Increased aflatoxin contamination of dried figs in a drought year

Dried figs (4917 samples) destined for export from Turkey to the European Union were collected between September and December during the very dry crop year of 2007 and tested for aflatoxins B₁, B₂, G₁ and G₂ by immunoaffinity column clean-up and reverse-phase high-performance liquid chromatography (RP-HPLC). While 32% of the samples contained detectable levels of total aflatoxins, 9.8% of them exceeded the European Union limits. Aflatoxin levels were in the range of 0.2–259.46 µg kg^?1 and 2.04–259.46 µg kg^?1 for all samples and samples that exceeded the limits, respectively. A substantial increase in the incidence of aflatoxins was observed in 2007 compared with previous years, most likely due to the drought stress, high temperatures and low relative humidity encountered during the period from January to September of that year. In 2007, the mean temperature was 1–2°C higher, there was 300 mm less total rain, and the mean relative humidity was 10–15% lower than in 2002–06. The average concentration of individual aflatoxins present in the samples was quantified to determine whether the drought conditions promoted certain types of aflatoxins. Among the contaminated samples, aflatoxin B₁ occurred in 97% of the contaminated samples, followed by G₁ in 47%, B₂ in 24%, and G₂ in 6% of samples. Concentrations of individual aflatoxins exhibited great variability among the samples but were not significantly different from those reported in previous studies, which were conducted under conditions without drought and high temperatures.     

Preliminary studies of the effects of heat and gamma irradiation on the production of aflatoxin B1 in static liquid culture,by Aspergillus flavus link NRRL 5906

Aflatoxin B₁ production by a strain of Aspergillus flavus NRRL 5906 was examined in static liquid culture in maize meal broth (MMB) and maize meal broth supplemented with 2% glucose and 2% peptone (AMMB). Erlenmeyer flasks were inoculated with 1.0 ml aliquots of fungal spores which had been heat-treated (60°C for 30 min) under low humidity (< 45% R.H. dry heat) or high humidity conditions (>85% R.H., moist heat) followed by gamma irradiation with either 0.0, 3.5 or 4.0 kGy. AMMB supported 6–17 times more vegetative growth (depending on the heat and dose combination) than spores incubated in MMB alone. High inoculum size of control unheated spores (log CFU/g, 6.9) yielded the least aflatoxin B₁ in flasks containing AMMB (8.2–19.3 μg/ml). A dose of 3.5 kGy reduced by 3.2–3.8 log cycles the viable inoculum of control unheated spores, resulting in 2–5 fold increase in aflatoxin B₁ formed in flasks containing AMMB. Increasing the applied load to 4.0 kGy, however, reduced aflatoxin B₁ levels formed in AMMB to similar or lower levels than found in flasks inoculated with control unirradiated spores. Combination treatment of A. flavus with dry heat and 3.5 kGy reduced the spore inoculum size by about 4 log cycles and yielded the highest amount (41.1 μg/ml) of aflatoxin B₁ in AMMB. However, moist heat treatment of spores receiving the same dose (3.5 kGy) reduced toxin level formed by 25%. Aflatoxin B₁ formation by A. flavus spores incubated in AMMB was completely prevented by a combination treatment of moist heat and 4.0 kGy of gamma irradiation. This same treatment attenuated aflatoxins B₂, G₁ and G₂ production which are formed with B₁ by A. flavus NRRL 5906. Spores raised in all flasks containing MMB did not form aflatoxin except when the medium MMB was autoclaved twice at 121°C for 15 min.     

Bacteria Associated with Spoilage of Braunschweiger

Refrigerated braunschweiger was spoiled mainly by Gram positive, catalase negative coçci identified as Streptococcus faecalis and Pediococcus pentosaceus. P. pentosaceus was isolated from sausage without nitrite held at refrigeration for 12 wk and from sausages made with 156 ppm nitrite stored at 22°C for 21 days. It produced souring and a low pH in the sausage. S. faecalis was isolated from refrigerated sausages and produced a perfumy or scented odor under anaerobic conditions. S. faecalis survived 65°C for 5 min and 60°C for 60 min. P. pentosaceus at levels of 10⁸ cells/ml of broth survived 65°C for 5 min but did not survive when the number of cells was 10³/ml.     

Role of Acetaldehyde Production in the Removal of Astringency from Persimmon Fruits under Various Modified Atmospheres

Astringency of persimmons was removed by enclosing the fruits in polyethylene bags under vacuum or by replacing air with N₂ or CO₂. Acetaldehyde produced by the fruit under these conditions accumulated at different rates. The rate of the deastringency process was directly proportional to the level of acetaldehyde accumulation. Thus, the fruit held at 20°C in CO₂ was the first to lose its astringency, but showed internal browning after 1 wk. Fruits under vacuum or N₂, where less volatiles accumulated, maintained their high quality and firmness for 2 wk at 20°C or 3 months at ? 1°C. However, fruit held under vacuum began to show internal browning when acetaldehyde accumulated above a certain level.     

Mould contamination and the influence of water activity and temperature on mycotoxin production by two aspergilli in melon seed

Both the moisture levels and the incidence of mould contamination recorded for shelled water melon seed samples (22) obtained from 9 markets were generally higher as those recorded for the unshelled seed samples. 16 fungi, mostly toxigenic, were isolated from the surface-disinfected mouldy seeds. Of these isolates, 7, 3 and 2 species belonged to Aspergillus, Penicillum and Fusarium genera, respectively, while Botryodiplodia, Rhizopus, Sclerotium and Syncephalastrum had one respresentative each. Production of aflatoxins (B₁, B₂) by 5 toxigenic strains of Aspergillus flavus and of ochratoxin A by 4 toxigenic strains of A. ochraceus in melon seed at varying water activity (a_w) and temperature levels were investigated. Of the a_w levels (0.65, 0.70, 0.80, 0.90 and 0.98) provided, toxins were detected only at and above 0.80 with the peak production recorded at either 0.90 or 0.98 a_w level. Whereas aflatoxins were produced and detected under all the test temperatures (15, 20, 25, 30, 35, and 40 °C), the elaboration of ochratoxin A was detected only as from 25 to 40 °C. Optimum temperature for toxin production by all the strains of the two fungi used was 30 °C.     

Spoilage moulds and aflatoxins from poultry feeds

Aflatoxin producing strains of Aspergillus flayus Link (IMI 280819) and A. oryzae (Ahlb.) Cohn (IMI 280831) were among the eleven spoilage moulds isolated from five types of poultry feeds. The recorded pH and moisture content values of the various feeds are conducive to mould deterioration. All the four principal aflatoxins (B₁, B₂, G₁, G₂) were detected in the analysed feeds though at toxicologically ‘safe’ levels for most farm animals. Significant quantities of aflatoxin B₁ were produced by the two fungal isolates in all the five classes of poultry feeds with A. flavus yielding the larger amounts. Optimum aflatoxin B₁ production and mycelial growth in chick mash infusion medium were recorded for both species at 30 and 35 °C, respectively and similarly on the 8th and 6th day respectively when cultures were incubated at 30 °C.     

The production of aflatoxins in fresh date fruits and under simulated storage conditions

Sixteen varieties of date fruit (Phoenix dactylifera) at three stages of maturation (Kimri, Rutab and Tamr) were examined for the presence of fungi and analysed for aflatoxins B₁, B₂, G₁ and G₂ and sterigmatocystin. Single samples of each variety were used in the study. Samples as received were initially examined for mycoflora and toxin levels and then stored at 98% relative humidity and 30 °C for 14 days to investigate the effects of possible adverse storage conditions on mycoflora and, in particular, aflatoxin formation. All samples showed an absence of aflatoxins and their precusor, sterigmatocystin, after adverse storage for 14 days, although aflatoxin‐producing Aspergillus flavus isolates were identified in 10 varieties at the first stage of maturation (Kimri). High fungal counts were associated with the Rutab stage and low counts with the Tamr stage. The counts of A flavus ranged from 5.00 to 8.16 log₁₀(cfu g^?1) under simulated storage conditions, and three varieties contained significant levels of aflatoxin B₁ or B₂ ranging from 35 to 11 610 µg kg^?1. Sterigmatocystin was not detected in any of the samples as received or under simulated storage conditions. © 2002 Society of Chemical Industry     

Life history studies of externally feeding pests of stored sorghum: Corcyra cephalonica (Staint.) and Tribolium castaneum (Hbst)

A laboratory study of the ecology of single-species populations of C. cephalonica (Staint.) and T. castaneum (Hbst) was made on sorghum at three temperatures (25, 30 and 35°C) and three relative humidities (60, 70 and 80% r.h.). The effects of two lower humidities (40 and 50% r.h.) on both species were also studied at 30°C. The optimal conditions for multiplication of C. cephalonica were found to be 30°C and 60–80% r.h., while for T. castaneum the optimal temperature was 35°C at the same range of humidity. Lower humidities (40 and 50% r.h.) had a small adverse effect on both species. The results are compared with those of other workers and discussed in relation to the distribution of the two species in Sudan. It is concluded that the pest potential of C. cephalonica has been underestimated in the past.     

Quality of Green Beans, Bell Peppers and Spinach Stored in Polyethylene Bags

Quality attributes of packaged and unpackaged vegetables generally decreased nonlinearly during storage at 10°C or 20°C, and most of the decrease was greater at 20°C than at 10°C. Packaging reduced weight loss of green beans and spinach kept at 20°C; and reduced chlorophyll loss of green beans at 10°C and of spinach at 20°C. Ascorbic acid (vitamin C) benefited by packaging of green beans and spinach kept at 10°C. Packaging had an effect on thiamin (vitamin B₁) of only spinach held at 10°C and 20°C and had no effect on riboflavin (vitamin B₂). Loss of these quality attributes appears to be enhanced with water loss.     

Observations on the biology of Oryzaephilus acuminatus Halstead with comparative notes on the common species of Oryzaephilus (Coleoptera; Silvanidae)

The development of Oryzaephilus acuminatus Halstead was investigated over a range of temperatures from 17.5–40°C in combination with humidities from 15–90% r.h. on oatmeal. Development was also studied on groundnuts and copra meal at 30°C, 70% r.h. Eggs failed to hatch at 15°C but eclosion occurred at all other temperatures. The shortes mean egg period was 3 days at 32.5–40°C and the longest 16 days at 17.5°C. Egg mortality was very high outside the range 20–37.5°C but at 25°C, relative humidity had little effect on duration or mortality. Larval periods on oatmeal ranged from 11.2 days at 32.5°C to 110 days at 17.5°C. The highest temperature at which larvae completed development was 37.5°C. Low humidity increased the larval period and at 15% r.h. all larvae died outside the range 25–35°C. The shortest pupal period recorded was 3 days at 32.5°C and the longest mean period was 15.7 days at 20°C. At 17.5°C no pupae survived. Relative humidity had little effect on duration of the pupal period, but over the range 25–35°C mortality increased at lower humidities. Larvae failed to develop on copra meal unless yeast was added and on groundnuts larval mortality was reduced from 59-26% by the addition of yeast. Larvae at 30°C. 70% r.h. passed through 4 instars before pupation, the first being the shortest (3.5 days) and the last the longest (9 days) in duration. At 32.5°C, 70% r.h. oviposition was highest during the first week of laying. The maximum oviposition period lasted 9 weeks and the mean egg production per female was 45 eggs. No eggs were laid at 20°C, 70% r.h.     

Dry inoculation methods for nonfat milk powder

Carriers with inoculated microorganisms are often used to validate low-moisture food safety interventions. In this study, we evaluated dry inoculation methods using silicon dioxide (SiO₂) and a small portion of nonfat milk powder (NFMP) as dry carriers for NFMP. Silicon dioxide was characterized by vapor sorption analysis. One milliliter of inoculum of a 5-strain Salmonella cocktail (serovars Agona, Reading, Tennessee, Montevideo, and Mbandaka) or Enterococcus faecium NRRL B-2354 was inoculated onto 1 g of SiO₂ or 10 g of NFMP as carriers. Both inoculated carriers were air-dried for 72 h [22°C, relative humidity (RH) ～30%], equilibrated to water activity (a_w) 0.25 ± 0.02 (24 h at 22°C, RH 25%), and mixed with preconditioned NFMP (a_w = 0.25 ± 0.02) to reach an inoculation level of 8.2 ± 0.2 log cfu/g. Inoculated NFMP was stored at 22°C, RH 25%, and its bacterial populations were monitored for 30 d. Both sets in equilibrated NFMP were subjected to isothermal treatments in closed aluminum cells at 85, 90, and 95°C. Silicon dioxide maintained moisture content (0.29 ± 0.03%, dry basis) at different water activities. The NFMP inoculated with both carriers exhibited stable bacterial populations over 30 d at 22°C. Strains in NFMP inoculated with SiO₂ showed equal or higher D-values but equal z-values compared with those inoculated with a small portion of NFMP. Enterococcus faecium exhibited comparable thermal resistance to Salmonella under all tested conditions. This study supports E. faecium as a Salmonella surrogate in thermal processing of NFMP and the use of SiO₂ to inoculate NFMP.     

Histamine Production in Soy Extended Tuna Salads

Histamine production in tuna salads extended with textured soy protein (TSP) was evaluated. Salads were inoculated with five known histamine-producing bacteria and held at 8°C, 24°C, and 37°C for up to 48 hr. Addition of 30% TSP to tuna salads resulted in higher initial pH and favorable growth conditions for microorganisms and histidine decarboxylase activity. Addition of 15% TSP provided an initial pH for maximal enzyme and histamine production but somewhat slower microbial growth. Tuna salad extended with either 15% or 30% TSP developed toxic levels of histamine (>50 mg/l00 g) when held at either 24° or 37°C for 6 hr. Nonextended tuna salads did not develop toxic levels of histamine even when inoculated with known histamine-producing bacteria and held at 24° or 37°C for 48 hr.     

Listeria monocytogenes Inactivation in Turkey Rolls and Battered Chicken Nuggets Subjected to Simulated Commercial Cooking

Cured and uncured turkey rolls inoculted with 10⁷Listeria monocytogenes CFU/g were vacuum packaged and cooked to internal temperatures of 68°C and 74°C, respectively, in a steam-injected chamber. Samples were stored up to 15 wk at 4°C. Battered chicken nuggets were also inoculated internally with about 10⁷L. monocytogenes CFU/ g. Nuggets enclosed in bags were cooked under moist heating conditions in a convection oven to an internal temperature of 71°C. Nuggets were flushed with 30% CO₂, 70% N₂ atmosphere and sealed. Chicken nuggets were stored at 4°C up to 30 days. No Listeria monocytogenes were recovered from the cooked products suggesting that similar commercial processes are adequate to reduce populations of L. monocytogenes below detection limits.     

Effects of Processing and Storage on the Water-Soluble Vitamin Content of Human Milk

Effects of four heat treatments (62.5°C, 30 min; 72°C, 15 sec; 88°C, 5 sec; and 100°C, 5 min) and frozen storage (?20°C, 4 wk) on water-soluble vitamin content of composite samples of mature human milk were determined. No changes in riboflavin, biotin, and total pantothenic acid content were observed after any of the treatments. Heating at 100°C for 5 min decreased thiamin, vitamin B₁₂, and vitamin C contents. Vitamin Bs content was reduced by heating at 88°C and 100°C. Free folate was not affected by heating while total folate concentration was decreased similarly by all heat treatments. During frozen storage at ?20°C, niacin and free pantothenic acid concentrations were reduced; riboflavin, vitamin Bs, biotin, total pantothenic acid, vitamin C, and vitamin B₁₂ were unaffected; while measurable thiamin and free folate concentrations increased. Overall, the two lower temperature treatments were less detrimental to the water-soluble vitamins in human milk.     

Paddy rice stored under hermetic conditions: The effect of relative humidity,temperature and storage time in suppressing Sitophilus zeamais and impact on rice quality

The aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality.Hermetic bags, GrainPro^® SuperGrainbag^® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 °C, 17 °C and 24 °C, both monitored by Hobo^® Data loggers, with the probe placed inside the bags. CheckpointII Portable O₂ and CO₂ Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (a_w). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer.The results showed that the response of the stored-product insects changes with environmental conditions, O₂ and CO₂ contents. Other parameters were considered; a_w increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O₂ and high CO₂ contents, at different average temperatures, 14 °C and 17 °C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 °C, S. zeamais attained 100% mortality before producing progeny.The increase on respiration rate, registered by CO₂ increase and O₂ decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice.The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes.     

Modeling Growth Rate and Assessing Aflatoxins Production by Aspergillus flavus as a Function of Water Activity and Temperature on Polished and Brown Rice

Abstract: The aim of this study was to model the radial growth rate and to assess aflatoxin production by Aspergillus flavus as a function of water activity (a_w 0.82 to 0.92) and temperature (12 to 42 °C) on polished and brown rice. The growth of the fungi, expressed as colony diameter (mm) was measured daily, and the aflatoxins were analyzed using HPLC with a fluorescence detector. The growth rates were estimated using the primary model of Baranyi, which describes the change in colony radius as a function of time. Total of 2 secondary models were used to describe the combined effects of a_w and temperature on the growth rates. The models were validated using independent experimental data. Linear Arrhenius–Davey model proved to be the best predictor of A. flavus growth rates on polished and brown rice followed by polynomial model. The estimated optimal growth temperature was around 30 °C. A. flavus growth and aflatoxins were not detected at 0.82 a_w on polished rice while growth and aflatoxins were detected at this a_w between 25 and 35 °C on brown rice. The highest amounts of toxins were formed at the highest a_w values (0.90 to 0.92) at a temperature of 20 °C after 21 d of incubation on both types of rice. Nevertheless, the consistencies of toxin production within a wider range of a_w values occurred between 25 to 30 °C. Brown rice seems to support A. flavus growth and aflatoxin production more than the polished rice. Practical Application: The developed models can be used to estimate to what extent the change in grain ecosystem conditions affect the storage stability and safety of grains without the need for running long‐standing storage study. By monitoring the intergranular relative humidity and temperature at different locations in the storage facility and inputting these data into the models, it is directly possible to assess either the conditions are conductive for the growth of A. flavus or aflatoxin production.     

Survival and detection of Escherichia coli O157:H7 and Listeria monocytogenes during the manufacture of dry sausage using two different starter cultures

A sausage batter (35% pork, 35% beef, 30% fat) was inoculated with high (5·46–5·68), medium (3·78–4·54) or low (2·30–2·60 log₁₀cfug⁻¹) levels of Escherichia coli O157:H7 and with high (5·05–5·41) or medium (2·92–3·35 log₁₀cfug⁻¹) levels of Listeria monocytogenes serovar 4b and fermented using starter cultures A (Staphylococcus xylosus DD-34 with bacteriocin-producingPediococcusacidilactici PA-2 and Lactobacillus bavaricus MI-401) and B(S. carnosus MIII withLb. curvatus Lb3). Sausages were manufactured (fermented and dried) in a smoke chamber at 17–23°C for 15 days and further stored at 15–17°C for 34 days. The numbers of E. coli O157:H7 decreased more using starter B than starter A (first experiment P<0·0015, second experiment P<0·0002) but the organism was not eliminated. Small numbers of E. coli O157:H7 were more often detected after enrichment for 18–24 h than for 6 h (P=0·0044) when tested after deep freezing. By contrast, L. monocytogenes decreased more rapidly in the high-inoculum sausages produced with starter A (P<0·0001) but no significant difference was detected between the starters in the medium-inoculum sausages. L. monocytogenes was eliminated from the medium-inoculum sausages after 49 days.     

Survival ofEscherichia coliO157:H7,Listeria monocytogenesandSalmonella kentuckyin Norwegian fermented,dry sausage

Raw, newly produced sausages containing a mixed starter culture of lactobacilli and micrococci were each inoculated at separate locations (using a syringe) with low (10³–10⁴cfu) and high (10⁵–10⁷cfu) numbers of eitherEscherichia coliO157:H7, Listeria monocytogenes orSalmonella kentucky. Three identically prepared sausages were analysed at each sampling day during fermentation, maturation and storage at 4 and 20°C. In the low-inoculum samples, growth was observed initially (2 days) during fermentation forE. coliO157:H7 (3log₈increase in cfu) andL. monocytogenes(five-fold increase in cfu) but not forS. kentuckywhich decreased below the detection limit (150cfu sample^–1). None of the pathogens was detected after 5.5 months, neither at 4 nor 20°C. In the high-inoculum samples there was a decrease during fermentation and maturation for all the pathogens. After 5.5-months storage at 4°C, there was only about 90% reduction of the original inoculate ofL. monocytogenes, whereasE. coliO157:H7 survived at a low number (500cfu sample^–1) andS. kentuckydisappeared below the detection limit. After 5.5-months storage at 20°C, all the pathogens had disappeared below the detection limit. These results indicate that, from a safety point of view, it may be better to store these kinds of sausages at room temperature than in the cold, provided that the sensory qualities are retained and that similar results are obtained with other food pathogens.     

Aspergillus Parasiticus Growth and Aflatoxin Production on Dehydrated Taro

A study was made of Aspergillus parasiticus growth and aflatoxin production on four taro media. The critical equilibrium relative humidity (ERH) for natural mold growth on unsterilized dehydrated taro was 88% at 20°C. However, nontoxigenic A. parasiticus NRRL 1957 did not grow at this ERH on dehydrated raw taro incubated at 20°, 30°, or 40°C. Instead, the growth of A. parasiticus NRRL 1957 on dehydrated taro was optimum at 30°C and an ERH of 96%. Aflatoxin production by toxigenic A. parasiticus NRRL 2999 was investigated on four taro media under optimal growth conditions. Only moderate quantities of aflatoxins were produced by A. parasiticus NRRL 2999 on uncooked dehydrated taro, but cooking or supplementation with peptone stimualted mycelial growth and aflatoxin production slightly. Nevertheless, growth and aflatoxin production on cooked or peptone-supplemented taro media was low.     

Poststorage Behavior of Apple Fruit After Low Oxygen Storage as Influenced by Temperatures During Storage and in Transit

‘Delicious’, ‘Newtown’ and ‘Granny Smith’ apples (Malus domestica Borkh.) maintained acceptable flesh firmness and high levels of titratable acids and soluble solids after 9 months of storage in 1% 0₂ at either 0°C or 3.3°C. Low-0₂-stored ‘Delicious’ were kept at 0°C for 6 wk without developing physiological disorders before or after 8 days of ripening at 20°C. Storage at 3.3°C caused ‘Delicious’ to soften faster during 6 wk of post-storage holding plus 8 days of ripening. ‘Newtown’ apples developed flesh browning and alcohol flavor after 9 months of low 0₂ storage at 0°C. ‘Newtown’ fruit stored at 3.3°C developed only minimal incidence of flesh browning and alcohol flavor. ‘Granny Smith’ fruit were free from scald, core flush, flesh browning and alcohol flavor after low 0₂ storage, regardless of storage temperature. However, core flush and flesh browning appeared when ‘Granny Smith’ were kept for 6 wk at 0°C plus 8 days at 20°C.