Drying behavior and instrumental color development of beef slices untreated or pretreated with salt or salt and vinegar solutions were monitored by determining the moisture content and the color ...change by measuring CIELAB values during drying at 50, 60, and 70 °C. Time-series hyperspectral imaging (400–1000 nm) was applied with regard to the development of non-invasive measurement systems based on robust models to predict moisture and color independent of the pre-treatment and drying temperature. Samples pretreated with salt dried the slowest which became more prominent at increasing drying temperatures and the least color change (∆E = 23) was observed at 60 °C drying temperature. Robust prediction models for moisture content and CIELAB values irrespective of pre-treatment and processing conditions were developed successfully and improved by wavelengths selection with high R2 (0.94–0.98) and low RMSEP (1.05–5.22) which will support the future development of simple and cost-effective applications regarding non-invasive product monitoring systems for beef drying processes.
•Salt and salt/vinegar pre-treatments decrease drying rates of beef slices.•Pre-treatment does not impact the final color change after drying.•Prediction models for moisture and CIELAB during drying independent of treatment.•Maintained performance of simplified prediction models after wavelengths selection.
The present work aims to improve the understanding of the effect of different drying strategies at varying temperatures on the dynamic drying behaviour and quality of organic products such as carrots ...using non-invasive measurement techniques. For this purpose, carrot slices of 3 mm thickness were dried under three different strategies namely air temperature controlled (A), product temperature controlled (P) and stepwise temperature controlled (S) at different temperatures (50 °C, 60 °C and 70 °C) to measure and analyse the changes in moisture content, colour, total carotenoid retention, water activity, rehydration ratio and specific energy consumption. From the investigation performed, it was incurred that the application of different drying strategies influences rather significantly both the product quality as well as the overall process efficiency. Modelling the drying curves deemed Page model to be a good fit for all the strategies with
R
2
adj
= 0.99 and RMSE = 0.01. The results also show that implementing strategy P not only led to shorter drying times but also led to higher total carotenoid retention within the samples (TCR = 0.59–0.73). Colour changes, however, were observed to be maximum with strategy P as compared to strategy A and strategy S. Furthermore, the use of a non-invasive measurement technique such as infrared camera proved to be reliable in order to detect the phase transition of the product during the drying process.
This study investigated the influence of wheat flour substitution with 10–60% of peeled or unpeeled orange-fleshed sweet potato (OFSP) flour on dough rheological properties as well as the effects of ...the flour mixture, baking temperature (150–200 °C) and time (15–25 min) on the physical and textural properties of the composite bread. I-optimal (combined) design of the Design-Expert software was used for the experimental design whereas the flour mixture and baking conditions for wheat-OFSP composite bread formulation were optimized using the response surface methodology. Significant models were developed where lack-of-fit was insignificant (p > 0.05), coefficient of determination, R2 and adjusted R2 were greater than 0.90 for all response variables of the dough and bread. Farinograph optimum water absorption decreased whereas dough development time increased with increased OFSP flour addition. Moreover, increasing OFSP flour, baking temperature and time significantly (p < 0.05) decreased loaf volume, specific volume, crumb water activity, crust and crumb lightness, crumb springiness, cohesiveness and resilience whereas crust and crumb redness, hardness and chewiness increased. The substitution of wheat flour with 29.4 or 28.0% of peeled or unpeeled OFSP flour, respectively and baking at 180 °C for 15 min produced optimum dough and bread quality characteristics.
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•Orange-fleshed sweet potato (OFSP) flour increased dough development time.•Increasing OFSP flour and baking conditions decreased bread specific volume.•Increasing OFSP flour and baking conditions increased bread crumb hardness.•Wheat flour substitution with OFSP flour decreased bread crumb staling.•Optimized wheat-OFSP flour mixture and baking conditions for bread making.
Currently, an estimated 20% of the population in Sub-Saharan Africa is food insecure with the incidence of hunger and malnutrition still rising. This trend is amplified by the socio-economic ...consequences of the COVID-19 pandemic. In contrast, more than a third of the harvestable perishable produce is lost due to a lack of preservation or failure to utilize preservation as is the case for underutilized crops (UCs). Moreover, some of the preservation techniques utilized are poor, leading to the deterioration of food quality, especially the micronutrients. In this study, we thus exemplarily investigated the impact of different drying settings on the quality of two highly nutritious UCs, namely cocoyam and orange-flesh sweet potato (OFSP) (40, 60, and 80 °C for cocoyam and 40, 50, 60, and 70 °C for OFSP) to deduce the optimum quality retention and further develop a theoretical design of processing units and processing guidelines for decentralized food processing. Drying cocoyam at 80 °C and OFSP at 60 °C, respectively resulted in a relatively shorter drying time (135 and 210 min), a lower total color difference (2.29 and 11.49-13.92), greater retentions for total phenolics (0.43 mg GAE/100 g
DM
and 155.0-186.5 mg GAE/100 g
DM
), total flavonoid (128 mg catechin/100 g
DM
and 79.5-81.7 mg catechin/100 g
DM
) and total antioxidant activity (80.85% RSA and 322.58-334.67 mg AAE/100 g
DM
), respectively for cocoyam and OFSP. The β-carotene, ascorbic acid and vitamin A activity per 100 g
DM
of the OFSP flours ranged between 6.91- 9.53 mg, 25.90 − 35.72 mg, and 0.53 − 0.73 mg RAE, respectively.
The aim of the work was to develop an optimized routine for apple drying. The interaction of the drying parameters air temperature (35-85°C), dew point temperature (5-30°C), and air velocity ...(2.0-4.8 m/s) with drying time, color changes, and shrinkage was determined. Non-invasive online measurement techniques in the form of artificial vision systems in visible and infrared spectrum were developed and applied to guarantee an uninterrupted process. Quantification methods for the determination of color and shape changes of apple slices were established based on the images taken.
Results show that digital images are a feasible alternative for the monitoring of the relative changes in L* (R
2
= 0.92, p < 0.001), a* (R
2
= 0.96, p < 0.001), and b* (R
2
= 0.96, p < 0.001) during the drying of apples. It was observed that the color parameters as a function of moisture content follow a third-order development while shrinkage was linear (p < 0.001). The developed models for drying time t
dr
(R
2
= 0.99, p < 0.001), Total Color Difference ΔE (R
2
= 0.95, p < 0.001), and shrinkage S (R
2
= 0.68, p < 0.05) illustrate high interdependencies of the factors involved for the quality criteria studied. Throughout the parameter space investigated, increasing air velocity was shown to have a positive effect on the quality criteria investigated.
Summary
Cocoyam, an important staple crop especially among the low‐income earners in tropical regions of the world, is highly underutilised for industrial applications. This study investigates the ...nutritional, colour and rheological properties of instant flours (‘poundo’) from two cultivars of Colocasia esculenta (white‐NCe010 and purple‐NCe003) and Dioscorea rotundata (var. Oginni), and sensory attributes of doughs prepared from reconstituted flours. Tubers were processed into instant flours using cabinet and flash drying methods. Significant differences (P < 0.05) in the proximate and mineral composition and pasting properties of flours were found. Sensory panellists rated reconstituted poundo yam (8.17–8.20) and white cocoyam (7.50–7.95) higher than purple cocoyam (6.60–7.10) meals. Influence of drying method on sensory characteristics of flours was not significant. Instant poundo cocoyam and yam flours could serve as novel convenience and ready‐to‐eat food products which could contribute to increasing the commercial and industrial application options for these underutilised tubers beyond their present basic use.
Instant yam and cocoyam flours made from cabinet and flash drying methods were investigated for their nutritional, colour, rheological and sensory attributes. Varietal difference was more critical than drying methods to produce instant poundo flours with desirable quality attributes
•Development and implementation of an in process multi-sensor system.•Novel calibration approaches for HSI and color imaging are presented.•Investigation of dynamics of quality changes during drying ...of hops.•Quality changes are highly dependent on weather dependent raw material status.•(near to) real time measurement and control improves process and product performance.
Hops are a key ingredient for beer brewing due to their role in preservation, the creation of foam characteristics, the bitterness and aroma of the beers. Drying significantly impacts on the composition of hops which directly affects the brewing quality of beers. Therefore, it is pivotal to understand the changes during the drying process to optimize the process with the central aim of improving product quality and process performance. Hops of the variety Mandarina Bavaria were dried at 65 °C and 70 °C with an air velocity of 0.35 m/s. Bulk weights investigated were 12, 20 and 40 kg/m2 respectively. Drying times were 105, 135, and 195 and 215 min, respectively. Drying characteristics showed a unique development, very likely due to the distinct physiology of hop cones (spindle, bracteole, bract, lupilin glands). Color changes depended strongly on the bulk weight and resulting bulk thickness (ΔE 9.5 (12 kg), 13 (20 kg), 18 (40 kg)) whilst α and ß acid contents were not affected by the drying conditions (full retention in all cases). The research demonstrated that specific air mass flow is critical for the quality of the final product, as well as the processing time required. Three types of visual sensors were integrated into the system, namely Vis-VNIR hyperspectral and RGB camera, as well as a pyrometer, to facilitate continuous in-process measurement. This enabled the dynamic characterization of the drying behavior of hops. Chemometric investigations into the prediction of moisture and chromatic information, as well as selected chemical components with full and a reduced wavelength set, were conducted. Moisture content prediction was shown to be feasible (r2 = 0.94, RMSE = 0.2) for the test set using 8 wavelengths. CIELAB a* prediction was also seen to be feasible (r2 = 0.75, RMSE = 3.75), alongside CIELAB b* prediction (r2 = 0.52 and RMSE = 2.66). Future work will involve possible ways to improve the current predictive models.
BACKGROUND
It is well known that duration of pre‐drying storage impacts on hop quality. However, little knowledge exists regarding its actual effects on valuable hop components. To investigate these ...effects, fresh hop cones were stored for 5 or 24 h and dried for 210 min at 65 °C thereafter. Furthermore, to understand the effect of freezing hop cones on the essential oil content, both fresh and stored samples were frozen before and after drying.
RESULTS
The results from gas chromatography analysis show an increase in linalool, β‐caryophyllene, humulene, geraniol content and decrease in myrcene content dependent on the period of storage. Total colour difference ΔE values of 4.61 and 5.27 were obtained for fresh and stored hops respectively, indicating discoloration of hops during storage. Modelling of moisture curves revealed the Wang and Singh model to be suitable, with Radj2 values of 0.978 and 0.989 and root‐mean‐square error values of 0.037 and 0.019 for fresh and stored hops respectively.
CONCLUSION
The results from this study provide an in‐depth understanding on the changes occurring within the hop cones both during storage and drying and will further help hop processors optimize their storage times.
Commercial greenhouses are often referred to as the optimum heat dump for very low grade waste heat from a variety of sources. However availability, temperature levels and fluctuations in the ...availability necessitate a very different approach towards production planning as compared to traditional systems where energy supply is adapted to production demand and not the converse.
In this study, a commercial ornamental plant nursery that had switched its heat supply from natural gas to utilizing the waste heat of a commercial CHP system in 2007 was analysed. The differences between production planning and temperature regimes before and after switching to waste heat were compared. Furthermore, the degree of utilization of the waste heat available was evaluated.
The study undertaken showed three main results: Firstly, greenhouses present a good opportunity for the use of the low grade waste heat. However production needs to be planned very carefully to facilitate the production of high quality plants, for which traditional cultivation planning is unsuitable. Secondly, when planning on utilizing the heat (7.1 GWhth/a) of a CHP system which is sized based on electricity output (6.7 GWhel/a), to the full capacity, additional users need to be found and ideally heat storage integrated. Currently heat utilization amounts to less than 45% (3.1 GWhth) in total. Especially in summer most of the heat is discarded. Thirdly, several scenarios for utilization optimization were considered. The scenarios described allow for an increase of heat utilization to 62% or 4.4 GWhth using some of the heat to run absorption chillers to provide cooling in summer and storing excess heat in long term heat stores (300 MWhth) to reduce the additional gas demand. The results of the economic evaluation show that the integration of a cold store, supplied by the coolth by using an absorption chiller is financially attractive with a resulting payback period of 2.9 years, whilst consideration of integration of a PCM heat store is far from being viable with a payback period of almost 300 years.
•Greenhouses are a good heat sink for low grade waste heat.•Production performance is increased through availability of waste heat.•Additional sinks are needed to increase heat utilisation particularly in summer.•Absorption chillers are an economically viable addition to the process.
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