Refrigeration Storage Research Articles

Pengaruh Berbagai Macam Pendinginan dan Pengemasan Terhadap Umur Simpan Jagung Manis (Zea mays saccharata)

This research was aimed to study the influence of kinds of cooling and packing on the storage life of sweetcorn in order to obtain the simple postharvest technology and easy to practice. The research was done during the February - March of 2005 in the Research Laboratory of Agriculture Faculty, Muhammadiyah University of Yogyakarta. The reducing sugar analysis was done in the Agriculture Technology Faculty of Gadjah Mada University. The laboratory experiment was arranged ini 2 x 3 factorial completely randomized design with three replications. The cooling first factor was refrigerated in refrigerator to be compared to the hydro-cooling. Meanwhile, the polypropilene and polyethylene packaging were tested and compared to the unpackaged one. The flavor; reducing sugar, water content, percentage of nonconsumable part of sweetcorn, fresh weight of ears, and organoleptic properties were observed. The result showed that there was no significantly interaction between cooling and packaging on the storage life and quality of sweet corn. The cooling treatment was significantly influenced the starch and reducing sugar level as well as the packaging treatment. Refrigeration storage could significantly keep the level of reducing sugar to remain higher than the hydro-cooling, this treatment was also decreased the starch content, decreased the proportion of unconsumable part, and maintained the flavor. The polyethylene packaging significantly keep the level of reducing sugar to remain higher and relatively maintained the flavor than the polypropilene packaging or unpackaged, but decreased the portion of unconsumable part.

Study on the use of porous materials with adsorbed helium as the regenerator of cryocooler at temperatures below 10 K

Cryocoolers play a vital role in ground low-temperature experiments and space explorations. The regenerator is an important part of the cryocooler, which is used to store the cold produced by the expansion of the working fluid helium and absorb the heat produced during the next cycle of compression. However, the specific heat of helium at temperatures below 10 K is higher than that of almost all currently known regenerator materials, resulting in insufficient cold storage capacity and severely restricting the improvement of the cryocooler cooling performance. In this paper, the study of using porous material to absorb helium as the regenerator material for cryocoolers is carried out. An experimental system was built to test the helium adsorption capacity of super activated carbon in the temperature range of 3–10 K, and it was found that the activated carbon has a significant increase in specific heat compared with the current conventional materials. A thermodynamic calculation model was further established to investigate the dynamic cryogenic adsorption characteristics and the effect of adsorption/desorption heat on the performance of the regenerator. This work is an exploration in the research of low-temperature regenerators, which can provide useful help for the selection and use of regenerator materials for cryocoolers working below 10 K. It also has great application prospects in the fields of energy storage, low-temperature superconductivity, and sub-K refrigeration systems.

Antioxidant and Antimicrobial Effect of Plant Essential Oils and Sambucus nigra Extract in Salmon Burgers.

The antioxidant capacity of oregano (OEO) and clove (CLEO) essential oils and black elderberry (Sambucus nigra) flower extract (SNE) were compared with butylhydroxytoluene (BHT) regarding its protection against lipid peroxidation and microbial counts in salmon burgers stored at 4 °C for 14 days and after cooking. The content of total phenols was 5.74% in OEO, 2.64% in CLEO and 2.67 % in the SNE. The total phenolic content and the antioxidant capacity were significantly higher (p < 0.05) for SNE and OEO. Both essential oils showed a similar IC50 and inhibition percentage of lipid peroxidation to BHT. The combination of OEO and SNE reduced 29% of thiobarbituric acid reactive substances (TBARS), while BHT reduced 31% of TBARS generated during refrigeration storage in salmon burgers in relation to the control sample without antioxidants. Additionally, the microbial counts after 14 days of refrigeration were the lowest in burgers when the combination of OEO and SNE was used. This study concludes that OEO and SNE can be used as inhibitors of lipid oxidation in salmon products and as natural candidates to replace commonly used synthetic antioxidants and antimicrobials in these food products.

PENGARUH PENGGUNAAN MADU SUMBAWA DAN MADU OLAHAN BERBAGAI KONSENTRASI TERHADAP KUALITAS SPERMATOZOA EPIDIDIMIS DOMBA SETELAH PENYIMPANAN DALAM REFRIGERATOR

Artificial Insemination is used to conserve genetic resources. It is necessary to preserve spermatozoa in a certain diluent at certain temperature before artificial insemination. Information regarding the use of honey in the spermatozoa diluent is still less in number. This research aims to determine the effect of Sumbawa honey and processed honey in various concentrations on the quality of spermatozoa after storage in refrigerator. The main materials used were five ram testicles. Spermatozoa was collected from cauda epididymis by mincing and adding 5 ml PBS. The sample were divided into 7 groups of treatment: 1% Sumbawa honey, 2% Sumbawa honey, 3% Sumbawa honey, 1% processed honey, 2% processed honey, 3% processed honey, and control using 0.5 gram glucose in 100 ml Tris diluent. The assessment was carried out microscopically including motility and viability. Data were analyzed statistically using one-way analysis of variance (Anova) on the SPSS statistics 16.0 program. The results showed no significant difference (p &gt; 0.05) in the motility and viability of spermatozoa in all treatment of Sumbawa honey (1%, 2%, 3%), processed honey (1%, 2%, 3%), and control. The conclusion of this study is that honey in spermatozoa diluent has no effect on the quality of spermatozoa.

Effect of temperature and time storage towards alcohol level in cow milk kefir

Kefir is an acidic-alcoholic fermented milk product with little acidic taste and creamy consistency and has a distinctive yeasty aroma. Bacteria in the grain produce lactic acid and flavor components, carbon dioxide, and alcohol. Increased alcohol levels can occur with longer storage. The optimal temperature for the growth of alcohol-producing microorganisms can be at room temperature, whereas low temperatures can inhibit microbial growth and biochemical processes. This study aimed to determine the effect of temperature and storage time on the alcohol content of cow milk kefir. The research method used Randomized Block Design Factorial with two factors and three levels. The first factor was the storage time that consists of 7, 14 and 21 days. While, the second factor was storage temperature that consists of freezing storage (-10°C), refrigerator storage (15°C), and room storage (20°C). Data were analysed using ANOVA, then the further test DMRT with a 95% confidence interval. The best treatment result was tested using Zeleny. The best treatment result was attributed to freezing storage (day 7) at -10°C, with physical parameters include pH of 4.47 and total soluble solids of 10.00% Brix. Then, chemical parameters are total sugar (3.07%), total acid (0.26%), and alcohol content (0.04%). Lastly, microbiological parameters include the total of lactic acid bacteria (5.91 Log CFU/ml) and the total of yeast (6.56 Log CFU/ml). Kefir with the best treatment could decrease the alcohol level and safe for consumption.

Temperature distribution and hygienic status of domestic refrigerators in Lemnos island, Greece

Chilling is a common food preservation practice applied overwhelmingly in the domestic environment through refrigerator use. Nevertheless, the hygiene conditions and temperatures prevailing in household refrigerators are often inappropriate. Moreover, the way of life in non- or semi-urban settings (e.g., less stress intensive life), such as those encountered in most Greek islands, imposes changes in consumer behavior which are probably being reflected in the domestic hygiene. The purpose of this research was to investigate the hygienic status and temperature distribution of the domestic refrigerators in Lemnos island, Greece. Seventy refrigerators (n = 70) were surveyed by placing temperature data loggers in three different storage areas of each refrigerator (upper shelf, lower shelf, door) and temperature was recorded every 15 min for 24 h. Placement of food in the refrigerators was also monitored and assessed using a predetermined questionnaire. Two food-contact surface samples from each storage area of the refrigerator were collected by swabs (n = 6) for microbiological analyses (total viable count; TVC, total coliforms, Escherichia coli, Staphylococcus spp., Salmonella spp., and Listeria spp.). The results demonstrated that only 11.4% of the refrigerators were operating below or equal to 5 °C, whereas most refrigerators (68.6%) were found to operate at temperatures over 7 °C. The majority (77.1%) of survey participants did not correctly place their food commodities in the fridge, according to standard good hygiene practices (GHPs). Salmonella and Listeria were not detected in the refrigerators (i.e., absence in 100 cm2), while E. coli was not recovered (i.e., <1 CFU/cm2) from any of the refrigerator's storage areas. TVCs and total coliforms ranged above the adopted reference values of 1.3 and 1.0 log CFU/cm2 in 41.4 and 2.9% of the refrigerators, respectively. Staphylococci were above the settled limit of 1.0 log CFU/cm2 in 8.6% of the refrigerators, but S. aureus counts were always below this limit (i.e., <1.0 log CFU/cm2). Overall, although the monitored microbiological safety of the sampled domestic refrigerators was satisfactory, the percentage of refrigerators exceeding the acceptable limit in TVC indicates poor cleanliness of home fridges. In addition, both the operating temperatures and placement of food in the refrigerators in many cases did not comply with the recommended GHPs, suggesting a potential risk for the microbiological safety and expected shelf-life of refrigerated food in the kitchen environment. To sum, the present study highlights the necessity of increased consumer awareness and emphasizes the need for further education of the household consumer in proper GHP implementation in their fridges.

Assessment of (-) epicatechin as natural additive for improving safety and functionality in fresh "Piel de Sapo" melon juice.

Epicatechin (EC) is a very abundant flavonoid in vegetable tissues that presents high antioxidant activity in living systems. The minimum inhibitory concentration (MIC) of (‐)EC was determined in three species of bacteria commonly associated with foodborne illness of plant origin: Listeria (L.) monocytogenes, Escherichia (E.) coli ‐serogroups O157: H7 and O111‐ and Bacillus (B.) cereus; two strains of probiotic‐type lactic acid bacteria (PT‐LAB) and two control strains. All 10 strains were assayed under three temperature conditions (30º, 10º, and 4ºC) and at each temperature under two pH conditions (6.7 and 5.5). Mean EC MIC values were generally lower at refrigeration (4º and 10ºC) temperatures and at standard pH (6.7). By inoculating with each of the strains separately, both melon juice (MJ) and MJ supplemented with EC (ECSMJ), at the accepted maximum sensorial limit, and storing them at 4ºC for 10 days; the final counts (CFU/mL) were lower for ECSMJ than for plain MJ both for pathogenic bacteria and for PT‐LAB. The presence of EC during refrigerated storage counteracted the ability of MJ as a growth medium for all the pathogenic bacteria. ECSMJ increased the antioxidant activity of MJ significantly to levels similar to those of EC alone. (‐) Epicathechin would be a promising ingredient for increasing the functional properties of “Piel de Sapo” MJ (phenolic compounds and antioxidant ability) while contributing to improving the safety of this type of juice during prolonged refrigerated storage at 4ºC.

Effect of a chitosan-based nanocomposite containing ZnO and Zataria multiflora essential oil on quality properties of Asian sea bass (Lates calcarifer) fillet.

This research aimed to estimate the effects of chitosan (CH) coating in combination with zinc oxide nanoparticles (ZnONPS) andZataria multifloraessential oil (ZEO) on the bacterial and biochemical properties of the Asian sea bass (Lates calcarifer) fillets during refrigeration storage (4 ± 1 °C). The fillets were randomly divided into five treatments (CH, CH-ZnONPS, CH-ZEO, CH-ZnONPs-ZEO, and control). Then, the treated fillets were kept at 4°C and quality analysis was performed on days 0, 4, 8, 12, and 16. The results revealed that the combination of ZnONPs and ZEO with CH coating is an active coating with antimicrobial effects. Also, the coated fillets improved the biochemical properties (such as FFA, TBA, TVBN, pH) as well as color properties during refrigeration storage. The highest rate of FFA (3.59 ± 0.08%oleic acid), TBA (1.43 ± 0.00mg MDA/kg), TVBN (30.82 ± 0.30mg/N100g), and pH (7.38 ± 0.03) was recorded in control fillets while the lowest rate of FFA (2.19 ± 0.00%oleic acid), TBA (0.61 ± 0.00mg MDA/kg), TVBN (19.60 ± 0.20mg/N100g), and pH (6.99 ± 0.04) was recorded in CH-ZnONPs-ZEO coated fillets (p < 0.05) on day 16. The sensory acceptance score was better than that of the control treatment on days 8 and 12 in Sea bass fillet coated with CH-ZnONPs, and CH-ZnONPS/CH-ZEO, respectively, and it was lower the critical score for fishery products. The combination of nanoparticles or essential oils (individually or in combination together) with edible coatings (chitosan) could increase and optimize the storage time of refrigerated seafood.

Comprehensive effects of black cumin (Nigella sativa) and synthetic antioxidant on sensory and physicochemical quality of beef patties during refrigerant storage

This study investigated the effective utilization of black cumin ( Nigella sativa ) extract as natural antioxidant source in cooked beef patties at refrigeration storage for 15 days and its efficacy was figured out against synthetic antioxidant butylated hydroxyl anisole (BHA). For this purpose, beef patties were formulated having five treatments namely control group (T 0 ), 0.1% BHA (T 1 ), 0.1%, 0.2% and 0.3% black cumin extract as (T 2 ), (T 3 ) and (T 4 ) respectively. Day's intervals of this study were on 0, 5th, 10th, and 15th day. Black cumin extract revealed an excellent antioxidant activity over BHA in terms of sensory (color, flavor, tenderness, juiciness, and overall acceptability) and physicochemical (pH, free fatty acids (FFA), peroxide value (POV) and thiobarbituric acid reactive substance (TBARS)) qualities in patties. Sensory attributes and pH value were decreased significantly (p < 0.05) in different treatment groups. FFA, POV and TBARS values were increased significantly (p < 0.01) in different treatment groups with advancement of storage period. So, black cumin extract treated patties qualities remain stable with minor change during 15 days storage. Considering the outcome of current investigation it may be concluded that black cumin extract having antioxidant characteristics as synthetic antioxidant and could be successfully used in producing value added meat products. • The present study investigated the effective utilization of black cumin extract as natural antioxidant source. • Black cumin extract revealed an excellent antioxidant activity over BHA in terms of sensory. • Sensory attributes and pH value were decreased significantly in different treatment groups. • FFA, POV and TBARS values were increased significantly in different treatment groups. • So, black cumin extract treated patties qualities remain stable with minor change during 15 days storage.

Effect of Zatariamultiflora essential oil and potassium sorbate on inoculated Listeriamonocytogenes, microbial and chemical quality of raw trout fillet during refrigerator storage.

Human listeriosis is predominantly associated with contaminated food consumption, including seafood, shrimp, and RTE foods. Listeria monocytogenes is a foodborne pathogen that is mainly found in freshwater, seawater, and fish mucus. Seafood contamination can occur during food processing. L.monocytogenes levels of below 100 cfu/g can be found in seafood samples. The present study was conducted to investigates the effect of Zataria multiflora essential oil (ZEO) and potassium sorbate (PS) on microbial and chemical changes in raw rainbow trout at 4°C to extent shelf life and improve food safety. First, the chemical compositions of ZEO were identified. Then, different percentage of ZEO (1.5, 0.8, and 0.5%) and PS (2%) were inoculated in raw fish fillets and analyzed for TVC, TBA, TVB‐N, pH, sensory attributes, Pseudomonas aeruginosa, and inoculated L. monocytogenes (1 × 105 cfu/g) survival at 4°C for 12 days. The best sensory evaluation score was observed for the samples treated with 0.8% and 1.5% ZEO. Overall, this study results indicated that the treatment of rainbow trout fillet with 1.5% ZEO is the best method for controlling the growth of L. monocytogenes at refrigerator temperature without any undesirable sensory effects.

Post-Harvest Use of Ultraviolet Light (UV) and Light Emitting Diode (LED) to Enhance Bioactive Compounds in Refrigerated Tomatoes

Different strategies have been developed to increase the concentration of bioactive compounds in tomatoes during post-harvest, with ultraviolet light (UV) and light emitting diodes (LEDs) being interesting tools. The aim of this study was to evaluate the effect of ultraviolet (UVA at 366 nm and UVC at 254 nm) pre-treatment (1 kJ/m2) and red–blue LED light (25.4 µmol/m2/s) on the concentration of carotenoids, (poly)phenols and hydrophilic/lipophilic antioxidant capacity during 7 days of refrigeration storage of green tomatoes (Solanum lycopersicum L.) cultivar “Raf”. In addition, special attention was paid to quality parameters (weight loss, colour, acidity, soluble solids and ripening index). Tomatoes exposed to LED light at 6 °C for 7 days increased up to three times the total carotenoids content (mainly β-carotene and E-lycopene) compared to tomatoes refrigerated in the dark, while UV treatments alone did not significantly affect the carotenoid content. Besides, exposure to LEDs increased the hydrophilic and lipophilic antioxidant capacity of tomatoes by 30%, without affecting phenolic contents. Thus, LED treatments alone during refrigerated storage fostered ripening and improved the nutritional value of tomatoes, without compromising quality parameters. Further studies must be carried out to evaluate the impact on sensory attributes and consumer acceptance.

Влияние режимов замораживания, сроков хранения и способов дефростации на микробиологические показатели качества абрикосов

Introduction. Low-temperature freezing technology extends the shelf life of perishable fruits as it causes a sharp slowdown in the biochemical and microbiological processes in frozen products. However, it cannot provide complete destruction of microorganisms.&#x0D; The present research featured the reaction of apricot microbiota to the technological techniques of shock freezing. The research objective was to study the effect of low-temperature freezing modes (t = –25, –30, and –35°C), storage time (3 and 9 months), methods, and defrosting modes (in air at t = 5 and 22°C; in water at t = 5, 16, and 22°C; under the effect of microwave irradiation) on the surface microflora of apricots.&#x0D; Study objects and methods. The experiment featured apricots of the varieties Uzden, Untsukulskiy Pozdniy, Honobah, Krasnoshchyokiy, and Shalakh. The microbiological profile of defrosted apricots was based on the State Standard.&#x0D; Results and discussion. Fast freezing at t = –25°C provided a better inhibition of epiphytic microflora than at t = –30 and –35°C: aerobic-mesophilic and optionally anaerobic microorganisms – by 65.2–68.6%, yeast – by 61.5–69.0%, and mold – by 59.3–68.4%,&#x0D; compared to their initial content on fresh apricots. During the initial period of refrigeration storage, the number of microorganisms decreased, while the subsequent nine-month storage (t = –18°C) led to a slight increase in microbiota. After nine months of storage, the number of microorganisms on defrosted fruits, depending on the variety, was the following: aerobic-mesophilic and optionally anaerobic microorganisms – 1.2×103–2.0×103 CFU/g, yeast – 14–26 CFU/g, and molds – 75–108 CFU/g. Defrosting of apricots by microwave irradiation resulted in a greater destruction of microorganisms than after traditional thawing in air and water.&#x0D; Conclusion. The results of microbiological studies indicate that the shock freezing technology ensures the production of quick-frozen apricots that meet the requirements of Technical Regulations of the Customs Union No. 021/2011.

Effect of high hydrostatic pressure (HHP) and supercooling storage in leaf mustard (Brassica juncea L.) kimchi: Modelling of microbial activity and preservation of physicochemical properties

Kimchi products have a short shelf life due to continuous bacterial growth and fermentation. Herein, the microbiological and physicochemical properties of leaf mustard (Brassica juncea L.) kimchi were evaluated after high hydrostatic pressure (HHP) treatment (400 and 600 MPa for 5 min) and storage under supercooling (˗4.5 °C) or refrigeration (4 and 8 °C) conditions. Moreover, predictive models describing the growth kinetics of total lactic acid bacteria (TLAB) in leaf mustard kimchi were constructed. Treatment with 600 MPa reduced the total LAB and coliform counts in the samples before storage to 1.30 and > 1 log CFU/g, respectively. Supercooling storage prevented microbial growth for 30 days and allowed the maintenance of the titratable acidity, reducing sugar content, instrumental colour, total phenolic content, and antioxidant capacity of the samples. The Logistic and Gompertz models were relatively more acceptable to predict the growth behaviour of TLAB in leaf mustard kimchi treated/non-treated with 400 MPa during supercooled or refrigerated storage. Altogether, these findings suggest that HHP treatment combined with supercooling storage conditions that delay O2 and CO2 concentration changes in packaged kimchi's headspace could help maintain the initial microbiological and physicochemical qualities of leaf mustard kimchi.

Effect of starch based edible antimicrobial films and modified atmospheric packaging (MAP) on extended life of composite sweetmeat.

The objective of the study was to evaluate the synergistic action of edible antimicrobial packaging with MAP to extend the shelf life of composite dairy confection. GRAS-approved- nisin and natamycin incorporated edible films were tried for their efficacy against Bacillus cereus and Aspergillus niger, in comparison with control films (without antibacterial agents) under MAP environment (N2 and CO2; 70:30) followed by refrigeration storage (4±2 °C). Results depicted a statistically significant (p ≤ 0.05) difference in the shelf-life of control and treated samples with reduced microbial proliferation, better sensory scores, and thereby achieving the shelf-life for treated samples of 42 days in contrast to 21 days in control. However, the variation between the two different antimicrobial films remained non-significant (p ≤ 0.05). The treated product remained significantly (p ≤ 0.05) more acceptable in terms of microbiological, physic-chemical, and sensory quality compared to control. Therefore, the developed antimicrobial edible films could be successfully used along with MAP for shelf-life extension of composite dairy foods.

Sensory, Nutritional and Microbiological Characteristics of Fermented Finger Millet Beverage (Kunun-Tamba) Treated with Various Preservatives during Refrigerated Storage

Six types of ‘kunun-tamba’ produced in this study using finger millet (Eleucine coracana L) were treated with (sodium benzoate, lime and lemon juice extracts singly or in combination) or without preservatives and evaluated for its microbiological (lactic acid bacteria-LAB), chemical and sensory quality characteristics throughout four weeks of refrigerated (4o C) storage. The molecular characteristics of the seven (7) LABs isolated showed that Lactobacillus plantarum, Lactococcus lactis, Leuconostoc masenteroides, L paeudo-mesenteroides and two (2) unidentified LABs were the predominant. The ‘kunun-tamba’ treated with 5ml lime+lemon showed a low LAB count (Log10 0.86-1.25cfu/ml), pH (3.90-4.08) and sensory attributes (taste: 6.7-6.9, appearance: 6.6-6.9, aroma: 6.1-6.8) evaluated throughout the study period (4 weeks) which differed (p&lt;0.05) from those of the other products produced in this study. The results of this study shows that the use of the combinations of lime and lemon (5ml) natural preservatives gave a better shelf stable product than an artificial preservative (sodium benzoate) and therefore could be a suitable alternative meeting consumers aspiration for replacement of artificial preservatives with natural ones.

Effect of ginger extract and papain powder incorporation on physico-chemical and microbial quality of buffalo male calf meat rolls during refrigeration (4±1 °C) storage studies

The study was conducted with an objective to evaluate the effect of Ginger Extract and Papain Powder on shelf life of buffalo male calf meat rolls at refrigeration (4±1 °C) storage. The meat rolls were prepared with incorporation of 5% Ginger Extract (GE1) and 0.25% Papain Powder (PP1) and Combination of Ginger extract and Papin Powder in ration of 1:3 and compared with control (C) meat rolls. The products were assessed for their physico-chemical, sensory and microbiological quality at 0, 4, 8, 12, and 16 days. However, the sensory scores and moisture content decreased and microbial load, TBA value and free fatty acids (FFA) increased as the days of storage increased for control as well as treated products. The rate of decline in sensory score and moisture content and rate of increase in microbial load, TBA vale and FFA during storage were higher in control samples as compared to treated meat rolls. It was concluded that Ginger Extract (5%) and Papain Powder (0.25%) incorporation also showed their antioxidant and antimicrobial effects, by keeping the treated products organoleptically acceptable and microbiologically safe up to16 days of refrigeration storage.

Assessment of Chemical and Bacterial Indices of Common Carp (Cyprinus carpio) Surimi under Various Concentrations of Basil (Ocimum basilicum) Extract During Storage in Refrigerator

Assessment of Chemical and Bacterial Indices of Common Carp (Cyprinus carpio) Surimi under Various Concentrations of Basil (Ocimum basilicum) Extract During Storage in Refrigerator

Method-Dependent Implications in Foodborne Pathogen Quantification: The Case of Campylobacter coli Survival on Meat as Comparatively Assessed by Colony Count and Viability PCR.

The aim of the present study was to address method-dependent implications during the quantification of viable Campylobacter coli cells on meat over time. Traditional colony counting on selective and non-selective culture media along with an optimized viability real-time PCR utilizing propidium monoazide-quantitative PCR (PMA-qPCR), spheroplast formation and an internal sample process control (ISPC), were comparatively evaluated for monitoring the survival of C. coli on fresh lamb meat during refrigeration storage under normal atmospheric conditions. On day zero of three independent experiments, lamb meat pieces were artificially inoculated with C. coli and then stored under refrigeration for up to 8 days. Three meat samples were tested on different days and the mean counts were determined per quantification method. An overall reduction of the viable C. coli on lamb meat was observed regardless of the applied quantification scheme, but the rate of reduction followed a method-dependent pattern, the highest being observed for colony counting on modified charcoal cefoperazone deoxycholate agar (mCCDA). Univariate ANOVA indicated that the mean counts of viable C. coli using PMA-qPCR were significantly higher compared to Columbia blood agar (CBA) plating (0.32 log10 cell equivalents, p = 0.015) and significantly lower when mCCDA was compared to CBA plating (0.88 log10 CFU, p < 0.001), indicating that selective culture on mCCDA largely underestimated the number of culturable cells during the course of meat storage. PMA-qPCR outperformed the classical colony counting in terms of quantifying both the culturable and viable but non-culturable (VBNC) C. coli cells, which were generated over time on meat and are potentially infectious and equally important from a public health perspective as their culturable counterparts.

Effect of Cartridge Storage Time and Ambient Laboratory Conditions on the Stability of Mechanical Properties of Bis-Acryl Interim Resin Materials.

To investigate the stability of mechanical properties during the entire shelf life of chemically-activated bis-acryl interim resin materials stored at ambient laboratory conditions. Four bis-acryl interim resin materials with no explicit recommendation for refrigerator storage were selected (Luxatemp Plus, Visalys Temp, Structur3, Structur Premium). Following cartridge storage at ambient laboratory conditions in 6-month intervals, 30 specimens (2.0 × 2.0 × 25.0mm3 ) were prepared in each case and stored in distilled water (37.0 ± 1.0 °C) with 3 different water storage times (2hours, 24hours, 7days). Flexural strength, modulus of elasticity, modulus of toughness, and elastic recovery were determined (3-point bend test). Data were subjected to a three-way multivariate analysis of variance (MANOVA) to determine overall significance, followed by a series of separate one-way ANOVAs after data were split, using Tukey and Games-Howell posthoc tests to identify significant differences between groups (α = 0.05). While Luxatemp Plus showed no significant decrease for all mechanical properties during the investigated shelf life of 21 months (p > 0.05), Visalys Temp exhibited a continuous decline of the corresponding values (p < 0.05), irrespective of the water storage time. Structur3 and Structur Premium properties remained almost unchanged during the first 6 months of the examination period. Subsequently, a progressive decrease was observed for flexural strength and modulus of elasticity, while most modulus of toughness and elastic recovery results revealed little alteration. Depending on the bis-acryl interim resin material, mechanical properties appeared to be susceptible to continuous degradation processes during cartridge storage at ambient conditions, especially towards the end of the material shelf life. For some materials, the chemical stabilization and recommended storage conditions should be revised by the manufacturers to prevent premature aging during shelf life.

Non-invasive assessment of metabolic responses to food restriction using urinary triiodothyronine and cortisol measurement in macaques

Regulation of energy allocation and metabolic rate plays an important role in determining behavior and fitness in wild animals, calling for the validation of non-invasive markers of energetic condition. Recently, the thyroid hormone triiodothyronine (T3) has emerged as a promising marker as concentrations decrease to lower the metabolic rate during energetically challenging periods. However, it remains largely unclear whether T3 merely represents an alternative or provides additional information compared to other compounds involved in the regulation of energy acquisition and allocation, like cortisol and C-peptide, as few joint measurements have been conducted to date in non-invasively collected samples. We aimed to validate the non-invasive measurement of immunoreactive urinary total T3 (uTT3), in comparison to urinary cortisol (uCort) and urinary C-peptide (uCP), as a marker of metabolic response to variation in food intake in macaques, and to address a number of issues regarding the collection, storage and processing of samples which are important for application of uTT3 measurements under field conditions. We used daily samples and body mass measures from a prior food restriction-refeeding experiment over 4 weeks with six captive macaques and analyzed concentrations of uTT3 and uCort in samples collected prior to (fasting) and after morning feeding (non-fasting). Concentrations of uTT3 decreased in response to restriction in food supply and were also lower during weeks of food restriction compared to weeks of refeeding. Variation in uTT3 also correlated positively with variation in body mass and concentrations of uCP. As expected, uCort showed the reverse pattern, increasing during food restriction and decreasing following refeeding, but was not associated with variation in body mass. Generally, compared to fasting samples, concentrations were higher in post-morning feeding, i.e. non-fasting, samples for uTT3 but not uCort. Contamination of urine samples with fecal matter, but not soil, and exposure to UV light led to a decrease in uTT3. uTT3 was largely unaffected by repeated freeze–thaw cycles and by refrigeration for medium-term storage (2 days) but degraded substantially when stored at ambient temperature for the same period. In conclusion, uTT3 measurements inform on the effect of food intake and its associated metabolic response to variation in energetic status. Since uTT3 is reasonably robust to many issues associated with collection and storage of urine samples under field conditions, it is a promising biomarker for studies of energetic condition and basal metabolic rate in wild macaques.