Modelling the effect of temperature on respiration rate of fresh cut papaya (Carica papaya L.) fruits

A respiration rate (RR) model based on Peleg’s equation was developed for predicting RRs of fresh cut papaya. Respiration data for fresh cut papaya at 3/4 maturity were generated at temperatures 5, 10, 15, 20, 25 and 30°C using a closed system. RRs was found to be significantly influenced by storage temperature and increased from 0.021 to 0.289 mL[O₂]/kg·h and 0.063 to 0.393 mL[CO₂]/kg·h as a function of O₂ and CO₂ gas concentrations, respectively. Peleg’s constant K ₁ and K ₂ were obtained from linear regression analysis using GraphPad Prism 5.0 software and regression coefficients have good fit with values close to unity. The model was verified to assess the capability of its predictability of the RRs over the temperatures. There was good agreement with the experimentally estimated RRs. Information derived from the model can contribute in the design of successful modified atmospheric systems for storage of fresh cut papaya.     

Evaluation of Models for Spinach Respiratory Metabolism Under Low Oxygen Atmospheres

Anaerobic respiration is a major problem that causes the deterioration of fresh produce packaged under low O₂ atmospheres. The problem becomes more severe and causes high losses in the packages handling at ambient conditions, especially in developing countries. In designing modified atmosphere packaging, the risk of anaerobic development greatly depends upon the accuracy of respiration rate prediction; therefore, the respiration rate model for a particular produce has to be identified. In this study, different atmospheric storage conditions in a closed system were realized to examine the adaptability of respiration rate models for spinach storage under low O₂ at an expected ambient temperature of 25 °C. Six models were applied and it was found that, for aerobic conditions, the respiration rate could be described with a constant respiratory quotient by three models, viz., (a) Michaelis–Menten model without inhibition, (b) Michaelis–Menten model with uncompetitive inhibition, and (c) Langmuir adsorption model, whereas three other models, viz. (d) Michaelis–Menten model with competitive inhibition, (e) Michaelis–Menten model with noncompetitive inhibition, and (f) Michaelis–Menten with mixed inhibition could not be fitted. Among the three successful models, the Michaelis–Menten with uncompetitive inhibition was found to be the most suitable model for practical applications in developing countries where cold-chain systems are lacking. This model can be applied for the prediction of gas composition and optimize the packages, particularly to ensure the aerobic respiration.     

Modelling the respiration rate of guava (Psidium guajava L.) fruit using enzyme kinetics, chemical kinetics and artificial neural network

The respiration rate prediction of fresh produce is crucial for designing and operating postharvest storage systems. This paper constructs and evaluates respiration models of guava fruit by using not only the enzyme, chemical kinetics but also artificial neural network (ANN) with the experimental data obtained from 5, 10, 15, 20, 25 and 30 °C (for constructing) as well as 12 and 22 °C (for evaluating) by closed system method. All of the developed models showed good agreement with actual observations. As regards fidelity the ANN model with topologic structure of 3 × 9×1 trained by the Levenberg–Marquardt algorithm, evaluation results were such that the mean absolute percentage error (MAPE) and the two-tailed Pearson correlation coefficient (r) were 5.31 and 0.997 for 12 °C, 4.85 and 0.995 for 22 °C, had superiority over the two other models. The results indicate that the ANN approach is a more precise method, and can be used for predicting the respiration rate of guava fruit.     

Preservation of hermaphrodite and female papaya fruits (Carica papaya L?., Cv Sunrise, Solo group) by freezing: physical, physico-chemical and sensorial aspects

 The physical, physico-chemical and sensorial changes that occur during the freezing and frozen storage of hermaphrodite and female papaya slices (Carica papaya L., cv Sunrise, Solo group) were studied. Samples were evaluated by panellists throughout a 1-year period of storage at –24°C; the panellists described the fruit in terms of physico-chemical measurements of texture (firnmess and total pectins content), colour [L, a _L , b _L , peroxidase (POD) and polyphenoloxidase (PPO) activities] and flavour/taste [soluble solids content, pH, tritatable acidity and quality index (^oBrix/acidity)], and ranked them in order of preference. Desserts prepared from frozen slices of hermaphrodite and female papaya fruits mixed with orange, lemon and sugar were also evaluated. The freezing process itself did not result in significant changes in the more commonly assessed quality parameters of texture, colour and flavour/taste. However, during storage at –24°C, changes in sensorial characteristics occurred that became more evident as storage continued (≤ 9 months). Nevertheless, these quality changes can be masked by using these papaya slices as an ingredient in fruit products, with frozen female papaya slices being especially suitable for this purpose. Received: 1 August 1997 / Revised version: 14 November 1997     

Measurement and Modeling of Respiration Rate of Guava (CV. Baruipur) for Modified Atmosphere Packaging

Several experiments were conducted at different storage temperatures for generating respiration data using close system method for respiration. A respiration rate model, based on enzyme kinetics and the Arrhenius equation was proposed for predicting the respiration rates of Guava as a function of O₂ and CO₂ concentrations and storage temperature. Temperature was found to influence the model parameters. In this model, the dependence of respiration rate on O₂ and CO₂ was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O₂ and CO₂ concentration were used to fit the Arrhenius equation against different storage temperature. The activation energy and respiration pre-exponential factor were used to predict the model parameters of enzyme kinetics at any storage temperature between 0–30°C. The developed models were tested for its validity at 12°C and it was found to be in good agreement (the mean relative deviation moduli between the predicted and experimental respiration rates were found to be 8.95% and 8.02% for O₂ consumption and CO₂ evolution, respectively) with the experimentally estimated respiration rates.     

Modeling of Respiration Rate of Litchi Fruit under Aerobic Conditions

Respiration of the produce and permeation of gas through the packaging films are the processes involved in creating a modified atmosphere inside a package that will extend shelf life of agricultural perishables. Thus modeling respiration rate of the selected produce is crucial to the design of a successful modified atmosphere packaging system. Two different models based on regression analysis and enzyme kinetics were developed with the help of respiration data generated at temperatures 0, 5, 10, 15, 20, 25, and 30 °C for litchi fruit using the closed system method. Temperature was found to influence the model parameters. In the model, based on enzyme kinetics, the dependence of respiration rate on O₂ and CO₂ was found to follow the uncompetitive inhibition. The enzyme kinetic model parameters, calculated from the respiration rate at different O₂ and CO₂ concentration were used to fit the Arrhenius equation against different storage temperature. The regression coefficients values were used for the prediction of respiration rate using regression model. The activation energy and respiration pre-exponential factor were used to predict the model parameters of enzyme kinetics at any storage temperature. The developed models were tested for its validity at 2 °C. The models showed good agreement with the experimentally estimated respiration rate.     

Solar drying characteristics of papaya (Carica papaya) latex

Dripped, congealed and a mixture of dripped and congealed papaya latexes of varying charge sizes were dried in a rock-bed solar dryer over a temperature range of 40–60°C. The time taken for the fresh latex to dry from an initial moisture content of between 73 and 80% (wet basis) to an equilibrium moisture content of between 6 and 8% varied from about 1·5 to 36 h depending upon the charge size. The latex, whether dripped or congealed, dried as pale yellow flakes which could easily be powdered and had a proteolytic activity slightly higher than that of the fresh latex.     

Modeling the effect of storage temperature on the respiration rate and texture of fresh cut pineapple

The effect of temperature on the respiration rate and texture of fresh cut pineapple was studied over the course of 10 days of storage. The thermal exchange between the pineapple trays and the cooling environment was simulated using the finite element method and tested at 6 °C. The temperatures on pineapple wedges differed between the cold point and points near the surface, indicating that the respiration rate may be affected in pineapple subjected to temperature abuse. The experimental respiration rates obtained were used to develop a model relating respiration to O₂ and CO₂ concentrations at different temperatures using the closed system method. The O₂ consumption and CO₂ production of pineapple wedges was accurately modeled using Michaelis–Menten kinetics. The texture degradation of pineapple wedges follows a zero-order kinetic reaction at different temperatures and the thermal dependence of the model’s parameters for both respiration rate and texture degradation was described by Arrhenius-type equations.     

Impact of Mixtures of Different Fresh‐Cut Fruits on Respiration and Ethylene Production Rates

Packaging and storage of fresh‐cut fruits and vegetables are a challenging task, since fresh produce continue to respire and senesce after harvest and processing accelerates the physiological processes. The response on respiration and ethylene production rates of fresh produce to changes in O₂ and CO₂ concentrations and temperature has been extensively studied for whole fruits but literature is limited on processed and mixed fresh‐cut fruits. This study aimed to investigate the effects of mixing various proportions of fresh‐cut fruits (melon chunks, apple slices, and pineapples cubes) on respiration and ethylene production rates and to develop predictive models for modified atmosphere packaging. The experiment was designed according to a simplex lattice method and respiration and ethylene production rates were measured at 10 °C. Results showed that single component pineapple cubes, apple slices, and melon chunks, in this order, had significant constant coefficients (P = 0.05) and the greatest impact on respiration rate while the interactive binary and tertiary coefficients were insignificant. For ethylene production rates, single component apple slices, melon chunks, and pineapple cubes, and their 3‐component mixtures, in this order, had significant constant coefficients (P = 0.05) while binary coefficients were insignificant. Mathematical models were developed and validated; the cubical model was the best to describe the influence of proportion of fruit on respiration and ethylene production rates, however, considering simplicity the linear part of the model is recommended to quantify respiration and ethylene production rates of mixed fresh‐cut fruits.     

Application of a qualitative and quantitative real-time polymerase chain reaction method for detecting genetically modified papaya line 55-1 in papaya products

Genetically modified (GM) papaya (Carica papaya L.) line 55-1 (55-1), which is resistant to papaya ringspot virus infection, has been marketed internationally. Many countries have mandatory labeling regulations for GM foods, and there is a need for specific methods for detecting 55-1. Here, an event- and construct-specific real-time polymerase chain reaction (PCR) method was developed for detecting 55-1 in papaya products. Quantitative detection was possible for fresh papaya fruit up to dilutions of 0.001% and 0.01% (weight per weight [w/w]) for homozygous SunUp and heterozygous Rainbow cultivars, respectively, in non-GM papaya. The limit of detection and quantification was as low as 250 copies of the haploid genome according to a standard reference plasmid. The method was applicable to qualitative detection of 55-1 in eight types of processed products (canned papaya, pickled papaya, dried fruit, papaya-leaf tea, jam, puree, juice, and frozen dessert) containing papaya as a main ingredient.     

Phenolic and carotenoid profiles of papaya fruit (Carica papaya L.) and their contents under low temperature storage

BACKGROUND: Tropical fruits are rich in phenolic and carotenoid compounds, and these are associated with cultivar, pre‐ and postharvest handling factors. The aim of this work was to identify major phenolics and carotenoids in ‘Maradol’ papaya fruit and to investigate their response to storage temperature. RESULTS: Ferulic acid, caffeic acid and rutin were identified in ‘Maradol’ papaya fruit exocarp as the most abundant phenolic compounds, and lycopene, β‐cryptoxanthin and β‐carotene were identified in mesocarp as the major carotenoids. Ranges of contents of ferulic acid (1.33–1.62 g kg^?1 dry weight), caffeic acid (0.46–0.68 g kg^?1 dw) and rutin (0.10–0.16 g kg^?1 dw) were found in papaya fruit, which tend to decrease during ripening at 25 °C. Lycopene (0.0015 to 0.012 g kg^?1 fresh weight) and β‐cryptoxanthin (0.0031 to 0.0080 g kg^?1 fw) were found in fruits stored at 25 °C, which tend to increase during ripening. No significant differences in β‐carotene or rutin contents were observed in relation to storage temperature. CONCLUSION: Phenolics and carotenoids of ‘Maradol’ papaya were influenced by postharvest storage temperature with exception of β‐carotene and rutin. Ripe papaya stored at 25 °C had more carotenoids than those stored at 1 °C. Low (chilling) temperature (1 °C) negatively affected the content of major carotenoids, except β‐carotene, but preserved or increased ferulic and caffeic acids levels, as compared to high (safe) temperature (25 °C). Copyright © 2010 Society of Chemical Industry     

Model for Gas Exchange Dynamics in Modified-Atmosphere Packages of Fruits and Vegetables

A model for atmosphere in a package containing fresh fruits was analyzed theoretically and validated by experiments with red bell pepper fruit. The model was based on two processes: fruit respiration and film permeability. Mathematical analysis showed that when rates of O₂ consumption and CO₂ evolution due to respiration are equal, and film permeability to CO₂ is greater than that to O₂, the time course curve of CO₂ concentration has a maximum. In a closed system, the time course of the sum of the gases could indicate a change of respiratory quotient. These results are independent of model for respiration. To predict extent of overshoot and for a computerized simulation, the equation of Michaelis-Menten type with noncompetitive inhibition was adopted to describe respiration. Utilizing computer simulations enabled evaluation of film specifications and package dimensions best for a given commodity.     

Freezing time prediction for partially dried papaya puree with infinite cylinder geometry

Dehydrofreezing which is the drying of foods to intermediate moisture content and subsequent freezing has the advantages of lowering the transportation costs due to reduced weight and improved texture. The available empirical equations for freezing time prediction and the experimental data on thermo-physical properties are for fresh produce. Some of these empirical equations were used to predict the freezing times of papaya puree infinite cylinders with initial moisture contents ∼52% to ∼91%. The accuracies of these methods to predict the freezing times for final center temperatures of −10 °C and −18 °C were discussed. The most accurate methods for fresh and partially dries papaya puree were suggested.     

Coumarin Extraction from Cuscuta reflexa using Supercritical Fluid Carbon Dioxide and Development of an Artificial Neural Network Model to Predict the Coumarin Yield

Coumarin found in Cuscuta reflexa (a medicinal herb) is a phytochemical that possesses blood-thinning, anti-fungicidal and anti-tumor activities, and increases the blood flow in the veins and decreases capillary permeability. Supercritical fluid carbon dioxide extraction is an effective method for extraction and separation of organic compounds. Coumarin was extracted using supercritical fluid carbon dioxide associated with a small amount of a co-solvent methanol to increase the selectivity of carbon dioxide and identified by high-performance liquid chromatography comparing with authentic coumarin standard. Determination of proper extracting temperature, time, and pressure is essential for the maximum extract of coumarin yield. Coumarin was extracted under different extraction conditions of temperature (35–75 °C), time (30–150 min), and pressure (15,160–34,450 kPa). Central composite rotate design was used to plan the experimental extraction conditions. The highest yield of coumarin was 90.13 ± 0.11 (μg/g), while extraction was done at 55°C for 150 min under 24,805 kPa. A feed-forward multilayer backpropagation artificial neural network (ANN) model was developed for the prediction of coumarin yield (μg/g), where input variables were temperature, time, and pressure. Several configurations were evaluated while developing the optimal ANN model. The optimal ANN model consisted of one hidden layer and five neurons. This model was able to predict coumarin yield quantitatively. Prediction of coumarin yields using the ANN model was proven to be a simple, convenient, and accurate method.     

响应面法优化番木瓜籽蛋白质提取工艺

作为食用和工业生产的废弃物番木瓜籽,提高其蛋白质提取率,实现资源的回收利用和扩大副产品价值。以番木瓜籽为原料,使用响应面法优化碱溶酸沉法提取番木瓜籽蛋白质提取工艺。以番木瓜籽蛋白质提取率为指标,研究pH值、液料比、时间、温度对蛋白质提取率的影响。结果表明番木瓜籽蛋白质提取率最优条件为:pH 11.3、料液比1∶45(g/mL)、时间224 min、温度47.5℃,针对蛋白质提取率的模型显示失逆项不显著,R2值为94.26%,表明模型拟合良好。在此试验条件下,验证试验结果平均值为53.74%,与理论值55.21%接近。     

Glass transition phenomenon on shrinkage of papaya during convective drying

A differential scanning calorimeter was used to determine the T_g of papaya pieces equilibrated with several water activities. Thermograms revealed the existence of two T_g. The first, which presented lower value, is due to the matrix formed by sugar and water. The second one, less visible and less plasticized by water, probably corresponds to macromolecules. The data of T_g were satisfactory correlated by the Gordon-Taylor model. A convective tray dryer was used for the drying experiments, which were carried out at air temperatures of 40 °C and 70 °C and air velocity of 1.0 m/s. The shrinkage behavior was accomplished by total area and apparent volume alterations along drying. Samples were photographed during process, and their length and lateral areas were measured using the ImageJ® software. As result, the effect of air temperature on shrinkage was significant and the highest temperature (70 °C) induced higher extent of shrinkage values. At this condition, papaya sample was in a rubbery state, characterized by great matrix mobility, and remained so until the end of process, since product temperature (T_p) was above the T_g along the process. At lower temperature (40 °C), shrinkage stopped at a critical value of moisture content (0.21 g/g, wet basis), which coincided with the point in which the T_g was close to T_p.     

Effects of freezing and canning of papaya slices on their carotenoid composition

An HPLC study of the carotenoid composition of fresh, frozen and canned papaya fruit slices was done. There were no qualitative differences between the carotenoid patterns of fresh and frozen papaya fruit slices (cultivar Sunrise). The major carotenoids found in papaya extracts were lycopene and carotenol fatty acid esters of-cryptoxanthin and-cryptoxanthin-5, 6-epoxide. Other xanthophylls detected were-crypto-xanthin,trans-zeaxanthin and cryptoflavin. It was possible to determine the quantitative losses of carotenoids in papaya slices as a result of the freezing process and frozen storage, since samples of these fruits were available before processing. The pigment pattern of the canned product showed lycopene as being a major pigment. Thermal treatment induced the degradation of carotenol fatty acid esters of xanthophylls. The freezing and canning processing of papaya slices led to significant decreases in the total carotenoids quantified by HPLC, with frozen female slices and canned samples showing lower amounts of pigments. Hunter colour values of frozen slices were similar to those of fresh papaya fruit slices.     

Purification and properties of pectinesterase from papaya

Pectinesterase (PE) was partially purified from papaya pulp, and its biochemical properties were studied. The enzyme was eluted in a single peak after DEAE-cellulose and Sephadex G-100 chromatography. The PE had a molecular weight of 53000 and showed an optimum pH of 8.0. Its activity was dependent on an NaCl concentration of 0.2M . The enzyme was heat stable: approximately 80% of the original activity remained after 60 min of heating at 50°C but completely inactivated by incubation at 80°C for 1 min. The activity was linear with time and protein concentration. The maximum reaction in 3 min was found at 60°C and the initial rate increased 9-fold from 20 to 60°C. The estimated K_m was 0.12g litre^?1 with citrus pectin as the substrate. The kinetic study revealed that polygalactur-onic acid is a competitive inhibitor, and a K_i value of 0.07 g litre^?1 was determined. On the basis of this study, papaya PE properties resembled those of pectinesterase from other sources.     

供应链中生鲜果蔬品质劣变机制、共性管控及智能检测技术研究进展

供应链中生鲜果蔬由于呼吸作用、蒸腾作用和乙烯释放等因素,持续消耗有机物质(如糖和淀粉),导致生鲜果蔬品质降低。在整个供应链中,生鲜果蔬的生理、生化变化受内在因素(种类与品种、产地与采收期、成熟度或生长期)和环境因素(如温度、湿度、O₂和CO₂体积分数、乙烯体积分数、挤压、撞击、振动等)的影响。目前,供应链中应用了许多采后技术来提高品质和保留率,以减少生鲜果蔬的品质劣变,提高其市场竞争力。作者简要介绍了供应链中生鲜果蔬品质劣变(如霉变、萎蔫、褐变、软化、黄化等)机制、生鲜果蔬品质劣变影响因素,以及通过采用共性管控技术减缓生鲜果蔬的品质劣变,并综述了智能标签在生鲜果蔬新鲜度检测中的研究进展。