Modelling respiration of packaged fresh-cut ‘Rocha’ pear as affected by oxygen concentration and temperature

Respiration rates were measured in fresh-cut ‘Rocha’ pear (Pyrus communis L.) stored at four temperatures (0, 5, 10 and 15 °C) and with oxygen partial pressures ranging from 0 to 18 kPa. Respiratory quotient and ethanol production were used to determine the fermentation threshold. The oxygen concentration effect on the respiration rate was accurately described using Michaelis–Menten kinetics, without non-competitive inhibition by CO₂, and the effect of temperature on the respiration rate was well modelled by exponential functions. The oxygen level at which respiration was half its maximum (apparent _Km,O₂$K_{{\text{m,O}}_2}$) was similar to or only slightly greater than the fermentation threshold. The narrow range of oxygen between _Km,O₂$K_{{\text{m,O}}_2}$ and the fermentation threshold, suggests that modified atmosphere packaging technology has a limited applicability toward extension of the shelf-life of fresh-cut ‘Rocha’ pear.     

Use of galactomannan edible coating application and storage temperature for prolonging shelf-life of “Regional” cheese

The objectives of this work were to determine the influence of the application of two different coatings (galactomannan and chitosan) and of storage temperature on the gas exchange rate of “Regional” cheese; subsequently, the coating that showed the greatest influence on the cheese gas exchange and simultaneously decreased the O₂ consumption (_RO₂)$(R_{{\text{O}}_2})$ and the CO₂ production (_RCO₂)$(R_{{\text{CO}}_2})$ rates was applied on cheese, being the shelf-life parameters monitorized through the performance of chemical and microbiological analyses. Both coatings caused a reduction of _RO₂$R_{{\text{O}}_2}$ and _RCO₂$R_{{\text{CO}}_2}$ of the cheese (between 0.19- and 1.30-fold for _RO₂$R_{{\text{O}}_2}$ and between 0.19- and 1.50-fold for _RCO₂$R_{{\text{CO}}_2}$, depending on the temperatures). The cheese coated with the galactomannan coating was the one with the lower values of _RO₂$R_{{\text{O}}_2}$ (between 0.195 and 0.635 mL kg⁻¹ h⁻¹) and _RCO₂$R_{{\text{CO}}_2}$ (between 0.125 and 0.900 mL kg⁻¹ h⁻¹). Temperature was also found to have an important effect on _RO₂$R_{{\text{O}}_2}$ and _RCO₂$R_{{\text{CO}}_2}$, its influence being well described by an Arrhenius equation with coefficients of determination, R², of 0.85 and above. The chemical and microbiological analyses showed that the application of the coating in cheese samples can be used to decrease the water loss and the colour changes during the storage time. The presence of the coating decreased the moisture loss of the cheese in 2.5% and 1.9%, and the weight loss in 3.8% and 3.1% at 4 °C and 20 °C, respectively. Also, the hardness of the cheese can be decreased as a result of the interaction of the presence of the coating with changes in the storing temperature. In the studied range (4–20 °C) temperature has a statistically significant effect in moisture loss, colour change, hardness and total mesophilic bacterial growth.