Headspace Atmosphere Research Articles

A hurdle strategy based on the combination of non-thermal treatments to control diarrheagenic E. coli in cheese

This study aimed to assess the efficacy of a multi-hurdle process combining mild High Hydrostatic Pressure (HHP) treatments and Thyme Oil (TO) edible films as a non-thermal method to combat pathogenic E. coli (aEPEC and STEC) in raw cow's-milk cheese stored at 7 °C and packaged under modified atmosphere. Changes in headspace atmosphere of cheese packs and treatment effects on Lactic Acid Bacteria (LAB) counts and diarrheagenic E. coli strains (aEPEC and STEC) were evaluated over a 28 d storage period. The results demonstrated that the combined treatment exhibited the most significant antimicrobial effect against both strains compared to individual treatments, achieving reductions of 4.30 and 4.80 log cfu/g after 28 d of storage for aEPEC and STEC, respectively. Notably, the synergistic effect of the combination treatment resulted in the complete inactivation of intact cells for STEC and nearly completed inactivation for aEPEC by the end of the storage period. These findings suggest that the combination of HHP with selected hurdles could effectively enhance microbial inactivation capacity, offering promising alternatives for improving cheese safety without affecting the starter microbiota.

Effect of modified atmosphere package on attributes of sweet bamboo shoots after harvest.

Tender bamboo shoots undergo rapid senescence that influences their quality and commercial value after harvest. In this study, the tender sweet bamboo shoots ('Wensun') were packed by a passive modified atmosphere packaging (PMAP) to inhibit the senescence process, taking polyethylene package as control. The increase in CO2 and the decrease in O2 gas concentrations in the headspace atmosphere of the packages were remarkably modified by PMAP treatments. The modified gas atmosphere packaging inhibited the changes in firmness, as well as the content of cellulose, total pectin, and lignin in the cell walls of bamboo shoots. The enzymatic activities of cellulase, pectinase, and polygalacturonase that act on cell wall polysaccharides, and phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, peroxidase, and laccase regulating the lignin biosynthesis were modified by PMAP treatment different from control during storage. The expression levels of the lignin biosynthesis genes PePAL3/4, PeCAD, Pe4CL5, PeC4H, PeCCOAOMT, PeCOMT, cellulose synthase PeCESA1, and related transcription factors PeSND2, PeKNAT7, PeMYB20, PeMYB63, and PeMYB85 were clearly regulated. These results suggest that PMAP efficiently retards the changes in lignin and cell wall polysaccharides, thus delaying the senescence of tender sweet bamboo shoots during storage.

A model integrating fruit physiology, perforation, and scavenger for prediction of ethylene accumulation in fruit package

The modelling of headspace atmosphere (O2, CO2), relative humidity, condensation, and shelf life of packaged fresh produce has been extensively reported. However, there has been a lack of effort in modelling ethylene (C2H4) accumulation within the packaging or storage environment. This study aimed to address this significant research gap by developing a model for the prediction of C2H4 accumulation within fruit package. This model integrated fruit physiology, gas transmission through perforation, and C2H4 removal by a scavenger made up of KMnO4. The experimental validation was conducted using packaged avocados, encompassing various storage conditions, package (perforation), scavenger, and fruit parameters. The use of perforation effectively maintained C2H4 accumulation below 2 µL L−1 in the avocado package for 12 days within the temperature range of 5 to 25ºC. Moreover, the scavenger successfully kept C2H4 accumulation below 1 µL L−1 within just 8 h for all experimental conditions. The scavenger demonstrated a higher efficacy in C2H4 removal compared to perforation, achieving a complete removal. The level of accuracy through statistical parameters underscores the acceptability and reliability of the model in predicting C2H4 accumulation in fruit package. The model was used to optimize the perforation size according to the required equilibrium O2 and C2H4 accumulation in the avocado package.

Texture design of gluten-free bread by mixing under controlled headspace atmosphere

Gluten-free breads often show a reduced specific bread volume, in comparison to gluten-containing products, caused by non-adapted processing technologies of gluten-free dough. In this investigation, different mixing speeds and durations (600–3000 rpm for 3 min, 5 min or 8 min, respectively) as well as variations in the pressure (prel – 50 to prel + 130 kPa) in the headspace atmosphere during mixing (Stephan mixer) and pressure ratios of overpressure/negative pressure of 8 min mixing (20/80, 50/50, 80/20) were studied to determine their impact on the gas volume fraction of dough and specific volume of breads. A pressure rise of prel 50 kPa, prel 100 kPa or prel 130 kPa increased the gas volume fraction in dough of 60%, 100% or 120%, respectively, and led to a significant higher specific bread volume (7%) and the reduction of crumb hardness (35%) at prel 130 kPa. A linear correlation (R2 = 0.843) between the pressure and specific volume of breads was found. An extended first mixing phase at overpressure resulted in the formation of a very fine pore structure, whereby a short overpressure phase caused the formation of big pores. Thus, the control of the headspace atmosphere during mixing is a suitable parameter to adjust the density of dough and consequently, the pore size distribution for a specific texture design.

In vitro toxic synergistic effects of exogenous pollutants-trimethylamine and its metabolites on human respiratory tract cells

The wide presence of volatile organic amines in atmosphere has been clarified to relate to adverse effects on human respiratory health. However, toxic effects of them on human respiratory tract and their metabiotic mechanism of in vivo transformation have not been elucidated yet. Herein, cell viability and production of reactive oxygen species (ROSs) were first investigated during acute exposure of trimethylamine (TMA) to bronchial epithelial cells (16HBE), along with identification of toxic metabolites and metabolic mechanisms of TMA from headspace atmosphere and cell culture. Results showed that cell activity decreased and ROS production increased with raising exposure TMA concentration. Toxic effects may be induced not only by TMA itself, but also more likely by its cellular metabolites. Increased dimethylamine identified in headspace atmosphere and cell solution was the main metabolite of TMA, and methylamine was also confirmed to be a further metabolite. In addition, TMA can also be oxygenated to generate N,N-dimethylformamide and N,N′-Bis(2-hydroxyethyl)-1,2-ethanediaminium by N-formylation or hydroxylation, which was considered to be the participation of cytochrome P450 (CYP) enzymes. Overall, we can conclude that respiratory tract cells may produce more toxic metabolites during exposure of toxic organic amines, which together further induce cellular oxidative stress and necrosis. Hence, the environment and health impact of metabolites as well as original parent atmospheric organic amines should be paid more attention in further researches and disease risk assessments.

Application of passive modified atmosphere packaging in the preservation of sweet corns at ambient temperature

The purpose of this study was to design a passive modified atmosphere packaging (PMAP) to effectively extend the shelf-life of fresh sweet corn under ambient temperatures. Oxygen permeable film (OPF) and water vapor permeable film (WPF) of different areas were used to prepare the PMAPs. By changing the areas of the OPF and WPF, different headspace atmospheres could be created in the PMAPs, and the effects of different atmospheres on the quality of sweet corn could be evaluated. The experiments were carried out under the temperature conditions of 25 ± 1 °C and relative humidity conditions of 60 ± 5%. The headspace gas, weight loss rate, hardness, total soluble solids content, total acid content, vitamin C content, and sensory quality were measured daily. The results showed that when the proportional area of WPF was 80%–85% and OPF was 15%–20%, the PMAP created a suitable atmosphere for fresh sweet corn, extending the shelf-life to 5 days at ambient temperature.

Effect of perforation-mediated modified atmosphere packaging on the quality and bioactive compounds of soft kale (Brassica oleracea L. convar. acephala (DC) Alef. var. sabellica L.) during storage

Abstract Perforation-mediated modified atmosphere packaging of soft kale (Brassica oleracea L. convar. acephala (DC) Alef. var. sabellica L.) was investigated to maintain freshness at 10 °C for 12 d. Kale was sealed in micro-perforated pouches with different oxygen transmission rates (OTRs: mL m–2 d–1 atm–1) at 1.66 × 106, 3.0 × 103 or 64. Headspace atmospheres (O2/CO2) of pouches at OTR 1.66 × 106, 3.0 × 103 and 64 were 21 %/0 % (normoxia), 1.9∼7.4 %/8.5∼9.6 % (modified atmosphere) and 0 %/> 20 % (hypoxia), respectively. Hue angles (degree of green color) of leaves in the OTR 3.0 × 103 and 64 pouches were significantly higher than that in the OTR 1.66 × 106 pouch. However, carotenoid and ascorbic acid concentrations in the leaf in the OTR 3.0 × 103 pouch was significantly higher than that in the OTR 64 pouch. The modified atmosphere created in the OTR 3.0 × 103 pouch was suitable for maintaining external (green color) and internal (bioactive compounds) qualities of soft kale.

Diversity and anaerobic growth of Pseudomonas spp. isolated from modified atmosphere packaged minced beef.

This study aimed to monitor development of spoilage-associated microbiota on high-oxygen modified atmosphere packaged (MAP) minced beef, assess diversity of Pseudomonas sp. therein employing a polyphasic approach and probe their ability to grow anaerobically in the presence of carbon dioxide. Headspace atmosphere and total viable count of MAP minced beef were monitored, and spoilage-associated microbiota was identified using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Pseudomonas spp. represented a major part of the spoilage-associated microbiota throughout the spoilage process and were characterized with a polyphasic approach including MALDI-TOF, randomly amplified polymorphic DNA biotyping, 16S rDNA and rpoD sequence analysis, and carA multiplex polymerase chain reaction. Pseudomonas isolates displayed high diversity and varying assertiveness under conditions employed in MAP minced beef with P. fragi, P. lundensis and P. weihenstephanensis as dominant species. The polyphasic approach enabled high-throughput characterization of Pseudomonas sp. Their adapted capability to grow anaerobically and resistance to high levels of CO2 is suggested to be a general feature within the genus, which is hitherto underexplored. This study shows that diverse Pseudomonas generally regarded as strict aerobes and CO2 -sensitive appear well adapted to grow under MAP conditions, leading to high cell counts in minced beef and ultimately contribute to spoilage of the product.

GC-MS application in determination of volatile profiles emitted by infected and uninfected human tissue

Volatile organic compounds (VOCs) released into the headspace air over human tissues infected with different bacteria were investigated in this work. The above-mentioned VOCs result both from bacterial metabolic processes (pathogen-specific signals) and from the matrix (tissue samples themselves). The objective of this study was to investigate whether one could reliably identify various microorganism strains that exist inside infected tissue samples by direct monitoring of the headspace atmosphere above their cultures. Headspace samples were directly interrogated using a GC-MS system, which produced distinct profiles for samples contaminated with single bacterial strains or with multiple strains (mixed infections). Principal component analysis (PCA) and predictive analysis based on receiver operating characteristics curves (ROC) were the statistical procedures utilized for differentiating between infected and uninfected samples, while network analysis and heat-mapping were used to highlight the connections between emitted volatiles and infectious pathogens. By using ROC curves, obtained results demonstrated that the area under the ROC (95% probability interval) was 0.86 in case of infected samples and 0.48 for uninfected samples. On the other hand, PCA highlighted separation between components coming from infected and uninfected patients, where 67% of variance was described from the first 2 principal components. The biomarker chemicals documented from this work, as well as the developed methodology may ultimately be applied to identify bacterial infections by analyzing exhaled breath.

A simple device for headspace sorptive extraction prior to gas chromatography–mass spectrometry analysis

A device for headspace sorptive extraction (HSSE) combined with gas chromatography separation and mass spectrometry detection (GC–MS) is presented. The gadget is based on a simple magnetic disk that permits the stir bar to be placed at the top of the sample vial. The complete surface of the coated stir bar is exposed to the headspace atmosphere, and the movement of the bar caused by the magnetic stirrer in the liquid sample facilitates the sorption process. The final consequence is increased sensitivity and repeatability when compared with a glass-made comercial device for the same purpose. Successful determination of ten chlorobenzenes in waters testifies the good performance of the new device.

Biomass-based edible film with enhanced mass barrier capacity and gas permeable selectivity

Edible films with desired mass transport properties have been receiving much attention for commercial packaging. In this paper, a modified nanofiltration setup using dialysis membrane was developed for the preparation of biomass-based edible (BE) film. The prepared films are effective barriers to oxygen by discriminating the molecular size and relative affinity between gas and film polymer matrix. Compared to the control film (co-blended film without the use of modified nanofiltration setup), the BE film possessed an enhanced gas/water vapor barrier effect and mechanical strength. In addition, the gas permeable selectivity [permeability ratio of CO2–O2 ( $${{{\text{P}}_{{({\text{CO}}_{2} )}} } \mathord{\left/ {\vphantom {{{\text{P}}_{{({\text{CO}}_{2} )}} } {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}} \right. \kern-0pt} {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}$$ )] was improved, which is beneficial for inhibiting the respiration rate. This was further confirmed by the fruits [Apricots (cv. Beijing Crystal)] respiration experiments. SEM results revealed a more uniform and smooth surface of the BE film with a compact lamellar cross section structure caused by the suction effect of the dialysis membrane. An increased optical transmittance (T600) and decreased swelling capacity were further obtained. Three-dimensional modeling of schematic diagram for the enhanced gas selectivity ( $${{{\text{P}}_{{({\text{CO}}_{2} )}} } \mathord{\left/ {\vphantom {{{\text{P}}_{{({\text{CO}}_{2} )}} } {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}} \right. \kern-0pt} {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}$$ ) of the BE film is presented, and the pore-suction layer is the functional layer. A modified nanofiltration setup was developed by using dialysis membrane for the preparation of biomass-based edible (BE) film. The prepared film, constitutes of methylcellulose (continuous phase) and cellulose nanocrystals (discontinuous phase), has a compact lamellar cross section structure with improved optical transmittance (T600). The BE film can be appraised as an effective barrier to mass transportation by discriminating the molecular size and relative affinity between the gas and polymer matrix. The improved mechanical strength/gas permeable selectivity [permeability ratio of CO2–O2 ( $${{{\text{P}}_{{({\text{CO}}_{2} )}} } \mathord{\left/ {\vphantom {{{\text{P}}_{{({\text{CO}}_{2} )}} } {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}} \right. \kern-0pt} {{\text{P}}_{{\left( {{\text{O}}_{2} } \right)}} }}$$ )] is beneficial for modifying the package’s quality and its headspace atmosphere.

Efficacy of limonene nano coatings on post-harvest shelf life of strawberries

Strawberries are highly demanded fruits because of their color, nutritional values and appearance. The aim of this study was to develop and characterize alginate and limonene liposomes as edible coating materials and to determine their efficacy in shelf life extension and maintaining quality parameters of ‘Chandler’ strawberries. Alginate solution (1.5% w/v) and Limonene liposomes prepared from 80% lecithin and 20% PDA were used as edible coating materials. Fungal decay percentage, total yeast and mold counts, headspace atmosphere analysis, total soluble solids, pH, titratable acidity, total anthocyanin content and total phenolics were analyzed to assess fruit quality during 14 days at 4 °C of storage. Days of storage was found to be significant in maintaining the quality of the strawberries. Among the coating types, limonene liposomes were found to be significantly more effective in maintaining the lower concentration of carbon dioxide (CO2), lower the change in pH (3.9), and had higher total anthocyanin (43.85) content during storage than those without a liposomal coating. Thus, limonene liposomes were found to be useful for extending the shelf life and maintaining quality of strawberry fruits.

Light barrier properties of extra virgin olive oil (EVOO) glass bottles—Effect of glass colour and decoration

The aim of this study was to evaluate the quality of some glass bottles used for extra virgin olive oil (EVOO) related to light barrier properties, including clear and coloured glass in different colour intensities, glass with shrink labels, and external ceramic decoration. Some of these glass bottles available on the Brazilian market were also evaluated for closure integrity and barrier to oxygen, headspace gas atmosphere, and the quality of the product according to legislation. An increase in light barrier properties was observed for the darkest glass bottle that depends on the pigment quantity and the wall thickness. A total light barrier was obtained for glass with black shrink labels and external ceramic decoration. Closure systems used for the analysed packaging showed good integrity and low oxygen permeability, and the inertness of headspace atmosphere ensured a lower availability of oxygen for product oxidation. In general, the products met the requirements imposed in the legislation.

Monitoring of spoilage-associated microbiota on modified atmosphere packaged beef and differentiation of psychrophilic and psychrotrophic strains.

This study aimed to explore the discriminatory power of MALDI-TOF MS as a high-throughput method to monitor growth dynamics of meat-spoiling bacteria on modified atmosphere packaged (MAP) beef and to differentiate psychrophilic and psychrotrophic spoilage-associated strains. MAP beef steaks were incubated for 21days at constant 4 and 10°C. Development of headspace gas composition, pH, CFU and spoilage-associated microbial composition were monitored. MALDI-TOF MS exhibited high discriminatory power for reliable, high-throughput identification of spoilage-associated, psychrotrophic microbiota. Microbiota development was highly dependent on initial abundance of specific species. Organoleptic onset of spoilage was concomitant with an alteration of headspace atmosphere and pH. Screening for psychrophiles at 4°C on beef revealed the abundance of Leuconostoc gelidum subsp. gelidum TMW2·1998 with characteristic psychrophilic growth behaviour. We suggest that control of initial contaminants is crucial to predict the onset of spoilage and that headspace atmosphere and pH are important parameters with spoilage-indicative potential. MALDI-TOF MS proved suitable for high-resolution monitoring of psychrotrophic and psychrophilic spoilage-associated microbiota and enables improved insights in the spoilage progress. The presence of psychrophilic strains on beef is the likely causative for unexplained spoilage events.

Characterization of an innovative device controlling gaseous exchange in packages for food products

The work describes both the characterization carried out and the experimental results from an innovative device allowing the gas exchange across a sealed package. The device is especially suitable for fresh fruit and vegetable preservation during cold storage, as it allows for the management of the headspace atmosphere inside sealed packages containing food products presenting metabolic activity.Characterization results confirm the device's suitability for managing the bidirectional gas flow. For each tested device, the hydro-dynamical parameter and the diffusion parameter have been measured to define its steady-state behaviour. The steady-state gas concentrations reached in the package show the aptness of the devices for use with specific products; these equilibrium gas concentrations depend on the device type and on the mass of product contained in the package.The results of simulated storage demonstrate that some products (pomegranate arils and table grapes) require preconditioning of the package free volume to reach the optimal gas concentrations in a short time. Other products (black truffle) with very high metabolic activity could reach the optimal condition without package preconditioning depending on the free volume.

Discrimination of bacteria by rapid sensing their metabolic volatiles using an aspiration-type ion mobility spectrometer (a-IMS) and gas chromatography-mass spectrometry GC-MS

The objective of our study was to investigate whether one may quickly and reliably discriminate different microorganism strains by direct monitoring of the headspace atmosphere above their cultures. Headspace samples above a series of in vitro bacterial cultures were directly interrogated using an aspiration type ion mobility spectrometer (a-IMS), which produced distinct profiles (“fingerprints”) of ion currents generated simultaneously by the detectors present inside the ion mobility cell. Data processing and analysis using principal component analysis showed net differences in the responses produced by volatiles emitted by various bacterial strains. Fingerprint assignments were conferred on the basis of product ion mobilities; ions of differing size and mass were deflected in a different degree upon their introduction of a transverse electric field, impacting finally on a series of capacitors (denominated as detectors, or channels) placed in a manner analogous to sensor arrays.Three microorganism strains were investigated – Escherichia coli, Bacillus subtilis and Staphylococcus aureus; all strains possess a relatively low pathogenic character. Samples of air with a 5 cm3 volume from the headspace above the bacterial cultures in agar growth medium were collected using a gas-tight chromatographic syringe and injected inside the closed-loop pneumatic circuit of the breadboard a-IMS instrument model ChemPro-100i (Environics Oy, Finland), at a distance of about 1 cm from the ionization source. The resulting chemical fingerprints were produced within two seconds from the moment of injection. The sampling protocol involved to taking three replicate samples from each of 10 different cultures for a specific strain, during a total period of 72 h after the initial incubation – at 24, 48 and 72 h, respectively. Principal component analysis (PCA) was used to discriminate between the IMS fingerprints. PCA was found to successfully discriminate between bacteria at three levels in the experimental campaign: 1) between blank samples from growth medium and samples from bacterial cultures, 2) between samples from different bacterial strains, and 3) between time evolutions of headspace samples from the same bacterial strain over the 3-day sampling period. Consistent classification between growth medium samples and growth medium inoculated with bacteria was observed in both positive and negative detection/ionization modes.In parallel, headspace air samples of 1 dm3 were collected from each bacterial culture and loaded onto Tenax™-Carbograph desorption tubes, using a custom built sampling unit based on a portable sampling pump. One sample was taken for each of 10 different cultures of a strain, at 24, 48 and 72 h after the initial incubation. These adsorption tubes were subsequently analyzed using thermal desorption – gas chromatography – mass spectrometry (TD-GC-MS). This second dataset was intended to produce a qualitative analysis of the volatiles present in the headspace above the bacterial cultures.

A study of CO/syngas bioconversion by Clostridium autoethanogenum with a flexible gas-cultivation system.

Bioconversion of CO/syngas to produce ethanol is a novel route in bioethanol production, which can be accomplished by some acetogens. Specific culture vessels and techniques are needed to cultivate these microorganisms since they are anaerobic and substrates are gaseous. In this work, gas-sampling bag was applied as a gas-cultivation system to study CO/syngas bioconversion by Clostridium autoethanogenum and was demonstrated to be efficient because of its flexibility and excellent ability to maintain the headspace atmosphere. C. autoethanogenum can use CO as the sole carbon and energy source to produce ethanol, acetate as well as CO2. In the experimental range, higher ethanol production was favored by higher yeast extract concentrations, and the maximum ethanol concentration of 3.45g/L was obtained at 1.0g/L of yeast extract. Study with various bottled gases showed that C. autoethanogenum preferred to use CO other than CO2 and produced the highest level of ethanol with 100% CO as the substrate. C. autoethanogenum can also utilize biomass-generated syngas (36.2% CO, 23.0% H2, 15.4% CO2, 11.3% N2), but the process proceeded slowly and insufficiently due to the presence of O2 and C2H2. In our study, C. autoethanogenum showed a better performance in the bioconversion of CO to ethanol than Clostridium ljungdahlii, a strain which has been most studied, and for both strains, ethanol production was promoted by supplementing 0.5g/L of acetate.

Response of Deep Subsurface Microbial Community to Different Carbon Sources and Electron Acceptors during ∼2 months Incubation in Microcosms.

Acetate plays a key role as electron donor and acceptor and serves as carbon source in oligotrophic deep subsurface environments. It can be produced from inorganic carbon by acetogenic microbes or through breakdown of more complex organic matter. Acetate is an important molecule for sulfate reducers that are substantially present in several deep bedrock environments. Aceticlastic methanogens use acetate as an electron donor and/or a carbon source. The goal of this study was to shed light on carbon cycling and competition in microbial communities in fracture fluids of Finnish crystalline bedrock groundwater system. Fracture fluid was anaerobically collected from a fracture zone at 967 m depth of the Outokumpu Deep Drill Hole and amended with acetate, acetate + sulfate, sulfate only or left unamended as a control and incubated up to 68 days. The headspace atmosphere of microcosms consisted of 80% hydrogen and 20% CO2. We studied the changes in the microbial communities with community fingerprinting technique as well as high-throughput 16S rRNA gene amplicon sequencing. The amended microcosms hosted more diverse bacterial communities compared to the intrinsic fracture zone community and the control treatment without amendments. The majority of the bacterial populations enriched with acetate belonged to clostridial hydrogenotrophic thiosulfate reducers and Alphaproteobacteria affiliating with groups earlier found from subsurface and groundwater environments. We detected a slight increase in the number of sulfate reducers after the 68 days of incubation. The microbial community changed significantly during the experiment, but increase in specifically acetate-cycling microbial groups was not observed.

Optimization of Temperature, Relative Humidity and Storage Time before and after Packaging of Baby Spinach Leaves Using Response Surface Methodology

Second-order polynomial models were used to relate the independent variables, temperature, relative humidity and storage time, to the quality attributes (electrolyte leakage, chlorophylls, weight loss, humidity and headspace gas composition inside packages before and after packaging) of ready-to-eat spinach leaves. Results show that while waiting for processing the best conditions to assure high quality spinach leaves before packaging were 4 °C, 83 % RH and 4 h. The weight loss of spinach leaves was time-dependent: increasing the exposure time under these conditions decreased the amount of wet leaves before packaging. Under the same conditions, the electrolyte leakage was lower (4.63 %) and the chlorophyll content (45.44) was higher. After packaging and while waiting for dispatch, temperature most affected the package headspace atmosphere. Indeed, an increase in storage temperature from 3 to 7 °C led to a significant increase in respiration. The best combination of conditions in the high-care room was 3 °C, 74 % relative humidity for a maximum of 1 day before dispatch. In this case, the moisture content (0.46 %) and electrolyte leakage (4.16 %) were lower and the chlorophyll content (43.37) and oxygen concentration inside the packages of ready-to-eat spinach leaves (19.55 kPa) were higher.

Quality evaluation of hot peppers stored in biodegradable poly(lactic acid)-based active packaging

The effect of poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL)/thymol(TH) composite film, PLA/PCL film, and polyethylene (PE) film on the microbial and physicochemical quality of hot pepper (Capsicum frutescens L.) stored at 4±1°C for 28 days was studied. The measured properties of hot peppers included weight loss, color, firmness, headspace atmosphere in package, vitamin C, total phenolic content, microbial, and sensory quality. The results indicated that the PLA/PCL/TH packaging can retard the harmful change of microbial, weight loss, anaerobic respiration, firmness, vitamin C, total phenolic content, and sensory quality. The color of hot peppers did not show significant (p<0.05) changes during the whole storage time. The results suggested that the PLA/PCL/TH composite film could maintain the quality of fresh hot peppers and extend its postharvest life.