Function Of Storage Time Research Articles

Aquaphotomics Monitoring of Lettuce Freshness during Cold Storage.

Fresh-cut leafy vegetables are one of the most perishable products because they readily deteriorate in quality even during cold storage and have a relatively short shelf life. Since these products are in high demand, methods for rigorous quality control and estimation of freshness that are rapid and non-destructive would be highly desirable. The objective of the present research was to develop a rapid, non-destructive near-infrared spectroscopy (NIRS)-based method for the evaluation of changes during cold storage of lettuce using an aquaphotomics approach to monitor the water molecular structure in lettuce leaves. The reference measurements showed that after 6 days of dark, cold storage, the weight and water activity of lettuce leaves decreased and β-carotene decreased, while chlorophylls slightly increased. Aquaphotomics characterization showed large differences in the lettuce leaves' spectra depending on their growth zone. Difference spectra, principal component analysis (PCA) and linear discriminant analysis (LDA) confirmed the differences in the inner and outer leaves and revealed that spectra change as a function of storage time. Partial least squares regression (PLSR) allowed the prediction of the time spent in storage with a coefficient of determination of R2 = 0.80 and standard error of RMSE = 0.77 days for inner, and R2 = 0.86 and RMSE = 0.66 days for outer leaves, respectively. The following water absorbance bands were found to provide the most information in the spectra: 1348, 1360, 1373, 1385, 1391, 1410, 1416, 1422, 1441, 1447, 1453, 1466, 1472, 1490, 1503, 1515, 1521, 1534 and 1571 nm. They were further used as water matrix coordinates (WAMACs) to define the water spectral patterns (WASPs) of lettuce leaves. The WASPs of leaves served to succinctly describe the state of lettuces during storage. The changes in WASPs during storage reveled moisture loss, damage to cell walls and expulsion of intracellular water, as well as loss of free and weakly hydrogen-bonded water, all leading to a loss of juiciness. The WASPs also showed that damage stimulated the defense mechanisms and production of vitamin C. The leaves at the end of the storage period were characterized by water strongly bound to collapsed structural elements of leaf tissues, mainly cellulose, leading to a loss of firmness that was more pronounced in the outer leaves. All of this information was reflected in the changes of absorbance in the identified WAMACs, showing that the water molecular structure of lettuce leaves accurately reflects the state of the lettuce during storage and that WASPs can be used as a multidimensional biomarker to monitor changes during storage.

Contamination of rare earth oxide surfaces stored in vacuum environment

Rare earth oxide (REO) ceramics have great potential to be applied as robust hydrophobic materials in several industrial applications. Compared to hydrophobic polymers, REO ceramics have outstanding hardness, thermal stability in addition to high water contact angle (up to 115°). However, the origin of REO hydrophobicity remains unclear. Currently, there are two competing mechanisms: (i) REOs are inherently hydrophilic and the high WCA observed is due to the adsorption of airborne hydrocarbons on the surface when exposed to air, (ii) REOs require a vacuum treatment to develop the hydrophobic behavior. The former is recognized by many independent studies while the latter has not been fully addressed due to inadequate investigation of the change in surface chemistry of REOs as they are exposed to vacuum conditions. Herein, we fabricated high quality CeO2 epitaxial films and explored the changes in surface chemistry as a function of storage time in an ultra-high vacuum (UHV) environment. We found that carbon and fluorine can build up on the surface with increasing storage time in UHV condition. Our results suggest that care needs to be taken in the interpretation of wettability data of REOs that have been stored in a vacuum environment.

Evaluation of rheological and optical properties plus stability of beverage cloud emulsions prepared with corn oil, gum rosin, and modified starch.

Rheological and optical properties as well as stability of beverage cloud emulsion prepared with corn oil, gum rosin (EG), and modified starch were evaluated in model juices. The emulsions were prepared with three levels of modified starch (6%, 12%, and 18% w/w), corn oil (5%, 7%, and 9% w/w), and gum rosin (1%, 3%, and 5% w/w). Experiments were designed using the Box-Behnken design. The analysis of variance (ANOVA) was used to evaluate the significance of the experimental factors and the factors were then optimized using response surface methodology (RSM). The stability of emulsions was measured through ring formation in both the primary emulsion and the model beverage as a function of storage time. Also, the effect of heat treatment was examined on the stability of emulsions in model beverages. The results revealed that heat treatment did not cause the formation of an observable ring in the model juice containing stabilized starch emulsion. Rheological examinations of the stable emulsion samples showed a pseudoplastic and time-independent non-Newtonian behavior. The optimum emulsion sample consistency coefficient was 0.46 Pa.sn and the flow behavior index was 0.88. The apparent viscosity of the optimum emulsion sample based on Herschel-Bulkley model at shear rate of 100 s-1 was 0.0439 Pa.s. The results indicated that the concentration of modified starch, gum rosin, and corn oil has a significant effect on the stability and creaminess of the emulsion. In general, with an increase in the percentage of modified starch, the stability rises while the rate of creaminess decreases (p < 0.05). Furthermore, elevation of the concentration of corn oil had a significant effect on the opacity of emulsions and the final product (p < 0.05).

Post-harvest of onion due to fertilization with micronutrient

The onion (Allium cepa L.) is the third most cultivated vegetable and has great socioeconomic importance worldwide. Because it is highly perishable and has greater demand than supply, many post-harvest losses occur, most of them caused by inadequate storage conditions affecting the bulbs quality. This study aimed to evaluate the postharvest quality of onion as a function of fertilization with micronutrients, using the cultivar “Rio das antas”. The experiment was divided into two stages: field and laboratory. In the field, an experiment was installed between June and December 2019 at Experimental Farm Rafael Fernandes, in completely randomized blocks with nine treatments and four replications. The treatments consisted of the combined doses of B, Cu and Zn. In the laboratory, the experimental design was in completely randomized blocks in 9 x 4 split-plot design, with four replications. The treatments (micronutrients B, Cu and Zn) were arranged in the plots and the storage times were arranged in the subplots (0; 20; 40 and 60 days after harvest). Bulb firmness, soluble solids (ºBrix), total soluble sugars and pungency were evaluated. The data were subjected to statistical analysis as a function of storage time, by the Sisvar program, applying regression analysis. The combined application of doses of 1-4-1 kg.ha-1 of Boron, Copper and Zinc, respectively, presented the best results for pungency, firmness and sugars during storage, this being the most recommended treatment for not significantly different from higher doses, promoting more efficient use of inputs.

Sustainable and eco-friendly poly (Lactic acid)/cellulose nanocrystal nanocomposite films for the preservation of oxygen-sensitive food

The development of enzymatic browning constitutes one of the key issues in the preservation of highly perishable fresh-cut and oxygen-sensitive fruits such as avocados. This study explored the use of a packaging solution based on PLA/cellulose nanocrystal (CNC) films produced using a solvent-free cast extrusion process with strong oxygen and UV barrier properties to reduce browning in cut avocados and to prolong shelf life. Specifically, the effects of packaging material types (neat PLA vs PLA/CNC nanocomposite) and storage conditions (temperature and time) on discoloration (browning), microbial growth, and shelf life were assessed. Enzymatic browning was visually evaluated and total discoloration (ΔE*) quantified as a function of storage time and temperature to estimate the shelf life of the avocados. Compared with neat PLA, nanocomposite packaging reduced the enzymatic browning more and resulted in additional shelf life extension of 1.3 days at 23 °C and 5.4 days at 4 °C. Both PLA-based films reduced the microbial growth. The potential of sustainable and eco-friendly nanocomposite film to prolong the shelf life of food that is oxygen sensitive is clearly demonstrated.

Evaluation of methodologies for chemical characterization of vinasse as a function of storage time

The objective of this study was to evaluate efficient analytical methods of wet digestion using the official method of analysis, a mixture of nitric acid and perchloric acid (HNO3 + HClO4), for the analysis of vinasse and also verify the effects of nutrients on stored vinasse. The analytical methods compared were: 1) Nitroperchloric (HNO3), 2) Nitric (HNO3); 3) Chloridric + Hydrogen Peroxide (HCl + H2O2); 4) Sulfuric + Hydrogen Peroxide (H2SO4 + H2O2) and 5) Solubilization with 1 molar Chloridric acid (HCl 1 Mol L-1). Phosphorus, potassium, calcium, magnesium and sulfur were determined over different storage periods, and these nutrients were analyzed at 5, 30, 90 and 150 days of storage, to verify the behavior of these nutrients over the time they are stored in laboratory conditions. The efficiency of the methods was evaluated by comparing the results of the nitroperchloric method obtained for each nutrient with the results obtained from the other methods. The results showed that the nitric (HNO3) and chloridric + hydrogen peroxide (HCl + H2O2) digestions presented good to excellent precision equivalent to the nitroperchloric digestion (HNO3) for the analyzed nutrients. The solubilization method with 1 molar chloridric acid (HCl 1 Mol L-1) presented a low accuracy and did not present the expected efficiency for quantification of any analyzed nutrient. With the exception of potassium contents, all the other nutrients analyzed in the study reduced at the end of the vinasse storage days.

Anomalous fading in thermoluminescence signal of ten different K-feldspar samples and correlation to structural state characteristics

The present work reports an extended study of anomalous fading (AF) in the TL signal of ten different pure K-feldspar samples from North Greece. A fading protocol was applied, including a standard series of TL measurements undertaken following a variety of storage times after irradiation, in order to plot the luminescence output as a function of storage time. Anomalous fading was found to be ubiquitous for the TL signal of all feldspars. The remnant signals are defined as the ratio of the TL signal remaining after storage time t, over the corresponding signal promptly measured. Two different fading rates were calculated, namely the value of g-factor which describes the luminescence signal loss in terms of percentage per decade of time as well as the g50-factor which describes the fading rate when the signal has been reduced to 50% of the prompt value measured after irradiation due to AF. Both aforementioned fading factors were calculated over the entire TL glow curves in step intervals of 10 °C and were eventually plotted versus glow curve temperature. The analysis indicated that fading factors yield maximum values within the temperature range between 200 and 350 °C, with a tendency to decrease with increasing temperature along the rest glow curve. As the 10 K-feldspar samples belong to three different groups (microclines, sanidines and orthoclases), possible correlation is studied between the fading factors and specific structural parameters of alkali feldspars, such as the probability of Al-cation to occupy specific sites in the forming tetrahedra and the volume of the unit cell.

Improvement of probiotic viability through the design of novel biomaterials using coffee pulp wastes and Lactobacillus rhamnosus.

The immobilization of bacteria cells has shown to be an efficient technology to improve cell viability. This study used lyophilized and pulverized coffee pulp (LPC) and LPC functionalized with theobromine at two concentrations, 3.1 w/w and 2.4 w/w named as LPF1 and LPF2, respectively, to immobilize Lactobacillus rhamnosus ATCC 53103 cells (biomaterials) and increase the viability of the cell at storage and gastrointestinal conditions. To characterize the biomaterials, SEM, Dynamic Light Scattering, TGA, , FTIR and Isoeletrc Point measurements (or zeta potential measurements) were carried out. To evaluate the effectiveness of immobilization, cell viability as a function of storage time and under simulated gastrointestinal conditions was evaluated. Regarding the characterization of the materials, the particle sizes were 21.7 to 334.4 nm and they experienced mass losses of less than 10% at 100 °C. The FTIR indicated the presence of functional groups related to caffeine, chlorogenic acid, sucrose, arabinogalactans, carbohydrates, and proteins in all biomaterials. The sorption kinetic parameters showed an adsorptive capacity between 3.0 × 109 and 8.0 × 109 CFU/g, being LPF1 the best materials to immobilize the cells, associated with LPF1 surface properties. The viability was higher for immobilized cells than for free cells, when left in storage and under simulated gastric conditions. Finally, the biomaterials could be used in the preparation of probiotic diets based on lactobacilli. To the best of our knowledge, this is the first study regarding the use of waste from coffee agribusiness to develop probiotic biocarriers which opens up possibilities for future developments.

DSC analysis of cryopreservation on the structure of porcine aortic biograft as a function of storage time

The utilization of cryopreserved human allografts is a recommended option in the septic vascular surgical field, if autologous graft is not available. These grafts are subjected to deep freezing and stored at − 80 °C until further utilization. The goal of our investigation was to determine the effect of cryopreservation on the structure of vessel wall as a function of storage time, using freshly excised porcine aortic grafts. The samples were subjected to deep freezing and cryopreservation at − 80 °C. Following immediately, 1, 2, 4, 6, 8 and 12 weeks after cryopreservation, differential scanning calorimetry (DSC) and routine histological examination were performed, comparing the structure of frozen grafts to fresh, native aortic wall. Light microscopy evaluation did not show significant changes in the structure of aortic wall at different time points; however, DSC measurements demonstrated a systematic decrease in the thermal stability up to the 6th week and then improvement and stabilization regarding this parameter till the 12th week. Our histological data suggest that cryopreservation causes only minor alteration in the microstructure of fibres in the first three months; thus, the utilization of deep-freeze biological grafts with this short storage time could give favourable outcome.

Greening efforts and deteriorating inventory policies for price-sensitive stock-dependent demand

Ecological safety and greening efforts are the highly addressed challenge for business enterprises. Greening efforts are the steps that are taken to reduce the role of trade activities on nature, to guarantee environmentally friendly products. Greening efforts not only help to improve the quality but also tends to increase the profit level of the retailers. In this article, an inventory model for perishable products is formulated for price and stock-dependent demand rate along with greening efforts. Instead of constant purchase cost, the problem deals with order size-dependent purchase cost by assuming all-units quantity discounts. The holding cost is the function of storage time and unit purchase cost as it increases with time. The objective is to calculate the retailer’s profit function with respect to cycle time, selling price, and greening effort. An algorithm is developed to solve the feasible solution. The concavity of the feasible solution is proved through graphs. A numerical example is calculated and sensitivity analysis is done to signify the effect of inventory parameters on decision variables.

Physicochemical characterization, kinetic parameters, shelf life and its prediction models of virgin olive oil from two cultivars (“Arbequina” and “Moroccan Picholine”) grown in Morocco

This works aimed at investigating shelf-life behavior of extra virgin olive oil (EVOO) extracted from two cultivars “Arbequina” and “Moroccan Picholine” as a function of storage time (8 weeks) at accelerated conditions (60 °C). Our outcomes revealed significant variations between EVOOs from both cultivars in terms of the investigated physicochemical characteristics. These were also affected by storage time and temperature except for fatty acids, for which storage time had no significant effects. While the changes in tocopherols showed a drastic reduction ranging from 48.18 (“Moroccan Picholine”) to 62.62% (“Arbequina”). Indeed, the changes of quality indices showed a linear increase. Moreover, “Arbequina” oil was the first to exceed the established upper limits for EVOO label. An increase in oxidation rate was observed with increasing temperature when oils were oxidized at six elevated temperatures (373, 383, 393, 403, 413 and 423 °K) under Rancimat test conditions. The natural logarithms of the kinetic rate constant varied linearly with respect to temperature, with temperature coefficient (TCoeff) ranging from 7.31 × 10−2 in “Arbequina” to 7.51 × 10−2 K−1 found in “Moroccan Picholine”. This had higher oxidative stability and shelf life as compared to “Arbequina”. These outcomes were confirmed by kinetic parameters of oxidative stability including reaction rate constant as well as Arrhenius equation and thermodynamic parameters.

Quality Parameters of Wheat Bread with the Addition of Untreated Cheese Whey.

Τhe present study was carried out to evaluate wheat bread of three different flour compositions prepared by replacing water with untreated cheese whey (WCB). Bread prepared with water was taken as the control (CB). All breads were stored at 24 ± 1 °C for up to 6 days. Microbiological, physicochemical, and sensory analyses were determined as a function of storage time. WCB had lower total viable counts (TVC) (3.81 log cfu/g for CB and 2.78 log cfu/g for WCB on day 2 of storage) and showed delayed mold growth by 1 day (day 4 for CB and day 5 for WCB). WCB also had lower pH (5.91 for CB and 5.71 for WCB on day 0), higher titratable acidity values (TTA) (2.5–5.2 mL NaOH/10 g for CB and 4.5–6.8 mL NaOH/ 10 g for WCB), and higher protein content (PC) (PC 7.68% for CB and 8.88% for WCB). WCB was characterized by a more intense flavor, reduced hardness but similar cohesiveness, springiness, and adhesiveness compared to CB. Based primarily on sensory (appearance/mold formation) data, the shelf life of WCB was 4–5 days compared to 3–4 days for CB stored at 24 ± 1 °C. The proposed use of whey in bread preparation contributes decisively to the environmentally friendly management of whey.

Effect of Seasonal Storage on Single-Stem Bark Extractives of Norway Spruce (Picea abies)

Increasing the net value of forestry side-streams has both ecological as well as economic benefits for emerging biorefining industries. Spruce bark represents one of the nature’s abundant sources of valuable extractives. In this study, the impact of storage on the quality and quantity of Norway spruce (Picea abies) extractives was examined as a function of storage time, environmental conditions and season (i.e., winter or summer). The bark from stored spruce saw logs was extracted with an accelerated solvent extractor (ASE) at 120 °C with hexane and water. The produced extracts were analysed qualitatively and quantitatively by gas chromatography with a flame ionisation detector (GC-FID) and high-performance liquid chromatography (HPLC) methods. The total amount of phenolics in the water extracts was evaluated by the Folin–Ciocalteu method, while the carbohydrate and lignin content of the extractive-free bark was estimated by acidic hydrolysis and acidic methanolysis. According to the results, storage season and temperature dramatically influenced both the chemical composition and degradation rate of bark extractives. After a storage period of 24 weeks, the winter-stored saw log bark retained 22% more hydrophilic extractives than the summer-stored bark. Lipophilic extractives, however, were 14% higher during the summer. Notably, the average amount of monomeric stilbenoids was 61% higher during the winter storage period. The initial total phenolic content in the water extracts was significantly higher during winter, but the degradation rate was about equal during winter and summer. The amount of cellulose in dry bark decreased from 17% to 11% and from 13% to 6% during winter and summer, respectively. By contrast, hemicelluloses increased from 17% to 26% and 15% to 30% during winter and summer, respectively. Overall, it was demonstrated that the seasonal factors of storage greatly affected the degradation rate of valuable spruce bark extractives, which should be considered in the planning stages of the raw materials procurement chain.

Temperature-induced changes in polymer-based fractal patterns due to Ag metal aggregation

The present study throws light on the formation of silver fractal patterns when temperature treatment is given to the chitosan–AgNO3 solution for different temperatures and time periods. Temperature treatment results in both an enhanced degradation of the polymer (i.e., chitosan) and reduction rate of Ag+ ions to the silver particles. Small-sized clusters of silver particles form in the polymeric matrix, which were confirmed by ultraviolet–visible spectroscopy and scanning electron microscopy. Silver clusters aggregate giving different patterns due to the different temperature treatments. Changes in Fourier transform infrared spectra were invoked to explain the reduction of the Ag+ ions and the degradation mechanism of chitosan due to the temperature exposure. Degradation of chitosan due to temperature treatment results in a change in the viscosity. Viscosity measurements were taken by using an Ubbelohde viscometer for the chitosan–AgNO3 system as a function of storage time and temperature treatment time. A decrement in the viscosity was observed in all the cases, which confirms the degradation of chitosan both with and without complexation of salt (AgNO3). The degradation behavior of the polymer in different experimental conditions significantly modifies the aggregation patterns due to silver particles.

Characterization of Artisanal Spontaneous Sourdough Wheat Bread from Central Greece: Evaluation of Physico-Chemical, Microbiological, and Sensory Properties in Relation to Conventional Yeast Leavened Wheat Bread.

In the present study, both yeast leavened bread (YLB) and artisanal sourdough wheat bread (SDB) were prepared. The physico-chemical, microbiological, and sensory properties of breads were monitored as a function of storage time (T = 25 °C). As expected, the titratable acidity (TA) values of SDB were higher than those of YLB. The aroma profile of SDB was similar to that of YLB, including classes of compounds such as alcohols, aldehydes, ketones, esters, organic acids, terpenes, and sulfur compounds; however, the concentrations between the two were different. Aroma deterioration of bread during storage was partly related to the loss of several volatiles. Texture and sensory analysis showed that SDB was harder, less elastic, but richer in aroma and light sour taste than YLB. Mold growth was apparent when the population of yeasts/molds reached approximately 4 log cfu/g. This yeast/mold count was reached on days 4–5 for YLB and day 18 + for SDB. A 16S amplicon meta-barcoding analysis showed that the bacterial profile of SDB was dominated by a single genus, (Lactobacillus). Analysis of the eukaryotic load showed that at the genus level, Saccharomyces and Alternaria were the most abundant genera, independently of the gene sequenced (18S or ITS). Based primarily on mold growth and texture data, which proved to be the most sensitive quality parameters, the shelf life was ca. 4–5 days for YLB and 10 days for SDB.

Stability of Diazepam Solution for Injection Following Long-Term Storage in an Ambient Temperature of the Mediterranean Climate.

Diazepam is utilized as a convulsion antidote following nerve gas attacks. As an emergency medicine, it requires storage at ambient temperatures which often doesn't meet manufacturers' requirements, leading to an early invalidation of the product. Current work investigated this issue. Long-term stability of diazepam ampoules for injection stored in an ambient temperature of the Mediterranean climate for ~10years vs storage at room temperature was studied. Diazepam assay and pH remained within pharmacopeial specifications irrespective of storage conditions. A major degradation product 2-methylamino-5-chlorobenzophenone (MACB) showed a clear trend of accumulation as a function of storage time, exceeding the permitted limit at ~2years, irrespective of storage conditions. A strong correlation between the discoloration of the solutions and the concentration of MACB was obtained. Intravenous administration of MACB to rats at doses ~2200-fold higher than permissible specification levels caused neither mortality nor any toxicological nor post-mortem findings. Regarding the parameters tested: diazepam assay, MACB assay, and pH, storing ampoules of diazepam solution for injection in field conditions of high temperatures of the Mediterranean climate did not cause accelerated degradation as compared to room temperature. These findings open an option for the usage of expired ampoules in special scenarios.

Elemental characterization of sparkling wine and cork stoppers

The variations of the elemental concentrations in sparkling white wine and respective cork stoppers throughout 18 months of storage time were determined with the PIXE (Particle-Induced X-ray Emission) technique. Three portions of the cork stoppers were analyzed: the top part (external layer), the inner part (bulk layer) and the bottom layer (which was in contact with the sparkling wine). Elements such as Na, Mg, Si, P, S, Cl, K, Ca, Mn, Fe, Zn and Rb were determined for both cork stoppers and sparkling wine samples. Similar concentrations of Si, P, S, Cl and Ca were found in the external and bottom layers of the corks. Distinct behaviors of the changes in the elemental concentrations as a function of the time were observed for cork stoppers and sparkling wines. The concentrations of Mg, S, K, Ca, Cu, Sr and Ba increased in the bottom layer of the cork as a function of storage time. On the other hand, concentrations of Al, Si, Cl, Ti, Zn and Br proved to be invariant, while the concentrations of P and Fe showed a slight decrease. Concerning the sparkling wine, an increasing trend of elemental concentrations was observed for most elements throughout the storage time. A diffusion mechanism of elements in the cork and the role of the secondary fermentation in the bottle are discussed.

How Long are Residual Newborn Screening Specimens Useful for Retesting when Stored in Suboptimal and Uncontrolled Conditions of Temperature and Humidity?

Residual DBS specimens from newborns diagnosed with Phenylketonuria, Congenital Hypothyroidism, Cystic Fibrosis, Congenital Adrenal Hyperplasia and Galactosemia collected within 1995-2018, stored in cardboard boxes at ambient temperature in uncontrolled conditions, were retested for phenylalanine (Phe), thyrotropin (TSH), immunoreactive trypsinogen (IRT), total galactose (TGal) and 17-hydroxyprogesterone (17OHP), to demonstrate how long are they stable in these conditions and useful to reconfirm a previous abnormal result. Recovery percentage at retesting and qualitative interpretation regarding the current cutoff were evaluated. Phe, TSH and IRT recoveries showed decreasing trends along time. Phe recovery was 64 % after 2-years storage; TSH decayed rapidly recovering 47.3 % at 1-year, while IRT showed recoveries of 60 % at 1-year. Although 17OHP recovery presented a wide variation of results, a decaying trend was also found. Results suggest 17OHP is more stable than TSH and IRT, as supported by recoveries > 71 % when stored ≤ 2-years. TGal recovery presented an erratic behavior, so that it was not possible to estimate expected concentrations as a function of storage time. TGal recoveries above 100 % were found in UDP-galactose-4-epimerase and galactose-1-phosphate uridyltransferase deficiencies, evidencing possible galactose liberation from other sources. These results make a very valuable contribution for programs storing residual DBS in uncontrolled conditions.

Stability of vitamin C in broccoli based on the chemical reaction kinetics, micro-region state diagram, and empirical correlations

ABSTRACT Vitamin C degradation of broccoli at different moisture and temperature was measured as a function of storage time and modeled by first-order reaction kinetics. The variation of rate constant was analyzed based on the activation energy, glass transition, BET-monolayer, micro-region state diagram, and empirical correlations. Three domains of chemical reactions were observed as a function of temperature. In the case of broccoli with freezable water (i.e. moist), the first critical temperature (i.e. Tc ) was observed at −20°C (Tc /Tg ′′′: 0.829), which was close to the Tg ′′′ (i.e. experimental ultimate maximal-freeze-concentration glass transition) (−32.2°C); while second critical temperature (i.e. Ts ) was observed at 60.0°C (i.e. Ts /Tg ′′′: 1.383). The activation energy values were 13.6, 75.0, and 43.6 kJ/mole for the phase 1 (moist-glassy), phase 2 (moist-glassy-rubbery) and phase 3 (moist-rubbery-flow), respectively. In the case of frozen-broccoli with un-freezable water, the first critical temperature (i.e. Tc ) was observed at 5°C (Tc /Tgi : 1.021), which was close to the Tgi (onset glass transition) (−0.8°C); while the second critical temperature (i.e. Ts ) was observed at 70.0°C (i.e. Ts /Tgi : 1.260). The second critical temperature was close to the mechanical glass transition temperature. The activation energy values were 13.1, 69.6, and 72.4 kJ/mole for phase 1, phase 2 and phase 3, respectively. Each experimental rate constant was located in the micro-regions of the state diagram. Principal component analysis showed that reaction rates can be grouped into different micro-regions, except one data point in the micro-region 12. This could be due to the wider domain of this region and further sub-micro-regions could be defined. Finally, empirical correlations were developed as dimensionless moisture, temperature, and rate constant, and explored the possibility of developing a generic universal equation.

Effect of oleogelation on physical properties and oxidative stability of camellia oil-based oleogels and oleogel emulsions

In this work, the camellia oil-based oleogels and O/W oleogel emulsions were prepared with glycerol monolaurate (GML) as an oleogelator, which had a critical gelation concentration of 3 wt%. Results showed that with the increasing GML concentration, a more densely needle-like morphology was formed by the network of GML crystals within the oil, presenting the enhanced thermal stability due to the occurrence of van der Waals interactions and intermolecular hydrogen bonds. In turn, a more compact three-dimensional network was obtained in the emulsions with a larger droplet size, leading to a transition from a predominately elastic to viscous state. Moreover, a lower oxidation rate was observed by the POV and TBARS values as a function of storage time in either the oleogels or oleogel emulsions, indicating a better oxidative stability. These results contribute to a better understanding of oleogelation in camellia oil-based oleogels and oleogel emulsions for formulating food, pharmaceutical and person care products with desired physical properties and oxidative stability.