Modified Atmosphere Conditions Research Articles

Production of Volatile Sulfur Compounds in Polyethylene Film Packaged Broccoli Held at Different Temperatures

The production of volatile sulfur compounds in modified atmosphere of packaged broccoli was investigated. Broccoli heads were sealed in 0.03-mm-thick low density polyethylene film and held at 10, 20 or 30ºC for 72 h. Nonpackaged heads were also stored at the same temperatures. In the package held at 30ºC, O2 and CO2 concentrations were less than 1% and more than 19%, respectively, and methanethiol was detected within 6 h. In the package held at 20ºC, O2 and CO2 concentrations were less than 0.4% and more than 17%, respectively, and methanethiol was detected within 18 h. The percentage of electrolyte leakage from packaged broccoli held at 20ºC and 30ºC increased to a greater extent than that of nonpackaged broccoli during storage. However, storing the packaged broccoli at 10ºC created a favorable modified atmosphere condition of around 3% O2 and 10% CO2 inside the package. In this condition volatile sulfur compounds were not detected and no significant change was observed in percentage of electrolyte leakage. At all temperatures, total chlorophyll contents were higher in packaged broccoli than in nonpackaged broccoli. These results indicate that, volatile sulfur compounds such as methanethiol were formed when the atmosphere inside the package had extremely low O2 and high CO2 even if broccoli was green and the visual quality had not deteriorated.

Effect of modified atmosphere packaging on the quality of minimally processed pineapple cv. ‘Smooth Cayenne’ fruit

SummaryThe effects of modified atmosphere (MA) conditions on the quality of minimally processed pineapple slices were determined. Commercial pineapple slice packs sealed with 40 μm thick polyester film were kept at 4.5°C for 14 d. The oxygen transmission rate of the film was 23 ml m–2 day–1 atm–1 (at 25 °C, 75% RH). In-built atmospheres and the quality of the products were determined. O2 concentrations within the packs stabilised at 2%, while CO2 concentrations increased to 70% by day 14. The high CO2 level suggested an inappropriate lidding film permeability for the product, and hence affected its quality. Three batches of pineapple slices were packed in the laboratory using lidding films with oxygen transmission rate of 75, 2790 or 5000 ml m–2 day–1 atm–1 (at 23°C, 0% RH). Headspace atmospheres from laboratory-packed pineapple slices suggested an optimum equilibrium modified atmosphere of ca. 2% O2 and 15% CO2. Respiration data from the laboratory-prepared packs were pooled together and used to develop a correlation model relating respiration rates to O2 and CO2 concentrations. The model showed a decrease in respiration rate with decreasing O2 and increasing CO2 concentrations. Respiration rate stabilised at 2% O2 and 10% CO2. The high concentrations of CO2 observed in the commercial packs did not fit the range in the respiration model. The model could aid in selection of MA conditions for minimally processed pineapple fruit.

Effect of natural variability among apples on the accuracy of VIS-NIR calibration models for optimal harvest date predictions

The prediction of the optimal harvest date of apples is of high importance as it controls the fruit quality after long-term storage in cooled and modified atmosphere conditions. As the present methodology to determine these dates is very time-consuming, the use of visible and near infrared (VIS-NIR) spectroscopy was examined to speed up the measurements. The root mean square error of prediction (RMSEP) of the near-infrared calibration models for the prediction of the optimal harvest date of individual fruit ranged, depending on the cultivar, from 5 to 9 days. In practice, the average prediction values of sample batches are used to predict optimal harvest dates of individual orchards rather than on a per fruit basis, and the accuracy of the calibration models then increases considerably. The accuracy of the calibration models to predict the optimal harvest date relative to the natural variability of the maturity of individual fruit has been assessed based on an analysis of the per fruit Streif index, a maturity index. The standard deviation of the physiological maturity defined as the days until the optimal picking date ranged from 2 to 8 days in 1999 and from 5 to 12 days in 2000 and was, therefore, of the same order of magnitude as the RMSEP of the VIS-NIR calibration models. As expected, the accuracy of the calibration models was better when the natural variability of the maturity between fruit was small and vice versa. The calibration models for Streif index were not very accurate, even after applying a logarithmic transformation.

Radiosensitization of Escherichia coli and Salmonella Typhi in Ground Beef

The radiosensitization of two pathogenic bacteria, Escherichia coli and Salmonella Typhi, was evaluated in the presence of thyme and its principal essential oil constituents (carvacrol and thymol) in ground beef. Ground beef was inoculated with E. coli or Salmonella Typhi (105 CFU/g), and each compound was added separately at various concentrations (0 to 3.5%, wt/wt). The antimicrobial potential of carvacrol, thymol, and thyme was evaluated in unirradiated meat by determining the MIC in percentage (wt/wt) after 24 h of storage at 4 ± 1°C. Results showed a MIC of 0.88 ± 0.12%, 1.14 ± 0.05%, and 2.33 ± 0.32% for E. coli in the presence of carvacrol, thymol, and thyme, respectively. MICs of 1.15 ± 0.02%, 1.60 ± 0.01%, and 2.75 ± 0.17% were observed for Salmonella Typhi in the presence of the same compounds, respectively. The best antimicrobial compound (i.e., carvacrol) was selected and added to the sterilized ground beef along with ascorbic acid (0.5%, wt/wt) and tetrasodium pyrophosphate (0.1%, wt/wt). Meat samples (10 g) were packed in air and then irradiated in a 60Co irradiator at doses of 0 to 0.7 kGy for the determination of E. coli radiation D10 and 0 to 2.25 kGy for the determination of Salmonella Typhi radiation D10. Addition of carvacrol increased the relative sensitivity of both bacteria 2.2 times. The radiation D10 was reduced from 0.126±0.0039 to 0.057±0.0015 kGy for E. coli and from 0.519±0.0308 to 0.235±0.0158 kGy for Salmonella Typhi. The addition of tetrasodium pyrophosphate did not affect significantly (P > 0.05) the radiosensitization of either bacterium. However, the presence of ascorbic acid in the media reduced significantly (P ≤ 0.05) the radiosensitivity of both bacteria. An additive effect of carvacrol addition and packaging under modified atmosphere conditions (60% O2–30% CO2–10% N2) was also observed on bacterial radiosensitization at 4°C. Compared with the control packed under air, modified atmosphere packaging conditions in the presence of carvacrol and tetrasodium pyrophosphate improved the relative sensitivity of E. coli by 2.7 times and Salmonella Typhi by 9.9 times.

Microbial and quality changes in minimally processed baby spinach leaves stored under super atmospheric oxygen and modified atmosphere conditions

The effect of super atmospheric O2 and modified atmosphere packaging (MAP) on plant metabolism, organoleptic quality and microbial growth of minimally processed baby spinach was studied. Packaging film O2 transmission rates and initial levels of super atmospheric O2 in the packages significantly affected the changes of in-package atmospheres during storage, and consequently quality of baby spinach leaves. In general, a barrier film maintained a higher O2 level for both 80 and 100 kPa O2 treatments during entire storage. Packages with the barrier film also exhibited a more rapid accumulation of CO2 than those with the permeable film, with CO2 levels ranging from 16.2 to 22.5 kPa in the barrier film packages, versus 6.1–10.6 kPa in the permeable film packages at the end of 12 days of storage at 5 °C. Packages prepared with the barrier film with an initial O2 level at 21% accumulated CO2 during storage and exhibited a significant reduction in aerobic mesophilic bacterial growth compared to the perforated film packages (control). However, this treatment also developed strong off-odor and a loss of tissue integrity. Adding super atmospheric O2 to the packages alleviated tissue injury in addition to reducing microbial growth and was beneficial in maintaining quality of fresh-cut baby spinach.

Microbial and quality changes in minimally processed baby spinach leaves stored under super atmospheric oxygen and modified atmosphere conditions

Microbial and quality changes in minimally processed baby spinach leaves stored under super atmospheric oxygen and modified atmosphere conditions

Modified atmosphere packaging as a means to alleviate package expansion of Korean fermented red pepper paste

Summary Korean fermented red pepper paste was packaged under a modified atmosphere (MA) of 30% CO2/70% N2 and 100% CO2. A plain air package was also prepared as a control for comparison. The MA conditions were applied with a high gas barrier film and subsequently with a gas permeable film. Throughout the storage period at 13 °C, package volume, headspace gas composition, microbial flora, surface colour, pH and acidity were measured. An MA of 100% CO2 suppressed the growth of aerobic bacteria and yeasts, and reduced the CO2 production from the paste without any adverse effect on product quality, and thus alleviated the volume expansion of flexible packages stored at 13 °C. However, the reduced volume expansion for the package of high‐barrier film was not sufficient in prolonged storage. An MA package of 100% CO2 using plastic film of appropriate gas permeability could be stored at 13 °C for 150 days without volume expansion or any adverse quality changes, and was also tolerant to temperature abuse conditions at 25 °C.

PHOTOCATALYTIC REACTION OF TIO2 TO DECOMPOSE ETHYLENE IN FRUIT AND VEGETABLE STORAGE

A photocatalytic reaction of TiO2 was studied as a possible method for ethylene decomposition in fruit andvegetable storage. Its effectiveness was clearly confirmed through both chemical analysis and a fruit storage test.Photooxidation of ethylene by TiO2 was examined using TiO2coated glass beads and a TiO2 solution in both closed and flowsystems, which were irradiated with a blacklight fluorescent lamp (300400 nm). Ethylene concentrations decreased inresponse to TiO2 photocatalyst treatment, while those of the control (without TiO2 photocatalyst) and of the system treatedwith TiO2 under dark conditions remained constant. Our results indicate that the photocatalytic reaction of TiO2 to decomposeethylene can be carried out under high humidity at both room temperature and low temperature, and under both normalairand modifiedatmosphere conditions, without excessively increasing the temperature of the storage air. In addition, in thefruit ripening test under modified atmosphere conditions at 90% to 95% RH, a photocatalytic reaction of TiO2 successfullydelayed the ripening of green tomatoes into red tomatoes. No ethylene gas was found in the storage atmosphere under theTiO2 reaction condition throughout the experimental period. The exposure of tomato fruit to UVA resulted in no symptomsof disorder when the fruits ripened. The results suggest that use of TiO2 photocatalytic technology may be useful in fresh fruitand vegetable postharvest storage.

Extension of the postharvest life of `Pollock' avocado using modified atmosphere packaging

Introduction. The postharvest life of 'Pollock' avocado, a popular cultivar grown in Sri Lanka, is 7-10 d at room temperature. A short postharvest life limits its export volume by sea freight. Materials and methods. Pollock avocado fruit were packaged in 0.05 mm thick low-density polyethylene (LDPE) bags to create a modified atmosphere (MA), and they were stored at 12 o C and 94% relative humidity. The effect of the potassium permanganate, an ethylene absorber, and of the granular charcoal, a carbon dioxide absorber, on modifying the in-package atmosphere was tested. During storage, carbon dioxide, oxygen and ethylene contents were measured. The packages were opened after MA storage, and the fruit ripened naturally under ambient conditions. The weight loss, changes in firmness, total soluble solids (TSS), pulp color, visual quality rating (VQR), chilling injury index (CI) and disease index (DI) during or after storage were determined. Results. Compared with the samples packaged with- out absorbers, those packaged with absorbers had significantly lower carbon dioxide and eth- ylene contents. MA packaging was effective in extending the postharvest life of Pollock avo- cado up to 17 d. Inclusion of absorbers further extended the postharvest life up to 29 d. Firmness, TSS, pulp color, VQR, CI and DI of the ripened fruits were not significantly affected by the MA conditions. Discussion. The MA conditions did not alter the ripening process and were successful in preventing the chilling injury and diseases. Packaging of Pollock avocado in 0.05 mm LDPE bags at 1:1 surface to weight ratio (cm 2.g -1 ) with ethylene and carbon diox- ide absorbers and storing at 12 °C and 94% relative humidity can be recommended to extend their storage life up to 29 d.

The growth of Listeria monocytogenes in fresh goat cheese (Cameros cheese) packaged under modified atmospheres

The effect of modified atmosphere packaging (MAP) on the growth of Listeria monocytogenes in inoculated and non-inoculated Cameros cheese was evaluated. Three different modified atmosphere conditions were studied (20%CO2/80%N2, 40%CO2/60%N2 and 100%CO2). Control cheeses were packaged in air. The product was stored at 4°C and evaluated periodically to investigate its microbiological quality.MAP presented an extended shelf-life. Those containing CO2 reduced the growth rate of mesophiles, psychrotrophs and anaerobes, which was lower when the CO2 concentration increased. A concentration of 100% CO2 showed the lowest microbial counts. L. monocytogenes growth was lower when the CO2 concentration increased. However, after 28 days the L. monocytogenes population was 1·3 log units lower in inoculated cheeses packaged at 100% CO2 than in those packaged in air. Listeria monocytogenes can grow in atmospheres containing 20, 40 and 100% CO2. L. monocytogenes were not found in any of the non-inoculated samples. It was concluded that MAP was not a suitable means to prevent the growth of L. monocytogenes in Cameros cheese.

Dietary vitamin E supplementation, an ascorbic acid preparation, and packaging effects on colour stability and lipid oxidation in mince made from previously frozen lean beef

The effect of extra vitamin E (2025 International Units animal–1 day–1) in the diet of bulls on the colour stability and lipid oxidation of lean mince was studied. Control and enriched diets were provided for the last 136 days before slaughter. Minces were prepared from M. biceps femoris and M. semitendinosus that had been stored for 2 months at –40 °C. Samples of minces with and without an ascorbic acid preparation (AAP) from control (CON) and supplemented (SUP) beef were packaged, half on trays over-wrapped with an oxygen-permeable foil and half in modified atmosphere (MA) packs (gas mixture applied: O2/CO2/N2, 75/20/5). Meats were displayed for 7days at 7 °C in an illuminated environment. The SUP meat was more resistant to lipid oxidation than the CON meat was. Also, the AAP consistently delayed lipid oxidation. A strong synergistic effect of both vitamins in this regard was demonstrated for the MA condition. MA packaging overall led to increased lipid oxidation. Colour measurements of SUP versus CON meats, without the AAP, generally failed to detect differences in redness values. The positive effect on the colour of freshly minced lean meats obtained by supplementation with vitamin E appeared to be almost nullified in minces made from previously stored frozen muscles. A sensory panel, however, still tended to judge the attractiveness of the colour of the SUP meat greater than that of CON meat. Addition of the AAP improved colour stability. Compared to the foil-overwrapped meat, colour was better retained in the MA packaged meat.

The effect of modified atmospheres on the rate of firmness change in ‘Braeburn’ apples

Gas exchange rates and softening of ‘Braeburn’ apples were measured under a range of modified atmosphere conditions to characterise their functional relationship. Both gas exchange (measured as CO2 production) and softening were maximally suppressed at around 1–1.5 kPa O2. At these low O2 levels, CO2 had no effect on the rate of softening. Both softening and gas exchange had comparable Km values indicating a common kinetic background. The integrated approach revealed a close quantitative relationship between rate of softening and rate of gas exchange of ‘Braeburn’ apples indicating that fruit softening is directly metabolically linked to gas exchange. Due to the less efficient character of fermentation, the softening of ‘Braeburn’ apples related more closely to respiration than to fermentation.

EFFECT OF MODIFIED ATMOSPHERE STORAGE ON HAZELNUT QUALITY

Hazelnut quality was studied after storage in selected modified atmosphere conditions. Hazelnuts of the Negret cultivar collected in Tarragona, Spain, were used in the experiments. The shelled and unshelled hazelnuts were stored with different oxygen concentrations (1%, 5%, 10% and 20% O 2 ) at two different temperatures (7Cand 25C). The quality of the hazelnuts during storage was monitored by determining the peroxide value, acid value, K 232 and K 270 indices, percentage of unsaturated fatty acids and sensory analysis of the hazelnuts. It was observed that after one year storage period, none of the storage modes had given rise to significant rancidity. It was also confirmed that the shell protected the hazelnut from oxidative deterioration. Nevertheless, storage in atmospheres with oxygen levels lower than 10%, autoxidation was significantly reduced and the low temperature delayed lipid rancidity. La qualite des moisettes est etudiee apres un entreposage dans des conditions selectionnees d'atmosphere modifiee. Les noisettes de cultivar Negret recoltees dans la province de Tarragona, en Espagne, sont utilisees pour l'experimentation. Les noisettes ecalees ou entieres sont entreposees sous differentes concentrations d'oxygene (1%, 5%, 10% et 20%) a 2 temperatures differentes (7 et 25°C). Leur qualite est controlee en determinant la valeur peroxyde, acide, les indices K 232 et K 270 , le pourcentage d'acides gras insatures ainsi que les proprietes sensorielles des noisettes, a la reception et apres 3, 6, 9 et 12 mois.

A proposed methodology to determine the sensory quality of a fresh goat's cheese (Cameros cheese): application to cheeses packaged under modified atmospheres

A sensory profile was proposed, together with a methodology which permited the quality control of a fresh goat's cheese (Cameros cheese) from the sensory standpoint. Samples of Cameros cheese from four different cheesemakers were evaluated by a jury of 10 members. All panelists attended five tasting sessions to define an agreed lexicon of sensory characteristics of Cameros cheese. In order to quantify each one of the sensory attributes, a scorecard was elaborated. The intensity of the attributes selected was quantified on a scale from 1 to 7 according to the indications given in the sensory description. For each attribute the optimum score was established by the panelists to obtain the numerical score of samples. Using the proposed system, the sensory quality of Cameros cheeses packaged under modified atmospheres was evaluated. Five different modified atmosphere conditions were studied (carbon dioxide/nitrogen mixtures and vacuum) and compared to control cheeses packaged in air. The product stored at 3–4°C was evaluated periodically. After 14 days of storage, the sensory characteristics of the control cheeses were unacceptable in all the parameters studied. However, the overall score for cheeses stored in 40 and 50% CO 2 did not change substantially, retaining a reasonable acceptability until the end of the storage period. The 100% CO 2 atmosphere had a very negative effect on the sensory quality specially in taste. Cheeses packaged under vacuum showed a fast deterioration of surface appearance and texture. The proposed methodology allowed the quantification of the sensory differences between the packaging conditions investigated. With regard to Cameros cheese, packaging in 50%CO 2/50%N 2 and 40%CO 2/60%N 2 were the most effective for retaining good sensory characteristics specially in taste and odour. However, texture and appearance were negatively affected by these conditions.

Involvement of Ethylene in Development of Chilling Injury in Fresh-cut Tomato Slices during Cold Storage

Experiments were conducted to determine if ethylene influences chilling injury, as measured by percentage of slices exhibiting water-soaked areas in fresh-cut tomato slices of `Mountain Pride' and `Sunbeam' tomato (Lycopersicon esculentum Mill.). Ethylene concentration in containers without ventilation significantly increased during storage at 5 °C, whereas little or no accumulation of ethylene occurred in containers with one or six perforations. Chilling injury was greatest for slices in containers with six perforations, compared to slices in containers with one perforation, and was over 13-fold greater than that of slices in control containers with no perforations. An experiment was also performed to investigate the effectiveness of including an ethylene absorbent pad in containers on subsequent ethylene accumulation and chilling injury. While ethylene in the no-pad controls increased continually during storage of both `Mountain Pride' and `Sunbeam' tomatoes at 5 °C under modified atmosphere conditions, no increase in accumulation of ethylene was observed in containers containing ethylene absorbent pads throughout storage. The ethylene absorbent pad treatment resulted in a significantly higher percentage of chilling injury compared with the no-pad control. In studies aimed at inhibiting ethylene production using AVG during storage of slices, the concentration of ethylene in control containers (no AVG) remained at elevated levels throughout storage, compared to containers with slices treated with AVG. Chilling injury in slices treated with AVG was 5-fold greater than that of controls. Further, we tested the effect of ethylene pretreatment of slices on subsequent slice shelf life and quality. In slices treated with ethylene (0, 0.1, 1, or 10 μL·L-1) immediately after slicing, ethylene production in nontreated controls was greater than that of all other ethylene pretreatments. However, pretreatment of slices 3 days after slicing resulted in a different pattern of ethylene production during storage. The rate of ethylene production by slices treated with 1 μL·L-1 ethylene 3 days after slicing was greater during storage than any of the other ethylene treatments. With slices pretreated with ethylene, both immediately and 3 days after slicing, the rate of ethylene production tended to show a negative correlation with chilling injury. Chemical name used: 1-aminoethoxyvinylglycine (AVG).

Characterization of Leuconostoc gasicomitatum sp. nov., associated with spoiled raw tomato-marinated broiler meat strips packaged under modified-atmosphere conditions.

Lactic acid bacteria (LAB) associated with gaseous spoilage of modified-atmosphere-packaged, raw, tomato-marinated broiler meat strips were identified on the basis of a restriction fragment length polymorphism (RFLP) (ribotyping) database containing DNAs coding for 16S and 23S rRNAs (rDNAs). A mixed LAB population dominated by a Leuconostoc species resembling Leuconostoc gelidum caused the spoilage of the product. Lactobacillus sakei, Lactobacillus curvatus, and a gram-positive rod phenotypically similar to heterofermentative Lactobacillus species were the other main organisms detected. An increase in pH together with the extreme bulging of packages suggested a rare LAB spoilage type called "protein swell." This spoilage is characterized by excessive production of gas due to amino acid decarboxylation, and the rise in pH is attributed to the subsequent deamination of amino acids. Protein swell has not previously been associated with any kind of meat product. A polyphasic approach, including classical phenotyping, whole-cell protein electrophoresis, 16 and 23S rDNA RFLP, 16S rDNA sequence analysis, and DNA-DNA reassociation analysis, was used for the identification of the dominant Leuconostoc species. In addition to the RFLP analysis, phenotyping, whole-cell protein analysis, and 16S rDNA sequence homology indicated that L. gelidum was most similar to the spoilage-associated species. The two spoilage strains studied possessed 98.8 and 99.0% 16S rDNA sequence homology with the L. gelidum type strain. DNA-DNA reassociation, however, clearly distinguished the two species. The same strains showed only 22 and 34% hybridization with the L. gelidum type strain. These results warrant a separate species status, and we propose the name Leuconostoc gasicomitatum sp. nov. for this spoilage-associated Leuconostoc species.

Microbiological, physicochemical and sensory characteristics of Cameros cheese packaged under modified atmospheres

This study evaluated the shelf-life quality of Cameros cheeses packaged under modified atmospheres. Five different modified atmosphere conditions were studied (carbon dioxide/nitrogen mixtures and vacuum). Control cheeses were packaged in air. The product stored at 3–4°C was evaluated periodically to investigate its sensory quality, microbiological condition and physicochemical characteristics. Weight loss and pH evolution were similar in vacuum and air packaging. Cheeses packaged in 100% CO2showed the greatest weight losses and lower pH values. CO2reduced proteolysis and lipolysis during storage in all conditions studied. Fat acidity and NPN/TN values were slightly higher in vacuum than in CO2, but lower than in air. Modified atmosphere packaging presented an extended shelf life. Those containing CO2reduced the growth rate of mesophiles, psychrotrophs, Enterobacteriaceae and coliforms, which was lower when the CO2concentration increased. The lowest microbial counts were at 100% CO2while vacuum conditions presented microbial counts only slightly lower than the controls. Salmonella spp.,Staphylococcus aureus and Listeria spp. were not found in any of the samples. Faecal coliforms, moulds and yeasts were not detected under CO2atmospheres or in vacuum. After 7 days of storage, the sensory characteristics of the control cheeses were unacceptable in all the parameters studied. However, the overall score for cheeses stored in 40% and 50% CO2did not change substantially, retaining a reasonable acceptability until the end of the storage period. The 100% CO2atmosphere had a very negative effect on sensory quality. With regard to Cameros cheese, packaging in 50%CO2/50%N2and 40%CO2/60%N2are the most effective for extending shelf life and retaining good sensory characteristics.

Use of modified atmospheres to prolong the postharvest life of Burlat cherries at two different degrees of ripeness

The effects of degree of ripeness and packaging atmosphere on the quality of the very early season cherry (Prunus avium) cultivar ‘Burlat’ have been studied. Cherries were classified into two groups depending on their stage of ripening, taking colour as a maturity index (red and purple). After rapid chilling, cherries were sealed in 50 µm low-density polyethylene (LDPE) bags in four different atmosphere compositions. Packages were stored at 2 °C and cherries were analysed weekly until they were deemed to be commercially unacceptable (after 4 weeks for red cherries and 3 weeks for purple cherries). Changes in atmosphere composition, skin colour, pigment content, titratable acidity, soluble solids, firmness and sensory quality were monitored. Acceptability was higher for the less mature group of cherries. Colour shifted in both groups, initially from red to blue/red and later on back to red. Titratable acidity decreased at the end of the experimental period for all samples. Firmness increased at first, but towards the end of the experiment it was similar to the initial value. The gas composition of the four modified atmosphere conditions approached a final equilibrium consisting of 9–12% CO2 and 1–3% O2. For long-distance transportation of Burlat cherries the following procedure is recommended: harvest at the red colour stage, package in air using LDPE bags and maintain the temperature at 2 °C. Under these conditions, red Burlat cherries can be kept in an excellent commercial state for 3 weeks. © 2000 Society of Chemical Industry

Colour stability and lipid oxidation of fresh beef. Development of a response surface model for predicting the effects of temperature, storage time, and modified atmosphere composition

Samples of fresh beef muscles ( Longissimus dorsi) were packed under varying modified atmosphere conditions (20–80% oxygen) and stored at 2–8°C for 10 days. At 2 day intervals meat samples were analysed for surface colour and extent of lipid oxidation (TBARS). Response surface models for predicting the effects of temperature, storage time and modified atmosphere composition on colour stability and lipid oxidation were developed. Temperature and time were found to be the most important factors for retaining meat colour and minimizing lipid oxidation. However, the oxygen content also had a significant effect on both quality parameters. A stable interval of maintaining a good meat colour was found between 55 and 80% O 2. Response surface modelling was found to be very promising for modelling of chemical quality changes in meat stored under different conditions, but the large biological differences between animals may complicate the development of generally valid models.

470 Ethylene Inhibits the Development of Chilling Injury in Fresh-cut Tomato Slices during Storage at Low Temperature

Experiments were conducted to determine if ethylene influences chilling injury, as measured by percent of slices showing some water-soaked areas and associated fungal growth in fresh-cut tomato slices (Lycopersicon esculentum Mill.; cvs. Mountain Pride and Sunbeam). Ethylene concentration in containers without a perforation (perforations were made by piercing the lid of the container forming a 0.7-mm hole) significantly increased during storage at 5 °C, while little or no accumulation of ethylene occurred in containers with from one to six perforations. Chilling injury was greatest in slices in containers with six perforations, compared to slices in containers with one perforation an,d was over 12-fold greater than that of slices in control containers with no perforations. The percent ofage visible fungal growth of slices was roughly correlated with the degree of chilling injury. An experiment was also performed to investigate the effectiveness of including an ethylene absorbent pad in containers on subsequent ethylene accumulation and chilling injury. While ethylene in the no-pad control increased continually during storage at 5 °C under modified-atmosphere conditions, no increase in accumulation of ethylene was observed in containers containing ethylene absorbent pads throughout storage with `Sunbeam' and `Mountain Pride' tomatoes. The ethylene absorbent pad treatment resulted in a significantly higher percent of chilling injury and visible fungal growth compared with the no-pad control. In studies aimed at inhibiting ethylene production using 1-aminoethoxyvinylglycine (AVG) during storage of slices, the concentration of ethylene in control containers (no AVG) remained at elevated levels throughout storage compared to containers with slices treated with AVG. Chilling injury in controls was 5-fold greater than that in slices treated with AVG. All slices treated with AVG had visible fungal growth, while the percent of slices showing visible fungal growth in no-AVG controls was 54%. Furthermore, we tested the effect of ethylene pretreatment of slices on subsequent slice shelf-life and quality. In slices treated with ethylene (0, 0.1, 1, and 10 μL·L-1) immediately after slicing, ethylene production in untreated controls was greater than that of all other ethylene pretreatments. However, pretreatment of slices at 3 days after slicing resulted in a different pattern of subsequent ethylene production during storage. The rate of ethylene production by slices treated with 1 μL·L-1 ethylene at 3 days after slicing was greater during storage than any of the other ethylene treatments. With slices pretreated with ethylene both immediately and 3 days after slicing, the rate of ethylene production tended to show an negative correlation with chilling injury.