Mathematical modelling of the kinetic of quality deterioration of intermediate moisture content banana during storage

Drying of banana paste in rotatory dryer with inert bed

The objective of this research was to study the drying of "nanica" banana paste (variety belonging to the subgroup Cavendish) in a rotary dryer with an inert bed (RDIB). Preliminary tests were carried out to adjust the operational process parameters. An experimental design (central composite design) was used for the final drying experiments with the following variables: the drying time and the mass of paste fed into the dryer, and as responses: the moisture content and the yield in banana flour. As a result of the tests carried out according to the experimental design, a beige-coloured product, composed of banana powder and flakes was obtained with a characteristic banana aroma. A multiple linear regression of the experimental results was used to determine the influence of the process variables. The best operational conditions allowed for the manufacture of a product with 8.0% moisture content (wet weight base) and a flour production efficiency of 72.9%.

Utilization of physicochemical variables developed from changes in sensory attributes and consumer acceptability to predict the shelf life of fresh-cut mango fruit

Sensory evaluation is the ideal tool for shelf-life determination. With the objective to develop an easy shelf-life indicator, color (L*, a*, b*, chroma and hue angle), total soluble solids (TSS), firmness (F), pH, acidity, and the sensory attributes of appearance, brightness, browning, odor, flavor, texture, color, acidity and sweetness were evaluated in fresh cut mangoes (FCM) stored at 5, 10, 15 and 20 °C. Overall acceptability was evaluated by consumers. Correlation analysis between sensory attributes and physicochemical variables was carried out. Physicochemical cut-off points based on sensory attributes and consumer acceptability was obtained by regression analysis and utilized to estimate FCM shelf-life by kinetic models fitted to each variable. The validation of the model was done by comparing the shelf life estimated by kinetic models and consumers. It was recorded large correlations between appearance, brightness, and color with L*; appearance and color with chroma and hue angle; sweetness and flavor with TSS, and between F and texture. The shelf life estimated based on consumer using a 9 point hedonic scale was in the range of 10-12, 2.3-2.6, 1.3-1.5 and 1.0-1.1 days for 5, 10, 15 and 20 °C. It was recorded large correlation coefficients between the shelf life estimated by consumer acceptability scores and physicochemical variables. Kinetic models based on physicochemical variables showed a tendency to overestimate the shelf life as compared with the models bases on the sensory attributes. It was concluded that physicochemical variables can be used as a tool to estimate the FCM shelf life.

State diagram of salmon (Salmo salar) gelatin films

BACKGROUND

A state diagram presents different physical states of a biomaterial as a function of solid content and temperature. Despite their technological interest, little information is available on protein systems such as gelatin/water mixtures. The objective of this work was to develop state diagrams of salmon gelatin (SG) and bovine gelatin (BG) in order to determine maximal freeze concentration parameters (T'(g) , T'(m) and X(s') ) and to relate possible differences to their biochemical characteristics.

RESULTS

Biochemical characterisation of SG showed lower molecular weight and iminoacid concentration compared with BG. Likewise, the glass transition temperature (T(g) ) was lower for SG at X(s) > 0.8, which was associated with its lower molecular weight. Unexpectedly, the depression of freezing temperature (T(f) ) was greater for SG at X(s) > 0.1, which was associated with its higher ash content. Isothermal annealing produced effective values of T'(g) ≈ - 52 °C, T'(m) ≈ - 46 °C and X'(s) ≈ 0.6 for both gelatins. Interestingly, the enthalpy change associated with T'(m) (ΔH T m) was significantly higher for SG than for BG after annealing, indicating a higher proportion of ice present at about - 50 °C.

CONCLUSION

Maximal freeze concentration parameters were similar between the two gelatins, though differences in biochemical properties were evident. The results show that there are likely different ways of interaction of SG and BG with water.

Modeling of the process of moisture loss during the storage of dried apricots

Moisture content is a reference parameter for dried food because the growth of most microorganisms is inhibited below certain water activity levels. In addition, it has a determining influence on the evolution of important parameters, such as color and flavor, and on other properties and deterioration reactions, such as texture, oxidation processes and nutritional value. During the storage of some dried fruits, moisture is produced due to Maillard reactions and exchanged with the surrounding environment through the packaging. The evolution of dried foods during their shelf life depends on the storage conditions. The aim of this study is to analyze the evolution of the moisture content in dried apricots packaged in different types of containers, namely glass and thermosealed polypropylene trays. The samples were stored at constant temperatures: 5, 15, 25 and 35 °C and were analyzed periodically over a period of 12 months. The sorption isotherms of apricots used in this study were also determined. In order to model how the moisture evolved, an empirical kinetic model was tested. This model considers both water transfer from the fruit and also water production as a result of the Maillard processes. The explained variance was higher than 95% in the samples stored in trays, which were thermosealed with film.

Modelling the biological variance of the yellow aspect of Granny Smith apple colour

BACKGROUND

The yellow aspect of colour is usually not considered for produce with a green-to-red or a green-to-yellow transition upon ripening. The magnitude of change is simply too small and, additionally, masked by a large variation. The colour of 'Granny Smith' apples, harvested from three orchards at two stages of maturity, was measured individually using the CIE L*a*b* system during storage in a regular atmosphere at three temperatures: 1, 4 and 10 degrees C. A model was developed based on a simplified mechanism, consisting of two consecutive reactions, to describe the development of the apple colour expressed as b* and L* values during storage.

RESULTS

Monitoring individual apples made it possible to include and describe the biological variance of colour in batches of apples and to extract information on chilling injury, as a process active at 1 degrees C. All variations could be attributed to a single source related to the amount of yellowing compounds at the moment of harvest, indicating differences in state of maturity between individual apples. The obtained explained part (R(2) (adj)), using nonlinear mixed effects regression analysis was well over 90% for all data combined over more than 3000 observations.

CONCLUSION

Orchard location had a slight effect on the mean initial colour value, indicating differences in development stage, most probably due to differences in assessing the harvest date. The magnitude of the variation in these colour values was, however, the same for all three orchards. The behaviour of the green colour aspect (a* value) has been reported separately, as this represents the major change in perceived colour. The changes in b* and L* values are rather small, while the biological variation between the individual fruit is at least of the same magnitude. The model presented here is, as far as known, the first model on b* and L* values for green-coloured products. Analysing b* and L* data using this model provides additional information with respect to the stage of maturity at harvest in a batch or for an orchard of Granny Smith apples. All the variation in the yellow colour aspects could be attributed exclusively to the initial level of yellow compounds.