐OMs of FC 1‐3 tuna. The muscle fibre diameter of the CD‐OM of FC 3 tuna was significantly lower than that of wild fish (P < 0.05). Myofibrils in the CD‐OM of wild tuna were surrounded by a developed sarcoplasmic reticulum and mitochondria; however, there were many glycogen granules among the myofibrils and a large quantity of fat in the CD‐OM of full‐cycle cultured fish. In particular, the glycogen content of the CD‐OM of FC 3 tuna was significantly higher (about 50 times) than that of wild fish. These results indicate that feeding and exercise conditions affect the histological structure and metabolism of the bluefin tuna muscle. Copyright © 2006 Society of Chemical Industry     

Effects of curcumin-based photodynamic method on protein degradation of oysters

Photodynamic treatment (PDT) is a novel cold-sterilisation technology, but the evaluation of the protein quality of shellfish was scarce. In this study, the effects of curcumin (CUR)-mediated PDT on delaying protein degradation of oysters during cold storage at 4 ℃ and the mechanisms were investigated. The protein-degradation indexes and related enzymes were determined every 2 days. The results showed that the content of total volatile basic nitrogen (TVB-N), polypeptide nitrogen (PeN), amino acid nitrogen (AN) and free amino acid (FAA) in photodynamic group was significantly different from the control group since the first 2 days (P < 0.05). The pH value was significantly changed by PDT at the 4th and 8th day (P < 0.05). Interestingly, the activities of serine and aspartic protease were significantly inhibited by PDT during the whole cold storage (P < 0.05). Therefore, the study indicated that PDT has a positive effect on preventing protein degradation.     

Effects of 4-hydroxy-2-nonenal on beef heart mitochondrial ultrastructure, oxygen consumption, and metmyoglobin reduction

The effects of 4-hydroxy-2-nonenal (HNE) on mitochondria isolated from bovine hearts (n = 5) were assessed using ultrastructure, oxygen consumption, membrane permeability, HNE binding, and metmyoglobin reduction in vitro. Pre-incubation (pH 5.6 and 7.4 at 25 °C) of mitochondria with HNE decreased oxygen consumption compared with samples without HNE (P < 0.05). Electron microscopy revealed that HNE-treated mitochondria were swollen and had increased membrane permeability at pH 7.4, compared with ethanol controls. Conversely, mitochondria incubated with HNE at pH 5.6 had decreased volume and permeability. Fluorescence studies indicate that HNE binds to the membrane of mitochondria isolated from bovine cardiac muscle (at pH 5.6 and 7.4). HNE-treated mitochondria at both pH 5.6 and 7.4 had lower metmyoglobin reduction and NADH dependent metmyoglobin reductase activity compared with control mitochondria without HNE (P < 0.05). In addition to covalent binding with myoglobin, HNE may influence beef color stability by interacting with mitochondria.