Days Of Room Temperature Storage Research Articles

Changes in the Quality and Microbial Communities of Precooked Seasoned Crayfish Tail Treated with Microwave and Biological Preservatives during Room Temperature Storage.

The qualities of precooked foods can be significantly changed by the microorganisms produced during room temperature storage. This work assessed the effects of different antibacterial treatments (CK, without any treatment; microwave treatment, MS; microwave treatment and biological preservatives, MSBP) on the physicochemical properties and microbial communities of precooked crayfish tails during room temperature storage. Only the combination of microwave sterilization and biological preservatives significantly inhibited spoilage, as evidenced by the total viable count (4.15 log CFU/g) after 3 days of room temperature storage, which satisfied the transit time of most logistics companies in China. Changes in pH and TVB-N were also significantly inhibited in the MSBP group compared with those in the CK and MS groups. More than 30 new volatile compounds were produced in the CK groups during room temperature storage. However, in the MSBP groups, the volatile compounds were almost unchanged. The correlations between the microbial composition and volatile compounds suggested that specific bacterial species with metabolic activities related to amino acid, energy, cofactor, and vitamin metabolism, as well as xenobiotics biodegradation and metabolism, were responsible for the changes in volatile compounds. These bacteria included Psychrobacter, Arthrobacter, Facklamia, Leucobacter, Corynebacterium, Erysipelothrix, Devosia, Dietzia, and Acidovorax. Overall, our findings provide a foundation for the development of strategies to inhibit spoilage in precooked crayfish tails stored at room temperature.

Comparison of Emulsion Stabilizers: Application for the Enhancement of the Bioactivity of Lemongrass Essential Oil.

Recent focus on cellulose nanomaterials, particularly biodegradable and biocompatible cellulose nanocrystals (CNCs), has prompted their use as emulsion stabilizers. CNCs, when combined with salt, demonstrate enhanced emulsion stabilization. This study explored three emulsion stabilizers: Tween 80, soybean CNCs with salt (salted CNCs), and a combination of salted CNCs with Tween 80. Soybean CNCs, derived from soybean stover, were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Antifungal testing against Aspergillus flavus revealed increased bioactivity in all lemongrass essential oil (EO)-loaded emulsions compared to pure essential oil. In addition, all three emulsions exhibited a slight reduction in antifungal activity after 30 days of room temperature storage. The release experiment revealed that the EO-loaded nanoemulsion exhibited a slow-release profile. The nanoemulsion stabilized by salted CNCs and Tween 80 exhibited significantly lower release rates when compared to the nanoemulsion stabilized solely by Tween 80, attributed to the gel network formed by salted CNCs. The findings of this study highlight the efficacy of cellulose nanocrystals procured from soybean byproducts in conjunction with synthetic surfactants to create nanoencapsulated essential oils, resulting in improved antimicrobial efficacy and the achievement of sustained release properties.

Performance evaluation of maltogenic amylases on nixtamalized corn flour tortilla

AbstractBackground and ObjectivesA high‐performing maltogenic amylase was developed to provide better water‐binding properties to delay staling more effectively than first‐generation maltogenic amylases. This study evaluated the effects of this high‐performing maltogenic amylase and a first‐generation maltogenic amylase (referred to as “maltogenic amylase”) for delaying staling in nixtamalized corn flour tortillas. The maltogenic amylase and high‐performing maltogenic amylase were tested at 25, 50, and 100 ppm and were compared to control tortillas.FindingsTortillas with 100 ppm high‐performing maltogenic amylase were 66% softer and performed better in foldability than control tortillas after 35 days of room temperature storage and rated better in taste and tenderness than the control.ConclusionsBoth maltogenic amylases delayed staling and prolonged softness and foldability.Significance and NoveltyOverall, the high‐performing maltogenic amylase did not outperform the first‐generation maltogenic amylase at 25 and 50 ppm. However, at a higher dosage (100 ppm), the high‐performing maltogenic amylase is capable of producing overall softer tortillas with improved tenderness and taste across 35 days of storage. This research is novel as this high‐performing maltogenic amylase has not been studied by others to improve the quality of tortillas.

Characterization and Antifungal Activity of Lemongrass Essential Oil-Loaded Nanoemulsion Stabilized by Carboxylated Cellulose Nanofibrils and Surfactant.

Nanocellulose is an emerging green, biodegradable and biocompatible nanomaterial with negligible toxicities. In this study, a carboxylated nanocellulose (i.e., 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TEMPO-CNF)) was prepared from corn stover and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA). Corn stover-derived TEMPO-CNF was explored as an emulsion co-stabilizer together with Tween 80 for lemongrass essential oil-loaded emulsions. Droplet size, phase behavior and thermodynamic stability of oil-in-water emulsions stabilized by Tween 80 and TEMPO-CNF were investigated. The optimal nanoemulsion stabilized by this binary stabilizer could achieve a mean particle size of 19 nm, and it did not form any phase separation against centrifugal forces, freeze-thaw cycles and at least 30 days of room temperature storage. The nanoencapsulated essential oil had better inhibition activity against the mycelial growth of Aspergillus flavus than pure essential oil. Results from this study demonstrate the potential of using agricultural byproduct-derived nanomaterial as nanoemulsion stabilizers for essential oils with good emulsion thermodynamic stability as well as enhanced antifungal activities.

Abstract 5605: Ambient storage and stabilization of proteins and cell-free nucleic acids in whole blood samples

Abstract Introduction: Highly anticipated advancements in biotechnology and instrumentation now allows for simultaneous detection of multiple biomarkers. This is accelerating the cancer research field towards the development of multianalyte-based in vitro diagnostic tests for early detection and/or monitoring of cancer. These multianalyte liquid biopsy tests are often based on detection of cancer-related proteins and/or tumor-specific genomic and transcriptomic changes (circulating cell-free nucleic acids) in plasma. A specialized and proprietary stabilization reagent has been developed for use in a blood collection tube with the capability to simultaneously stabilize protein biomarkers of interest and cell-free nucleic acids. Methods: Blood samples from self-proclaimed healthy donors were drawn into evacuated blood collection tubes containing a new stabilization reagent and stored at room temperature. Plasma was isolated using a general double-spin protocol (1800 × g for 15 min and 2800 × g for 15 min) and frozen at -80 °C until use. Plasma levels of proteins of interest including cancer markers and immuno-oncology checkpoint markers were measured by Ella Simple Plex Assays (Bio-Techne) and Luminex xMAP® Technology Assays (Bio-Techne, samples tested by LuminexPLORE Lab). Total cell-free nucleic acids were isolated using the QIAamp Circulating Nucleic Acid Kit and the resultant cfDNA or cfRNA was analyzed with fluorometric-based assay (quantitative) and Bioanalyzer/Tapestation (qualitative). Results: Compared with blood samples collected in EDTA and ACD-A tubes, the new stabilization reagent maintained the draw time levels of plasma proteins of interest such as TGF-β1, MMP-9, IL-8/CXCL8, CCL5/RANTES, Granzyme B, CEA and PD-L1 for up to 5 days of room temperature storage in whole blood. The reagent also effectively maintained draw time levels of plasma cell-free nucleic acids to near draw time levels. In addition, the new reagent also minimized in vitro hemolysis during room temperature storage. Conclusion: This new and breakthrough stabilization reagent simultaneously maintains the draw time levels of proteins of interest and cell-free nucleic acids for an extended period of time in whole blood. It provides cancer researchers and clinical assay developers confidence in blood sample integrity and flexibility in sample storage, transport, and processing at ambient temperature for multianalyte analysis or multiomics profiling. Citation Format: Jing Li, Lisa Bartron, Jordan LaRue, Sama Mehta, Nicholas M. George. Ambient storage and stabilization of proteins and cell-free nucleic acids in whole blood samples. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5605.

Coating Application to Extend the Shelf Life of Sweet Potatoes cv. Cilembu

Sweet potato (Ipomoea batatas L.) cv. Cilembu (Cilembu) is one of the commodities listed in Geographical Indications (IG) with number IDIG000000019. The specialty of Cilembu is that it tastes sweet like honey, making it attractive to the export market. The export market distribution process takes a relatively long time, so treatment is needed to maintain quality. Coating application is one of the efforts to slow down the process of respiration and transpiration which causes a decrease in quality. The purpose of the study was to determine the best coating application made from aloe vera flour and carrageenan in maintaining the quality of Cilembu sweet potato. The stages of the research were sample preparation, coating solution making, application of coating, and observation for 30 days of shelf life. The concentration of coating solution was aloe vera (AL) 1% and 2%, and carrageenan (K) 0.01% and 0.02%. The best coating formulation was selected based on quality parameters of Cilembu, namely browning index, weight loss, total dissolved solids and hardness. Based on the value of these parameters, AL2K2 coating (combination of 2% aloe vera and 0.02% carrageenan) is the best coating formulation that can minimize quality loss after 30 days of room temperature storage (27°C-30°C). The application of AL2K2 coating can maintain a browning index of 2.3, weight loss of 7.82%, total dissolved solids 15.2 °brix, and hardness of 5.59 kgf while the control (without treatment) value of these quality parameters are 4.30, 9.59%, 14.4 °brik, and 5.52 kgf for each of these parameters

Assessment of Bioactive Compounds, Physicochemical Properties, and Microbial Attributes of Hot Air–Dried Mango Seed Kernel Powder: an Approach for Quality and Safety Evaluation of Hot Air–Dried Mango Seed Kernel Powder

The presence of carbon and nitrogenous compounds in mango processing by-products makes them excellent substrates for the biosynthesis of many microbial metabolites using fermentation processes. Pretreatment of the substrate with retention of crucial growth supporting compounds is vital for designing and optimizing fermentation media for enhanced production of desired metabolites. The present study investigated the effect of hot air drying (HAD) (50, 60, 70, and 80 °C) on the bioactive compounds, physio-chemical and mineral profile, fermentable sugar, and microbial safety of mango (cv. chausa) seed kernel powder. Results indicated that different drying temperatures non-significantly (P<0.05) affected the carbohydrates, starch (except at 60 and 80 °C), nitrogen, and protein content. The pH (except at 70 °C), total phenolics, and antioxidant activity decreased with an increase in drying temperatures. Inductively coupled plasma–optical emission spectrometry (ICP-OES) analysis revealed the increase in concentrations of majority minerals with incremental drying temperature. The microbial load of powdered seed kernel after 30 days of room temperature storage was within safe limits, as samples were devoid of food pathogens. Briefly, the study suggests HAD (at 70–80 °C) to convert mango kernels into stable powdered form for prolonged storage. The powdered kernels can be utilized in diversified food industry and as a feedstock (with safe storability, preserved bioactive, mainly carbon and nitrogen compounds) for biosynthesis of valuable metabolites via microbial fermentation route.

Assessing the Effectiveness of Natural Coating Application in Prolonging Shelf-Life in Plumcot Fruits

This study was carried out to assess the morphological characteristics, fruit quality, and antioxidant levels in sucrose ester-coated ‘Harmony’ plumcots (Prunus salicina Lindl. × P. armeniaca L.). Fruit samples in the control group were left untreated, with two further groups undergoing coating either after 0 days of cold storage (0 d CS) or after 7 days of cold storage (7 d CS) to evaluate changes in post-harvest quality at three-day intervals throughout 12 days of room temperature storage (12 DAS). Coating treatment significantly reduced fruit respiration during storage time in the 0 d CS samples, with this being attributed to the clogging of pores in peel stomata and lenticel, as observed on the fruits under scanning electron microscopy; however, the same effect was not observed in the 7 d CS samples from fruits with a high initial CO2 concentration. The coating delayed fruit softening and discoloration during storage in the 0 d CS samples, extending the shelf-life of the fruits for approximately 9 days. However, the coating treatment was found to reduce total flavonoid and anthocyanin content at 6 DAS and 12 DAS in both groups.

The quality properties, thiobarbituric acid (TBA) values and microstructure of chicken sausage with local red beetroot powder

This research was aimed to determine the quality properties, the microstructure of chicken sausage and Thiobarbituric acid (TBA) values with locally Indonesia red beetroot powder. The main ingredients of chicken sausage-making in this research were broiler chicken, filler, binder, beetroot powder, and spices. Red beetroot powder function as a filler was substituted tapioca starch in chicken sausage batter in three different levels. The combination of red beetroot powder with level 0, 1.0, 2.0 and 3.0% of total batter and shelf life at room temperature for 0, 1, 2 and 3 days. Each treatment consisted of five replications. The variables observed using quality properties (moisture, ash, fat, protein, crude fiber and calorie), microstructure and peroxide value of chicken sausage. The data of quality properties and peroxide value were analyzed by using one-way analysis (ANOVA) of Completely Randomized Design. The differences between means were analyzed by Duncan's New Multiple Ranges Test. The data of microstructure was analyzed by descriptive analyses. The moisture, protein, fat and ash contents for chicken sausages were significantly different (p&lt;0.05). The chicken sausage with 2% substitution of beet powder produced chicken sausages with a high protein content of 14.77±0.02% while a low-fat content is 0.42±0.01%. Thiobarbituric acid (TBA) values of chicken sausages increased throughout the three days of room temperature storage (38°C). Chicken sausage formulated with red beetroot powder showed a significantly lower TBA value compared to the samples without red beetroot powder (p&lt;0.05). In conclusion, a higher level of beetroot powder will improve the quality of chicken sausage and also the microstructure. The best level of beetroot powder addition was 2.0%. The addition of beetroot powder able to maintain fresh sausage conditions up to 2 days of storage at room temperature.

Preservation of stewed beef chunks by using ϵ-polylysine and tea polyphenols

Tea polyphenols and ϵ-polylysine have antibacterial activities, and tea polyphenols have antioxidant activity. In this study, the combination of ϵ-polylysine and tea polyphenols was used to preserve stewed beef chunks during room-temperature storage. The beef chunks stewed in the broth containing 0.02% ϵ-polylysine and 0.02% tea polyphenols exhibited no change in bacterial growth, pH, total volatile basic nitrogen (TVB-N) and thiobarbituric acid-reactive substance (TBARS) contents and sensory quality during room-temperature storage for 12 days. The beef chunks stewed in the control broth had significant increases in bacterial growth, pH, TVB-N content and TBARS content by 220% (P < 0.05, based on log colony-forming unit/g), 40% (P < 0.05), 239% (P < 0.05) and 153% (P < 0.05), respectively, and a significant decrease in sensory quality by 46% (P < 0.05) after 12 days of room-temperature storage. Results indicated that the combination of ϵ-polylysine and tea polyphenols could be a promising method to preserve stewed beef chunks during room-temperature storage.

Coatings with chitosan and phenolic-rich extract from acerola (Malpighia emarginata D.C.) or jabuticaba (Plinia jaboticaba (Vell.) Berg) processing by-product to control rot caused by Lasiodiplodia spp. in papaya (Carica papaya L.) fruit

This study evaluated if coatings with chitosan (Chi) and phenolic-rich extract from acerola (Malpighia emarginata D.C., PEA) or jabuticaba (Plinia jaboticaba (Vell.) Berg, PEJ) processing by-products are effective to control the development of rot caused by Lasiodiplodia pseudotheobromae, L. viticola, L. euphorbicola, L. theobromae and L. hormozganensis in papaya (Carica papaya L.) fruit. Effects of formulated coatings on some physicochemical parameters indicative of postharvest quality of papaya were investigated. Twenty-six different phenolics were found in PEA and PEJ, including flavonoids, stilbenes, tannins and phenolic acids. Chi (1–5 mg/mL), PEA and PEJ (25–100 mg/mL) separately caused mycelial growth inhibition on all isolates. Combinations of Chi (3 and 4 mg/mL) and PEA (50 and 75 mg/mL) or PEJ (75 and 100 mg/mL) had additive interactions. Coatings with Chi (4 mg/mL) and PEA (50 or 75 mg/mL) or PEA (75 or 100 mg/mL) inhibited rot development in papaya fruit infected with Lasiodiplodia isolates during 8 days of room temperature storage. Coatings with 4 mg/mL Chi and 75 mg/mL PEA or 100 mg/mL PEJ were the most effective to control rot development. These coatings did not affect negatively physicochemical parameters indicative of postharvest quality of papaya fruit during storage. Coatings with combined Chi and PEA or PEJ could be novel strategies to control postharvest rot caused by Lasiodiplodia in papaya fruit.

A Novel LC-MS/MS Method for Improving Long-Term Stability of Retinol in Dried Blood Spots and Quantification of Its Levels

Abstract Objectives To establish an accurate and reliable method for stabilizing vitamin A (retinol) in Dried blood spots (DBS), quantifying and comparing DBS retinol concentrations with their equivalent plasma retinol levels. Methods Antioxidants pretreated on paper combined with vacuum treatment were used to increase retinol stability on DBS. A surrogate matrix of whole blood prepared using mixture of human erythrocytes and 2% BSA in PBS was firstly used in DBS retinol determination based on the fact that retinol is excluded from erythrocytes. Results DBS retinol was stable during 120 min of air drying and 30 days of room-temperature storage. The method was linear in the concentration range of 0.04–300 μg/mL. Accuracy was calibrated using two National Institute of Standards and Technology (NIST) calibrants generated serum at concentrations of 0.1962 and 0.3948 g/mL, relative errors (RE% values) of 0.07% and 4.95% were found, respectively. Both the between-run (n = 5) and within-run (n = 6) precision (relative standard deviations, RSD%) were below 8.42%. The spiked recoveries at 3 concentrations ranged from 86.48% to 98.13%. A reliable calibration model was first developed to convert DBS retinol concentration to the equivalent plasma retinol concentration. Conclusions The validated method can be applied to the nutritional assessment of vitamin A, using the established calibration model, DBS retinol can compare with clinical reference ranges and with studies using serum or plasma samples. Funding Sources The National Key Research and Development Program of China (2018YFC1002503); The National Natural Science Foundation of China (Grant No. 81,400,848, 81,701,441); The CAMS Initiative for Innovative Medicine (2016-I2M-1–008); The Beijing municipal program of medical research (Grant No. 2016–04); The National Key Research and Development Program of China (No. 2016YFC1306204).

A Novel LC-MS/MS Assay for Vitamin B1, B2 and B6 Determination in Driedblood Spots and Its Application in Children

Abstract Objectives Several HPLC assays can be used to determine vitamin B1 (thiamin), B2 (riboflavin) and B6 (PLP) in biological matrix. However, no existing LC-MS/MS methods have been developed for quantifying thiamin, riboflavin and PLP in dried blood spots (DBSs), which are often used as a sampling/storage vessel for finger blood from infants and children. This study firstly used vacuum package in DBS cards storage, and evaluated the validity, reliability and stability of an LC-MS/MS assay for measuring thiamin, riboflavin and PLP in DBS cards. Methods DBS samples were deproteinized by adding trichloroacetic acid containing thiamine-[13C4], riboflavin-[13C4,15N2] and pyridoxal-d3 as internal standards. Thiamin, riboflavin and PLP were separated on a C8 column with a 5-min run time. Results Thiamin, riboflavin and PLP were stable on the DBS card during at least 15 days of room-temperature storage under vacuum in the dark. Both the between-run and within-run variable coefficients (CV% values) were &amp;lt;8.56%. The accuracies (relative errors RE% values) were from −7.40% to 3.12%. Lower limits of quantifications (LLOQs) ranged from 0.2 to 0.5 ng/mL, and the recoveries were from 81.49% to 112.23% for all 3 analytes. Measurements of thiamin, riboflavin and PLP in the DBSs showed good agreement with the corresponding concentrations determined from liquid blood (R2 values &amp;gt;0.96). Conclusions This validated method can be applied to the nutritional assessment of vitamins B1, B2, and B6. Funding Sources This work was supported by the National Natural Science Foundation of China (Grant No. 81,400,848), Beijing Municipal

Encapsulated Bdellovibrio Powder as a Potential Bio-Disinfectant against Whiteleg Shrimp-Pathogenic Vibrios.

Liquid preparations of bdellovibrios are currently commercialized as water quality improvers to control bacterial pathogens in whiteleg shrimp Penaeus vannamei. However, the efficacy of these liquid preparations is significantly impaired due to a dramatic loss of viable cells during long-term room temperature storage. Thus, new formulations of bdellovibrios are greatly needed for high-stablility room-temperature storage. In the present study, the encapsulated powder of Bdellovibrio sp. strain F16 was prepared using spray drying with 20 g L−1 gelatin as the coating material under a spray flow of 750 L h−1, a feed rate of 12 mL min−1, and an air inlet temperature of 140 °C. It was found to have a cell density of 5.4 × 107 PFU g−1 and to have spherical microparticles with a wrinkled surface and a diameter of 3 μm to 12 μm. In addition, the encapsulated Bdellovibrio powder presented good storage stability with its cell density still remaining at 3.5 × 107 PFU g−1 after 120 days of room-temperature storage; it was safe for freshwater-farmed whiteleg shrimp with an LD50 over 1200 mg L−1, and it exhibited significant antibacterial and protective effects at 0.8 mg L−1 against shrimp-pathogenic vibrios. To our knowledge, this is the first report on a promising Bdellovibrio powder against shrimp vibrios with high stable room-temperature storage.

A novel LC-MS/MS assay for vitamin B1, B2 and B6 determination in dried blood spots and its application in children

Thiamin, riboflavin and pyridoxal phosphate (PLP) concentrations are useful indices for evaluating vitamin B1, B2 and B6 status. Several HPLC assays have been developed for determining thiamin, riboflavin and PLP in biological matrix. However, no existing LC-MS/MS methods can be used to quantify thiamin, riboflavin and PLP in dried blood spots (DBSs), which are often used as a sampling/storage vessel for blood from infants and children. This study evaluated the validity, reliability and stability of an LC-MS/MS assay for measuring thiamin, riboflavin and PLP in DBS cards. DBS samples were deproteinized by adding trichloroacetic acid containing thiamine-[13C4], riboflavin-[13C4,15N2] and pyridoxal-d3 as internal standards. Thiamin, riboflavin and PLP were separated on a C8 column with a 5-min run time. Both the between-run and within-run variable coefficients (CV% values) were < 8.56%. The accuracies were good and showed relative errors (RE% values) from −7.40% to 3.12%. The lower limits of quantification (LLOQs) ranged from 0.2 to 0.5 ng/mL, and the recoveries were from 81.49% to 112.23% for all 3 analytes. The matrix effects (ME% values) were acceptable, and the CV% values of the internal standard-normalized matrix factors were <15% (n = 6). Thiamin, riboflavin and PLP were stable on the DBS card during at least 15 days of room-temperature storage under vacuum in the dark, and the measurements of thiamin, riboflavin and PLP in the DBSs showed good agreement with the corresponding concentrations determined from liquid blood (R2 values >0.96). The validated method was successfully applied to the nutritional assessment of vitamins B1, B2, and B6 in 48 Chinese children.

Long-term storage and preservation of tissue engineered articular cartilage.

With limited availability of osteochondral allografts, tissue engineered cartilage grafts may provide an alternative treatment for large cartilage defects. An effective storage protocol will be critical for translating this technology to clinical use. The purpose of this study was to evaluate the efficacy of the Missouri Osteochondral Allograft Preservation System (MOPS) for room temperature storage of mature tissue engineered grafts, focusing on tissue property maintenance during the current allograft storage window (28 days). Additional research compares MOPS to continued culture, investigates temperature influence, and examines longer-term storage. Articular cartilage constructs were cultured to maturity using adult canine chondrocytes, then preserved with MOPS at room temperature, in refrigeration, or kept in culture for an additional 56 days. MOPS storage maintained desired chondrocyte viability for 28 days of room temperature storage, retaining 75% of the maturity point Young's modulus without significant decline in biochemical content. Properties dropped past this time point. Refrigeration maintained properties similar to room temperature at 28 days, but proved better at 56 days. For engineered grafts, MOPS maintained the majority of tissue properties for the 28-day window without clearly extending that period as it had for native grafts. These results are the first evaluating engineered cartilage storage.

Freeze Drying Improves the Shelf-Life of Conductive Polymer Modified Neural Electrodes.

Coating microelectrodes with conductive polymer is widely recognized to decrease impedance and improve performance of implantable neural devices during recording and stimulation. A concern for wide-spread use of this approach is shelf-life, i.e., the electrochemical stability of the coated microelectrodes prior to use. In this work, we investigated the possibility of using the freeze-drying process in order to retain the native low impedance state and, thereby, improve the shelf-life of conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT)-PSS modified neural electrodes. Control PEDOT-PSS coated microelectrodes demonstrated a significant increase in impedance at 1 kHz after 41–50 days of room temperature storage. Based on equivalent circuit modeling derived from electrochemical impedance spectroscopy, this increase in impedance could be largely attributed to a decrease in the interfacial capacitance consistent with a collapse and closing of the porous structure of the polymeric coating. Time-dependent electrochemical impedance measurements revealed higher stability of the freeze-dried coated microelectrodes compared to the controls, such that impedance values after 41–50 days appeared to be indistinguishable from the initial levels. This suggests that freeze drying PEDOT-PSS coated microelectrodes correlates with enhanced electrochemical stability during shelf storage.

Preservation of urine free catecholamines and their free O-methylated metabolites with citric acid as an alternative to hydrochloric acid for LC-MS/MS-based analyses.

Measurements of urinary fractionated metadrenalines provide a useful screening test to diagnose phaeochromocytoma. Stability of these compounds and their parent catecholamines during and after urine collection is crucial to ensure accuracy of the measurements. Stabilisation with hydrochloric acid (HCl) can promote deconjugation of sulphate-conjugated metadrenalines, indicating a need for alternative preservatives. Urine samples with an intrinsically acidic or alkaline pH (5.5-6.9 or 7.1-8.7, respectively) were used to assess stability of free catecholamines and their free O-methylated metabolites over 7 days of room temperature storage. Stabilisation with HCl was compared with ethylenediaminetetraacetic acid/metabisulphite and monobasic citric acid. Catecholamines and metabolites were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Free catecholamines and their O-methylated metabolites were stable in acidic urine samples over 7 days of room temperature storage, independent of the presence or absence of any stabilisation method. In contrast, free catecholamines, but not the free O-methylated metabolites, showed rapid degradation within 24 h and continuing degradation over 7 days in urine samples with an alkaline pH. Adjustment of alkaline urine samples to a pH of 3-5 with HCl or 4.8-5.4 with citric acid completely blocked degradation of catecholamines. Ethylenediaminetetraacetic acid/metabisulphite, although reducing the extent of degradation of catecholamines in alkaline urine, was largely ineffectual as a stabiliser. Citric acid is equally effective as HCl for stabilisation of urinary free catecholamines and minimises hazards associated with use of strong inorganic acids while avoiding deconjugation of sulphate-conjugated metabolites during simultaneous LC-MS/MS measurements of free catecholamines and their free O-methylated metabolites.

Emulsification Capacity of Microgels Assembled from β-Lactoglobulin and Pectin

Microgels formed from beta-lactoglobulin were used to prepare oil-in-water emulsions in order to examine their emulsifying capacity. Corn oil emulsions prepared with microgels of pure beta-lactoglobulin at pH 5.8 were initially stable, but a fraction of the droplets quickly flocculated to form a creamed layer that could not be dispersed by shear, which was attributed to hydrophobic attractions between the microgels on adjoining droplets. Emulsions prepared from microgels of beta-lactoglobulin and pectin at pH 4.75 possessed greater droplet sizes at lower concentrations, yet all emulsions were relatively stable to irreversible flocculation. Increased stability of emulsions stabilized by BP-gels was attributed to the presence of pectin on the surface of microgels, which increased repulsions between adjoining droplets. Stable corn oil emulsions were still prepared from microgels that were previously dialyzed to remove non-aggregated protein, which verified that the microgels were responsible for stabilizing emulsion droplets. Equilibrium surface pressure of corn oil droplets was similar between microgels and the unheated beta-lactoglobulin and pectin, yet the dynamic surface pressure was reduced at intermediate times and indicated a slow relaxation and deformation of the microgels at the interface. Microgels formed with pectin stabilized emulsions containing 90 % limonene for up to 5 days of room temperature storage, demonstrating the capacity of such protein microgels to stabilize flavor oil emulsions.

마늘의 저온저장 후 2차 건조가 품질에 미치는 영향

마늘은 일반적으로 0~-4°C의 저온에서 저장하는 방법이 널리 이용되고 있으며, 저온저장 후 상온보관 시 마늘은 휴면이 일직 타파되고 생육이 촉진되어 품질이 떨어지게 된다. 그리고 저장온도가 낮고 상온과의 온도 차이로 마늘의 표면에 결로가 생기며, 이 결로로 인해 발생된 수분이 마늘의 미생물 생장을 촉진시켜 부패율 증가에 큰 원인이 되고 있다. 그러나 이러한 문제점에도 불구하고 저온저장 후 상온 유통 시 후처리에 대한 연구가 매우 미진한 상태이다. 따라서 본 연구에서는 마늘의 저온저장 후 건조처리 방법에 따라 상온 보관성 향상 및 품질에 미치는 영향을 분석하고, 적정 저장 및 2차 건조조건을 확립 제시하였다. 연구 결과를 요약하면 다음과 같다. 마늘의 중량감소율은 2차 건조조건에 따라 40°C 2일 건조조건에서 2.5~4.1%로 가장 크게 나타났다. 그러나 2차 건조 후 상온보관에 따른 마늘의 중량감소율은 40°C 2일 건조조건에서 5% 낮은 것으로 나타났다. 2차 건조 후 상온보관 기간에 따른 마늘의 맹아율은 상온보관 15일까지 20% 급속히 증가하는 것으로 나타났으며, 30일이후부터는 소폭 증가하는 것으로 나타났다. 2차 건조조건에 따른 마늘의 맹아율은 건조하지 않은 조건에서 그 증가폭이 10% 정도 큰 것으로 나타났으며, 2차 건조조건 중 35°C 3일과 40°C 2일 건조조건에서의 맹아 생장이 가장 작은 것으로 나타났다. 저온저장 후 2차 건조조건에 따른 마늘의 부패율 변화는 저온저장 후 2차 건조하지 않은 조건에서 부패율이 5~10% 높았으며, 40°C 2일 건조조건에서의 부패율이 가장 낮은 것으로 나타났다. 저온저장 후 상온보관에 따른 마늘의 경도변화는 저온저장 후 2차 건조를 수행하지 않은 조건에서 그 변화 폭이 20~50 gf 크게 나타났고, 2차 건조 후 상온보관에 따른 마늘의 경도 감소는 35°C 2일과 40°C 2일 건조조건에서 작은 것으로 나타났다. 따라서 마늘의 저온저장 후 상온보관 시 적정조건은 저온저장 직후 2차 건조를 하며, 2차 건조조건 중 40°C 2일 동안 건조하는 것이 마늘의 고품질 유지를 위해 바람직한 것으로 판단된다.