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

Influence of low oxygen and high carbon dioxide on shredded Galega kale quality for development of modified atmosphere packages

Respiration rate, sensory attributes, colour alterations, and water, chlorophyll and ascorbic acid contents were monitored during storage of shredded Galega kale (Brassica oleracea var. acephala DC.) at 20 ◦C to define an adequate range of O2 and CO2 partial pressures for product preservation. Different low O2 and high CO2 atmospheres were tested. First, tolerance to low O2 partial pressures (1, 2, 3 or 21 kPa O2 with balance N2) was tested. Quality retention was improved as O2 partial pressure was reduced and there was no induction of anaerobic respiration. Then, tolerance to high CO2 partial pressures (0, 10, 15 or 20 kPa CO2 plus 21 kPa O2 and balance N2) was tested. The high CO2 partial pressures extended the shelf life of the shredded kale and no symptoms of CO2 injury were detected. Finally, combinations of low O2 and high CO2 (1 or 2 kPa O2 plus 15 or 20 kPa CO2, with balance N2, and an air control) were analysed. No differences were observed among the different gas combinations. An atmosphere of 1–2 kPa O2 plus 15–20 kPa CO2 and balance N2 extends the shelf life of shredded Galega kale to 4–5 days at 20◦C, compared with 2–3 days in air storage. Predictive models of chlorophyll a and b degradation as a function of time and gas composition were developed

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

Perforation-mediated modi®ed 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. Di erent 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 coe cients 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 signi®cant e ect on the mass transfer coe cients. A multiplicative non-linear equation was found to yield a good prediction of the dependence of the O2 mass transfer coe cient on tube diameter and length. The ratio between the CO2 and O2 mass transfer coe cients, an important parameter in the design of MAP, was 0.81 and none of the factors tested in¯uenced its value

Physicochemical changes during strawberry development in the field compared with those that occur in harvested fruit during storage

‘Chandler’, ‘Oso Grande’ and ‘Sweet Charlie’ strawberry cultivars were harvested at four stages of color development ranging from color break to full red and stored in the dark for 8 days at 1 ◦C. Changes in the physical and chemical characteristics of fruit during storage were compared with those occurring during development in the field. Strawberry fruit harvested at the three-quarters colored and full red stages continued their development and ripening during storage. However, fruit harvested at the color break and half-colored stages did not develop like those ripened in the field. Strawberries harvested at the three-quarters colored stage developed the same pH, acidity, soluble solids, ascorbic acid and total phenolics content during storage as the at-harvest levels present in strawberries harvested at the full red stage. In addition, three-quarters colored strawberries were as firm and red after storage as the full red stage fruit were at the time of harvest. Thus, strawberries harvested at the three-quarters colored stage can be stored for a longer period than strawberries harvested full red while retaining better color and firmness

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

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. 2002 Elsevier Science Ltd. All rights reserved

Review of Challenges and Advances in Modification of Food Package Headspace Gases

Modified Atmosphere Packaging (MAP) has been widely used as an effective way to preserve foods. Fresh produce, meat and meat products, seafood, and dairy products can benefit from modified gaseous atmospheres, which are usually achieved by reducing oxygen and increasing carbon dioxide concentrations, within limits, defined by product tolerances. MAP of fresh produce is particularly challenging because products are living and respiring. Respiration rates depend on several factors including temperature, oxygen, and carbon dioxide concentrations. Balancing package permeation with respiration is challenging, often due to limited selection of practical packaging materials. Failing to remain within tolerance limits of products leads to rapid quality loss. Gas barrier properties of packages determined rate of gas exchange with the external environment and is a critical factor for achieving tolerable levels. Availability of packaging materials that meet requirement of specific produce is essential. Relative permeability of common films to carbon dioxide is about 3 to 6 times of that to oxygen, often leading to package collapse for package atmospheres that benefit from carbon dioxide. Films often fail to provide desired oxygen transmission rates, high carbon dioxide to oxygen selectivity and desired mechanical properties simultaneously. Despite advances, minimal availability and high cost of selective barrier films limit applications of MAP for fresh produce packaging. Therefore, active packaging components and films are being developed and designed to overcome these limitations. Inserts or films that contain active mixtures as gas emitters and/or scavengers are now commercially available. “Clean label” trends are motivating alternative approaches using active packaging components

Divergence-Free Adaptive Mesh Refinement for Magnetohydrodynamics

In this paper we present a full-fledged scheme for the second order accurate, divergence-free evolution of vector fields on an adaptive mesh refinement (AMR) hierarchy. We focus here on adaptive mesh MHD. The scheme is based on making a significant advance in the divergence-free reconstruction of vector fields. In that sense, it complements the earlier work of Balsara and Spicer (1999) where we discussed the divergence-free time-update of vector fields which satisfy Stoke's law type evolution equations. Our advance in divergence-free reconstruction of vector fields is such that it reduces to the total variation diminishing (TVD) property for one-dimensional evolution and yet goes beyond it in multiple dimensions. Divergence-free restriction is also discussed. An electric field correction strategy is presented for use on AMR meshes. The electric field correction strategy helps preserve the divergence-free evolution of the magnetic field even when the time steps are sub-cycled on refined meshes. The above-mentioned innovations have been implemented in Balsara's RIEMANN framework for parallel, self-adaptive computational astrophysics which supports both non-relativistic and relativistic MHD. Several rigorous, three dimensional AMR-MHD test problems with strong discontinuities have been run with the RIEMANN framework showing that the strategy works very well.Comment: J.C.P., figures of reduced qualit

Preoperative Risk-Stratification of High-Risk Prostate Cancer: A Multicenter Analysis

Background: Cancer-specific survival (CSS) within high-risk non-metastatic prostate cancer varies dramatically. It is likely that within this heterogenous population there are subgroup(s) at extraordinary risk, burdened with an exaptational poor prognosis. Establishing the characteristics of these group(s) would have significant clinical implications since high quality preoperative risk stratification remains the cornerstone of therapeutic decision making to date. Objective: To stratify high-risk prostate cancer based on preoperative characteristics and evaluate cancer specific survival after radical prostatectomy. Method: The EMPaCT multi-center database offers an international population of non-metastatic high-risk prostate cancer. Preoperative characteristics such as age, biopsy Gleason score, PSA and clinical stage were subcategorized. A multivariate analysis was performed using predictors showing significant survival heterogeneity after stratification, as observed by a univariate analysis. Based upon the hazard ratios of this multivariate analysis, a proportional score system was created. The most ideal group distribution was evaluated trough different score cut-off's. The predictive value was tested by the herald C index. Results: An overall 5-years CSS of 94% was noted within the entire high-risk cohort (n = 4,879). Except for age, all preoperative risk factors showed a significantly differing CSS. Multivariate analysis indicated, T4 stage as being the strongest predictor of CSS (HR: 3.31), followed by ISUP grade 5 group (HR 3,05). A score system was created by doubling the hazard ratios of this multivariate analysis and rounding off to the nearest complete number. Multivariate analysis suggested 0, 4, 8, and 12 pts as being the most optimal group distribution (p-value: 0.0015). Five-years CSS of these groups were 97, 93, 87, and 70%, respectively. The calculated Herald C-index of the model was 0.77. Conclusion: An easy-to-use pre-operative model for risk stratification of newly diagnosed high-risk prostate cancer is presented. The heterogeneous CSS of high-risk non-metastatic prostate cancer after radical prostatectomy is illustrated. The model is clinically accessible through an online calculator, presenting cancer specific survival based on individualized patient characteristics

C-Jun N-terminal kinase (JNK) isoforms play differing roles in otitis media

BACKGROUND: Innate immunity and tissue proliferation play important roles in otitis media (OM), the most common disease of childhood. CJUN terminal kinase (JNK) is potentially involved in both processes. RESULTS: Genes involved in both innate immune and growth factor activation of JNK are upregulated during OM, while expression of both positive and negative JNK regulatory genes is altered. When compared to wildtypes (WTs), C57BL/6 mice deficient in JNK1 exhibit enhanced mucosal thickening, with delayed recovery, enhanced neutrophil recruitment early in OM, and delayed bacterial clearance. In contrast, JNK2(−/−) mice exhibit delayed mucosal hyperplasia that eventually exceeds that of WTs and is slow to recover, delayed recruitment of neutrophils, and failure of bacterial clearance. CONCLUSIONS: The results suggest that JNK1 and JNK2 play primarily opposing roles in mucosal hyperplasia and neutrophil recruitment early in OM. However, both isoforms are required for the normal resolution of middle ear infection. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12865-014-0046-z) contains supplementary material, which is available to authorized users

Strawberry fruit resistance to simulated handling

Harvest operations are currently the main source of mechanical injury of strawberry (Fragaria x ananassa Duch.). Experiments were designed to simulate conditions encountered during commercial handling. Individual fruits were subjected to impact or compression forces with similar energy to determine the sensitivity to mechanical injury. Bruise volume was used as the measurement of injury. Bruise severity increased as a function of impact energy for both impact types. However, dropped fruits had larger bruise volume than fruits submitted to pendulum impactor at the same energy level. Doubling the impact energy (0.040 to 0.083 J) increased bruise volume by 7 times (13 to 91 mm³). Fruits dropped from 380 mm (0.075 J) showed 71% greater bruise volume than those dropped from either 130 mm (0.025 J) or 200 mm (0.040 J). Compressed fruits showed higher bruise volume than other tests. Some cultivars are more susceptible to compression forces than others. 'Sweet Charlie' berries showed bruise volume 40% higher than the others cultivars when subjected to compression. Fruits subjected to impact showed bruise volume lower than the compressed fruits, indicating the possibility to be handled and graded in a packing line.A etapa de colheita é a principal fonte de danos físicos ao morango (Fragaria x ananassa Duch.). Experimentos foram realizados para simular condições encontradas durante manuseio. Frutos foram submetidos individualmente às forças de impacto e compressão em energias similares para determinar sensibilidade dos frutos a danos físicos. Volume da injúria física foi utilizado para mensurar a incidência do dano físico ocorrido. Severidade da lesão aumenta, com incremento da energia, tanto para força de impacto como para compressão. Todavia, frutos submetidos à queda livre demonstraram maiores volumes de danos físicos do que frutos submetidos a danos ocasionados por pendulo no mesmo nível de energia. Dobrando a energia de impacto (0,040 para 0,083 J) ocorreu aumento no volume da injúria em sete vezes (13 para 91 mm³). Frutos submetidos à queda de 380 mm (0,075 J) demonstraram volumes de danos físicos 71% superiores do que aqueles ocasionados em queda de 130 mm (0,025 J) ou 200 mm (0,040 J). Frutos em teste de compressão mostraram maiores volumes de injúrias físicas do que outros testes. Alguns cultivares são mais sensíveis à força de compressão do que outros. Frutos cultivar 'Sweet Charlie' apresentaram volume de injúria 40% superiores do que outros quando submetidos à força de compressão. Morangos submetidos à força de impacto demonstraram volume de injúria inferior do que aqueles comprimidos, indicando a possibilidade dos morangos serem classificados e manuseados em uma linha de beneficiamento