Frozen Storage Research Articles

Demonstration of potential DNA contamination introduced by laboratory consumables using Fluorescein

The development of increasingly efficient DNA extraction and profiling kits has increased the amount of allelic information obtained from trace DNA samples, but also inadvertently, increased the detection of DNA contamination. This study aimed to evaluate the potential of DNA transfer using fluorescein, fluorescent under an alternate light source, in the use of a range of forensically relevant DNA profiling consumables. An evaluation of two pre-lysis methods adopting three different sample tubes, some with deliberate seal damage, showed the PrepFiler™ Automated Forensic DNA Extraction Kit caused leakage and crusting when the rim of the PrepFiler™ LySep column was compromised, but no leakage was observed under the same conditions using the Investigator STAR Lyse&Prep kit. The AutoLys tube showed minimal leakage using the PrepFiler™ chemistry. A DNA extract tube with an external thread, similar to the AutoLys tube, showed no leakage after fridge or freezer storage. However, it highlighted that a centrifugal spin does not guarantee all the DNA will pool at the base of the tube. A comparison of adhesive plate sealing films to 8-well strip caps for sealing 96-well PCR plates showed the adhesive plate sealing films presented a lower risk of DNA transfer, largely due to the adhesion of dispersed liquid on the sticky surface of the film. Overall, this study highlighted a number of variables that may be considered in the development of more refined contamination minimisation protocols in respect to increased sensitivities of DNA profiling.

Unveiling the structural and physico-chemical properties of glutenin macropolymer under frozen storage: Studies on experiments and molecular dynamics simulation

Glutenin macropolymer (GMP) plays an important role in wheat gluten fractions, and extensively presents in the frozen dough. However, the effects of freezing treatment on GMP remain not abundantly understood. In this study, we investigated the structure and physico-chemical properties of GMP under frozen storage through experimental methods and bioinformatics algorithms. Results revealed that freezing treatment weakened the structure and properties of GMP to varying degrees, and GMP might have tolerance to short-term freezing storage. During frozen storage, portions of α-helix in GMP were converted into β-turn and random coil, slight changes in the tertiary structure, and its surface hydrophobicity increased by 4.8 %. SDS-PAGE profiles indicated that the depolymerization behavior mainly occurred above the Mw of 70.0 kDa. Slight changes were observed in the content of free thiol groups and disulfide bonds during frozen storage. Combination of fluorescence spectroscopy and intermolecular interactions suggested that hydrogen bonds and hydrophobic interactions were probably important indicators for evaluating the deterioration of GMP. Frozen storage resulted in an unfolded and open protein network. Moreover, freezing treatment led to a main conversion from strongly bond water to weakly bond water. However, no significant changes in water distribution were observed during the first 7 days of frozen storage. The viscoelastic loss of GMP primarily occurred in the first fourteen days, but tan δ did not significantly increased, indicating that protein has not been seriously deteriorated. Molecular dynamics simulation further supplemented and validated these experimental results from molecular level through analysis of root mean square deviation, root mean square fluctuation, solvent-accessible surface area, radius of gyration and the number of hydrogen bonds.

Horseradish (Armoracia rusticana L.) leaf juice encapsulated within polysaccharides-blend-based carriers: Characterization and application as potential antioxidants in mayonnaise production

This study aimed to encapsulate cold-pressed horseradish leaf juice within maltodextrin/alginate (MD/AL), maltodextrin/guar gum (MD/GG), and maltodextrin/gum Arabic (MD/GA) by spray-drying, to characterize the encapsulates, and to test their potential as mayonnaise oxidation-preventing ingredients. The encapsulates exhibited desirable physicochemical, morphological, structural, and thermal properties, highlighting MD/GA-containing encapsulates, especially regarding high encapsulation yield (78.50 %). Also, encapsulates contained a significant amount of phenolics, which were stable during freezer storage. The encapsulates successfully delayed the mayonnaise oxidation: 31.91–38.94 % more than the synthetic antioxidant ethylenediaminetetraacetic acid, especially highlighting MD/AL-containing encapsulates. Also, the encapsulates improved product quality with a higher pH and lower acidity after storage compared to the controls. Overall acceptability of encapsulates-containing mayonnaises and commercial mayonnaise did not differ significantly. This study contributes to sustainable development by providing new insights into the valorization of horseradish leaves, as a promising alternative to synthetic additives to prolong the oxidative stability and shelf-life of high-oil-containing foods.

Assessment of lyophilized microencapsulated multi strain probiotic for improved shelf life and stability

A Multi species Probiotics (MSP) of calf gut origin was encapsulated either with chitosan (ECMSP) or without chitosan (EMSP). Further, the probiotic was encapsulated and lyophilized (ELMSP) using three types of cryoprotectant solutions sucrose (ELMSP(S)), skim milk (ELMSP(SM)) and sucrose + skim milk combination (ELMSP (SSM)). The encapsulation yield was good and ranged from 75 % to 80 % for MSP products. These MSP products were stored at refrigeration temperature (4 °C), deep freeze and room temperature for 12 weeks. The shelf life (mean CFU) of encapsulated microcapsules was significantly better (P < 0.001) at the refrigeration temperature (9.44 Log10 CFU/g) than deep freeze (7.42 Log10 CFU/g) and room temperature (6.67 Log10 CFU/g). At the end of the 12 weeks storage period, EMSP maintained 25.1 %, 49.6 % and 32.6 % viable counts at room temperature, refrigeration and deep freeze condition respectively. For the lyophilized-encapsulated MSP, the mean probiotic counts of ELMSP(S) and ELMSP (SSM) were significantly (P < 0.001) higher (9.62 Log10 CFU/g) than those of ELMSP(SM) ((9.36 Log10 CFU/g) at room temperature. At refrigeration temperature, the mean probiotic counts for ELMSP (SSM. (10.1 Log10 CFU/g)) were significantly higher (P < 0.001) than ELMSP(S, (9.97 Log10 CFU/g) and ELMSP(SM, (9.86 Log10 CFU/g). Further, a 12 weeks storage study for ELMSP (SSM) showed that the microcapsules stored at refrigeration temperature (4°C) showed only 6.4 % drop in viability which was significantly lower (P < 0.001) than that of room temperature showing 15.3 % drop and deep freeze storage with 17.1 % drop in viability. It was appreciable that even at room temperature; there was only one log drop in the viability of MSP showing that it can be comfortably stored at room temperature for longer periods at field level.

Changes in Protein Levels during the Storage and Warming of Breast Milk in a Domestic Environment.

Background/Objectives: Storage and warming can impact the protein concentration of breast milk (BM). This study aimed to explore the effects of routine BM handling, from storage to warming, on BM protein concentration. Methods: Forty BM samples were collected from 40 mothers with full-term infants. Fresh BM samples were analyzed within 24 h of expression as a baseline. Additional samples were stored in a refrigerator for up to 4 days and in either a freezer compartment of a refrigerator with a separate door (refrigerator freezers) or a deep freezer for up to 6 months. We compared four warming techniques: rapid thawing in water at 25 °C and 37 °C immediately after freezer removal, and slow thawing in a refrigerator for 12 h, followed by warming in water at 25 °C and 37 °C. The protein concentration was measured using the Lowry method. Results: No significant decrease in BM protein concentration was observed across all storage conditions compared to baseline. BM with a higher protein content benefited more from storage in deep freezers than in refrigerator freezers. Thawing immediately after removal from the freezer at 25 °C preserved significantly higher total protein levels compared to alternative heating techniques. Conclusions: Our findings support the recommendation for mothers to store BM in either type of freezer for up to 6 months. Our results suggest that rapid thawing at 25 °C is the most effective method for preserving protein levels compared to other thawing techniques used in our study.

New insights in the flavor and chemistry of Huanglongbing tolerant citrus hybrids with/without Poncirus trifoliata in their pedigree

IntroductionCitrus hybrids with Poncirus trifoliata L. Raf. introgression have gained interest due to their tolerance to Huanglongbing (HLB), a devastating disease for Florida citrus agriculture. While these hybrids inherit disease tolerance from P. trifoliata, they sometimes also suffer from undesirable off-flavors.MethodsA selection of thirteen genotypes were harvested over the 2020-2021 and 2021-2022 seasons. Their juices were evaluated by a trained sensory panel and were comprehensively analyzed for their chemical makeup, including soluble solids content (SSC), titratable acidity (TA), volatiles, flavonoids and limonoids.Results &amp;amp; discussionOverall, along with the commercial orange cultivars ‘Valencia’ and ‘Hamlin’, the HLB-tolerant Poncirus hybrid ‘US SunDragon,’ and the mandarin hybrids Sugar Belle®, FF-5-51-2, and ‘US Superna’ had positive citrus flavor quality. Esters, some sesquiterpenes, along with flavonoids, eriocitrin and quercetin-3-(3R-glucosylrutinoside), were positively correlated with orange flavor while β-ionone and eucalyptol were highly abundant in the mandarins. The flavonoid linarin, was more abundant in Poncirus hybrids with off-flavors than in the Poncirus hybrid ‘US SunDragon’, having high orange flavor. Two mandarin hybrids, FF-5-6-36 and FTP-6-32-67, were not bitter at harvest, but the juice exhibited delayed bitterness after storage at -20°C, which was associated with significant increases of limonin, nomilin, naringenin, and prunin. Interestingly, during freezer storage, a newly identified flavonoid in citrus, tricin-C-hexoside, increased dramatically across all of the genotypes. The identification of disease-tolerant hybrids with satisfactory flavor quality at juicing as well as after storage where delayed bitterness may develop, has great significance for future breeding efforts for fresh fruit or for use in stand-alone juice/juice blends.

Optimization of pulsed electric fields-assisted thawing process conditions and its effect on the quality of Zhijiang duck meat

Freezing storage is a common preservation method for industrialized duck meat. However, both the frozen storage and thawing processes of meat can affect meat quality. Therefore, appropriate thawing methods are crucial for maintaining good meat quality. In this study, a pulsed electric field (PEF) was used for thawing zhijiang duck meat and the freshed duck meats were used as control. Optimization of the PEF-assisted thawing process and its effect on the quality of zhijiang duck meat were analyzed. Our data showed that the shear force in the 2 kV/cm PEF-assisted thawing group was the lowest in PEF-assisted thawing groups. The color of zhijiang duck meat in the 2 kV/cm PEF-assisted thawing group was optimal. The 2 kV/cm PEF-assisted thawing could improve the texture characteristics of zhijiang duck meat and enhance water holding capacity of zhijiang duck meat. PEF-assisted thawing could better maintain the microstructure of zhijiang duck meat. Our data showed that if the intensity or duration of PEF treatment is too high, the quality of duck meat will actually decrease. Therefore, appropriate parameters should be selected in practical applications, which will provide a reference for the application of PEF-assisted thawing on the market.

EFFECT OF SUBZERO STORAGE ON THE QUALITY OF MUTTON FROM SHEEP AND GOATS IN D.I KHAN DISTRICT, KHYBER PAKHTUNKHWA

Mutton is widely recognized for its excellent nutritional value, containing essential components such as proteins, vitamins, and minerals. The objective of this research was to investigate the effects of subzero storage on the freshness and quality of mutton. To evaluate the attributes of frozen and stored mutton, we employed fresh control samples that underwent standard freezing procedures at -18°C. Determining the quality and freshness of the product required the evaluation of numerous parameters over a five-month storage period. Drip loss (comprising boiling and thawing loss), water-holding capacity (WHC), texture profile analysis (TPA), thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen encompassed these parameters. Temperature influenced leak loss and water holding capacity (WHC), with severe freezing resulting in a reduction in moisture loss during frozen storage in comparison to standard freezing conditions. Extremely low-temperature freezing and subsequent storage of lamb resulted in a notable enhancement in tenderness when compared to standard freezing conditions. More precisely, sheep that underwent freezing at temperatures below -60℃ exhibited a tenderness akin to that of recently slaughtered mutton. Following a five-month period, frozen samples of mutton exhibited no indications of lipid oxidation, irrespective of temperature. The storage temperature of the samples, nevertheless, had an impact on the TVBN (total volatile basic nitrogen) concentration. In conclusion, our research indicates that mutton can maintain its freshness for a period of five months through the utilization subzero temperatures. A temperature of -60℃ is determined to be the most favorable condition for freezing and storing frozen mutton, taking into account both economic and qualitative considerations.

Basic Theory of Ice Crystallization Based on Water Molecular Structure and Ice Structure.

Freezing storage is the most common method of food preservation and the formation of ice crystals during freezing has an important impact on food quality. The water molecular structure, mechanism of ice crystal formation, and ice crystal structure are elaborated in the present review. Meanwhile the methods of ice crystal characterization are outlined. It is concluded that the distribution of the water molecule cluster structure during the crystallization process directly affects the formed ice crystals' structure, but the intrinsic relationship needs to be further investigated. The morphology and distribution of ice crystals can be observed by experimental methods while simulation methods provide the possibility to study the molecular structure changes in water and ice crystals. It is hoped that this review will provide more information about ice crystallization and promote the control of ice crystals in frozen foods.

Investigation of the effects of psyllium powder addition on the quality of fresh and frozen gluten-free bread

The interest in gluten-free (GF) products has been growing since both the increase in prevalence of celiac disease and the preferences of GF diet. In this study, the contribution of psyllium powder (PP) to gluten-free (GF) bread quality, dough rheology and volatile compounds (VCs) profile was investigated throughout the frozen storage period of GF dough (-30 °C for 0, 7, 15, and 30 days). GF doughs containing 7.5% PP (PSY1) and 15% PP (PSY2) had lower tanδ value than GF control dough (p&amp;lt;0.05) according to the results obtained from fundamental rheological analysis. Frozen storage caused no effect on the tanδ value of PSY1 and PSY2 (p ≥ 0.05). PP addition increased the specific volume (SV) of GF breads (p&amp;lt;0.05). No significant effect of frozen storage on SV was shown for PSY2 while SV values of GF control bread (GFB) and PSY1 decreased (p&amp;lt;0.05). Lower crumb hardness was shown for PSY1 and PSY2 on day 0. Significant effect of frozen storage on crumb hardness was observed for PSY1 on day 30 while harder crumb structure was shown for GFB throughout the frozen storage (p&amp;lt;0.05). Psyllium addition led to a significant reduction in both L* value of crust and crumb color (p&amp;lt;0.05). In the VCs analysis performed by HS/GC-MS, ethanol and 1-butanol, 3-methyl from alcohol group, butanal, 3-methyl- and hexanal from aldehydes were common for GFB and GF breads containing psyllium. 1-butanol, 3-methyl-, butanal, 3-methyl- and hexanal were the VCs of PSY1 and they were also shown after frozen storage. This study suggested that quality deterioration due to frozen storage was less in gluten-free breads containing psyllium.

Quality monitoring of glutinous rice processing from drying to extended storage using hyperspectral imaging

The quality of glutinous rice (GR) is susceptible to deterioration and losses due to biological or environmental factors during storage. Traditional quality assessment techniques are often time-consuming and challenging. In this study, a rapid and reliable hyperspectral imaging (HSI) technique is utilized to monitor GR quality during storage. Paddy samples were dried at 50 °C, 60 °C and 70 °C. Subsequently, these samples were milled and stored under three conditions: freeze storage (−10 °C), cold room (6 °C) and ambient (∼26 °C) for 6 months. The methodology involved data acquisition from both HSI and standard references methods, with data on hyperspectral reflectance, head rice yield (HRY), broken rice yield (BRY) and milled rice yield (MRY) collected every two weeks. Five machine learning (ML) models were evaluated for quality prediction using Python3, with Random Forest (RF) identified as the best performer, achieving a coefficient of determination (R2) of 0.995. Hyperparameter tuning (HPT) further improved the RF model’s R2 by 0.3 %. Parity plot analysis confirmed the accuracy of the RF model in describing GR quality during storage. The study demonstrates the significant impacts of different storage and drying temperatures on HSI data and GR quality attributes. Significant differences in reflectance were observed, with higher reflectance for samples dried at 60 °C and freeze-storage, while lower reflectance for samples dried at 70 °C and cold-room storage. These findings align with reference method results and ML predictions, revealing that drying paddy at 60 °C and storing it under freeze conditions enhances HRY and increases the commercial value of GR. Overall, this study highlights the potential of the HSI for real-time quality monitoring of GR and its applicability to other grains.

Comparison of shipping versus immediate freezer storage of vaginal samples for vaginal microbiota assessment

ObjectivesWe evaluated how storing vaginal samples at room temperature in stabilising solutions versus immediate freezing affects 16S rRNA gene amplicon sequencing-based microbiota studies, aiming to simplify home and field collection.MethodsTwenty...

Effect of Garlic Paste Addition on the Fatty Acid Profile and Oxidative Stability of Shrimp Analogue Fortified with PUFA-rich Fish Oil During Frozen Storage at -20°C

Effect of Garlic Paste Addition on the Fatty Acid Profile and Oxidative Stability of Shrimp Analogue Fortified with PUFA-rich Fish Oil During Frozen Storage at -20°C

Experimental study on improving the thermal performance of isobutane refrigeration system by parameter optimization

Improvement of thermal efficiency for isobutane refrigeration system could match well with the building requirements of low-carbon, and sustainable development. The electric radiant heater (ERH) is widely used for the freeze and cold storage (FCS) system, but it has problems of high electric consumption and high freezer compartment temperature rise (FCTR) as a result of low heat-transfer efficiency under defrosting. Therefore, a novel FCS system with an additional electric radiant heater (AERH) based on the heat required for frost melted and synchronous defrosting is proposed. The defrosting consumption and the FCTR of the novel FCS system are comprehensively evaluated by a novel evaluation method. Besides, the effect of the thermal parameters (i.e., the defrosting pause temperature, the position, and electric power of the AERH) on the heat transfer characteristics are compared and optimized by the experimental method. Finally, a novel method is presented to predict the optimum thermal conditions. The results show that the optimum system thermal performance is obtained, the defrosting duration and defrosting consumption are reduced by 44.02 % and 37.03 %, and the defrosting efficiency and energy efficiency could be increased by 17.92 % and 9.96 %, respectively, as compared to the conventional FCS system. The proposed FCS system has better economic performance and heat transfer efficiency. Meanwhile, 30.54 kg of CO2 emissions could be avoided during the annual operation period, and the environmental benefits are also considerable. This study not only reaffirms the benefit of using the AERH for defrosting in the FCS system but also provides a reference for the promotion and application of efficient heat transfer technology in building refrigeration engineering.

Efficient generation of recombinant anti-HER2 scFv with high yield and purity using a simple method.

We developed a method to produce a soluble form of a single-chain fragment variable (scFv) targeting human epithelial growth factor receptor 2 (HER2) in Escherichia coli. By optimizing the orientations of the variable heavy (VH) and variable light (VL) domains and the His-tag, we identified the HL-His type antibody with the highest HER2-binding activity. Purification of HL-His yielded 40.7mg from a 1 L culture, achieving >99% purity. The limit of detection was determined to be 2.9ng, demonstrating high production yield, purity, and sensitivity. Moreover, we successfully labeled HER2+ cell lines with fluorescent dye-conjugated scFv, resulting in a significantly higher observed signal-to-background ratio, compared to that of HER2- cell lines. This highlights the potential of these fluorescent scFvs as valuable probes for HER2+ breast cancer diagnostics. Notably, the process for the complete scFv production was streamlined and required only 4-5 days. Additionally, the product maintained its activity after freeze storage, allowing for large-scale production and a wide range of practical applications.

Impact of frozen storage and pretreatment conditions on health-related compound stability kinetics in leeks and Brussels sprouts

Frozen vegetable chain variables can impact health-related compounds and their corresponding unique (bio)chemical reactions. To delve into this dynamism, kinetic shelf life studies were undertaken, focusing on several compounds (vitamin C, vitamin K1, carotenoids, glucosinolates, S-alk(en)yl-l-cysteine sulfoxides (ACSOs)) present in Brussels sprouts and leek. Frozen storage was conducted after industrial freezing and performed at −7, −15, −20 and −40 °C over one year. Glass transition temperature was about −24 °C for leek (Tg’) and about −27 °C for Brussels sprouts (Tg”). Overall, compound stability was higher when stored close to the glass transition temperature, influenced by (bio)chemical conversations related to substrate-enzyme location. Losses of 0–30% glucosinolates, 17–100 % vitamin C in blanched Brussels sprouts and 7–80% ACSOs, 87–100% vitamin C, 39–100% carotenoids in unblanched diced leeks were determined. Mathematical models were used to describe and compare the stability of these compounds as impacted by frozen storage. Additionally, different pretreatments (blanching, pureeing) were applied before freezing. Pretreatment type impacted initial compound concentrations, but had no impact on compound behavior during frozen storage of nine months, except for vitamin C which was stabilized by blanching but destabilized by pureeing. Overall, vitamin K1 was the only compound not impacted by storage temperature or pretreatment type.

Impact of Aging Methods and Frozen Storage on Beef Quality Attributes from Different Finishing Diets

The effects of finishing diet (pasture or grain) and meat preservation method on beef&amp;rsquo;s physicochemical, micro- biological, and sensory attributes were evaluated. The preservation methods assessed were dry aging in bag (DAb) and wet aging (WA) for 40 d, and then frozen storage (Fr) ([DAb + Fr] and [WA + Fr]) for 180 d. Sixty striploins (Longissimus lumborum) from British breed steers (n = 15 from pasture and n = 15 from grain-based diet) were used. Lightness (L*) was only affected by finishing diet where meat from grain-fed steers was lighter than those fed on pasture (P &amp;lt; 0.01). DAb meat had higher pH (P &amp;lt; 0.01) and lower cooking losses (P &amp;lt; 0.01) than WA. DAb + Fr had the highest Psychotrophic bacteria counts compared to WA + Fr, DAb and WA (P &amp;lt; 0.01). DAb and DAb + Fr increased Enterobacteriaceae bacteria counts (P &amp;lt; 0.01) compared to WA and WA + Fr. DAb + Fr samples had the lowest L*, a*, and b* values. No interaction between physicochemical characteristics (color coordinates, pH, cooking losses, and shear force) and surface microbiological load was observed (P &amp;gt; 0.05). Greater polyunsaturated fatty acids (PUFA), PUFA n-3, conjugated linoleic acid (c9, t11 &amp;ndash; 18:2) (P &amp;lt; 0.01), and PUFA/saturated fatty acid ratio (P &amp;lt; 0.05) and lower n-6:n-3 ratio (P &amp;lt; 0.01) were observed in pasture- than grain-fed steers. The consumer sensory panel showed acceptable scores for all treatments, although some differences between attributes were detected by cluster analysis. Different aging methods followed by a frozen storage period could be used to produce and export meat with the required quality attributes to meet consumer expectations

Real-time detection of lysine decarboxylase activity and cellular energy pool under inducible CadA expression system in engineered Escherichia coli

BackgroundBiocatalysts hold significant promise in the production of 1,5-diaminopentane (cadAverine) due to its wide-ranging applications. However, the process of screening recombinant cells expressing lysine decarboxylase (LdcC or CadA) activity via high-performance liquid chromatography is labor-intensive and time-consuming. MethodsThis study has devised a straightforward colorimetric assay to quantify lysine decarboxylase activity. It utilizes the pH indicator bromocresol purple (BCP). As cadAverine is produced from l-lysine, it elevates the reaction pH, leading to a corresponding change in BCP color. Significant findingsReal-time monitoring of CadA activity was conducted using an inducible T7 promoter system, built upon the CadA/-CadB co-expression framework within Escherichia coli BL21(DE3). Analysis of Michaelis-Menten kinetics revealed that pyridoxal-5′-phosphate (PLP) was efficient in substrate conversion compared to pyridoxal (PL) and pyridoxine (PN) as cofactors. Supplementation of PN with ATP successfully restored Vmax to levels comparable with PLP. However, following freezer storage of biocatalysts, insufficient PLP generation from PN was observed due to variations in the cellular metabolic pool and ATP levels. The optimal conditions for CadA/B activity were achieved with 7 μM IPTG induction at 32 °C for 8 h, resulting in a maximum specific activity of 18.2 ± 1.1 mmol/min/g dried cell weight. The BCP-based colorimetric assay showcased its efficacy in rapidly detecting and quantifying CadA/B activity, thereby facilitating high-throughput screening of recombinant libraries.

Sample processing time but not storage time affects complement activation markers C4a, C4d, C3a, iC3b, Bb, C5a, and sC5b-9 levels in EDTA-plasma of individuals at clinical high-risk for psychosis

The complement system is an important part of the innate immune system and plays a key role in inflammatory processes. Concentrations of complement activation fragments in plasma are markers of systemic activation and have been found to be altered in a wide range of diseases. Some plasma activation marker levels can be influenced by sample processing and storage time. We quantified seven complement activation markers (C4a, C4d, C3a, iC3b, Bb, C5a, and sC5b-9 (TCC)) in EDTA-plasma as part of a multi-centre clinical study analysing complement activation in individuals with clinical high-risk (CHR) for psychosis compared with healthy controls. Samples had been collected, processed, and subsequently stored at -80°C over a period of 9.5–13.6 years, according to a standard operating protocol (SOP). Complement activation markers were quantified using commercially available and standardised enzyme-linked immunosorbent assays (ELISA). In a post hoc analysis of variables affecting the analyses we investigated the impact of EDTA-to-freezer processing time (<1–7.35 hours) and freezer storage time (9.5–13.6 years). EDTA-to-freezer processing time moderately correlated positively with C4a, C3a, iC3b and sC5b-9 levels. Storage time at -80°C was not significantly correlated with any complement activation marker. This study provides valuable insight into the impact of sample processing and long-term sample storage in complement activation marker studies. The results suggest that storage time in -80°C is not a confounding factor affecting non-specific complement activation in EDTA-plasma. Sample-processing time does moderately affect the levels of some complement activation markers. This should be considered as a co-variate when analysing complement activation marker levels. Further, the impact may vary for healthy or clinical samples where immune activation is part of the pathology. These findings are important when planning large-scale clinical studies that include quantification of complement components and its activation fragments as biomarkers. It supports the collection of EDTA-plasma and fast sample processing to be included into a study standard operating procedure.

The Effect of Freezing, Frozen Storage and Thawing on the Strawberry Fruit Composition

ABSTRACT Strawberries intended for processing are usually frozen to withstand storage and distribution. However, freezing and thawing can cause the degradation of bioactive compounds. The aim of this study was to determine the optimal conditions for frozen storage and thawing to minimize any loss of nutrients prior processing. Different freezing treatments (−20°C, shock-freezing with liquid nitrogen, −80 °C) up to 6 months of storage and thawing treatments (4°C, room temperature, 37°C, microwave) were compared based on the content of organic acids, sugars, and phenolic compounds as well as the activity of peroxidase and polyphenol oxidase. During frozen storage at −20°C over 6 months, the sucrose content decreased by 59%, but only a 17% loss of ascorbic acid was observed, and no significant loss of anthocyanins was detected. However, more significant changes in composition were detected after thawing. When thawed at 4°C for 24 h, ascorbic acid content decreased by 32%, anthocyanin content by 30%, and sucrose content by 66%. Based on our study, the frozen storage caused smaller changes in the fruit’s composition than thawing. From the thawing procedures, the microwave thawing showed minimal changes in the composition of strawberries.