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The major objective of this study was to assess the application of commercially available ‘clean label’ fermentates as preservatives in dressings. This study was performed in two parts. In the first, the inhibitory activities of the reference preservative (potassium sorbate) and selected fermentates – MicroGARD® 200, Nabitor, Nabitor WS, Biogard ND, Defence AM-P and Polyfence™ 35TD - towards Zygosaccharomyces bailii were assessed as a function of pH (3.5–5.0) on Sabouraud agar. In the second part, challenge, shelf-life and sensorial tests were used to determine the potential of selected fermentates to replace potassium sorbate in dressings. All preservatives had significant (p

The major objective of this study was to assess the potential of commercially available ‘clean label’ fermentates to replace the preservative function of propionate in bread. This study was performed in two parts. In the first part of the study the inhibitory activities of selected fermentates, FA (cultured corn syrup and citric acid), FB (cultured wheat solids), FC (cultured dextrose) and FD (cultured dextrose), towards Penicillium chrysogenum and Penicillium paneum were assessed as a function of pH (4.5–6.5) on malt extract agar (MEA). In the second part of the study, challenge, shelf-life and sensorial tests were used to determine the suitability of these fermentates to replace calcium propionate in bread. All the fermentates evaluated in this study had appreciable inhibitory activities towards P. chrysogenum and P. paneum . As expected the antifungal activity of the fermentates was greater the lower the pH of the growth medium. Additionally, P. paneum was generally more tolerant to the fermentates than P. chrysogenum . The challenge and sensorial tests showed that bread prepared with FA (1.3%), FB (2%) and FC (1.3 and 2%) were as microbiologically stable and sensorially acceptable as the reference. Therefore, fermentates can be used as ‘label friendly’ preservatives in bread products.

The major objective of this study was to assess the antifungal activities of commercially available 'clean label' fermentates and their potential to replace the preservative function of sorbate and propionate in cake. This study was performed in two parts. In the first part of the study the inhibitory activities of selected fermentates - FA, FB, FC and FD - towards Aspergillus tritici and Aspergillus amstelodami were assessed as a function of pH (5.0-6.5) on malt extract agar (MEA). In the second part of the study, challenge, shelf-life and sensorial tests were used to determine the suitability of these fermentates to replace potassium sorbate and calcium propionate in quarter pound cake. All the fermentates evaluated in this study all had significant (p0.05) inhibitory activities towards A. tritici and A. amstelodami within the recommended dosage range for application in bakery products. In all cases, the inhibitory activity of the fermentates increased with a decrease in the pH and an increase in concentration. FC was generally the most inhibitory whilst FD was the least inhibitory. Significant (p0.05) synergistic interactions were determined to occur between the effects of pH and concentration for all fermentates evaluated in this study. The sensorial tests with FC showed that cakes produced with ≤1% FC (on basis of the batter) did not differ significantly (p0.05) in flavour from the reference cake (0.5% calcium propionate and 0.54% potassium sorbate). However, the challenge and shelf-life tests showed that cakes produced with ≤1% FC were not as microbiologically shelf-stable as the reference cake, especially when sliced. Therefore, it can be concluded that whilst fermentates have appreciable antifungal effects, their use could potentially result in reduced shelf-stabilities. Robust challenge and shelf-life tests would be recommended before the marketing of cakes were propionate and/or sorbate has been replaced to ensure accurate shelf-lives are stated.

This study evaluated the effect of residual O2 level (0% to 5%) on microbial growth and volatile metabolite production on par-fried French fries packaged in a modified atmosphere with 60% CO2 (rest N2 ) at 4 °C. The results obtained showed that the initial headspace (IH) O2 level had an effect on growth of Leuconostoc mesenteroides on French fry simulation agar, whereby growth was slightly faster under 5% O2 . In terms of quantity, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were the most significant volatile metabolites produced by L. mesenteroides. The production of ethanol by L. mesenteroides was highest on simulation agar packaged under low IH O2 levels (0% to 1%), indicating that the fermentative metabolism was induced under these conditions. In agreement with the results observed on the simulation medium, growth of native lactic acid bacteria was faster under an IH O2 level of 5%. In addition, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were also quantitatively the most important volatile metabolites. However, in contrast, greater quantities of ethanol and dimethyl disulphide were produced on par-fried French fries packaged under 5% O2 . This was attributed to the limited growth of the native flora on the par-fried French fries under residual O2 levels of 0% and 1%. Although some significant differences (P < 0.05) occurred between the French fries packaged in 0%, 1%, and 5 % residual O2 during storage, all products were considered to be acceptable for consumption. The results of this study can be used to optimize the shelf-life of packaged chill stored potato products.

This study evaluated the decontamination of Pangasius fillets in chlorine or peracetic acid treated wash water. First, the decontamination efficacy of the washing step with chlorinated water applied by a Vietnamese processing company during trimming of Pangasius fillets was evaluated and used as the basis for the experiments performed on a laboratory scale. As chlorine was only added at the beginning of the batch and used continuously without renewal for 239 min; a rapid increase of the bacterial counts and a fast decrease of chlorine in the wash water were found. This could be explained by the rapid accumulation of organic matter (ca. 400 mg O 2 /L of COD after only 24 min). Secondly, for the experiments performed on a laboratory scale, a single batch approach (one batch of wash water for treating a fillet) was used. Chlorine and PAA were evaluated at 10, 20, 50 and 150 ppm at contact times of 10, 20 and 240 s. Washing with chlorine and PAA wash water resulted in a reduction of Escherichia coli on Pangasius fish which ranged from 0–1.0 and 0.4–1.4 log CFU/g, respectively while less to no reduction of total psychrotrophic counts, lactic acid bacteria and coliforms on Pangasius fish was observed. However, in comparison to PAA, chlorine was lost rapidly. As an example, 53–83% of chlorine and 15–17% of PAA were lost after washing for 40 s (COD = 238.2 ± 66.3 mg O 2 /L). Peracetic acid can therefore be an alternative sanitizer. However, its higher cost will have to be taken into consideration. Where (cheaper) chlorine is used, the processors have to pay close attention to the residual chlorine level, pH and COD level during treatment for optimal efficacy.

Preservation of emulsions relies on factors including pH, temperature, structure and the application of carboxylic acid preservatives, such as sorbic and benzoic acid. Organic acid preservatives tend to migrate to the lipid phase of emulsions. Taking into account the fact that organic acid in the aqueous phase is solely responsible for antimicrobial activity, this partitioning behavior is considered as a loss of preservative. The influence of microstructure properties on sorbic acid distribution and preservation effect was investigated in model food systems comprising of aqueous phase, and liquid oil and solid fat as lipid phase, which represent major constituents of water-oil emulsions. The aqueous phase of the food model systems was comprised of Yeast Nitrogen Broth (YNB) in phosphate buffer and buffered at pH 4.5, 5.5, 6.5. Sorbic acid (100 mg/L) in the form of potassium sorbate was added to the aqueous phase. Candida guilliermondii (2 log CFU/mL) was inoculated in the aqueous phase to resemble industrial post-contamination CFU levels. Growth parameters, generation time (GT) and lag phase (λ) of C. guilliermondii in the aqueous phase of the food model systems were quantified during 1 month at 7 °C and maximum 80 h at 22 °C. HPLC analyses were performed to evaluate total sorbic acid content in each food model system. Sorbic acid inhibited growth of C. guilliermondii in YNB + SA at pH 4.5 at 7 °C and 22 °C. The presence of liquid oil caused partitioning of sorbic acid into the lipid phase in YNB + SA|oil at pH 4.5 at 7 °C and 22 °C, reducing its inhibitory effect. Adding solid fat into the model food systems significantly prolonged lag phase duration in the YNB + SA|oil + fat system at pH 4.5 at 22 °C and growth was inhibited at 7 °C. HPLC analysis showed a final aqueous sorbic acid concentration of 34 mg/L and 44 mg/L in YNB + SA|oil system at pH 4.5 at 7 °C and 22 °C after 1 month and 168 h, respectively. In YNB + SA|oil + fat system at pH 4.5, 87 mg/L of aqueous sorbic acid was measured after 1 month at 7 °C and 168 h at 22 °C, indicating that the presence of solid fat retards sorbic acid partitioning. Results show that structural components such as liquid oil and solid fat have an effect on the aqueous sorbic acid concentration and its preservation effect. The presence of solid fat reduces the tendency of sorbic acid to partition into the lipid phase, which is reflected in the inhibitory effect of sorbic acid on C. guilliermondii.

The effect of initial headspace (IH) O2 level on the shelf-life of fresh-cut pineapple was evaluated in this study. The results showed that although the IH O2 level had a minor effect on the growth of Candida argentea, Candida sake and Meyerozyma caribbica on pineapple agar, the quantities of the volatile organic metabolites produced by these yeasts was generally smaller the lower the IH O2 level. The only exception was the production of ethyl acetate by C. argentea, which was higher at low IH O2 levels. In triangle tests performed with trained panellists, pineapple cubes packaged in an IH of 5% O2 were determined to be significantly different (P < 0.05) to those packaged in 21% O2 from day 5 of storage. Preference was shown for the pineapple cubes packaged in an IH of 5% O2. The results imply that packaging in an IH O2 level of 5% could be used to extend the shelf-life of fresh-cut pineapple.

Fresh-cut fruit such as pineapple have a very limited shelf-life. The study aims at prolonging the shelf-life of fresh-cut pineapple by means of modified atmospheres (MAs). The effect of MAs combining high O2 (21–70%) and CO2 (21–50%) levels on microbial spoilage and sensory quality of fresh-cut pineapple was therefore evaluated. In the first part of the study, the behaviour of two spoilage yeasts (Candida sake and Candida argentea) and one lactic acid bacterium (Leuconostoc citreum), which had previously been isolated from spoiled commercial fresh-cut pineapple cubes, were monitored on pineapple agar separately. In the second part of the study, the shelf-life of commercial fresh-cut pineapple cubes packaged in selected MAs was evaluated at 7 °C. The results showed that MAs combining high O2 and high CO2 levels had a large inhibitory effect on the growth and volatile metabolite production of C. sake and C. argentea on pineapple agar. A MA with 50% O2 and 50% CO2 was in both cases the most inhibitive. Although MAs induced the production of ethyl acetate by the yeasts, the quantity of ethyl acetate was much lower in high O2 and high CO2 than that in air due to lower yeast population density in MAs. With regards to growth, L. citreum was not sensitive to high O2 and CO2 levels. The fresh-cut pineapple packaged in air had deteriorated and were not acceptable any more by day 7, while those packaged in 50% O2 combined with 50% CO2, which also retarded the growth of aerobes and yeasts on pineapple cubes during storage, were still acceptable. It can be concluded that a MA with 50% O2 and 50% CO2 shows the best potential for extension of the shelf-life of fresh-cut pineapple.

The growth-inhibiting effects of simple and commercial salt replacers on the growth of Listeria monocytogenes were determined in broth at 7C. The divalent chlorides, CaCl2 and MgCl2, had the largest antilisterial activities at equivalent water phase concentrations or molalities followed by NaCl ≈ KCl and MgSO4 in decreasing order of antilisterial effect. Additional antilisterial activities other than their water activity depressing effects were observed for CaCl2 and MgCl2. Challenge tests performed on cooked ham and white sauce showed that reduction of NaCl levels by ≤28 and 33%, respectively, did not affect the stability of these products to L. monocytogenes. It can be concluded from the study that changes in the stability to L. monocytogenes are most likely to occur when NaCl is fully reduced and/or replaced or partially replaced by either CaCl2 (increased stability) or MgSO4 (reduced stability). Practical Applications The association of high dietary NaCl levels to hypertension and cardiovascular diseases has led to concerted efforts in the food industry to reduce NaCl levels. To date, several studies have been performed, which have focused primarily on addressing the sensorial, technological and shelf life aspects, with far less emphasis being placed on the food safety aspects. The results of this study provide much needed insight into the potential food safety consequences of reduction and/or replacement of NaCl in food products.

The ability of the meat isolate Staphylococcus sciuri I20-1 to inhibit food-borne pathogens in view of its application as a functional starter culture for the production of clean-label fermented meats was investigated. The strain produced a heat-stable antibacterial compound of a proteinaceous nature that was released following primary metabolite production kinetics. Its specific inhibitory spectrum included different strains of Staphylococcus aureus and both vegetative cells and spores of Clostridium botulinum . These two species pose potential biosafety hazards, in particular when producing fermented meats with a mild pH and without added nitrate and nitrite salts. Up till now, starter-culture based strategies to restrain S. aureus and C. botulinum have barely been explored in fermented meats, in contrast to the frequently investigated use of antilisterial cultures of lactic acid bacteria. When added to a fermented sausage model, S. sciuri I20-1 acted as a persistent culture throughout the fermentation process, during which it was able to produce its antibacterial compound in situ . In co-culture experiments, an immediate two-log inactivation of a S. aureus strain was found, even before production of the antibacterial compound could be detected. This was probably due to an instant pH-driven desorption of the antibacterial molecules from the producer cells when added to the meat batter. However, a sub-population of S. aureus that was resistant to the antibacterial compound was able to grow out to the same final counts as in the control experiment performed with a non-inhibitory strain of S. sciuri . This finding is indicative of the potential pitfalls when extrapolating promising in vitro results to the true complexity of fermented food matrices.

This study evaluated the effect of modified atmospheres (MAs) with different O(2) concentrations on microbial growth and volatile metabolite production in gray shrimp (Crangon crangon) during storage at 4 °C. Eight MAs were evaluated in total. Four of the MAs evaluated were without CO(2): 0/0/100, 0/10/90, 0/30/70, 0/50/50 (% CO(2)/O(2)/N(2)) whilst the other four MAs all contained 50% CO(2): 50/0/50, 50/10/40, 50/30/20, 50/50/0 (% CO(2)/O(2)/N(2)). Volatile spoilage metabolites were identified by thermal desorption GC-MS and quantified during storage by selective ion flow tube mass spectrometry (SIFT-MS). In comparison to microbial growth observed with an atmosphere of 100% N(2), microbial growth was stimulated by the addition of O(2) in the MAP in the absence of CO(2.) Under these conditions the total psychrotrophic counts exceeded 7 log cfug(-1) after just 3 days of storage. However, in the presence of 50% CO(2) the total psychrotrophic count exceeded 7 log cfug(-1) after 5 days of storage. The combination of 50% CO(2) and 50% O(2) significantly inhibited microbial growth. For this MA condition, a diminishing effect on the production of metabolites was also observed, especially for amines and sulfur compounds, which constituted the major fraction of components causing the offensive odor.

In the presence of oxygen, ascorbic acid (AA) is readily degraded to dehydroascorbic acid (DHA), which is prone to further degradation, hereby losing its vitamin C activity. In this study, the influence of different initial headspace O 2 concentrations on the oxidation of AA and the subsequent formation and breakdown of DHA was investigated in a model fruit juice. Kinetic rate constants for solely AA degradation were estimated using zero and first order kinetics, while first order irreversible and reversible consecutive models were used to describe the degradation kinetics of AA combined with the oxidative formation and irreversible breakdown of DHA. A linear relationship was found between the first order AA degradation constants and the initial headspace oxygen concentrations. Further, a similar relationship was found for a commercial fruit juice. In this way a tool is provided to predict the AA content in fruit juices at different stages during storage, knowing the residual headspace oxygen concentration after packaging, the O 2 -permeability of the packaging material and the initial AA and DHA concentration.

The relationship between water activity ( a w ) and concentration of NaCl, sucrose and various simple and commercial salt, sugar and fat replacers was determined. The model originally developed by Favetto and Chirife (1985) and extended by Roa and Tapia (1998) was successfully used to model the relationship between a w and molality of the binary and multi-component aqueous solutions. These models were then reparameterized to enable the a w to be modeled as function of the water phase concentrations of binary and multi-component solutions. This reparameterization enables the modeling of the a w depressing effects of compounds for which sufficient data required to calculate the molecular weight cannot be obtained. Both models were successfully used to predict the a w of some food products including meat and fish products and mayonnaises with average deviations of 0.0052 from the measured a w , and bias and accuracy factors of 0.995 and 1.0057, respectively.

The exposure to fumonisins from the maize harvest of 2006 (before and after sorting and storage) for 67 families was assessed along with its statistical association with agronomic practices in Rombo, Tanzania. Fumonisins were determined by high-performance liquid chromatography (HPLC) and exposure estimated based on 60 kg body weight and maize intake of 356 g per person day-1. Based on contamination in the unsorted maize, exposure for 27% of the families would exceed the provisional maximum tolerable daily intake of 2 µg kg-1 body weight. The odds ratio of fumonisin exposure from maize hybrid 614 (H614) were: two times higher compared with non-H614 maize (p = 0.089); and five times higher when the maize was grown without fertilizer (p = 0.004). Sorting maize before storage reduced the percentage of families with unacceptable exposures to 6%. Therefore, the results imply that planting of the non-H614 seeds using fertilizers combined with pre-storage sorting of maize significantly minimizes fumonisins exposure in Rombo. A field experiment to verify these findings is needed.

The combined effects of water activity (a(w)) and ammonium/sodium bicarbonate on growth and mycotoxin production in corn by Fusarium and Aspergillus species were investigated. Interaction was observed between the salts and a(w) on the colony growth rates and lag phase durations of all isolates. Growth stimulation at low salt levels was observed only for the Fusarium isolates as the fastest growth of F. verticillioides and F. proliferatum occurred at levels of 0.1-0.2 and 0.5% ammonium and sodium bicarbonate, respectively. Although the complete inhibition of the growth of the Fusarium and Aspergillus isolates investigated took place at a level of 1% ammonium bicarbonate as much as 4% sodium bicarbonate failed to completely inhibit the growth of the Aspergillus isolates. Increase in concentration of either salt generally resulted in large reductions of both fumonisin B(1) and aflatoxin B(1) production. According to the sensorial analysis performed, corn treated with up to 1% ammonium bicarbonate was still acceptable for consumption, whereas corn treated with at least 2% sodium bicarbonate was determined to be sensorially unsuitable. Ammonium bicarbonate can be concluded to be more suitable for protecting stored corn from fungal contamination as it was capable of completely inhibiting both growth and mycotoxin production of the Fusarium and Aspergillus isolates of most importance to corn at levels that were still sensorially acceptable. Therefore ammonium bicarbonate could possibly be applied as a cheap and easy to apply treatment for use in resource limited developing countries.

The two major fumonisin-producing Fusarium species are Fusarium verticillioides and Fusarium proliferatum. The growth and fumonisin production of these two isolates on corn was studied at water activities (a(w)) between 0.860 and 0.975 and at temperatures between 15 and 30 degrees C. Growth rates (g, mm/day) were obtained by linear regression during the linear phase of growth. In general, growth rates for both isolates increased significantly (P < 0.05) with increases in a(w) and temperature. Both fumonisin production and radial growth (mycelial development) for both isolates increased with a(w) at all temperatures investigated, but the effect of temperature on this relationship was not obvious. The effect of temperature on fumonisin production at high a(w) values optimal for growth was only marginal, whereas at lower a(w) values the effect of temperature was more pronounced, with more fumonisin production occurring at temperatures not optimal for growth. The optimum temperature for fumonisin production was between 15 and 25 degrees C. For F. proliferatum, the optimum temperature for growth at all a(w) values, 30 degrees C, resulted in the poorest fumonisin production. For both isolates, the slowest initial rate of fumonisin production was at 15 degrees C, the temperature at which the slowest growth rates were obtained.

This study evaluated the potential of modified atmospheres (MAs) combining high oxygen (O₂) and high carbon dioxide (CO₂) levels to extend the shelf-life of fresh-cut honeydew melon. Firstly, the effect of MA on the growth and volatile organic metabolite production of Candida sake, Leuconostoc mesenteroides and Leuconostoc gelidum, which had all been previously isolated from spoiled commercial fresh-cut honeydew melon, was evaluated separately on honeydew melon agar at 7 °C. Additionally, the effect of selected MAs on the microbial, physico-chemical and sensory quality of commercial fresh-cut honeydew melon cubes was evaluated at 7 °C. The results showed that MAs with high O₂ and high CO₂ levels greatly retarded the growth, CO₂ and volatile metabolite production (i.e. ethanol, 2-methyl-1-butanol, ethyl acetate, phenylacetic acid, nonanal) of C. sake on honeydew melon agar; especially MAs consisting of 50% O₂+50% CO₂ and 70% O₂+30% CO₂. In contrast, the MAs evaluated only had a minor effect on the growth and volatile metabolite production of L. mesenteroides and L. gelidum. Overall, the effect of MAs on colour, juice leakage, juiciness, and firmness of fresh-cut honeydew melon was small during storage. Sensory preference was generally for fresh-cut honeydew melon cubes packaged in MA of 50% O₂+50% CO₂. These were still acceptable on day five of storage and had appreciably lower populations of yeasts and lactic acid bacteria, lower quantities of volatile organic compounds, but slightly stronger colour oxidation compared to honeydew melon that was packaged in air. Additionally, most of the samples packed in air had blown by day five due to the large quantity of CO₂ production during storage. Therefore, 50% O₂+50% CO₂ is a potential MA solution for extending the shelf-life of fresh-cut honeydew melon.

The major objective of this study was to evaluate and model the combined effect of the water activity (a(w)) and pH of the heating menstrum on the heat resistance of spores of a psychrotolerant Bacillus cereus strain isolated from béchamel sauce. Two models, a quadratic polynomial equation and a reparameterized function, were assessed for their ability to describe the combined influence of a(w) and pH on the D(85°C)-values of the B. cereus isolate in tryptone soy broth. The performance of the models was validated by challenging the models with data independently collected in broth and béchamel sauce. Both models were found to adequately describe the validation data obtained in broth. However, it was determined that in béchamel sauce the predictions of the polynomial function not only showed bias (bias factor = 1.156) but were also fail-dangerous, as they deviated from the validation data by 17.2%. The reparameterized function was determined to be a good predictor of the D(85°C)-values in béchamel sauce as it showed no bias (bias factor = 1.033) and its predictions differed by only 7.9% from the validation data. The reparameterized function can be used to provide estimates of the minimum processing conditions required to achieve desired levels of spore inactivation within the a(w) and pH ranges studied and to determine the potential changes in heat resistance of B. cereus spores when a(w) and pH are changed, for example, during product reformulation. As validation of heat resistance models is rarely performed, let alone in actual food products, the models evaluated and validated in this study (in particular the reparameterized function) are of immediate relevance to the food industry.

The major objectives of this study were to determine the incidence, diversity and characteristics of Bacillus cereus group spp. isolated from food products marketed in Belgium. The food products investigated in this study included cooked pasta, lasagna, bechamel sauce, bolognaise sauce, fresh minced beef, fresh-cut vegetables and raw basmati rice. B. cereus group spp. were detected in 56.3% (324 of 575) of the samples giving rise to 380 strains. The highest incidence (100%) occurred in the raw basmati rice. Although only 10 (2.6%) of the 380 isolates were determined to be psychrotolerant (able to grow at ≤7°C), 25 (6.2%), 189 (49.7%) and 334 (87.9%) isolates were able to grow at mild temperature abuse conditions of 8°C, 9°C and 10°C, respectively. The large diversity of the isolates obtained (overall and between isolates obtained from the same product type) was highlighted by the results of the (GTG)(5) PCR fingerprinting of 80 selected isolates. Sixty-one of these 80 isolates belonged to 15 distinct clusters (≥85% Pearson correlation) whereas the remaining 19 were each clustered separately. Further diversity was also found in the distribution of toxin genes as 16 different profiles were observed in the 80 selected isolates. Whilst none of 80 selected strains harboured the ces gene required for the production of the emetic toxin cereulide, 42 strains (52.5%) carried all seven genes required for the production of the diarrhoeal enterotoxins: haemolytic BL, non-haemolytic enterotoxin and cytotoxin K. The results of this study highlight not only the omnipresence but also the highly diverse ecology of B. cereus spp. within and across several food product types available on the retail market in Belgium. They should also provide the impetus for more studies to enable detailed risk assessment studies to be performed.

Feeding children with maize may expose them to fumonisins (FBs). This study assessed FB exposure for infants consuming maize in Tanzania by modeling maize consumption data (kg/kg body weight (bw)/day) with previously collected total FB contamination (microg/kg) patterns for sorted and unsorted maize harvested in 2005 and 2006. Consumption was estimated by twice conducting a 24 h dietary recall for 254 infants. The exposure assessment was performed with the @RISK analysis software. Of the infants, 89% consumed maize from 2.37 to 158 g/person/day (mean; 43 g/person/day +/- 28). Based on the contamination for sorted maize; in 2005, the percentage of infants with FB exposures above the provisional maximum tolerable daily intake (PMTDI) of 2 microg/kg (bw) (26% (95% confidence interval (CI); 23-30)) was significantly higher than the level of 3% (90% CI; 2-12) in 2006. Pooling the datasets for sorted maize from the two seasons resulted in a seemingly more representative risk (10% (95% CI; 6-17)) of exceeding the PMTDI. However, infants who might have consumed unsorted maize would still be at a significantly higher risk (24% (95% CI; 15-34)) of exceeding the PMTDI. Sorting and other good maize management practices should be advocated to farmers in order to minimize FB exposure in rural areas.

The effect of natural phenolic compounds (vanillic and caffeic acid) and water activity (a(w)) on the growth and mycotoxin production on corn by Fusarium and Aspergillus isolates was investigated. Large differences were observed in the response of the Fusarium and Aspergillus isolates to the phenolic compounds, mostly determined by their genus. Generally for both F. verticillioides and F. proliferatum, an increase in concentration of either caffeic or vanillic acid resulted in a decrease in the colony growth rate and increase in the lag phase duration. Growth of the Fusarium isolates was not completely inhibited at the highest a(w) value evaluated of 0.967, with complete inhibition only being observed at combinations of high phenolic acid concentrations (> or =2000 microg g(-1)) and low a(w) values (0.948). Within the experimental limits investigated, growth of the Aspergillus species was not affected by the phenolic compounds. Application of the phenolic compounds significantly reduced fumonisin B(1) and aflatoxin B(1) production. Although the effects noted in artificial media appear to be carried over to corn, rather high concentrations are required to observe similar effects on corn and to completely inhibit growth where possible. This implies the occurrence of interactions of the phenolic compounds with some matrix components which may reduce their overall effectiveness.

This paper is the second in a series of two that describe the effect of modified atmospheres on the growth and mycotoxin production of Fusarium verticillioides and Fusarium proliferatum on corn. In this part, the effect of initial headspace (IH) oxygen concentration and its interaction with water activity (aw) on growth and fumonisin B1 production was investigated. In addition, the impact of vacuum packaging and in-cooperation of O2 scrubbing sachets was also studied. It was observed that at all aw values studied, reduction of IH O2 concentration from 20 to 2% had no significant effect on the colony growth rate (g, mm d− 1) and lag phase duration (λ, d). However, g and λ were positively and negatively correlated to aw. The IH O2 concentration was determined to have a aw dependent effect on the oxygen consumption rate. Although the maximum colony diameter (Dmax, mm) decreased with the reduction of the IH O2 level, the greatest mycelial density occurred at 10% IH O2 for both isolates. This observation was accompanied by a trend of a decrease in the value of the IH O2 level at which the most fumonisin B1 was produced from 15 to 5% when the aw was decreased from 0.976 to 0.930 for F. verticillioides. For F. proliferatum the optimum conditions for fumonisin B1 production shifted from 20% at aw 0.976 to 10% at both 0.951 and 0.930. Vacuum packaging and the in-cooperation of O2 absorbing sachets completely inhibited the growth of both isolates. These results together with those reported in Part I of the study indicate that O2 should preferably be completely excluded from modified atmospheres that are employed to protect stored corn from fungal growth and mycotoxin production.

The effect of mobile phase pH, column temperature, extraction method and derivatisation time on the fluorescence response and recovery of fumonisin B1 in corn was investigated. Column temperature and mobile phase pH were negatively and positively correlated with the fluorescence response, respectively. Use of an Ultraturrax blender for extraction resulted in higher FB1 recoveries compared to a rotary shaker. In contrast to other reports, maximum fluorescence response occurred after a derivatisation time of 8 min. These results reflect on the absolute requirement for standardisation of the aforementioned parameters.