Occurrence of certain mycotoxins in corn and corn‐based products and thermostability of fumonisin B1 during processing

A total of 57 samples of corn and corn‐based products collected from various districts of Egypt were analyzed for Fusarium mycotoxins (T‐2, diacetoxyscripenol (DAS( deoxynivalenol (DON) and fumonisin B₁ (FB₁) and aflatoxins. FB₁ was detected in about 80%, 53.85%, 33.3%, and 28.57% of yellow corn, corn meal, white corn, and popcorn samples, respectively. The levels of FB₁ ranged from 10 to 780 μg/kg. T‐2 and DAS were detected in 5% and 10% of yellow corn samples, respectively, and DON was detected in white corn and popcorn samples at levels of 28.8 and 10.1 μg/kg, respectively. Starch samples were found to be free from Fusarium mycotoxins. Baking balady bread at 450°C/min reduced FB₁ to 72.4% while baking Franco bread at 250°C/20 min reduced FB₁ to 57.4%. Boiling of macaroni and corn in water completely removed FB₁ from contaminated samples. On the other side, corn flakes samples were found to be contaminated with aflatoxins B₁ and G₁ at levels ranging from 6 to 10 ppm, whereas 2.9% of samples were contaminated with aflatoxin B₁ > 35 ppm and G1 > 16 ppm.     

Formation of fumonisins and other secondary metabolites by Fusarium oxysporum and F. proliferatum: a comparative study

The principal aim of this study was to estimate the formation of fumonisins (FB₁ and FB₂), moniliformin (MON), and ergosterol (ERG) by Fusarium oxysporum and Fusarium proliferatum, while the formation of beauvericin (BEA) was estimated by the latter Fusarium species only. Moreover, the effect of temperature on the biosynthesis of mycotoxins was also evaluated. Fumonisins were formed by F. proliferatum, with the highest yield at 18°C (720.0–1976.6 µg g^?1 for FB₁, 74.2–670.8 µg g^?1 for FB₂) and only by three of four F. oxysporum strains at a very low level (0.02–4.77 µg g^?1 for FB₁, 0.02–2.15 µg g^?1 for FB₂). The amount of MON formed by F. proliferatum was the highest (p < 0.001) at 32°C (3056.87 µg g^?1), while MON biosynthesis by F. oxysporum was lower 227.54 µg g^?1 (p < 0.001). BEA was produced by F. proliferatum with the highest level at 25°C (p < 0.001). ERG–recognized as an indicator of fungal biomass development and as a consequence of mycotoxin formation–was found at the highest concentration at a biosynthesis temperature of 25°C for F. proliferatum and F. oxysporum (p < 0.001).     

Thermal stability of moniliformin at varying temperature, pH, and time in an aqueous environment

Moniliformin (MON) is a widely occurring mycotoxin, produced mainly by Fusarium proliferatum and Fusarium subglutinans in corn, that has been shown to be acutely toxic for various animal species and is a suspected cause of Keshan disease in China. The effects of temperature (100, 125, and 150 degrees C) and pH (4, 7, and 9) on the stability of MON were determined in aqueous buffer solutions at processing times ranging from 10 to 60 min. The percentage of MON reduction was positively related to increasing temperature and pH. MON was most stable at pH 4. After 60 min at pH 4 and 150 degrees C, MON was reduced by only 5%. Heating at pH 10 caused major reduction of MON. After 60 min at pH 10 and 100, 125, and 150 degrees C, MON was reduced by 56, 72, and 83%, respectively. One trial done at 175 degrees C and pH 10 showed that less than 1% MON remained after 60 min of processing.     

Fermentation of Soybean Meal Hydrolyzates with Saccharomyces cerevisiae and Zymomonas mobilis for Ethanol Production

Most of the ethanol currently produced by fermentation is derived from sugar cane, corn, or beets. However, it makes good ecological and economic sense to use the carbohydrates contained in by‐products and coproducts of the food processing industry for ethanol production. Soybean meal, a co‐product of the production of soybean oil, has a relatively high carbohydrate content that could be a reasonable substrate for ethanol production after fermentable sugars are released via hydrolysis. In this research, the capability of Saccharomyces cerevisiae NRRL Y‐2233 and Zymomonas mobilis subsp. mobilis NRRL B‐4286 to produce ethanol was evaluated using soybean meal hydrolyzates as substrates for the fermentation. These substrates were produced from the dilute‐acid hydrolysis of soybean meal at 135 °C for 45 min with 0, 0.5%, 1.25%, and 2% H₂SO₄ and at 120 °C for 30 min with 1.25% H₂SO₄. Kinetic parameters of the fermentation were estimated using the logistic model. Ethanol production using S. cerevisiae was highest with the substrates obtained at 135 °C, 45 min, and 0.5% H₂SO₄ and fermented for 8 h, 8 g/L (4 g ethanol/100 g fresh SBM), while Z. mobilis reached its maximum ethanol production, 9.2 g/L (4.6 g ethanol/100 g fresh SBM) in the first 20 h of fermentation with the same hydrolyzate.     

Storage stability of pineapple slices preserved by combined methods

Storage stability during 3 months was evaluated for pineapple slices preserved by combined methods (blanching for 1 min with saturated vapour, a_w reduction by osmotic concentration in sucrose syrup, pH reduction by addition of citric acid, and the addition of 1000 parts per million (ppm) of potassium sorbate and 150 ppm of sodium bisulphite). Pineapple slices were microbiologically sound and their moisture content, °Brix, pH and a_w remained almost constant during storage with mean values of 71.8%, 26.1, 3.65 and 0.978, respectively. Total sulphite and potassium sorbate concentrations of the pineapple slices were reduced during storage at 5 and 25 °C, being final concentrations 51% and 38% and 63% and 48% of the initial concentrations, respectively. Colour, texture and sensory evaluation revealed that there were no significant (P < 0.05) changes between samples stored at 5 or 25 °C. Good overall acceptability (initial mean score 7.21) of preserved pineapple slices even after 3 months storage at 25 °C (final mean score 7.02) was observed.     

Factors Influencing the Heat Resistance of a Heat-Resistant Lipase of Pseudomonas

Pseudomonas spp. MC50 produced an extra-cellular lipase that was extremely heat resistant at 100–150°C when heated in water or emulsions. The D-values ranged from 40 min at 100°C to 84 sec at 150°C. The z_D-vallue was 36°C. When heated in water, the lipase exhibited greatest survival at pH 8.5. Below pH 6.5, survival was less than 10% of that at pH 8.5. Survival of lipase heated in emulsions was affected somewhat by the type of oil, corn oil concentration, and type of emulsifier. Type of stabilizer or stabilizer concentration had little effect on lipase survival. Lipase treated with ethylenediaminetetraacetate (EDTA) was fully heat resistant in water; survival declined when lipase was heated in CaCl₂ solutions of 3–120 mM.     

Thermal stability of corn oil flavoured with Thymus capitatus under heating and deep-frying conditions

BACKGROUND: The thermal stability of corn oil flavoured with thyme flowers was determined and compared with that of the original refined corn oil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep‐frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K₂₃₂ and K₂₇₀), colour and chlorophyll, carotenoid and total phenol contents were monitored. RESULTS: The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K₂₃₂ and K₂₇₀ than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep‐frying test showed the accelerated deterioration of both oils in the presence of French fries. CONCLUSION: Compared with the control oil, the thyme‐flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance. Copyright © 2011 Society of Chemical Industry     

Optimisation of osmotic dehydration process of guavas by response surface methodology and desirability function

Response surface methodology was used to assess the effects of osmotic solution concentration (40–60°Brix), process temperature (20–40 °C) and vacuum pulse application time (0–20 min) at 100 mbar on water loss (WL), weight reduction (WR), solid gain (SG), water activity (a_w), colour parameters and mechanical properties of guava slices. Optimal process conditions were determined through the desirability function approach and quality characteristics of osmotically dehydrated guavas were analysed. Only models obtained for WL, WR and a_w were suitable to describe the experimental data. The desirability function showed that optimal conditions for osmotic dehydration of guavas were: osmotic solution concentration at 60°Brix, process temperature at 32 °C and 20 min of vacuum pulse application. Under optimal conditions, colour and mechanical properties of treated guavas were similar to fresh fruit, presenting WL of 29.01 g/100 g, WR of 25.91 g/100 g, SG of 3.10 g/100 g and a_w of 0.979.     

Thermal Inactivation of the Kanagawa Hemolysin of Vibrio parahaemolyticus in Buffer and Shrimp

A semipurified thermostable direct hemolysin (Kanagawa hemolysin) was prepared from a clinical isolate of Vibrio parahaemolyticus (strain 533- 72). Preliminary experiments determined that the hemolytic activity and mouse lethality of the hemolysin were inactivated at the same rate, that the rate was linear, and that the pH range of optimum thermal stability was pH 5.5-6.5. When approximately 256 rat erythrocyte units/g of Kanagawa hemolysin were heated at 115°, 120°, 125°, and 130°C, D values ranged from 46.5-13 min (z_c= 27°C) in Tris buffer and 48.1-10.4 min (z_c= 23.2°C) in shrimp homogenate, both at pH 7.0.     

Extrusion Cooking Reduces Recoverability of Fumonisin B1 from Extruded Corn Grits

A split-split plot design was used to determine the effects of extrusion cooking on the recoverability of the mycotoxin Fumonisin B₁ (FB₁). Unextruded and extruded samples of spiked corn grits were analyzed for FB₁ by two methods, commercial enzyme linked immunosorbant assay (ELISA) and HPLC. Extrusion cooking resulted in more apparent loss of FB₁ with mixing screws than nonmixing screws. Losses of recoverable FB1 (p≤0.05) were observed at 120°C and 160°C with the mixing screws. A linear increase in loss of recoverable FB₁ was observed (with the nonmixing screws) as the moisture content increased.     

Heat Denaturation and Emulsifying Properties of Egg Yolk Phosvitin

Phosvitin in water at pH 7 had a denaturation temperature (T_d) of 79.7 ± 1.4°C when heated at 10°C/min. When dissolved in 0.1M and 1.0M NaCl, the T_d decreased to 77.7 ± 1.2°C and 77.2 ± 1.3°C, resoectivelv. and in 10 and 20% sucrose there was no change in T_d. Heat treatment of phosvitin solutions at ≥65°C led to decreased emulsifying activity (EA). The emulsion stability (ES) decreased when phosvitim solutioni were heated at 70, 80 or 96°C for up to 60 min. The ES was not affected (p < 0.05) for phosvitin solutions after heating at ≤67.5°C for up to 60 min.     

Heat Resistance of Sporolactobacillus inulinus

Sporolactobacillus inulinus was grown on 24 media varying in carbohydrate source and concentration. A heat-resistant total count (80°C–5 min) and the thermal resistance of the spores isolated from each cell crop were determined. The highest heat-resistant couunts were obtained when S. inulinus was grown on Sporolactobacillus agar with 2%α-methyl glucoside. Cells grown in Sporolactobacillus broth with 1%α-methyl glucoside yielded the most heat resistant spores. D values (decimal reduction times) and z values were determined for each spore crop. Average D values were 53.2 min at 75°C, 19.5 min at 80°C, 6.8 min at 85°C and 5.1 min at 90°C. The average z value was 13.0°C.     

Physicochemical and functional properties of whole and defatted meals from Mexican (Cucurbita pepo) pumpkin seeds

Chemical composition and some functional and thermal properties in whole pumpkin seed meal (WPSM) and defatted pumpkin seed meal (DPSM) were determined. The DPSM exhibited higher water absorption capacity (3 g H₂O per g sample), water solubility capacity (8.75%), oil absorption capacity (2.73 g oil per g sample), emulsifying capacity (61.71%), foaming capacity (51.92%) and gelling capacity (12% w/v) than the WPSM. The DPSM also had better swelling power (3.33% at 60 °C, rising to 4.31% at 90 °C), higher phase transition temperatures (T₀ = 80.04 °C, T_p = 86.50 °C and T_f = 93.20 °C) and a higher phase transition energy (0.93 J g^?1). However, the WPSM had higher bulk density (0.57 g cm^?3) and better foam stability (from 30 to 120 min). Micrographs showed defatting to cause microstructural changes in meal starch granules and proteins. Its high protein content makes the DPSM a potential alternative input in the food industry.     

Optimization and evaluation of heat-shock condition for spore enumeration being used in thermal-process verification: Differential responses of spores and vegetative cells of Clostridium sporogenes to heat shock

To evaluate a heat-shock condition for the enumeration of Clostridium sporogenes spores, a surrogate for C. botulinum spores, we examined the heat tolerance of C. sporogenes spores and vegetative cells exposed to a heat shock at 90°C. From the D values of the spores determined in the temperature range of 113–121°C, z value (±SD) and D_90°C value were estimated to be 10.16±0.90°C and 1,071.52 min, respectively, and the inactivation rates were predicted to be only approximately 2% at 90°C for up to 10 min. Meanwhile, the viable count of spores was significantly higher when activated under a heat-shock condition of 90°C for over 9 min than those activated for shorter time periods. The heat tolerance of vegetative cells was extremely low, showing a D_90°C value (±SD) of 0.21±0.01 min. Finally, 3 different heat-shock conditions were compared: 70°C for 30 min, 80°C for 20 min, and 90°C for 10 min, and the experimental comparative data showed no significant differences in viable spore counts. Consequently, these results support that the heat-shock treatment at 90°C for 10 min is suitable to activate spores and to inactivate vegetative cells of C. sporogenes.     

Enhancing oxidative stability of frying oils by low-frequency radio wave treatment

Radio wave treatment (approximately 50 kHz frequency) on the oxidative stability was evaluated in corn oil at 180 °C and chicken frying oil for 150 cycles. Radio wave treatment decreased moisture content and critical micelle concentration of lecithin in corn oil. Moisture content in frying oil remained higher when radio wave was treated for the first 30 frying cycles. Radio wave treatment prevented lipid oxidation significantly in corn oil heated at 180 °C when moisture was not added (P < 0.05). p-Anisidine value and total polar material in chicken frying oils treated with radio waves were significantly lower than those of frying oils without radio wave treatment (P < 0.05). Radio wave treatment enhanced the stability of tocopherols in corn oil heated at 180 °C in the absence of moisture, while the reverse result was observed with moisture addition. Overall, radio wave treatment can be a useful tool to enhance the oxidative stability of frying oils by modifying their moisture content and tocopherol stability.     

PARTIAL PURIFICATION AND CHARACTERIZATION OF PEACH PECTINESTERASE

Pectinesterase (EC 3.1.1.11) was extracted from peaches (Prunus persica) and partially purified by preparative free solution isoelectric focusing. On SDS-PAGE gels, protein bands at 36.3 and 33.9 kilodaltons represented the major bands; minor bands were observed at 108.4, 40.7, and 17.0 kilodaltons. The pH optimum for pectinesterase activity in the partially purified extract was 8.0. The enzyme was stable at 30°C for 30 min between pH values of 5 and 8. Peach pectinesterase is stable when heated at 55°C for 5 min in 0.1 M NaCl, 50 mM sodium phosphate, pH 7, buffer. However, residual activity decreased to 23% of 65°C for 5 min and was inactivated at 70°C for 5 min. The energy of activation of peach pectinesterase was determined to be 34, 600 J/mol °K. The Q₁₀ between 30°C and 60°C was estimated to be 1.5–1.6.     

Gaseous chlorine dioxide inactivation of microbial contamination on whole black peppercorns

Black peppercorn is a common ingredient imported and used in uncooked or ready-to-eat foods in the United States. They might be exposed to fecal coliforms and other microbial contamination due to a lack of good agricultural and manufacturing practices in some developing countries under which they were grown and harvested, thus causing economic losses to the peppercorn industry in the United States. We investigated the effect of gaseous chlorine dioxide (ClO₂) on reducing the microbial population levels of coliforms, aerobic bacteria, yeasts, and molds on unprocessed black peppercorns. Treatments on peppercorns were conducted in a 30-L airtight chamber, and equal amounts of dry media precursors were used to generate gaseous ClO₂. Whole peppercorns (200 g) were exposed to 20, 30, and 40 g of precursor dose for up to 60 min at 21 ± 0.4°C and in combination with mild heat at 40 ± 2°C. Aerobic bacteria, coliforms, yeasts, and molds on peppercorns were enumerated before (7.4, 7.2, and 7.1 log CFU/g, respectively) and after treatments. Results after treatment demonstrated 0.8–1 log₁₀ (90%) reduction for all the microbes post-treatment at 21 ± 0.4°C. The treatments conducted with a 30 g precursor dose for 60 min at 21 ± 0.4°C reduced statistically higher (p < .05) microorganisms than those at 40 ± 2°C. Our work demonstrated that gaseous ClO₂ could be used as a part of an overall hurdle technology to reduce the coliforms, aerobes, yeasts, and molds on black peppercorns without affecting the visual quality.     

The effect of long‐term alkali treatment on the molecular characteristics of native and extruded starches at 35°C

In this study the molecular characteristics of native and extruded starches of wheat, corn, and potato were observed under long‐term alkali treatment (0.5 M NaOH, 7 days, 35°C). The molar mass distribution of samples determined by means of calibrated semi‐analytical size exclusion chromatography (SEC) showed different profiles (double and single peak distribution) depending on the dissolution status of the starch polysaccharides with simultaneous loss of supermolecular structures because of disintegration of the aggregates. The molecular range was between 4 × 103 and 2 × 106 g/mol and their calculated average molar masses were M_w = 1.7 × 105–4.1 × 105 and M_n = 2.5 × 104–1.1 × 105 g/mol. The reduction value and the value of intrinsic viscosity were additional indicators for the dissolving status of starch polysaccharides as well as for the stability of starch molecules in alkaline solution.     

Ecophysiology of Fusarium temperatum isolated from maize in Argentina

The effect of water activity (a_w = 0.95, 0.98 and 0.995), temperature (15, 25 and 30°C), incubation time (7, 14, 21 and 28 days), and their interactions on growth and moniliformin (MON), beauvericin (BEA), fusaproliferin (FUS) and fumonisin B₁ (FB₁) production by two strains of Fusarium temperatum isolated from Argentinean maize were determined in vitro on sterile layers of maize grains. The results showed that there was a wide range of conditions for growth and mycotoxins production by F. temperatum. Both strains were found to grow faster with increasing a_w and at 30°C. In relation to mycotoxin production, the two strains produced more FUS than the other mycotoxins regardless of a_w or temperature evaluated (maximum = 50 000 μg g^?1). For FUS, MON and BEA, the maximum levels were observed at 0.98 a_w and 30°C (50 000, 5000 and 2000 μg g^?1 respectively). The lowest levels for these three mycotoxins were detected at 15°C and 0.95 a_w (1700 and 100 μg g^?1 for FUS and MON respectively), and at 0.98 a_w (400 μg g^?1 for BEA). The maximum levels of FB₁ were produced at 15°C and 0.98 a_w (1000 μg g^?1). At all a_w and temperatures combinations evaluated there was an increase in toxin concentrations with time incubation. The maximum levels were detected at 21 days. Statistical analyses of a_w, temperature, incubation time, and the two- and three-way interactions between them showed significant effects on mycotoxins production by F. temperatum. For its versatility on growth and mycotoxin production, F. temperatum represents a toxicological risk for maize in the field and also during grain storage.     

Treatment of wx corn starch dispersions in a microwave reactor and their hydrodynamic properties determined using asymmetrical flow field‐flow fractionation

Hydrodynamic properties of aqueous wx corn starch (native, un‐pregelatinised) dispersions treated in a dedicated single‐mode microwave reactor at temperatures ranging from 180 to 210°C were determined using asymmetrical flow field‐flow fractionation coupled with an RI detector. The dedicated microwave reactor enabled the fine control and monitoring of heating parameters (especially temperature) during the treatment. The translational diffusion co‐efficient and hydrodynamic radii (R_h) values determined for wx corn starch treated at 180 and 200°C indicate that the majority of the material (∼98%) consisted of highly mobile, small and compact molecules/particles, with R_h values ranging from 10 to 90 nm, while the remaining ∼2% of the material consisted of considerably larger molecules/particles R_h values ranging from ∼100 to ∼200 nm). Degradation of wx corn starch was observed at 210°C.