Jeffrey K. Brecht

Modelling respiration rate of fresh fruits and vegetables for modified atmosphere packages: a review

Respiration rate and gas exchange through the package material are the processes involved in creating a modified atmosphere inside a package that will extend shelf life of fresh fruits and vegetables. Thus, modelling respiration rate of the selected produce is crucial to the design of a successful modified atmosphere packaging (MAP) system. In this paper, general aspects of the respiration process are presented. The major methods for measuring respiration rates, along with their advantages and limitations are discussed. Factors affecting the respiration rate and respiratory quotient are outlined, stressing the importance of temperature, O2 and CO2 concentrations, and storage time. Respiration rate models in the literature are also reviewed. 2002 Elsevier Science Ltd. All rights reserved.

Effect of two edible coatings with different permeability characteristics on mango (Mangifera indica L.) ripening during storage

Two types of fruit coatings were tested for their effect on external and internal mango fruit atmospheres and quality factors during simulated commercial storage at 10 or 15°C with 90‐99% RH followed by simulated marketing conditions of 20°C with 56% RH. One coating was polysaccharide-based while the other had carnauba wax as the main ingredient. These two coatings exhibited markedly different O2 permeability characteristics under laboratory conditions. This confirmed what has been reported in the literature, that polysaccharide coatings are less permeable to respiratory gases, such as O2, and more permeable to water vapor compared to carnauba wax. When applied to fruit under simulated commercial conditions, however, the difference between the coatings in permeance to respiratory gases were much reduced, most likely due to the high humidity during chilled storage. Both coatings created modified atmospheres, reduced decay, and improved appearance by imparting a subtle shine; but only the polysaccharide coating delayed ripening and increased concentrations of flavor volatiles. The carnauba wax coating significantly reduced water loss compared to uncoated and polysaccharide-coating treatments.

Physical and chemical quality characteristics of strawberries after storage are reduced by a short delay to cooling

Abstract ‘Chandler’, ‘Oso Grande’ and ‘Sweet Charlie’ strawberries were forced-air precooled after delays of 0 or 6 h at 30 °C to study the effect of delaying precooling on physical and chemical quality characteristics of strawberry fruit. Fruit pulp temperatures were equilibrated to 30 °C prior to the start of each experiment to minimise water loss differences between treatments. Evaluations were made after storage for one week at 1 °C plus one day at 20 °C. Delaying the start of precooling resulted in about 50% greater water loss than in control fruit, which was evident as increases in superficial shrivelling. Tissue firmness values were also 14–22% lower in fruit from the delayed treatment. Fruits were darker (lower L ∗ value), less bright (lower chroma) and apparently less red (lower a ∗ value) with the cooling delay, although hue angle was also lower, which may reflect the occurrence of browning. No significant differences in pH were observed in these experiments, but titratable acidity was slightly lower with the delay to cooling. Delaying precooling also caused increased losses of ascorbic acid, soluble solids, fructose, glucose and sucrose compared to controls. In spite of differences related to harvest time and the variability among cultivars, the general responses were quite similar and illustrate the importance of rapid precooling and subsequent storage at low temperature for maintenance of acceptable appearance, texture and nutritive value of strawberries.

Modelling O2 and CO2 exchange for development of perforation- mediated modified atmosphere packaging

Perforation-mediated modified atmosphere packaging relies on the use of macro perforations or tubes to control the O2 and CO2 exchange and create the desired atmosphere inside an otherwise gas-tight package. In this work, the O2 and CO2 exchange through a single tube was studied. DiAerent temperatures (5‐20∞C) and tube dimensions (length from 9 to 17 mm and diameter from 6 to 30 mm) were tested. O2 and CO2 mass transfer coeAcients were determined according to a lumped mass transfer capacitance model that yielded a good description of the gas transfer. Temperature in the range tested did not show a significant eAect on the mass transfer coeAcients. A multiplicative non-linear equation was found to yield a good prediction of the dependence of the O2 mass transfer coeAcient on tube diameter and length. The ratio between the CO2 and O2 mass transfer coeAcients, an important parameter in the design of MAP, was 0.81 and none of the factors tested influenced its value. ” 2000 Elsevier Science Ltd. All rights reserved.

Maintaining optimal atmosphere conditions for fruits and vegetables throughout the postharvest handling chain

Optimal controlled and modified atmospheres (CA and MA) for fresh produce vary according to the specie, its maturity or ripeness stage, the temperature, and the duration of exposure. However, individual lots of produce are typically handled for different times and at different temperatures during storage, transportation, and retail display. In this paper, we review some of our previous work showing the potential for using different atmospheres for mangoes (Mangifera indica L.) and strawberries (Fragaria � /ananassa Duchesne) depending on the anticipated storage length and temperature. Since it would be desirable, especially for produce transported over extended distances, as in marine transport, to maintain optimal atmosphere conditions throughout the postharvest handling chain, we also describe our procedure for designing a combination CA/MAP system that involves first designing the MAP for a particular commodity that will produce an optimal atmosphere for retail display conditions, then selecting a CA that will interact with the MAP to produce the optimal atmosphere within the packages during transportation at a lower temperature. An example of the design procedure is given from our work with fresh-cut kale (Brassica oleracea var. acephala DC.). Another example of this proposed MAP/CA system deals with its application to mixed load transportation of strawberries and snap beans (Phaseolus vulgaris L.). # 2002 Elsevier Science B.V. All rights reserved.

Modelling respiration rate of shredded Galega kale for development of modified atmosphere packaging

Abstract The design of modified atmosphere packaging (MAP) for fresh-cut produce requires an adequate model for prediction of respiration rate as a function of both temperature and gas composition. In this work, the O2 consumption and CO2 production rates of shredded Galega kale were studied. The storage temperatures used were 1, 5, 10, 15 and 20 °C. The atmospheres tested were all combinations of 1, 5 and 10% v/v O2 plus 0, 10 and 20% v/v CO2 with the balance being N2, as well as ambient air. Temperature was the variable with the greatest influence on respiration rate and the effect of gas composition increased with temperature. The dependence of respiration rate on gas composition was well described by a Michaelis–Menten type equation with uncompetitive CO2 inhibition. The respiratory quotient (RQ) was found to be constant for the range of temperatures and gas compositions tested and was equal to 0.93±0.01. The constants of the Michaelis–Menten equation increased exponentially with temperature. The change over time of respiration rate of leaves exposed to air at 20 °C was also analysed. It was observed that respiration rate decreased with time and that the ratio between the respiration rate of shredded and intact leaves was approximately constant in the period tested and equal to 2.8.

Effects of Gas Concentrations and Temperature on O2 Consumption of Strawberries

The O2 consumption rate of strawberries was determined at 16 combinations of O2 and CO2 and at three levels of temperature in the ranges of 1 to 20%, 0 to 30%, and 5 to 20° C, respectively. Influence of temperature, O2 concentration, and CO2 concentration on O2 consumption rate was studied and an empirical model was developed for O2 consumption rate as a function of these three variables. The O2 consumption rate decreased significantly with a decrease in temperature and O2 levels. Especially at low O2 concentrations, CO2 had a lesser effect on O2 consumption rate. The O2 consumption rate decreased with an increase in CO2 concentration at higher levels of O2.

Ethylene feedback mechanisms in tomato and strawberry fruit tissues in relation to fruit ripening and climacteric patterns

Exposing pericarp tissue excised from immature tomato fruit to 4.5 mmol l 1 C2H4 revealed a negative C2H4 feedback mechanism in relation to its biosynthesis since ACC concentration and C2H4 production by the tissue were reduced. An opposite trend (positive C2H4 feedback mechanism) was observed in pericarp tissue excised from fruit at the pink stage. At the mature-green stage however, tissue showed a transition from negative to positive C2H4 feedback mechanism with the onset of tissue ripening. In strawberry tissues excised from green, white and half-coloured fruits however, C2H4 application caused a short-term increase in C2H4 production followed by a sharp reduction to the control level along with a marked reduction in ACC levels. In both tomato and strawberry fruit tissues, C2H4 application significantly induced ACC oxidase (ACO) activity at all ripening stages, as measured by in vivo ACC conversion to C2H4. This strongly suggests that ACC synthesis is the limiting step in C2H4 autocatalysis and the only limiting step in C2H4 autoinhibition. In tomato pericarp tissues, C2H4 autoinhibition and autocatalysis caused by C2H4 application in immature and pink fruits, respectively, were eliminated when tissues were transferred to air and re-occurred when tissues were returned back to C2H4. These responses did not occur in all strawberry tissues due to the sharp reduction in C2H4 production with the time course of C2H4 application. Inhibiting C2H4 action with STS pretreatment inhibited both negative and positive C2H4 feedback mechanisms in both tomato and strawberry tissues indicating that C2H4 feedback mechanism is one sort of C2H4 action. In addition, only tomato fruit tissue showed significant increases in CO2 production with C2H4 application. In contrast to the nonclimacteric behaviour of strawberry fruit which exhibits only a negative C2H4 feedback mechanism, these data strongly suggest that the transition of the C2H4 feedback mechanism from negative to positive, which occurs in tomato fruit only with ripening initiation and progress, may be the reason behind the climacteric behaviour of tomato fruit.

Modified atmosphere packaging for mixed loads of horticultural commodities exposed to two postharvest temperatures

A procedure to maintain desired levels of O2 and CO2 inside packages that are exposed to different surrounding temperatures was designed and tested. This procedure included the design of packages for a high temperature, ambient atmosphere conditions simulating retail display conditions and the use of a controlled atmosphere (CA) environment surrounding the packages at a lower temperature simulating storage or transport conditions. To test the concept, strawberries and snap beans were held at 7°C for 4 days and 19°C for 2 days to simulate mixed storage:transport and retail display at these respective temperatures. The strawberries were stored in jars fitted with a short tube to modify the interior atmosphere; snap beans were stored in commercially available, semipermeable plastic bags. Both package types were placed in a CA of 14.8% O2 plus 8.3% CO2 at 7°C followed by storage in air at 19°C. Under these conditions, it was possible to maintain atmospheres that were close to the desired atmospheres for the products at both temperatures.

Quality Curves for Highbush Blueberries as a Function of the Storage Temperature

SUMMARY Blueberries Vaccinium corymbosum cv. Patriot were harvested twice at the full ripe stage and held for 14 d at 0, 5, 10, 15, or 20°C. The objectives of this work were to (1) obtain quality curves for blueberries stored at different temperatures; (2) identify, for each temperature, which quality factor(s) limits blueberry marketability; and (3) compare the quality curves and shelf-life of blueberries based on quality evaluations with those predicted by respiration rates reported in the literature. Blueberry weight loss, instrumental color (L*a*b*), visual color, firmness, shriveling, decay, taste, and aroma were evaluated every 2 d for a 14-day storage period. Development of an unpleasant taste and aroma were the primary limiting factors for blueberries stored at 0 and 5°C. Darkening of the color and development of unpleasant aroma were the primary limiting factors for berries stored at 10 or 15°C, and darkening of the color was the primary limiting factor for those fruit stored at 20°C. Overall, fruit stored at 0 or 5°C had shorter shelf life compared with predicted values based on the Q10 for respiration, while those stored at higher temperatures had longer shelf life. Prediction of blueberry shelf life calculated from data reported in the literature is not precise unless the characteristics of the fruit and environmental factors involved are well known. The quality curves obtained from quality evaluations for each temperature showed that a single quality attribute cannot be used to express loss of quality of blueberries over the normal physiological range of temperatures.