Cultured C2C12 cell lines as a model for assessment of bacterial attachment to bovine primary muscle cells

The mechanisms of bacterial attachment to meat tissues need to be understood to enhance meat safety interventions. However, little is known about attachment of foodborne pathogens to meat muscle cells. In this study, attachment of six Escherichia coli and two Salmonella strains to primary bovine muscle cells and a cultured muscle cell line, C₂C₁₂, was measured, including the effect of temperature. At 37 °C, all but one strain (EC623) attached to C₂C₁₂ cells, whereas only five of eight strains (M23Sr, H10407, EC473, Sal1729a and Sal691) attached to primary cells. At 10 °C, two strains (H10407 and EC473) attached to C₂C₁₂ cells, compared to four strains (M23Sr, EC614, H10407 and Sal1729a) of primary cells. Comparing all strains at both temperatures, EC614 displayed the highest CFU per C₂C₁₂ cell (4.60 ± 2.02 CFU/muscle cell at 37 °C), whereas greater numbers of M23Sr attached per primary cell (51.88 ± 39.43 CFU/muscle cell at 37 °C). This study indicates that primary bovine muscle cells may provide a more relevant model system to study bacterial attachment to beef carcasses compared to cell lines such as C₂C₁₂.     

Extraction, thermal stability and kinetic behavior of pectinmethylesterase from hawthorn (Crataegus pubescens) fruit

Pectinmethylesterase (PME) extracted from hawthorn (Crataegus pubescens) fruit was evaluated for its thermal stability and kinetic behavior. The enzyme extraction process was established after studying different NaCl concentrations (0.5-3.0 moles/L). A maximum PME extraction of 51.61 units/mg protein was obtained using 2 moles/L NaCl. Kinetic parameters (K_m and V_max) were determined using a commercial citrus pectin and C. pubescens pectin as substrates. The effects of NaCl concentration, pH and temperature on PME activity were investigated. PME showed higher affinity for C. pubescens pectin (K_m and V_max of 2.84 mg/mL protein, and 64.10 units/mg protein, respectively) than for citrus pectin. C. pubescens PME extract showed maximum activity at 0.4 moles/L NaCl, pH 7.5, and 55 °C. The E_a and Q₁₀ for thermal activation were 36.27 kJ/mol and 2.01 (20-30 °C), respectively. About 50% of the activity still remained after heating for 25 min at 60 °C, and it was completely inactivated by incubation at 80 °C for 10 min. The Q₁₀ and E_a values for thermal inactivation reaction were 20.06 (70-80 °C) and 146.16 kJ/mol, respectively. These results provide useful information about the factors that affect the activity of C. pubescens PME, and might be used as a starting point for texture control during post-harvest handling and processing of this fruit.     

Phytochemical,sensory attributes and aroma stability of dense phase carbon dioxide processed Hibiscus sabdariffa beverage during storage

The effect of dense phase carbon dioxide (DPCD) processing (34.5 MPa, 8% CO₂, 6.5 min, and 40 °C) on phytochemical, sensory and aroma compounds of hibiscus beverage was compared to a conventional thermal process (HTST) (75 °C for 15 s) and a control (untreated beverage) during refrigerated storage (4 °C). The overall likeability of the hibiscus beverage for all treatments was not affected by storage up to week 5. DPCD process retained more aroma volatiles as compared to HTST. Aroma profiles in the beverages were mainly composed of alcohols and aldehydes with 1-octen-3-ol, decanal, octanal, 1-hexanol, and nonanal as the compounds with the highest relative percentage peak areas. A loss of only 9% anthocyanins was observed for the DPCD processed hibiscus beverage. Phytochemical profiles in the hibiscus beverage included caffeoylquinic acids, anthocyanins, and flavonols. No major changes in total phenolics and antioxidant capacity occurred during the 14 weeks of storage.     

Phytochemical changes in fresh-cut jackfruit (Artocarpus heterophyllus L.) bulbs during modified atmosphere storage

A minimal process was carried out for pitted jackfruit (Artocarpus heterophyllus L.) bulbs using additives CaCl₂, ascorbic acid (AA), and sodium benzoate in combination with mild acidified conditions for storage under modified atmosphere (MA), i.e., 3 kPa O₂ + 5 kPa CO₂, gas mixture flushed polyethylene (GFPE) bags, polyethylene terephthalate jars with silicon membrane on lid and polyethylene bag with air. Samples devoid of any additive based pretreatment but packaged in similar MA conditions were used as experimental control. A restricted loss of around 7%, 8%, 43%, and 31% was found for total phenolics (TP), total flavonoids (TF), total carotenoids (TC), and AA contents respectively in the pretreated samples kept under GFPE bags towards the end of 35 days storage at 6 °C. Among the phytochemicals evaluated, the radical-scavenging activity showed the highest correlation (r = 0.979) with AA followed by TP, TF and TC.     

Total phenolics,antioxidant properties and quality of fresh-cut onions (Allium cepa L.) treated with mild-heat

This study investigated the effect of mild-heat on fresh-cut onion slices by treating in hot water (50, 60, 70 °C) for 1 min. Total phenolics (TP), antioxidant properties, colour, and weight loss of slices were evaluated during 4 °C storage at 7-day intervals (21 days total). The 60 °C heat treatment resulted in a significant increase in TP, from 44.92 to 52.32 mg GAE/100 g. Except for 50 and 70 °C treatments, TP in control and 60 °C treated fresh-cut onions decreased during storage. The antioxidant properties of fresh-cut onions were 1.31, 0.99, and 62.49 μM TE/g using ABTS, DPPH, and ORAC assays, respectively. The mild-heat treatments did not affect ABTS and DPPH antioxidant activities and the colour of fresh-cut onions. The storage time had mixed effect on the antioxidant properties (ABTS decreased; DPPH and ORAC remained fairly stable). The 50 °C samples exhibited the lowest weight loss during 21-day storage.     

Antioxidant phytochemical and quality changes associated with hot water immersion treatment of mangoes (Mangifera indica L.)

Mangoes are an important tropical fruit crop worldwide and are best noted for their vibrant flesh colour, juicy texture, and sweet flavour, along with important nutrient contributions from their phytochemical constituents. Mangoes imported to the US must be exposed to thermal quarantine treatments, such as irradiation and hot water treatment (HWT), to eradicate invasive pests, yet limited data exist regarding polyphenolic changes to the fruit following hot water immersion treatment. Although the water temperature remains constant, the duration of treatment depends on fruit size. Therefore, these investigations focused on polyphenolic and antioxidant changes to mature, green mangoes following varying times of HWT and their changes during short-term storage. Experimentally, fruit were immersed in 46.1 °C water from 70 to 110 min; half evaluated within 2 h of treatment, while the remainder was evaluated after 4 days of storage at 25 °C for changes in polyphenolics, antioxidant capacity and fruit quality. Free gallic acid and four gallotannins were tentatively identified as the major polyphenolics present by HPLC analysis against authentic standards. Two major polyphenolics in mango, gallic acid and gallotannins, as well as total soluble phenolics, decreased as a result of prolonged HWT, while the antioxidant capacity remained unchanged in all heat-treated mangoes immediately after HWT. However, during 4 days storage, only minor changes were observed in gallic acid and gallotannin concentrations whereas total soluble phenolics and antioxidant capacity in all hot water-treated fruits decreased. The optimum hot water immersion times did not affect the external quality and polyphenolics of mangoes but all heat treatments reduced total soluble phenolics and antioxidant capacity, regardless of the duration of treatment times, during 4 days storage.     

Water activity and temperature effects on mycotoxin production by Alternaria alternata on a synthetic tomato medium

Alternaria spp. have been reported to be the most frequent fungal species invading tomatoes. Certain species, in particular the most common one, A. alternata, are capable of producing several mycotoxins in infected plants and in agricultural commodities. Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TA) are some of the main Alternaria mycotoxins that can be found as contaminants of food. The objective of this study was to determine the effect of water activity (a_w, 0.904, 0.922, 0.954, and 0.982) and temperature (6, 15, 21 and 35 °C) on mycotoxin production on a synthetic tomato medium of a cocktail inoculum of five strains of A. alternata isolated from tomato fruits affected by Blackmould. The optimum AOH production occurred at 0.954 a_w after 28 days of incubation at 21 °C. A temperature of 21 °C was the most favourable for AOH synthesis at all a_w levels. The maximum concentration of AME was determined at 0.954 a_w and 35 °C. The optimum conditions for TA accumulation were 0.982 a_w and 21 °C. At the 0.904 a_w no growth or germination was registered at 6 °C and 15 °C over the whole incubation period. At 21 °C and 35 °C growth occurred slowly but none of the toxins were detected at this a_w level. In general, high a_w levels were favourable for mycotoxin production. None of the other toxins was detected at quantifiable levels at 6 °C after the whole incubation period. A storage temperature of 6 °C or below could be considered as safe for tomato fruits and high moisture tomato products (a_w > 0.95), in relation with Alternaria toxins. The results obtained here could be extrapolated to evaluate the risk of spoilage in tomato fruits and tomato products caused by this pathogen.     

Changes in strawberry phenolics, anthocyanins, and antioxidant capacity in response to high oxygen treatments

Changes in fruit quality, decay, phenolic and anthocyanin content, and antioxidant capacity of strawberries (Fragaria × ananassa Duch. cv. Allstar) stored under air and high oxygen atmospheres at 5 °C were investigated. Freshly harvested strawberries were placed in jars and ventilated continuously with air or with 40, 60, 80, or 100 kPa O₂ at 5 °C for up to 14 days. Samples were taken initially, and after 3, 7, 10 and 14 days of storage. While fruit quality parameters such as titratable acidity, total soluble solids and surface color were only slightly affected by differing levels of O₂, the higher oxygen concentration treatments significantly reduced decay. Oxygen concentrations higher than 60 kPa also promoted increases in ORAC values, total phenolics and total anthocyanins as well as individual phenolic compounds analysed by HPLC during the initial 7 days of storage. However, this effect diminished with prolonged storage. No significant differences in ORAC values, total phenolics, total anthocyanins, or the individual phenolic compounds were observed among the high O₂ and air-stored fruits after 14 days of storage. These results indicate that high oxygen treatments exert the most effects on fruit quality and antioxidant capacity of strawberry fruit in the first 7 days of storage.     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

A preliminary evaluation of antioxidant compounds, reducing potential, and radical scavenging of pawpaw (Asimina tribloba) fruit pulp from different stages of ripeness

This study reports preliminary findings for total phenolics, flavonoids, ascorbic acid, reducing potential, and radical scavenging of pawpaw pulp extracts from underripe, ripe, and overripe fruits. Total phenolics were affected by ripeness {underripe = ripe > overripe}, as were flavonoids (ripe < underripe < overripe). Reducing potential and radical scavenging were highest in ripe pulp and lowest in overripe pulp. Total phenolics were positively correlated with reducing potential and radical scavenging. Storing pawpaws at 4 °C for 7 d prior to methanol extraction affected total phenolic levels, ascorbic acid, and flavonoids, but had no effect on reducing potential or radical scavenging. Cooking pawpaws prior to extraction did not decrease the reducing capacity or radical scavenging. Storing pawpaw pulp extracts at −18 °C for 300 d increased reducing potential and radical scavenging. Storing pulp at −18 °C for 300 d before extraction caused a fourfold increase in total phenolics and flavonoids. These results indicate that pawpaw pulp from varying ripeness levels is a potential source of natural phenolic and flavonoid antioxidants that could lead to the development of value-added products from pawpaw.     

Yield, composition and rheological characteristics of cheddar cheese made with high pressure processed milk

High Pressure (HP) treatment of milk prior to cheese-making was shown to increase the yield of cheese due to increased protein and moisture retention in cheese. Cheeses were made with raw milk or milk treated with high temperature short-time (HTST) pasteurization, and HP treatments at two levels (483 and 676 MPa) at 10 °C, 483 MPa HP at 30 °C, and 483 MPa HP at 40 °C. Cheese yield, total solids, protein, fat and salt contents were evaluated, and fat and protein recovery indices were calculated. Cheeses from HP treatments of 676 MPa at 10 °C and 483 MPa at 30 °C exhibited wet yields of 11.40% and 11.54%, respectively. Protein recovery was 79.9% for HP treatment of 676 MPa at 10 °C. The use of slightly higher pressurization temperatures increased moisture retention in cheese. Visco-elasticity of cheeses was determined by dynamic oscillatory testing and a creep-recovery test. Rheological parameters such as loss (G″) and storage (G′) moduli were dependent on oscillation frequency. At high (173 rad/s) and low (2.75 rad/s) angular frequencies, cheeses made from milk treated at 483 MPa at 10 °C behaved more solid-like than other treatments. Creep tests indicated that cheeses from milk treated with 483 MPa HP at 10 °C showed the smallest instantaneous compliance (J_o), confirming the more solid-like behavior of cheese from the 483 MPa at 10 °C treatment compared to the behavior of cheeses from other treatments. Cheeses made with pasteurized milk were more deformable, exhibited less solid-like behavior than cheeses made with HP treated milk, as shown by the J_o value. With more research into bacteriological implications, HP treatment of raw milk can augment Cheddar cheese yield with better curd formation properties.     

Consumer acceptance of roasted peanuts affected by storage temperature and humidity conditions

Consumer acceptance and intensity ratings of roasted peanuts stored at temperatures of 23, 30, 35, and 40 °C, and water activities (a_w) of 0.33, 0.44, 0.54, 0.67 and 0.75 were determined over time. Consumer acceptance ratings, including overall, appearance, color, and texture were affected by storage water activity and time, but not by storage temperature. Consumer intensity ratings of crunchiness were affected by storage water activity and time, but not storage temperature. Aroma acceptance, flavor acceptance, and roasted peanutty and stale/oxidized/rancid intensity ratings of roasted peanuts were dependent on storage temperature, water activity and time.Shelf-life of roasted peanuts was predicted by all consumer attributes (R²>0.60) and was best predicted by aroma acceptance (R²=0.75). Using contour plots with ratings >5.0 for all acceptance attributes, the shelf-life of roasted peanuts stored at 23 °C and between 0.33 and 0.75 a_w was limited by overall acceptance and decreased by approximately 50% with each 0.1 a_w increase. At accelerated temperatures of 30, 35 and 40 °C, shelf-life of roasted peanuts was predominantly limited by flavor acceptance (>5.0), and to a lesser extent by overall acceptance (>5.0). Shelf-life of roasted peanuts stored at accelerated temperatures decreased by 50% or more with each 0.1 a_w increase.     

Microbial inactivation by pressure-shift freezing: effects on smoked salmon mince inoculated with Pseudomonas fluorescens, Micrococcus luteus and Listeria innocua

Smoked salmon mince inoculated simultaneously with Listeria innocua, Micrococcus luteus and Pseudomonas fluorescens was subjected to different pressure-temperature conditions. Control freeze-thaw at 0.1 MPa with storage at −15°C or −40°C for 0-5 days did not induce microbial inactivation. Control pressurisation at 207 MPa for 23 min at 20°C (initial sample temperature) with fast (3 s) pressure release had no significant effect on Gram+bacteria while P. fluorescens underwent a 2.8 log cycle reduction. Pressurisation at 207 MPa for 23 min at −3°C (without ice crystal formation) enhanced microbial reduction to 3.8 log cycles for P. fluorescens and to about 0.5 log cycle for Gram+bacteria. “Pressure-shift nucleation” (PSN) from 207 MPa and −21°C (i.e. cooling at 207 MPa for 23 min followed by pressure release in 3 s) caused 1.2, 1.4 and 4.3 log cycle reductions of L. innocua, M. luteus and P. fluorescens, respectively. A reduction of 1.7 log cycle was observed for L. innocua and M. luteus (4.6 log cycle for P. fluorescens) when salmon mince was subjected to pressure-shift freezing (PSF) (i.e. PSN from 207 MPa and −21°C as above followed by further freezing to −25°C at 0.1 MPa). PSF with pressure release in 18 min enhanced reduction to 2 and 2.5 log cycles for L. innocua and M. luteus, respectively.     

High-pressure treatment of cloudy apple juice

A factorial design with four factors (pressure, holding time, temperature and waiting period between crushing of apple and high-pressure (HP) treatment) was built up to study the effect of HP treatment on pectin methylesterase activity (PME, EC 3.1.1.11) in cloudy apple juice. PME activity was measured by the methanol release during the storage of samples at 4 °C for 1 month. Only the holding time of the treatment and three interactions between factors (holding time×temperature, pressure×waiting and holding time×waiting) had significant effects on the PME level. Increasing the pressure or the holding time at moderate temperatures (15-40 °C) increased the activity. PME purified from apple was pressure stable in the range 100-600 MPa at 25 °C. The soluble pectin content was not changed after HP treatment. The particles size increased with the temperature reached during the treatment, in agreement with a diffusion-limited-aggregation model but were independent of pressure and holding time. In a separate experiment we found a positive correlation between the PME activity and the residual content of the catechins suggesting that polyphenoloxidase (PPO, EC 1.14.18.1) and oxidized polyphenols play a role in the PME activity level after HP treatment.     

Polyphenolic content and antioxidant activity of Eugenia pollicina leaf extract in vitro and in model emulsion systems

The polyphenolic profile of a leaf extract of the Mauritian endemic plant, Eugenia pollicina, was assessed as a source of natural antioxidants. The amounts of flavan-3-ol derivatives determined by HPLC, were in the order of (−)-epicatechin (EC) > (−)-epigallocatechin gallate (EGCG) > (+)-catechin (C) > (−)-epicatechin gallate (ECG) with the levels of Procyanidin B2 and B1 dimers ranging from 1 to 3 mg g⁻¹ FW. The trolox equivalent antioxidant capacity and ferric reducing antioxidant power values were 796 ??mol g⁻¹ FW and 302 ??mol g⁻¹ FW respectively. E. pollicina extracts also strongly inhibited the FeCl₃ and ascorbate-dependent microsome lipid peroxidation, a function that is linked to their flavonoid contents. The extent of DNA damage induced by the extract under study in the copper-phenanthroline assay was lower than the effect of a reference of 240 ??M ascorbate. E. pollicina extracts also inhibited lipid autoxidation in the 30% (v/v) olive oil and soybean oil oil-in-water (O/W) emulsions and was effective in slowing down the formation of hydroperoxides in the emulsions during 13 days storage at 40 °C as determined by the peroxide, conjugated diene and para-anisidine values. The high levels of total phenolics, flavonoids and procyanidins measured indicate that E. pollicina is a potential source of antioxidants relevant to the maintenance of oxidative stability of the food matrix, cosmetics and/or pharmaceutical preparations.     

Effect of high-pressure processing on reduction of Listeria monocytogenes in packaged Queso Fresco

The effect of high-hydrostatic-pressure processing (HPP) on the survival of a 5-strain rifampicin-resistant cocktail of Listeria monocytogenes in Queso Fresco (QF) was evaluated as a postpackaging intervention. Queso Fresco was made using pasteurized, homogenized milk, and was starter-free and not pressed. In phase 1, QF slices (12.7 × 7.6 × 1 cm), weighing from 52 to 66 g, were surface inoculated with L. monocytogenes (ca. 5.0 log₁₀ cfu/g) and individually double vacuum packaged. The slices were then warmed to either 20 or 40°C and HPP treated at 200, 400, and 600 MPa for hold times of 5, 10, 15, or 20 min. Treatment at 600 MPa was most effective in reducing L. monocytogenes to below the detection level of 0.91 log₁₀ cfu/g at all hold times and temperatures. High-hydrostatic-pressure processing at 40°C, 400 MPa, and hold time ≥15 min was effective but resulted in wheying-off and textural changes. In phase 2, L. monocytogenes was inoculated either on the slices (ca. 5.0 log₁₀ cfu/g; ON) or in the curds (ca. 7.0 log₁₀ cfu/g; IN) before the cheese block was formed and sliced. The slices were treated at 20°C and 600 MPa at hold times of 3, 10, and 20 min, and then stored at 4 and 10°C for 60 d. For both treatments, L. monocytogenes became less resistant to pressure as hold time increased, with greater percentages of injured cells at 3 and 10 min than at 20 min, at which the lethality of the process increased. For the IN treatment, with hold times of 3 and 10 min, growth of L. monocytogenes increased the first week of storage, but was delayed for 1 wk, with a hold time of 20 min. Longer lag times in growth of L. monocytogenes during storage at 4°C were observed for the ON treatment at hold times of 10 and 20 min, indicating that the IN treatment may have provided a more protective environment with less injury to the cells than the ON treatment. Similarly, HPP treatment for 10 min followed by storage at 4°C was the best method for suppressing the growth of the endogenous microflora with bacterial counts remaining below the level of detection for 2 out of the 3 QF samples for up to 84 d. Lag times in growth were not observed during storage of QF at 10°C. Although HPP reduced L. monocytogenes immediately after processing, a second preservation technique is necessary to control growth of L. monocytogenes during cold storage. However, the results also showed that HPP would be effective for slowing the growth of microorganisms that can shorten the shelf life of QF.     

Total phenolics,ascorbic acid,and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder as affected by illumination during storage

Total phenolics, ascorbic acid, and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder were determined during storage at 24 °C. After 2 weeks of storage, illuminated noni juice lost 32% of total phenolics, 89% of ascorbic acid, and 46–65% of antioxidant capacity—about 8%, 22%, and 9–15% more than unilluminated juice. Both illuminated and unilluminated juice lost 97% of ascorbic acid by 4 weeks. The difference in antioxidant characteristics between illuminated and unilluminated juice became insignificant at 12 weeks. After 12 weeks, illuminated noni powder lost 21% of total phenolics, 17% of ascorbic acid, and 23–36% of antioxidant capacity—about 13%, 4%, and 7–19% more than the unilluminated powder. Noni powder in brown bottles retained antioxidant characteristics significantly greater than that in clear bottles. Protection from light effectively reduced degradation of antioxidant characteristics of noni juice for only 2 weeks but those of noni powder for at least 3 months.     

Bioactive compounds and quantification of total ellagic acid in strawberries (Fragaria x ananassa Duch.)

Strawberries are one of the most popular edible fruits in Brazil and their consumption has increased with the development of new varieties available at almost all seasons. Fruit of seven full-ripened strawberry cultivars (Dover, Camp Dover, Camarosa, Sweet Charlie, Toyonoka, Oso Grande and Piedade) were characterized in relation to the total phenolics, vitamin C, flavonoids, free and total ellagic acid contents and antioxidant capacity. Camp Dover had the lowest values for anthocyanins and total phenolics but the highest total flavonoid content. Dover presented the highest anthocyanin, total phenolics and ellagic acid contents and also elevated antioxidant capacity. The best conditions for the determination of the total ellagic acid content in strawberries were also optimized and the results showed that the extraction with 80% acetone, and hydrolysis using 2 N TFA at 120 °C for 60 min allowed a 99% recovery.     

Persistence and activity towards Sitophilus zeamais (Coleoptera: Curculionidae) of pirimiphos-methyl sprayed at different temperatures on maize

The air temperature in storage units in tropical areas frequently exceeds 50°C during the warmest periods of the day. Since protectant insecticides are sprayed on grains under these conditions, such high temperatures may interfere with the insecticidal activity. To assess this possibility we sprayed maize grains with pirimiphos-methyl 500 EC (0.8 ml c.p./l and 1.5 l/t) at different temperatures (25°C, 30°C, 35°C, 40°C, 45°C, and 50°C) and 55% r.h. The grains were then maintained at 27±1°C and 55±5% r.h. throughout the experiment which lasted 90 days. Residues of pirimiphos-methyl on the sprayed grains were analyzed every 30 days. Grain samples were assessed every 15 days after the insecticide spraying for their effect on the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Insect mortality was evaluated after 24 and 48 h of exposure to the treated grain. The level of pirimiphos-methyl residue on maize grains decreased with an increase in storage period and air temperature during the insecticide spraying (varying from 11.0±0.1 to 1.1±0.1 ppm, corresponding to the residue levels at 25°C on the day of the spraying and after spraying at 50°C and 90 days of storage). The same trend was observed for mortality of the maize weevil, which dropped from 95.4±13.3% to 2.5±2.5% after 90 days storage after insecticide spraying at 50°C. These results indicate that temperature at spraying can affect insecticide persistence and activity during storage.