Diflubenzuron as a grain protectant for control of Sitophilus species

Diflubenzuron, applied to wheat at low doses (0.2–0.6 mg kg⁻¹), prevents development of first generation (F1) progeny of Sitophilus oryzae and S. granarius species except those developing from a short period of oviposition (1–2 weeks) immediately after application. These F1 progeny fail to produce F2 progeny when transferred to wheat dosed with diflubenzuron, and produce very few progeny when transferred to untreated wheat suggesting an effect on fertility in the adult insect. At 30°C, a dose of 0.4 mg kg⁻¹ is adequate to control S. oryzae and S. granarius, although a dose of 0.6 mg kg⁻¹ is required at 20°C. Strategies for use of diflubenzuron are discussed.     

Macronutrients content of Yellow Glacier Lily and Balsamroot; root vegetables used by indigenous peoples of northwestern North America

The macronutrients in two foods used by indigenous peoples of the British Columbia Plateau region were examined. Yellow Glacier Lily and Balsamroot were commonly harvested, processed and stored in large quantities, up until the last three decades, together with many other plant foods. The macronutrients of the two foods, in which the underground bulbs or roots are utilized, are mainly derived from the carbohydrates. Yellow Glacier Lily bulbs have a high starch content, (770 g kg⁻¹ in fresh bulbs, dry basis), and 57 g kg⁻¹ total dietary fibre. They also contain measurable amounts of simple sugars and fructans before and after cooking. Balsamroot, whose taproots were eaten, is another plant indigenous to the region, but unlike Yellow Glacier Lily it contains negligible amounts of starch. The edible portion of Balsamroot has a high total dietary fibre content (250 g kg⁻¹, dry basis), and high fructan content which is reduced to lower molecular weight sugars after pitcooking. The energy derived from the two foods is very similar on a dry basis ranging from 364 to 395 kcal 100 g⁻¹ in the fresh and pitcooked samples.     

The effect of ractopamine on myofibre distribution and morphology and their relation to meat quality in swine

One hundred and twenty-eight purebred Lacombe pigs (equal number of barrows and gilts) were assigned to one of four treatments at 64 kg and fed a commercial grower-finisher diet ad libitum to which ractopamine (RAC) was incorporated (0, 10, 15 or 20 mg kg⁻¹). Pigs were slaughtered at 100 kg. Histological samples were collected from the semimembranosus (SM) and the psoas major (PM) muscles from the 0 and 20 mg kg⁻¹ RAC groups. Meat quality and muscle composition data were collected for all pigs. A significant 3-way interaction for muscle weight involving treatment, muscle and gender (P = 0·01) indicated that for the SM, gilts appeared to respond to RAC at a lower level of incorporation (10 mg kg⁻¹) than barrows. Despite these differences in response at the gross muscle level, responses were similar at the cellular level for both muscles. The proportion of red fibres did not change (P = 0·21), the proportion of intermediate fibres decreased (P = 0·01) and the proportion of white muscle fibres increased (P = 0·02) in the mg kg⁻¹ RAC group compared to the controls. In addition, when compared to controls, average fibre diameters in the 20 mg kg⁻¹ RAC group remained constant in the red fibres, and increased significantly in both the intermediate and white fibres (P = 0·01 and 0·02, respectively). Over both muscles Kramer Press values were significantly higher (P = 0·030 in the RAC-fed pigs than in the controls. Incorporation of RAC into the diet did not result in any changes to crude protein or total and soluble hydroxyproline levels. Crude fat tended to increase in the 15 mg kg⁻¹ RAC treatment in the SM and decreased in the 20 mg kg⁻¹ RAC treatment in the PM. The shift in fibre type, and the associated changes in fibre size, may contribute to the increased shear values found in RAC-fed pigs.     

Biologically active polyamines in pig kidneys and spleen: Content after slaughter and changes during cold storage and cooking

Polyamines putrescine, spermidine (SPD) and spermine (SPM) were determined as dansyl derivatives using an HPLC method. Distribution of SPD and SPM in pair kidneys was homogenous. The mean SPD and SPM contents in pig kidneys 24 h after slaughter were 9.39 ± 3.35 and 53.1 ± 14.0 mg kg⁻¹, respectively with no significant differences between barrows and gilts. Putrescine content was below the detection limit of 1.2 mg kg⁻¹. In kidneys stored aerobically or vacuum-packaged at 2–3 °C for 7 and 21 days, respectively, SPD and SPM decreased significantly. Stewing decreased both polyamines more extensively in kidneys processed on day-1 after slaughter than on day-7 after storage at 2–3 °C. The mean SPD and SPM in 10 spleens 24 h after slaughter were 36.7 ± 5.70 and 34.0 ± 7.64 mg kg⁻¹, respectively. Thus, both pork kidney and spleen are foods with a high level of SPM and SPD.     

Fumigation trial on direct application of liquid carbonyl sulphide to wheat in a 2500 t concrete silo

Wheat (Australian Standard White) with a moisture content of 10.2% was fumigated with carbonyl sulphide (COS) at a calculated application rate of 24.14 g m⁻³, in a sealed concrete vertical silo (3512 m³, 2500 t wheat) located at Nevertire, NSW, Australia. The COS was applied as a liquid via the top of the silo and released 2 m below the grain surface. The application of 84.5 kg of COS was completed within 30 min. With 2 h of recirculation using a 0.4 kW fan, the in-silo concentrations of COS achieved equilibrium with a concentration variation less than 5% of the mean. After a two-day exposure period, the COS concentration in the silo remained at 29 g m⁻³. The concentration×time product (Ct) was then 1900 g h m⁻³, and this achieved complete kill of all life stages of mixed-age cultures of Sitophilus oryzae, Rhyzopertha dominica, Tribolium castaneum and Trogoderma variabile. After 2-days exposure, the silo was aired overnight with an aeration fan (25 kW) resulting in a COS in-silo concentration of below 4 ppm. This is 2.5 times lower than the Australian Experimental Threshold Limit Value (TLV) of 10 ppm. Residues of COS in the wheat declined to below the Australian Experimental Maximum Residue Limit (MRL) of 0.2 mg kg⁻¹ after overnight aeration. The COS was not detected in any outloading samples at concentrations above the detection limit (0.05 mg kg⁻¹). The workspace and environmental levels of COS were monitored during application, fumigation, aeration and outloading. The levels of COS and hydrogen sulphide (H₂S) were less than the detection limit of 0.1 ppm, which was 100 times lower than the TLV of 10 ppm. The treatment with COS had no affect on the wheat germination and seed colour when compared with untreated controls. Oil quality tests showed that COS had no effect on total lipid (made from treated wheat) content or the lipid colour.     

Content of biologically active polyamines in livers of cattle, pigs and chickens after animal slaughter

Dietary polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) participate in an array of important human physiological roles, including tumour growth. Physicians and dieticians thus need reliable information on polyamine contents in foods. However, data for livers are lacking. We determined therefore the content of these polyamines 24 h after slaughter in livers of young bulls, cows, pigs and chicken in 58, 19, 36 and 38 samples, respectively. Polyamines were determined as N-benzamides by micellar electrokinetic capillary chromatography. Mean PUT contents about 25 mg kg⁻¹ were found in cattle livers, while very low or negligible contents were determined in livers of the other animals. Extremely high mean SPD contents of 122 and 161 mg kg⁻¹ were found in livers of bulls and cows, respectively and mean levels of 32 and 57 mg kg⁻¹ in livers of pigs and chicken. An opposite relation was observed for SPM. Its mean contents were 43, 35, 115 and 120 mg kg⁻¹ for bulls, cows, pigs and chicken livers, respectively. Thus, livers of the tested animal species belong among foods with the highest polyamine contents. However, the contents ranged very widely, that makes application of the results for the control of human nutrition rather difficult. Polyamine contents in bovine blood were found to be below the detection limits of 2.1, 1.0 and 1.4 mg kg⁻¹ for PUT, SPD and SPM, respectively. Thus, the blood content did not contribute to the substantial polyamine contents in bovine liver found in this study.     

Fatty acid content and composition of english beef, lamb and pork at retail

We have determined the fatty acid content and composition of retail samples of meat and assessed them with respect to UK dietary recommendations. Fifty beef sirloin steaks, pork chops and lamb chops were purchased from four supermarkets on separate occasions. The percentage of muscle (boneless basis) in the samples was 84.4 ± 4.3, 69.8 ± 7.7 and 78.9 ± 7.1 for beef, lamb and pork, respectively, with fatty acid contents of 3.84 ± 1.3, 4.73 ± 1.66 and 2.26 ± 0.7 g per 100 g muscle, respectively. Adipose tissue fatty acid contents were 70.0 ± 8.2, 70.6 ± 8.6 and 65.3 ± 9.4 g per 100 g tissue. A range of C20 and C22 polyunsaturated fatty acids (PUFA) was present in the muscle of all three species and pork adipose tissue but their concentrations in lamb and beef adipose tissue were too low to measure. The mean P:S ratios for beef, lamb and pork muscle were (adipose tissue values in parentheses): 0.11 (0.05); 0.15 (0.09) and 0.58 (0.61), and the n−6:n−3 ratios were 2.1 (2.3), 1.3 (1.4) and 7.2 (7.6). We conclude that the muscles of red meat species are a valuable source of PUFA, particularly the C20 and C22 n−3 fatty acids, in the human diet and that, considered as part of a varied diet, the low P:S ratio of the ruminant muscle, the high n−6:n−3 ratio of pork and the total fatty acid contents do not detract significantly from the nutritional value of lean meat.     

Evaluation of two new diatomaceous earth formulations, enhanced with abamectin and bitterbarkomycin, against four stored-grain beetle species

Two new natural diatomaceous earth (DE) formulations, enhanced with abamectin (DEA-P/WP), or bitterbarkomycin (DEBBM-P/WP), were tested under laboratory conditions against adults of the rice weevil, Sitophilus oryzae, the lesser grain borer, Rhyzopertha dominica, the red flour beetle, Tribolium castaneum and the rusty grain beetle, Cryptolestes ferrugineus. The bioassays were carried out on wheat, at 30±1 °C and 70±5% r.h. The two enhanced DEs were applied either as dusts (P) or as wettable powders (WP) at the dose rates of 75, 100 125 and 150 ppm. Adult mortality was assessed after 14 and 21 d of exposure on the treated substrate. After this interval, the treated wheat was retained for an additional period of 49 d in the case of S. oryzae and 63 d in the case of the other three species, in order to evaluate progeny production. Generally, for all species tested, mortality was higher on wheat treated with powders in comparison with wettable solutions. After 14 d of exposure, all adult rice weevils were dead even at the lowest dose rate of DEA-P, while 100% mortality was noted at doses 125 ppm of DEBBM-P. For the other species, mortality was 100% on wheat treated with 75 ppm of DEBBM-P, with the exception of T. castaneum for which all adults were dead at doses 100 ppm. Progeny production was low, and no progeny were produced in the cases of R. dominica and C. ferrugineus, for both DEs. However, for S. oryzae, progeny production was high on wheat treated with WP formulations, at dose rates 100 ppm. Similar trends were noted for T. castaneum, at 100 ppm of DEBBM-WP. The results of the present study indicate that both DEA-P/WP and DEBBM-P/WP are more effective against the four beetle species examined in comparison with the currently commercially available DE formulations.     

Thermophysical properties of processed meat and poultry products

Thermophysical properties of various meat and poultry emulsions were evaluated at four temperatures (20, 40, 60 and 80 °C). Thermal conductivities (0.26–0.48 W m⁻¹ K⁻¹) increased linearly with temperature between 20 and 60 °C. Between 60 and 80 °C, it remained constant for most products except bologna. Curves for thermal conductivity as a function of temperature could be roughly grouped into two different categories: products containing meat particles and those containing meat emulsions. The application of various models was investigated for thermal conductivity prediction. It was found that a three phase structural based Kirscher model had the potential for predicting thermal conductivities with acceptable accuracy. Densities decreased slightly as a function of temperature from 20 to 40 °C. A transition phase was observed from 40 to 60 °C, which was followed by a decrease from 60 to 80 °C. There was a decrease of about 50 kg m⁻³ between the density of a raw product at room temperature (at maximum 1070 kg m⁻³) and the product heated to 80 °C (at minimum 970 kg m⁻³), due to the gelation or setting of the structure. After a transition period from 10 to 30 °C, the heat capacity increased linearly from 30 to 80 °C, and ranged from 2850 to 3380 J kg⁻¹ °C⁻¹, respectively. Densities and heat capacities were strongly influenced by the carbohydrate content (i.e. as the carbohydrate content increased the density decreased). The salt content adversely affected thermal conductivity and thermal diffusivity values. However, these parameters increased with moisture content.     

Supercooling point variability in the Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Factors affecting the supercooling point (SCP) of the Indian meal moth, Plodia interpunctella (Hübner), were investigated under various conditions. The effects of geographic origin, time under laboratory conditions, laboratory diet, stage of development, age within stage, and season on P. interpunctella SCP were examined. Overall, SCPs ranged from −28.6 to −2.4 °C. At the times of collection, differences in SCP between field-collected individuals and individuals from laboratory sources were negligible. The minimum observed SCP for most of the cultures tested soon after collection was below −20 °C. After 7 months under laboratory conditions, the mean SCP of field-collected and laboratory-reared cultures remained unchanged. No particular trend in SCP was observed when comparing cultures from northern and southern regions. Differences in laboratory diets did not affect mean SCP. Mean SCP for 1- and 4-d-old eggs was similar. Eggs (−24.4 °C), first instars (−23.5 °C), pupae (−22.2 °C), and adults (−22.4 °C) had lower mean SCPs than later instar larvae (−14.4 to −11.6 °C). When confined in the laboratory for 8 months under conditions which were not controlled, monthly mean SCP for the same culture varied by as much as 5.7 °C. Plodia interpunctella appeared to regulate its SCP as the season changed, with a relatively high mean SCP during summer and a marked decline of more than 10 °C in fall. The SCPs obtained in this study suggest that very low temperatures may be needed for disinfestation of P. interpunctella at all stages of development.     

Susceptibility of stored-product beetles on wheat and maize treated with thiamethoxam: effects of concentration, exposure interval, and temperature

Sitophilus zeamais Motschulsky, the maize weevil, Oryzaephilus surinamensis (L.), the saw-toothed grain beetle, and Tribolium castaneum (Herbst), the red flour beetle, were exposed for 1, 2, 3, and 6 d at 22°C, 27°C, and 32°C on maize treated with 0, 0.5, 1.0, 2.0, or 4.0 ppm thiamethoxam, a new-generation neonicotenoid insecticide. A second series of tests was conducted on hard winter wheat using S. oryzae (L.), the rice weevil, Rhyzopertha dominica (F.), the lesser grain borer, and T. castaneum. Mortality of all species on both commodities generally increased with insecticide concentration, exposure interval, and temperature, and data were described by linear and non-linear regressions with concentration as the independent variable. Mortality of S. zeamais ranged from 58% to 90% on maize treated with 0.5 ppm thiamethoxam, and approached 95–100% as concentration increased to 4 ppm. Oryzaephilus surinamensis appeared to be slightly less susceptible than S. zeamais; mortality ranged from about 18% to 80% at 5 ppm and there was a more gradual increase in mortality as concentration increased. Mortality of T. castaneum generally did not exceed 40% at any concentration unless the beetles were exposed for 6 d. Mortality of R. dominica and S. oryzae was less than 60% when exposed on treated wheat for 1 and 2 d, but increased to nearly 100% when exposed for 6 d at 27°C and 32°C. Mortality of T. castaneum did not exceed 20% at the 1- and 2-d exposures, and approached 100% only when beetles were exposed for 6 d at 32°C. Few F₁ adults of any species were found in treated maize or in treated wheat but the number of F₁ T. castaneum in untreated maize and untreated wheat was very low compared with the other species. Results show that thiamethoxam would be an effective protectant of stored maize seed and stored wheat seed.     

Effect of low pressures on the survival of three cocoa pests at 30°C

This study forms part of an effort to eliminate the need for methyl bromide fumigation to control insects in stored commodities, through development of a novel “vacuum-hermetic” technology. The effects of low pressures and exposure times on the mortality of insects in stored cocoa beans were studied at a temperature of 30°C in order to simulate cocoa bean storage conditions in tropical climates. Insects were exposed within test chambers containing the cocoa beans at a moisture content in equilibrium with 55% r.h. and at a constant temperature of 30°C. Three species of insects were used, all being major pests of cocoa beans in producer countries: Ephestia cautella (Walker), Plodia interpunctella (Hübner) and Tribolium castaneum (Herbst). At 50±5 mmHg, the egg stage was the most resistant in all three species, times needed to obtain 99% mortality being 45, 49 and 22 h, respectively. Results show that low-pressure treatment can provide an additional and more effective option to the 5 days fumigation with phosphine used today in the replacement of methyl bromide. The use of low pressures allows the control of insect pests at shorter exposure times without the need for toxic chemicals with their environmental impact.     

Fumigation with carbonyl sulfide: a model for the interaction of concentration, time and temperature

The new fumigant carbonyl sulfide offers an alternative to both methyl bromide and phosphine as a grain fumigant. Separate mathematical models for levels of kill, based on quantitative toxicological studies were developed for adults and eggs of the rice weevil Sitophilus oryzae (L.). These models suggest that fumigation exposure times for carbonyl sulfide will be a compromise between those of methyl bromide (typically 24 h) and phosphine (7–10 d) to achieve a very high kill of all developmental stages. S. oryzae eggs were more difficult to kill with carbonyl sulfide fumigation than the adults. At 30°C, a 25 g m⁻³ fumigation killed 99.9% of adults in less than 1 d, but took 4 d to kill the same percentage of eggs. Models were generated to describe the mortality of adults at 10, 15, 20, 25 and 30°C. From these models it is predicted that fumigation with carbonyl sulfide for 1–2 d at 30 g m⁻³ will kill 99.9% of adults. Furthermore the models illustrate that fumigations with concentrations below 10 g m⁻³ are unlikely to kill all adult S. oryzae. Significant variation was observed in the response of eggs to the fumigant over the temperature range of 10 to 30°C. Models were generated to describe the mortality of eggs at 10, 15, 20, 25 and 30°C. As the temperature was reduced below 25°C, the time taken to achieve an effective fumigation increased. Extrapolating from the models, a 25 g m⁻³ fumigation to control 99.9% of S. oryzae eggs will take 95 h (4 d) at 30°C, 77 h (3.2 d) at 25°C, 120 h (5 d) at 20°C, 174 h (7.5 d) at 15°C and about 290 h (11 d) at 10°C. The role of temperature in the time taken to kill eggs with carbonyl sulfide cannot be ignored. In order to achieve the desired level of kill of all developmental stages, the fumigation rates need to be set according to the most difficult life stage to kill, in this instance, the egg stage.     

Pre-selection of protective colloids for enhanced viability of Bifidobacterium bifidum following spray-drying and storage, and evaluation of aguamiel as thermoprotective prebiotic

The objective of this work was to demonstrate that Bifidobacterium bifidum viability to spray-drying and with storage time could be substantially enhanced by pre-selecting protective colloids offering resistance to oxygen diffusion (high activation energy) and adding aguamiel as a thermoprotector prebiotic. Three different protective colloids blends exhibiting relatively high, medium and low activation energies were mixed with B. bifidum harvested in the late log phase, with or without aguamiel, spray-dried at 130, 140 and 155 °C, and stored at 4 °C at a water activity of 0.32. Viability was determined by cell total count in MRS agar. Best viability was achieved when microencapsulating the microorganism in the protective colloids blend exhibiting highest activation energy (40.7 kJ mol⁻¹), with aguamiel, and dried at 140 °C. Viability ranged from 1.26 × 10⁸ cfu g⁻¹ immediately after drying to 6.0 × 10⁶ cfu g⁻¹ after 5 weeks storage time at 4 °C.     

Identification of halothane genotypes by calcium accumulation and their meat quality using live pigs

The three halothane genotypes (NN, Nn, and nm) were identified by measuring the capacity for Ca²⁺ accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of M. longissimus dorsi with a Ca²⁺ specific electrode at 35°C. Significant differences (P < 0·001) in deterioration (%) of Ca²⁺ accumulation, 12% for NN, 35% for Nn, and 81% for nn pigs, were observed after ageing the whole muscle homogenate preparations for 24 h in ice.

Predictions of meat quality in live pigs (n = 34) based on the values for water-holding capacity, assessed as fluid (g/0·5 g wet wt LD), and pH (fluid) by using small biopsy LD samples (Cheah et al. 1993) were performed on all the halothane genotypes. The halothane genotype NN (n = 11) showed a fluid value of 0·37 ± 0·01 and a pH (fluid) value of 6·62 ± 0·03 as compared with 0·61 ± 0·02 and 5·84 ± 0·04, respectively, for the halothane genotype nn (n = 13). The Nn pigs (n = 10) showed fluid (0·49 ± 0·03) and pH (fluid) (6·19 ± 0·11) values between those values observed for the two homozygotes (NN and nn). Predictions of meat quality in live pigs from biopsy LD muscles were confirmed from assessments on post-mortem LD muscles based on pH₁ and fibre optic probe (FOP) measurements.

The extent of deterioration (%) in Ca²⁺ accumulation showed high correlations with fluid (r = −0·861) and pH (fluid) (r = −0·831) in the biopsy LD samples, and with pH₁ (r = 0·663), FOP (r = −0·812), and drip (%) loss (r = −0·777) in the post-mortem LD samples.     

A comparison of the toxicity of pirimiphos-methyl and malathion to Typhaea stercorea (L.) when applied to stored maize

The toxicity of freshly applied and aged residues of pirimiphos-methyl and malathion were assessed against adult Typhaea stercorea (L.). Maize was treated with each pesticide at doses of 2, 4, 6, and 8 mg kg⁻¹ and stored at a constant 25 °C and 70% r.h. for 12 weeks. All fresh deposits of pirimiphos-methyl produced 100% mortality as did malathion at 4, 6 and 8 mg kg⁻¹. After four weeks storage pirimiphos-methyl still gave 100% mortality at 6 and 8 mg kg⁻¹ but this dropped to 96% at 4 mg kg⁻¹ and 60% at 2 mg kg⁻¹, while mortality for malathion was less than 31% even at 8 mg kg⁻¹. After 12 weeks storage only pirimiphos-methyl gave effective control with 78% mortality at the highest dose of 8 mg kg⁻¹, while control by malathion had completely broken down. The effect of exposure time on T. stercorea for both pesticides at a single dose of 4 mg kg⁻¹ was also assessed. Beetles were left in contact with treated maize for 2, 4, 6, 8 and 10 d. Fresh and four-week-old pirimiphos-methyl residues produced over 98% mortality at all exposure periods but on 12-week-old residues mortality had dropped and was only 61% following 10 d exposure. Only freshly applied malathion gave 100% mortality and even the maximum exposure of 10 d only produced 51% mortality of T. stercorea at four weeks and 39% at 12 weeks.     

Conventional freezing plus high pressure-low temperature treatment: Physical properties, microbial quality and storage stability of beef meat

Meat high-hydrostatic pressure treatment causes severe decolouration, preventing its commercialisation due to consumer rejection. Novel procedures involving product freezing plus low-temperature pressure processing are here investigated. Room temperature (20 °C) pressurisation (650 MPa/10 min) and air blast freezing (−30 °C) are compared to air blast freezing plus high pressure at subzero temperature (−35 °C) in terms of drip loss, expressible moisture, shear force, colour, microbial quality and storage stability of fresh and salt-added beef samples (Longissimus dorsi muscle). The latter treatment induced solid water transitions among ice phases. Fresh beef high pressure treatment (650 MPa/20 °C/10 min) increased significantly expressible moisture while it decreased in pressurised (650 MPa/−35 °C/10 min) frozen beef. Salt addition reduced high pressure-induced water loss. Treatments studied did not change fresh or salt-added samples shear force. Frozen beef pressurised at low temperature showed L, a and b values after thawing close to fresh samples. However, these samples in frozen state, presented chromatic parameters similar to unfrozen beef pressurised at room temperature. Apparently, freezing protects meat against pressure colour deterioration, fresh colour being recovered after thawing. High pressure processing (20 °C or −35 °C) was very effective reducing aerobic total (2-log₁₀ cycles) and lactic acid bacteria counts (2.4-log₁₀ cycles), in fresh and salt-added samples. Frozen + pressurised beef stored at −18 °C during 45 days recovered its original colour after thawing, similarly to just-treated samples while their counts remain below detection limits during storage.     

Efficacy of diatomaceous earth and methoprene, alone and in combination, against Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in rough rice

Combination treatments of diatomaceous earth (DE) (Protect-It^®) and the insect growth regulator (IGR) methoprene (Diacon^® II) were evaluated against Rhyzopertha dominica (F.), the lesser grain borer, on stored rough rice. Application rates of DE and methoprene ranged from 0 to 500 ppm and 0 to 1 ppm, respectively, in 25 treatment combinations. Tests were conducted by exposing 20 adults for 2 weeks at 32 °C and 75% relative humidity on single varieties of long-, short-, and medium-grain rough rice, removing adults, and holding the rice for 8 weeks at the same conditions to collect F₁ progeny. In the absence of methoprene, mortality of exposed adults increased as the concentration of DE increased, but even at the highest rate of 500 ppm, mortality was only 57.5±12% and 58.8±9.7% in long and medium-grain rice, respectively, and 26.3±4.7% in short-grain rice. Mortality of R. dominica exposed on short-grain rice was lower than mortality on long-and medium-grain rice at several combinations with 375 and 500 ppm DE. There was also an unexpected increase in adult mortality with the addition of methoprene so that at 1 ppm methoprene and 500 ppm DE, mortality in long-, medium-, and short-grain rice was 77.5±9.0%, 77.5±10.0%, and 58.5±3.0%, respectively. In the absence of methoprene, progeny produced on long- and short-grain rice ranged from 48.0±21.2 to 87.2±9.0, compared to 16.5±5.5 to 33.5±8.6 progeny produced on medium-grain rice. With the inclusion of methoprene there were few progeny produced in any of the treatment combinations, and the overall average was 0.6±0.3. Similarly, with no methoprene the range of insect-damaged kernels (IDK) was 5.2±2.7 to 12.2±3.1%, but with methoprene the overall average was reduced to 1.8±0.2%. While control of R. dominica was somewhat limited with DE, the differences among rice varieties seems to indicate that the specific type and possibly variety of rough rice may influence mortality and reproduction of R. dominica exposed to DE. With methoprene, progeny production was greatly suppressed regardless of DE concentration, but combining DE with methoprene would give some measure of adult control.     

The effects of residual oxygen concentration and temperature on the degradation of the colour of beef packaged under oxygen-depleted atmospheres

Samples of beef longissimus dorsi (LD), approximately 5 × 5 × 1 cm, were packaged in pairs under 10 litre volumes of N₂ or CO₂ containing O₂ at concentrations between 100 and 1000 ppm. The packaged samples were stored at temperatures of 5, 1, 0 or −1·5°C, for times between 4 and 48 h. Samples of beef psoas major (PM) were packaged under N₂ or CO₂ containing O₂ at between 100 and 600 ppm, and stored at −1·5°C for 24 or 48 h. After storage, each sample was assessed for colour deterioration and discoloration, and for the fraction of metmyoglobin in the surface pigment.

The results obtained with N₂ and CO₂ atmospheres were similar. The colours of all LD samples had deteriorated after 4 h storage at 5 or 1°C, although the degree of deterioration increased with increasing O₂ concentration. All LD samples stored for 12 h at 5 or 1°C were extensively discoloured, with metmyoglobin fractions generally exceeding 60%, but those stored at −1·5°C for 48 h or less, under O₂ concentrations ≤ 400 ppm had undergraded colours. The colours of some LD samples stored at −1·5°C under about 600 ppm of O₂ were also undergraded, but the colours of samples stored under 800 or 1000 ppm had deteriorated by 24 h. The colours of LD samples stored at 0°C under > 200 ppm had deteriorated after 24 h storage, and the colours of samples stored under 100 ppm O₂ had deteriorated after 48 h storage. All PM samples were wholly discoloured after storage at −1·5°C. Evidently, the colour of beef muscle of high colour stability is resistant to degradation by atmospheres containing < 600 ppm of O₂ when the meat is stored at sub-zero temperatures, but not when the storage temperature is at or above 0°C. Beef muscle of low colour stability, such as the PM, will discolour at all low concentrations of O₂ irrespective of the storage temperature.     

Effect of pretreatment and temperature on air-drying of Dioscorea alata and Dioscorea rotundata slices

Effects of pretreatment and drying conditions on yam varieties, namely Dioscorea alata and Dioscorea rotundata, in a fabricated laboratory scale hot air drier at temperature range of 50–80 °C and constant air velocity of 1.5 m²/s were investigated. Mass transfer during air-drying of yam slices was described using Fick’s diffusion model. Drying took place entirely in the falling rate period. Temperature dependency of moisture on diffusivity was illustrated by the Arrhenius relationship. Over the range of temperature, moisture diffusivities varied from 9.92 × 10⁻⁸ to 1.02 × 10⁻⁷ and 0.829 × 10⁻⁶ to 1.298 × 10⁻⁵ m²/s for D. alata and D. rotundata, respectively. Activation energy for drying of D. alata and D. rotundata varied from 25.25 to 46.46 and 41.75 to 72.47 kJ/mol, respectively.