Functional response of adult Cheyletus malaccensis (Acari: Cheyletidae) to different developmental stages of Aleuroglyphus ovatus (Acari: Acaridae)

Cheyletus malaccensis is an important natural enemy of stored pests. In the study, the functional response of C. malaccensis against Aleuroglyphus ovatus was investigated under five constant temperatures of 16, 20, 24, 28 and 32 °C. The results showed that the functional response of adult C. malaccensis to different stages of A. ovatus was conformed to Holling II. Under the temperature between 16 and 32 °C, C. malaccensis females consumed more larvae and nymphs, followed by male and females of A. ovatus. While male C. malaccensis merely consumed larvae and nymphs of prey. Adult C. malaccensis ate few eggs of A. ovatus. The daily consumption and instantaneous attack rate (a/Th) increased with the temperature increasing from 16 °C to 32 °C while the peak was at 28 °C. The maximum daily consumption for larva and a/Th of female C. malaccensis are 135.1 and 110.7, respectively. Cheyletus malaccensis showed positive preference to larvae and nymphs, while negative preference to adults and eggs of A. ovatus. Because of the competition and interference among predators, the predation efficiency decreased with the density of predator increasing, and the interference coefficient (m) was 0.485 at 28 °C. These results could be helpful to provide theoretical basis and practical instructions for the biological control of A. ovatus by C. malaccensis.     

Survival kinetics of Ephestia kuehniella eggs during 46–75 °C heat treatment

The effect of heat treatment on the survival of Ephestia kuehniella eggs was examined. Samples of 60 eggs were immersed in hot water at constant temperature in the 46–75 °C range for 5–1200 s. Following heat treatment and cooling, the eggs were stored at 24 ± 1 °C in a growth chamber for 7 days before survival evaluation. Statistical analysis of the data demonstrated that the thermal survival kinetics were best represented by a first-order reaction. The rate constant had an Arrhenius-type dependence over the 54–75 °C temperature range. Kinetic parameters were estimated by non-linear regression. The activation energy (E_a) and rate constant (k_ref) at the reference temperature (T_ref = 64.8 °C), were determined as 102.2 ± 6.2 kJ mol⁻¹ and 0.061 ± 0.003 s⁻¹, respectively, over the 54–75 °C temperature range. A 0.01% survival rate was obtained after 50 s at 75 °C. The data at temperatures below 50 °C were not in accordance with those at higher temperatures. Above this temperature, mortality was likely due to physiological disorders, as noted on a DSC thermogram.     

Inhibition of Bacillus cereus and Bacillus weihenstephanensis in raw vegetables by application of washing solutions containing enterocin AS-48 alone and in combination with other antimicrobials

Enterocin AS-48 is a broad-spectrum cyclic antimicrobial peptide produced by Enterococcus faecalis. In the present study, the bacteriocin was tested alone and in combination with other antimicrobials for decontamination of Bacillus inoculated on alfalfa, soybean sprouts and green asparagus. Washing with enterocin AS-48 solutions reduced viable cell counts of Bacillus cereus and Bacillus weihenstephanensis by 1.0–1.5 and by 1.5–2.38 log units right after application of treatment, respectively. In both cases, the bacteriocin was effective in reducing the remaining viable population below detection levels during further storage of the samples at 6 °C, but failed to prevent regrowth in samples stored at 15 or 22 °C. Application of washing treatments containing enterocin AS-48 in combination with several other antimicrobials and sanitizers (cinnamic and hydrocinnamic acids, carvacrol, polyphosphoric acid, peracetic acid, hexadecylpyridinium chloride and sodium hypochlorite) greatly enhanced the bactericidal effects. The combinations of AS-48 and sodium hypochlorite, peracetic acid or hexadecylpyridinium chloride provided the best results. After application of the combined treatments on alfalfa sprouts contaminated with B. cereus or with B. weihenstephanensis, viable bacilli were not detected or remained at very low concentrations in the treated samples during a 1-week storage period at 15 °C. Inhibition of B. cereus by in situ produced bacteriocin was tested by cocultivation with the AS-48 producer strain E. faecalis A-48-32 inoculated on soybean sprouts. Strain A-48-32 was able to grow and produce bacteriocin on sprouts both at 15 and 22 °C. At 15 °C, growth of B. cereus was completely inhibited in the cocultures, while a much more limited effect was observed at 22 °C. The results obtained for washing treatments are very encouraging for the application of enterocin AS-48 in the decontamination of sprouts. Application of washing treatments containing AS-48 alone can serve to reduce viable cell counts of bacilli in samples stored under refrigeration, while application of combined treatments should be recommended to avoid proliferation of the surviving bacilli under temperature-abuse conditions.     

Assessing biological control of Acarus siro by Cheyletus malaccensis under laboratory conditions: Effect of temperatures and prey density

In stored grain, the predatory mite Cheyletus spp. may be used to control the pest mite Acarus siro. The efficiency of control depends on many factors, particularly ambient temperature. In this study we investigated the effects of temperature and initial prey density on the prey–predator system under laboratory conditions. Ratio–response models were fitted to estimate the efficiency of control for three temperatures. At 15 °C a 90% reduction of A. siro was achieved by releasing nine Cheyletus malaccensis individuals into a population of 100 A. siro individuals in 1 kg of grain. At 20 °C, 90% reduction required seven C. malaccensis individuals and at 25 °C, it required three C. malaccensis individuals. Without the predator the intrinsic rates of increase of A. siro populations increased with temperature and were highest for an initial density of 100 individuals, revealing some form of positive interaction among A. siro individuals during food processing. The intrinsic rates of increase of C. malaccensis populations also increased with temperature and decreased with increasing density of the predator, presumably as a result of interference competition among predators.At 15 °C the rate of increase for A. siro was higher than that for C. malaccensis, while at higher temperatures it was the other way around. Lower developmental thresholds were 10 °C for A. siro and 13.6 °C for C. malaccensis. In order to find when an artificial release of C. malaccensis is most efficient we simulated a population increase of A. siro using temperature records from one grain store. In Central Europe this type of biological control can be efficient only when the predator is released at the beginning of storage, i.e. in September and October.     

Evaluation of the effect of defrosting practices of ground beef on the heat tolerance of Listeria monocytogenes and Salmonella Enteritidis

The effect of common defrosting practices of ground beef, including (i) defrosting in the refrigerator (5 °C for 15 h), (ii) defrosting at room temperature (25 °C for 12 h) and (iii) defrosting in the microwave, on the heat tolerance of artificially inoculated Listeria monocytogenes and Salmonella Enteritidis, was studied. The thermal inactivation of S. Enteritidis was not, overall, affected by defrosting practices. In contrast, defrosting at room temperature resulted, overall, in an increased heat tolerance of L. monocytogenes compared to the rest tested defrosting practices. Inactivation kinetics of the two pathogens for the different defrosting practices were determined by fitting the data to the Weibull model. The δ parameter of the Weibull model (heat challenge time (min) required for the first 1-log reduction) for S. Enteritidis and for defrosting at 25 °C, microwave defrosting, defrosting at 5 °C and for the control (fresh ground beef inoculated with the pathogens just before the heat challenge trials) was 1.13, 1.62, 1.60 and 0.96, respectively, while the corresponding values for L. monocytogenes were 20.13, 10.82, 9.95 and 9.47, respectively. The findings of this study should be useful in risk assessments and in developing food handling guidelines for the consumers.     

Storage stability of jackfruit (Artocarpus heterophyllus) powder packaged in aluminium laminated polyethylene and metallized co-extruded biaxially oriented polypropylene during storage

Total colour difference (ΔE), rates of adsorbed moisture and sensory attributes of drum-dried jackfruit powder packaged in aluminium laminated polyethylene (ALP) and metallized co-extruded biaxially oriented polypropylene (BOPP/MCPP) pouches stored at accelerated storage (38 °C, with 50%, 75% and 90% relative humidity (RH)) were determined over 12 weeks period. The changes in total colour followed zero order reaction kinetics. Packaging materials, storage temperature and RH values significantly (p < 0.05) influenced the rates of adsorbed moisture of jackfruit powder. There was a significant (p < 0.05) decrease in the intensities of the fruity odour, taste and increase in the lumpiness of the jackfruit powder stored at 38 °C with 90% RH. The shelf life of jackfruit powder stored at 38 °C and 90% RH was limited by overall acceptability and the intensity of fruity odour, taste and lumpiness at week 8 of storage. Jackfruit powder stored at 28 °C remained stable and acceptable throughout the storage period for all RH values. The powder packaged in ALP significantly (p < 0.05) reduced total colour change, rates of adsorbed moisture, lumpiness intensity of jackfruit powder and was rated higher in terms of overall acceptability over BOPP/MCPP. Results of this study suggested that ALP packaging with storage conditions of 28 °C and RH less than 75% was better suited for keeping jackfruit powder.     

Adult longevity and oviposition of Trogoderma parabile Beal (Coleoptera, Dermestidae) at different temperatures

Adult longevity and egg production of Trogoderma parabile Beal were determined at 14 temperatures from 4·4 to 40°C and 70±5 per cent r.h. In the range 12·8 to 32·5°C male and female longevity decreased with increasing temperature, particularly above 17·5°C. At temperatures below 12·8°C longevity decreased rapidly. From 22·5 to 37·5°C females had a shorter life span than males; but at all other temperatures females outlived males. The lengths of the preoviposition and oviposition periods were inversely related to temperature. Eggs of normal appearance were laid at temperatures from 17·5 to 37·5°C, a few deformed, non-viable eggs were laid at 15·6°C, and none beyond this range. Most eggs were laid at temperatures of 27·5 and 30°C. The number of fecund females rose as the temperature increased from 17·5 to 35°C and declined beyond 37·5°C. As the temperature increased above 17·5°C there was generally an inverse relationship between oviposition period and temperature. Females alternately exposed for 24-hr periods at 32·5 and 15·6°C during their adult life produced about the same total number of eggs as those held continuously at 32·5°C. The number of laying females and egg production per female on individual days was directly related to temperature. The finite rate of increase (λ) of T. parabile at 32·2±0·3°C and 70 per cent r.h. was 1·7 per 8 days. The results suggest that in Canada T. parabile is unlikely to become a serious pest of stored grain because of low winter temperatures and relatively short summers in the primary grain-growing regions.     

Effects of rapid chilling of carcasses and time of deboning on weight loss and technological quality of pork semimembranosus muscle

The effect of rapid air chilling of carcasses in the first 3 h of chilling at −31 °C (then at 2–4 °C, till 24 h post-mortem) and the possibility of earlier deboning (8 h post-mortem) after rapid air chilling, compared to conventional air chilling (at 2–4 °C, till 24 h post-mortem) on weight loss and technological quality (pH value, tenderness, drip loss, cooking loss and colour - L^*a^*b^* values) of pork M. semimembranosus was investigated. Under the rapid chilling conditions, weight loss was 0.8% at 8 h post-mortem and increased to 1.4% at 24 h post-mortem when weight loss was 2.0% under conventional chilling. Carcasses that were rapid chilled had significantly lower (P < 0.001) internal temperature in the deep leg at 4 (25.7 °C), 6 (13.0 °C), 8 (6.2 °C) and 24 h (3.8 °C) post-mortem compared to conventional chill treatment (32.7, 24.2, 19.1 and 5.1 °C, respectively). Rapid chilling reduced significantly (P < 0.05) the rate of pH value decline at 8 h (6.02) post-mortem in M. semimembranosus compared to conventional chill treatment (5.88). Compared to conventional chilling, in M. semimembranosus deboned in different time post-mortem, rapid chilling had a positive significant effect on drip loss (P < 0.05, muscles deboned 8 h post-mortem), cooking loss (P < 0.001) and incidence of pale colour (L^* value). Rapid chilling i.e. rapid chilling and earlier deboning had neither positive nor negative significant effects (P > 0.05) on other investigated technological quality parameters of M. semimembranosus (tenderness, a^* value and b^* value) compared to conventional chilling.     

Crystalline stability of self-assembled fibrillar networks of 12-hydroxystearic acid in edible oils

The stability of organogels differs based on the organogelator concentration, storage temperature, and solvent type. Organogel post-crystallization annealing was monitored at 5 °C, 15 °C, 20 °C or 30 °C for up to 1 month. Gels, stored at 5 °C, had highly immobilized oil, as judged from large T₂ relaxation peaks at 50–70 ms determined by pulsed nuclear magnetic resonance (pNMR) and visual observations. When the gels were stored at 30 °C, the 50–70 ms T₂ relaxation peak shifted to longer relaxation times, indicating that the oil was more mobile than at 5 °C. Along with the increase in syneresis at 30 °C, the 12HSA network’s crystallinity was also greater, having fewer inclusions of liquid oil, as determined by pNMR. The highly branched network observed at 5 °C changed more in time with regards to crystallinity although it entrained the oil to a much greater extent than the gels stored at 30 °C.     

Byssochlamys nivea inactivation in pineapple juice and nectar using high pressure cycles

The aim of this work was to assess the inactivation of Byssochlamys nivea ascospores in pineapple juice and nectar by combining pressure sequences involving high pressure cycles with relatively mild thermal processing. The effect of 550 and 600 MPa sustained pressures (holding time of 15 min), combinations of sustained pressures and pressure pulses (holding time of 10 s), and pressure cycles (two, three and five cycles of 550 and 600 MPa for 7.5, 5 and 3 min, respectively), at 20, 40, 60, 70, 80 and 90 °C were compared. B. nivea ascospores were inactivated by applying sustained a pressure of 600 MPa at 90 °C for 5 min (juice) and 15 min (nectar), and three and five cycles of pressure at 600 MPa and 80 °C for nectar with holding time of 5 and 3 min, respectively, and in all pressure cycles for juice. In general, pressure cycles were more effective for inactivating B. nivea ascospores than the application of sustained high pressures.     

Identification and characterization of Dekkera bruxellensis, Candida pararugosa, and Pichia guilliermondii isolated from commercial red wines

Yeast isolates from commercial red wines were characterized with regards to tolerances to molecular SO₂, ethanol, and temperature as well as synthesis of 4-ethyl-phenol/4-ethyl-guaiacol in grape juice or wine. Based on rDNA sequencing, nine of the 11 isolates belonged to Dekkera bruxellensis (B1a, B1b, B2a, E1, F1a, F3, I1a, N2, and P2) while the other two were Candida pararugosa (Q2) and Pichia guilliermondii (Q3). Strains B1b, Q2, and Q3 were much more resistant to molecular SO₂ in comparison to the other strains of Dekkera. These strains were inoculated (10³–10⁴ cfu/ml) along with lower populations of Saccharomyces (<500 cfu/ml) into red grape juice and red wine incubated at two temperatures, 15 °C and 21 °C. Although Saccharomyces quickly dominated fermentations in grape juice, B1b and Q2 grew and eventually reached populations >10⁵ cfu/ml. In wine, Q3 never entered logarithmic growth and quickly died in contrast to Q2 which survived >40 days after inoculation. B1b grew well in wine incubated at 21 °C while slower growth was observed at 15 °C. Neither Q2 nor Q3 produced 4-ethyl-phenol or 4-ethyl-guaiacol, unlike B1b. However, lower concentrations of volatile phenols were present in wine incubated at 15 °C compared to 21 °C.     

Impact of differing population levels of Rhyzopertha dominica (F.) on milling and physicochemical properties of sorghum kernel and flour

The effects of different population levels of Rhyzopertha dominica (F.), the lesser grain borer, on physiochemical properties of sorghum kernels and flour, were investigated through a laboratory study at 27 and 32 °C, and 57% relative humidity. Initial population level and temperature, and their interaction, were significant for the number of F₁ progeny and feeding damage (P<0.01). A strong positive correlation was also found between initial population size, number of F₁ progeny, percentage of insect-damaged kernels (IDKs) and feeding damage. The impact of R. dominica on the milling quality of sorghum was seen through a reduction in abrasive hardness, milling yield, and kafirin content. Initial population and temperature affected most pasting properties, and overall pasting viscosity increased with initial population, number of F₁ progeny, and percentage of IDK at 32 °C. Results show that R. dominica can potentially impact the milling quality of sorghum and also alter the physicochemical properties of sorghum flour.     

Life history studies of the yam moth, Dasyses rugosella Stainton (Lepidoptera: Tineidae)

A life history study of the yam moth, Dasyses rugosella Stainton, was carried out in the laboratory at an ambient temperature of 28±2 °C and 75±5% relative humidity. Freshly emerged male and female adults were paired in glass vials and average fecundity determined. Eggs were incubated in Petri dishes lined with filter paper underneath which was moistened cotton wool. Hatchability and incubation period were noted. Freshly emerged first instar larvae were then reared on small Dioscorea alata L. tubers in plastic containers until adult emergence.The average fecundity per female D. rugosella was 107.4±9.9 eggs at an average oviposition period of 3.8±0.2 days. Most of the eggs were laid on the second day of oviposition. The eggs, which were laid singly, in groups and in chains, were elliptical in shape and measured 0.80±0.01 mm long and 0.42±0.01 mm wide. Hatchability was 66.7%. The mean incubation period was 5.1±0.2 days. Dasyses rugosella passed through six larval instars. The mature larva was eruciform with a large uniformly sclerotised head. The pupa was obtect, adecticous and highly sclerotised with a stout profile. The mean larval and pupal developmental periods were 44.5±1.8 and 11.9±0.2 days, respectively. The mean total developmental time from egg to adult was 61.6±3.7 days (range 53-75 days). The females were always bigger than the males. The wing span measurement of the female ranged from 18.0-18.5 mm, while that of the male ranged from 13.0-14.0 mm. The body length of the female ranged from 7.8-8.5 mm while that of the male ranged from 5.3-6.8 mm. The unmated males lived longer (8.5 days) than unmated females (7.1 days), mated males (3.8 days) and mated females (4.1 days).The maximum daily mean progeny production was 25.7 on the 63rd day of pivotal age. The innate capacity for increased r_c was 0.06 per female per day. The cohort generation time T_c was 63.0 days and the finite rate of increase h_c was 1.06. The net reproductive rate R_o was 52.9.     

Quality and microbial stability of partially baked bread during refrigerated storage

Partially baked bread was prepared and stored at 1 °C or 7 °C for 28 days. Periodically, this product was subjected to moisture, hardness, and microbiological analyses. After storage, the baking process of part-baked bread was completed and product evaluated according to microbiological, physical, and sensorial tests, as well as hardness analysis. Part-baked breads stored at 7 °C showed mold growth at day ninth, while the product stored at 1 °C did not show mold growth through 28 days. The full-baked bread obtained from part-baked samples stored at 1 °C showed higher values of hardness and change in crumb hardness, and lower sensorial quality than bread from part-baked samples stored at 7 °C. Moisture content, specific volume, and width/height ratio in the full-baked bread were not affected by storage time and temperature.     

Viability of multi-strain mixtures of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 inoculated into the batter or onto the surface of a soudjouk-style fermented semi-dry sausage

The fate of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on soudjouk. Fermentation and drying alone reduced numbers of L. monocytogenes by 0.07 and 0.74 log₁₀ CFU/g for sausages fermented to pH 5.3 and 4.8, respectively, whereas numbers of S. typhimurium and E. coli O157:H7 were reduced by 1.52 and 3.51 log₁₀ CFU/g and 0.03 and 1.11 log₁₀ CFU/g, respectively. When sausages fermented to pH 5.3 or 4.8 were stored at 4, 10, or 21 °C, numbers of L. monocytogenes, S. typhimurium, and E. coli O157:H7 decreased by an additional 0.08–1.80, 0.88–3.74, and 0.68–3.17 log₁₀ CFU/g, respectively, within 30 days. Storage for 90 days of commercially manufactured soudjouk that was sliced and then surface inoculated with L. monocytogenes, S. typhimurium, and E. coli O157:H7 generated average D-values of ca. 10.1, 7.6, and 5.9 days at 4 °C; 6.4, 4.3, and 2.9 days at 10 °C; 1.4, 0.9, and 1.6 days at 21 °C; and 0.9, 1.4, and 0.25 days at 30 °C. Overall, fermentation to pH 4.8 and storage at 21 °C was the most effective treatment for reducing numbers of L. monocytogenes (2.54 log₁₀ CFU/g reduction), S. typhimurium (5.23 log₁₀ CFU/g reduction), and E. coli O157:H7 (3.48 log₁₀ CFU/g reduction). In summary, soudjouk-style sausage does not provide a favorable environment for outgrowth/survival of these three pathogens.     

The survival of Campylobacter jejuni in red meats stored at different temperatures

The survival of 4 strains of Campylobacter jejuni was studied in raw minced beef and raw pork sausage mixture stored in plastic stomacher bags at freezer temperatures (−19°C) for up to 10 weeks, refrigirator temperatures (< 10°C) for 6 days and 22°C for 24 h. At each of the 3 storage temperatures survival was better in minced beef. Similarly, there was less variation in percentage survival between the 4 strains in minced beef than in sausage mixture after storage at each temperature. Detailed studies were carried out with one strain of C. jejuni. Viable counts were relatively unchanged in minced beef at refrigerator temperatures and 22°C, but showed a decrease in corresponding samples of sausage mixture. At freezer temperatures decreases in count of approximately 1 log unit were observed during the first week for both meats followed by a more gradual decrease. The effect of desiccation by exposure was studied in minced beef and lamb outer carcass meat (breast) at refrigerator temperatures (≤ 10°C). Decreases in viable count were observed in lamb carcass meat after 32 h although large variations were sometimes observed between duplicate samples for the same strain of C. jejuni. Counts were unchanged in exposed minced beef after storage for 48 h.     

Effects of delayed mating on reproductive performance of Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Virgin male and female Indianmeal moths, Plodia interpunctella (Hübner), were mated soon after emergence or delayed from mating for 1-5 d, to determine the effect of age at mating on the number of spermatophores transferred by males to females, number of eggs laid (fecundity), egg viability, and adult longevity. When male and female moths were mated without delay, all females mated successfully. On average, each mated female had 2.2 spermatophores and laid 161 eggs. About 99% of the eggs laid were viable. Fecundity and egg viability were significantly and positively correlated with the number of spermatophores/female. For each day that mating of virgin male or female P. interpunctella was delayed, fecundity decreased by about 25 eggs. Egg viability decreased by 22%/d only when females were delayed from mating. Males delayed from mating for 5 d were unable to inseminate females. However, about 23% of females had one spermatophore when females or both males and females were delayed from mating for 5 d. On average, 22-39 non-viable eggs were laid by a female in treatments where male or female moths were delayed from mating for 5 d. Similarly, unmated (virgin) females laid 33 non-viable eggs. These results suggest that methods that can delay and disrupt mating may be effective behavioral strategies for managing this important pest of stored commodities and processed foods.     

Effect of packaging chickpeas with CO2 modified atmospheres on mortality of Callosobruchus chinensis (Coleoptera: Chrysomelidae)

High CO₂ modified atmosphere packaging (MAP) is a sustainable alternative for pest control in stored products. The effectiveness of this method varies depending on the CO₂ concentration used, insect exposure time, temperature, humidity, the tested insect species, and the insect's stage of development. One factor that substantially influences the concentration of CO₂ available inside the packages, and therefore the effectiveness of the treatment, is the sorption of gas in the commodity. This study evaluated the impacts of packaging chickpeas in modified atmospheres of 50% and 90% CO₂ with filling ratios (proportion of grain relative to the volume of the package) of 1% and 96% grain on the mortality of C. chinensis eggs and pupae and on the fecundity of the females emerging from the surviving individuals. In packages with a 96% filling ratio, CO₂ concentration in the headspace of packages reduced to 60% and 30% from initial concentrations of 90% and 50% (respectively) in the first 24 h of exposure. Despite this reduction in CO₂ concentrations, no differences in the mortality of C. chinensis eggs and pupae were observed between these packages and those with a 1% filling ratio. The estimated exposure time to achieve 95% mortality (LT₉₅) of the eggs ranged from 38 to 68 h; for pupae, it ranged from 142 to 248 h. The fecundity of females that emerged from the surviving pupae decreased after 48 h of exposure to CO₂, but the fecundity of females that emerged from surviving eggs was not affected by exposure time, MAPs, or filling ratio. Therefore, effective pest control can be accomplished with the use of sufficient treatment times to eradicate the most tolerant developmental stages, regardless of whether the packages are full or not.     

Application of Kubelka–Munk analysis to the study of translucency in fresh-cut tomato

In order to assess the development of translucency in fresh-cut tomato (Lycopersicum esculentum cv. Belissimo) during refrigerated storage, two experiments were conducted. In the first one, tomato slices obtained from fruits at breaker and at red stage were stored at 5 ± 0.5 °C and monitored at regular intervals for 9 days. In the second one, slices obtained from fruits at the light-red stage were stored at 5 ± 0.5 °C, 9 ± 0.7 °C and 13 ± 0.7 °C for 4 days. Intact (control) fruits were stored at the same conditions and sliced immediately before the evaluations. In both experiments, translucency was assessed using Kubelka–Munk analysis and through visual evaluation using a scale from 0 to 4. The translucency of cut tomato slices increased during storage in both experiments. Fruits at red stage got translucent faster than fruits at breaker stage and the intensity of translucency was also higher for more ripe fruit. The storage temperature did not influence significantly the development of translucency, indicating that the water soaking of the pericarp tissue is not a result of chilling injury. The K/S (absorption coefficient/scattering coefficient) ratio increased during storage for cut fruits and remained practically constant for intact fruits, reflecting the effects of treatment observed visually. Additional experiments indicated that the removal of the locular gel combined or not with washing and drying the slice cut surface inhibited the development of translucency.

Industrial relevance

The development of translucency is a common alteration in the appearance of fresh-cut fleshy tissue after processing, which renders the product unappealing for consumption. It is of interest for the fresh-cut industry to be able to assess the development of translucency and then evaluate the effect of different procedures in its occurrence and intensity. This paper presents the use of Kubelka–Munk analysis, a technique of widespread use in other fields like printing and painting, to assess the development of translucency in sliced tomato and to study how this process is affected by storage temperature and maturity stage of the fruit.     

Life history parameters of Lasioderma serricorne (F.) as influenced by food sources

Fecundity, egg to adult survival rate, developmental time, and adult body weight of the cigarette beetle, Lasioderma serricorne (Coleoptera: Anobiidae) were evaluated on seven food sources at 28 °C. Ground chili, paprika, cayenne pepper, chewing leaf tobacco, cigar tobacco, a commercial insect bait referred to as NOW bait, and wheat flour were used to evaluate mean lifetime fecundity. The highest fecundity (52.4±4.8 eggs/female) was observed in wheat flour, whereas the lowest fecundity (5.8±0.8 eggs/female) was observed in cigar tobacco. Among the seven food sources, beetles reared in wheat flour showed the highest survival rate of 91.0±2.7%. Only 15% of the eggs laid in NOW bait developed to the adult stage. In the three food sources containing Capsicum spp. the survival rate ranged from 30% to 40%. The egg, larval, and pupal development times varied from 3 to 5, 38 to 92 and 4 to 18 d, respectively, among food sources. Body weight and adult longevity studies showed that the heavier adults also had the longest life span. Ovipositing female L. serricorne appear to discriminate among different food sources. Although L. serricorne laid eggs in all food sources evaluated, larval and pupal survival were lowest in NOW bait. Information on the biology and host use pattern of L. serricorne may help to explain how various stored commodities are affected by this species and may lead to develop appropriate pest management strategies for this insect pest.