Monoacylglycerol Production from Butteroil by Glycerolysis with a Gel-Entrapped Microbial Lipase in Microaqueous Media

Reaction parameters were optimized to support polyethyleneglycol-based and polypropyleneglycol-based gel-entrapped lipase-mediated glycerolysis of butteroil to yield monoacylglycerol. Single liquid-phase reactive mixtures contained 25% (w/w) butteroil dissolved in t-butanol, to which glycerol and water was added. Optimum reaction conditions were 35–40 °C, and 5–10 mg enzyme reagent and 0.10g glycerol/mL substrate solution. Optimum acyl group:glycerol molar ratio was about 0.64. The optimum water content was dependent on glycerol content and was about 6% (w/w) of the glycerol at 0.10g glycerol/mL substrate solution. The gel-entrapped lipases had half-lives of about 35–46 cycles of 72 hr each.     

The effect of temperature and humidity on the developmental period and mortality of Typhaea stercorea (L.) (Coleoptera: Mycetophagidae)

The development of Typhaea stercorea (L.) on kibbled wheat was investigated at temperatures from 15 to 30°C in combination with humidities from 70 to 90% r.h. Eggs hatched at 17.5–30°C but not at 15°C. Incubation periods ranged from 2.5 days at 30°C to 9.5 days at 17.5°C. Larval periods ranged from 9.7 days at 30°C, 90% r.h. to 83.6 days at 17.5°C, 80% r.h. and were more than doubled for each 10% decrease in humidity. At 70% r.h. all larvae died outside the temperature range 22.5–27.5°C. Mortality increased with decreasing humidity in the range tested. Pupal periods ranged from 2.9 days at 30°C, 80% r.h. to 13.8 days at 17.5°C, 90% r.h. At 70% r.h. the lowest temperature for pupal development was 25°C whereas at 90% r.h. it was 17.5°C. The results suggest that this species is essentially a mould feeder and confirm that it requires relatively high humidity to develop.     

Low temperature storage of the predatory mite Cheyletus eruditus (Schrank) for future use in biological control

Populations of the predatory mite Cheyletus eruditus (Schrank) survive at temperatures ranging from −1·7 to +2·0°C and relative humidities of 80–90% for 5–6·5 months and retain their ability to reproduce upon transfer to favourable conditions. Populations obtained from natural aggregations and preserved under low temperatures could be used for the biological control of stored product mites.     

Design, fabrication, and testing of a returnable, insulated, nitrogen-refrigerated shipping container for distribution of fresh red meat under controlled CO2 atmosphere

In today's market, fresh red meat is cut and packaged at both the wholesale and retail level. Greater economies could result if the wholesaler prepared all consumer cuts centrally, but the short storage life of meat limits distribution. Use of CO₂-controlled atmosphere, master packaging, and strict temperature control (−1.5±0.5°C) can enhance storage life and, therefore, distribution ease. An insulated shipping and storage container was designed and tested for its suitability to distribute master-packaged meat. Shelves in the container supported 36 master trays (508 × 381 × 60 mm), with the source of refrigeration being injected liquid nitrogen (N₂). Electric fans dispersed the N₂ gas throughout the container. To reduce costs, 36 saline water bags (10% w/v NaCl) were used to thermally simulate the meat. Temperatures of 20 bags were recorded during storage experiments. The container was tested at outside temperatures of 15, 0 and −15°C with 4 internal fans and at 30°C with 2, 4 and 6 fans. In all instances, bags cooled from 10°C to an equilibrium temperature of −1.5°C within 5.5 h. Minimum equilibrium temperatures during any 8 h trial were −2.6, −2.0 and −2.0°C for 2, 4 and 6 fans, respectively. Correspondingly, maximum temperatures were −0.2, −0.7 and −0.3°C. Initial chilling of the product required, on average, 19 kg of N₂, while equilibrium was maintained at a N₂ consumption rate of 5.5, 4.0, 2.6 and 0.93 kg/h at outside temperatures of 30, 15 0 and −15°C, respectively, with 4 fans. The N₂ use for 2 and 6 fans was 5 and 6.3 kg/h, respectively, at an outside temperature of 30°C. During simulated power failure or when the N₂-tank ‘ran dry', temperatures in the container rose 0.9 and 2.0°C/h, respectively. When the door to the container was opened long enough to remove three trays, temperature was restored within 5 min. Convective heat transfer coefficients between saline water bags and circulating N₂ were in the range of 80–100, 115–135, and 140–155 W/(m²·K) for 2, 4 and 6 fans, respectively. Heat transfer to meat will be limited by conduction in master packaged meat if similar convection coefficients prevail.     

Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7

The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10¹, 10³ and 10⁵ CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10–35 °C), pH (3.52–7.32), and NaCl concentration (0–10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a_w values permitting growth. Differences in the pH and a_w growth limits among inoculum concentrations increased at 15 and 10 °C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 °C, growth initiation of nonadapted cultures stopped at higher a_w compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants.     

Life history studies of internally feeding pests of stored sorghum: Sitotroga cerealella (Ol.) and Sitophilus oryzae (L.)

A laboratory study of the ecology of single species populations of Sitotroga cerealella (Olivier) and Sitophilus oryzae (L.) was made at 3 temperatures (25, 30 and 35°C) and 3 relative humidities (60, 70 and 80% r.h.). The effects of 2 lower humidities (40 and 50% r.h.) on both species were also studied at 30°C. The optimum conditions for multiplication of S. cerealella were found to be 25–30°C and 60–80% r.h. while for S. oryzae the optimum was more clearly defined (30°C and 80% r.h.). However S. cerealella could tolerate a higher temperature (35°C) and lower humidities (40 and 50% r.h. at 30°C) than S. oryzae. The results are compared with those of other workers on sorghum and other cereals, and discussed in relation to the distribution of the two species in Sudan.     

Survival of enterohaemorrhagic Escherichia coli O157:H7 strain in Turkish soudjouck during fermentation, drying and storage periods

Soudjouck (a kind of Turkish sausage) batter was inoculated with Escherichia coli O157:H7 at a level of 10⁵ colony-forming unit (CFUg) and kept overnight at 4°C. After stuffing the soudjouck batter into natural casing, fermentation was carried out at 24±2°C and 90–95% relative humidity (RH) for 3 days with subsequent drying at 22±2°C and 80–85% RH for 5 days. Then, half of soudjouck samples were vacuum-packed in polyethylene bags and the rest were kept open. All samples were stored at 4°C (55% RH) for 3 months. E. coli O157:H7 and lactic acid bacteria counts, moisture contents and pH values of the samples were determined during fermentation, drying and storage periods. Results showed that count of E. coli O157:H7 decreased by 3 log unit during fermentation and drying periods. It was observed that this pathogen survived longer in vacuum-packaged samples (more than 2 months) than non-vacuum samples (more than 1 month).     

Sorption isotherms of salted minced pork and of lean surface of dry-cured hams at the end of the resting period using KCl as substitute for NaCl

The effect of KCl on sorption isotherms was determined on salted minced meat (with 0%, 30% and 100% molar substitution of NaCl by KCl) at 5 °C and 25 °C and meat from a 3 mm thick slice from the surface of dry-cured hams (with 0% and 35% molar substitution of NaCl by KCl) held at 70–75%, 75–80% and 80–85% air relative humidity during the resting period.

The sorption isotherms were determined gravimetrically by exposing the meat samples to several atmospheres of known relative humidity controlled by different saturated salts according to the COST90 method. The sorption equipment consisted of a chamber containing 11 containers, covering the water activity (a_w) range from 0.112 to 0.946 at 25 °C. The hermetically closed sorption containers filled with KCl and minced meat samples were irradiated at 3 kGrey (gamma irradiation ⁶⁰Co). The water content at equilibrium was higher in minced meat with NaCl than in minced meat with KCl (100% molar substitution of NaCl by KCl) at 5 °C within the range of 0.4313 and 0.7565 a_w. However, when substitution was 30% in minced meat and 35% in hams the isotherms were similar to isotherm without substitution.     

Enthalpy-Entropy compensation in food vapor adsorption

Enthalpy-entropy compensation was analysed for sorption isotherms of potatoes, macadamia nuts, apricots, figs, currants, prunes and raisins. Plots of (ΔH_dif)_T vs (ΔS_dif)_T for potatoes and macadamia nuts presented two isokinetic temperatures: T_B1 = 272.0 ± 57.7 K (− 1 °C) for potatoes, T_B1 = 265.0 ± 18.8 K (− 8 °C) for macadamia nuts and T_B2 = 382.5 ± 7.3 K (109.5 °C) for both products. The first isokinetic temperature (T_B1) appeared only at the upper portion of the temperature range tested (50, 60 and 70 °C for potatoes and 50 and 60 °C for macadamia nuts). The two isokinetic temperatures observed for potatoes and macadamia nuts suggested that during the initial stages at low a_w T_B1 is controlled by changes in the entropy of water, whereas the second isokinetic temperature (T_B2) is considered to be enthalpy-controlled. Dried fruits presented only one isokinetic curve T_B = 315.7 ± 3.5 K (42.7 °C), for raisins, currants and figs (75.2–82.3% d.b. sugars) and T_B = 317.7 ± 4.6 K (44.7 °C) for prunes and apricots (51.5–54.5% d.b. sugars), indicating an enthalpy-controlled adsorption process for the whole range of moisture contents covered.     

Comparison of catechins and aromas among different green teas using HPLC/SPME-GC

Green tea polyphenols (GTP) from Camellia sinensis (L.) O. Kuntze are the major water soluble components in tea liquor. The GTP extraction yield was determined using different extraction times from 10 to 60 min at 70°C, and also at different temperatures from 50°C to 100°C, keeping the extraction time constant. The composition of the GTP (catechins) from samples of different origins was determined by RP–HPLC, measuring the absorbance at 280 nm. The calibration curves of the catechins were linear between 5 ng and 2 μg, and their C.V. values for the quantitation were less than 4.0% for four replicates using four different sets of each type. The total epicatechin derivatives (EPD) and epigallocatechin-3-gallate (EGCG) from Azorean green tea, accounted for 74.5 and 47.9% (w/w) of the total GTP, respectively, and were compared with that from tea samples of different origins. The EGCG:caffeine ratio in Azorean green tea was fourfold higher as compared with others, which suggested a good source of a chemopreventive agent. The aroma composition of different green tea samples was compared using the SPME/GC headspace methodology.     

Enzyme-Catalyzed Production and Chemical Composition of Diacylglycerols from Corn Oil Deodorizer Distillate

Diacylglycerols (DAG) were enzymatically synthesized by lipase-catalyzed esterification of glycerol with fatty acids from corn oil deodorizer distillate (CrODD). Effects of reaction parameters such as reaction time, temperature, enzyme type, enzyme load, substrate mole ratio, and water content, as well as the effect of molecular sieves as a water adsorbent were investigated. Rhizomucor miehei lipase (Lipozyme RM IM) was found to be most effective among the lipases screened. The following conditions yielded 70.0% (w/w) DAG: 5 h reaction time, 65°C reaction temperature, 10% (w/w) Lipozyme RM IM, 2.5:1 fatty acid to glycerol molar ratio, and 30% (w/w) molecular sieves. DAG synthesis of 12.4% (w/w) was still observed at 10% (w/w) water content. 84.2% (w/w) of DAG was obtained after purification. The DAG oil comprised predominantly of 1-oleoyl-3-linoleoyl-glycerol (28.5%), 1,3-diolein (22.7%), 1-oleoyl-2-linoleoyl-glycerol (17.9%), and 1,2-diolein (10.9%). Fatty acid profile was similar to that of refined, bleached and deodorised (RBD) corn oil. The ratio of 1,3- to 1,2-positional isomers of DAG was at 1.82:1.     

The influence of oxygen on the differentiation of temperature-sensitive and temperature-insensitive Lactococcus lactis subsp. cremoris starter strains

The differentiation of temperature-insensitive and temperature-sensitive strains of Lactococcus lactis subsp. cremoris by using a modified sodium-β-glycerophosphate/milk medium is described (temperature-insensitive strains are defined as those that continue to grow at 38°C and temperature-sensitive strains as those that do not grow, or grow poorly, at 38°C). The physiological basis for the differentiation assay was examined by using L. lactis subsp. cremoris strains 2146 (temperature-insensitive) and 2182 (temperature-sensitive) as test strains. After aerobic incubation on the medium, strain 2146 formed uniform colonies, 0·5 mm in diameter, while strain 2182 formed larger colonies, 1·0–1·5 mm in diameter. The differential was dependent on the medium constituents, on an aerobic gas phase, and on the effects of H₂O₂ generated within the colonies. The addition of 0·5% (w/v) pyruvate to the medium facilitated the growth of colonies of strain 2146 to 3-mm diameter, while the colony size of strain 2182 remained at 1-mm diameter, and thus the colony-size differential between strains was reversed. The growth of both strains was inhibited at 0·4–0·8% air saturation during suspension culture in sodium-β-glycerophosphate/milk medium. The inclusion of catalase in the cultures overcame the growth inhibition. There was no observable difference between the two strains in their oxygen sensitivity or NADH oxidase/peroxidase enzymology.     

The influence of relative humidity and thermal acclimation on the survival of adult grain beetles in cooled grain

The influence of humidity and thermal acclimation on the survival of Cryptolestes ferrugineus, Oryzaephilus surinamensis, Rhyzopertha dominica, Sitophilus granarius, S. oryzae and Tribolium castaneum in cooled wheat or flour at 45 and 70% relative humidity was studied in the laboratory. Young adults were held continuously at 30 or 32°C; cooled gradually to 13.5°C and held at that temperature; cooled gradually to 9°C and held at that temperature; or transferred directly to 9°C.

Survival at low temperatures differed, often considerably, between species, being generally shortest in T. castaneum (0.7–16 weeks) and longest in S. granarius (5–40 weeks). There was considerable interaction between the effects of temperature and humidity, with survival being, to varying degrees, shorter in 45% r.h. than in 70% r.h. At 45% r.h., an equilibrium relative humidity common in Australian storages, all species survived when the grain was cooled to 13.5°C but only S. granarius survived 26 weeks in grain cooled to 9°C.

Chill-coma temperature and acclimation temperature were linearly related in all species at each humidity. Neither the slopes nor intercepts of the relationships were influenced by humidity. There was generally an inverse relationship between survival and chill-coma temperature.

At 45% r.h., the increase in survival at 9°C attributable to acclimation ranged from 2-fold in S. oryzae (0.9 weeks) to 3.5-fold in C. ferrugineus (3.8 weeks). Corresponding values for beetles at 70% r.h. ranged from 2.3-fold in R. dominica (2.4 weeks) to 7.9-fold in C. ferrugineus (6.9 weeks).     

Application of multi-component biopolymer layers to improve the freeze–thaw stability of oil-in-water emulsions: β-Lactoglobulin–ι-carrageenan–gelatin

This study examines the influence of interfacial composition on the freeze–thaw stability of oil-in-water emulsions. Three 5% w/w oil-in-water emulsions (5 mM phosphate buffer, pH 6.0) were prepared using the layer-by-layer electrostatic deposition method that had different interfacial compositions: (i) primary emulsion (β-Lg); secondary emulsion (β-Lg–ι-carrageenan); (iii) tertiary emulsion (β-Lg–ι-carrageenan–gelatin). The primary, secondary and tertiary emulsions were subjected to from one to three freeze–thaw cycles (−20 °C for 22 h, +40 °C for 2 h) in the absence or presence of sucrose (10% w/w), and then their stability was assessed by ζ-potential, particle size, microstructure and creaming stability measurements. In the absence of sucrose, the primary and secondary emulsions were highly unstable to droplet aggregation and creaming after three freeze–thaw cycles, whereas the tertiary emulsion was stable, which was attributed to the relatively thick biopolymer layer surrounding the oil droplets. In the presence of 10% w/w sucrose, all of the emulsions were much more stable, which can be attributed to the ability of sucrose to increase the amount of non-frozen aqueous phase in the emulsions. The interfacial engineering technology used in the study could therefore lead to the creation of food emulsions with improved stability to freezing and thawing.     

Temperature shows greater impact on bovine Longissimus dorsi muscle glycogen debranching enzyme activity than does salt concentration

The degradation of glycogen progresses by the co-operation of two enzymes: glycogen phosphorylase (phosphorylase) and glycogen debranching enzyme (GDE). We studied the effect of temperature (4–42 °C) and salt concentration (0–3% NaCl) on bovine M. longissimus dorsi GDE activity. GDE activity (n = 4) decreased significantly with decreasing temperature from about 40–4 °C. GDE exhibited 52% activity at 25 °C and 11% at 4 °C compared to its optimum activity measured at 39 °C. In rapidly chilled meat, the reduction in GDE activity may substantially delay the rate of glycolysis. However, residual GDE activity at 4 °C seems sufficient to enable the attainment of normal ultimate pH if the available time is long enough. An increase in salt concentration from 0% to 2% and to 3% induced a significant (P < 0.001) increase in the ultimate pH of ground bovine meat (n = 6), but showed no effect on GDE activity.     

Conformational changes in the muscle proteins of cured beef during heating

Structural changes caused by heating in the proteins of cured beef longissimus dorsi muscle were examined by fluorescence and differential scanning calorimetry. Denaturation occurred in four temperature ranges—40–55°C, 55–61°C, 62–70°C and above 70°C, in contrast to the three endothermic transitions reported for non-cured meats.     

Impact of sorbitol on the thermostability and heat-induced gelation of bovine serum albumin

The influence of sorbitol (0–40 wt.%) on the thermal denaturation and gelation of bovine serum albumin (BSA, pH 7.0) in aqueous solution has been studied. The effect of sorbitol on heat denaturation of 0.5 wt.% BSA solutions was measured using ultrasensitive differential scanning calorimetry. The unfolding process was irreversible and was characterized by the thermal denaturation temperature (T_m). As the sorbitol concentration increased from 0 to 40 wt.%, T_m increased from 73.0 to 80.9 °C. The rise in T_m was attributed to the increased thermal stability of the globular state of BSA relative to its native state. The dynamic shear rheology of 4 wt.% BSA solutions containing 200 mM NaCl was monitored as they were heated from 30 to 90 °C at 1.5 °C min⁻¹, held at 90 °C for 120 min, and then cooled back to 30 °C at −1.5 °C min⁻¹. Sorbitol increased the protein gelation temperature (ΔT_gel +10 °C for 40 wt.% sorbitol), decreased the isothermal gelation rate at 90 °C, but increased the final shear modulus of the gels cooled to 30 °C. The impact of sorbitol on gel characteristics was attributed to its ability to increase protein thermal stability, increase the attractive force between proteins and decrease the protein–protein collision frequency.     

Optimization of oven toasting for improving crispness and other quality attributes of ready to eat potato-soy snack using response surface methodology

Ready-to-eat potato-soy snacks were developed with high temperature short time air puffing process followed by oven toasting for increasing crispness. Oven toasting experiments were conducted with varying temperature (85.86–114.14 °C) and time (12.69–35.31 min) based on central composite rotatable design. The final product was evaluated in terms of quality attributes such as crispness, moisture content, ascorbic acid loss, colour (L and ΔE) values and overall acceptability. The optimum product qualities in terms of crispness (38.7), moisture content (3.35%, db), ascorbic acid loss (20.87%, db), L value (52.03), ΔE (8.60) and overall acceptability (7.8) were obtained at temperature of 104.4 °C and time of 27.9 min.     

Honey inhibits lipid oxidation in ready-to-eat ground beef patties

Our objective was to evaluate the antioxidant capabilities of clover (CH) and wildflower honeys (WH) in delaying lipid oxidation in cooked and reheated ground beef patties stored in refrigerated and frozen states. CH and WH (5%, 10%, or 15% w/w) were each mixed separately into ground beef chuck (18% fat) and formed into 30 g patties mixed with 1% salt (w/w). A control (CON) with no honey and a control with sodium tripolyphosphate (STP; 0.25% w/w) were used for comparison. Patties were cooked to 71 °C, overwrapped with oxygen-permeable PVC film and either stored refrigerated (4 °C) for 12 days or frozen (−18 °C) for 45 days. Cook yield, pH and water activity were measured on day 0. On designated sampling days, patties were reheated to 71 °C. Thiobarbituric acid-reactive substances (TBARS) and lipid hydroperoxides (LOOH) were measured spectrophotometrically to assess lipid oxidation. TBARS and LOOH of ready-to-eat (RTE) ground beef patties containing either CH or WH were lower (P < 0.01) than CON patties following storage; however, STP patties had lower TBARS values than honey-containing patties (P < 0.01). WH and CH at 15% were equally effective in suppressing LOOH compared to STP in refrigerated and frozen patties. All honey concentrations improved cook yield, with 10% WH being more effective than STP. Both CH and WH delayed lipid oxidation in RTE ground beef patties stored at 4 °C and −18 °C, with WH decreasing LOOH formation in refrigerated patties as effectively as STP. Honey may be a natural alternative to phosphates to delay lipid oxidation.     

Effects of temperature and humidity on development of four pyralid moth pests of stored products

The development of Plodia interpunctella, Ephestia cautella, E. kuehniella and E. elutella was followed carefully at selected temperatures. Infertility prevented successful breeding of the latter two species at 30°C. The first two species bred successfully at 30°C, failed to complete development at 15°C, and, at 20–30°C, completed development more quickly than the other two. All species took longer to develop and survived less well at 25% r.h. than at 70% r.h., and their pupal stages lasted about twice as long as the egg stages at temperatures allowing development of both. At 25°C, the pupal stage lasted about 9 days in P. interpunctella and E. cautella, 11–12 days in E. kuehniella and about 13 days in E. elutella.

In all species other than E. elutella, eggs held at 25°C became more tolerant of cold when aged over 1 day. Younger eggs of P. interpunctella were less tolerant of cold than any eggs of the other species, and were killed outright by holding for 19 days at 15°C.

Stocks of all four species recently collected from the field generally tolerated low r.h. and low temperature a little better than laboratory stocks, but at higher temperatures developed from egg to adult a little more slowly.