Impact of drying temperature and salt pre-treatments on drying behavior and instrumental color and investigations on spectral product monitoring during drying of beef slices

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

Method comparison between real-time spectral and laboratory based measurements of moisture content and CIELAB color pattern during dehydration of beef slices

In this study, partial least square (PLS) regression models were developed to predict moisture content (MC) (model 1), CIELAB color (model 2) or all four parameters (model 3) of beef slices during drying. Model development was based on data from two measurement campaigns of MC (%), CIELAB L*, a* and b*values and hyperspectral data in the range of 500–1009 nm. To increase the robustness of the models, the beef samples varied dependent on cattle breed, cut and pre-treatment. With low-cost, non-invasive continuous monitoring systems in mind, the models were simplified by wavelengths selection. The Deming and Passing-Bablok regression and the Bland-Altman plot revealed high model performances. Mean differences (full/reduced model) of −0.64/-0.64 for MC, −0.14/-0.15 for CIELAB L*, 0.05/0.04 for a* and 0.08/0.06 for b* values were achieved for model 3, which shows the high potential for simple real-time monitoring applications combining all investigated factors and parameters

Influence of pre‐drying storage time on essential oil components in dried hops (Humulus lupulus L.)

BACKGROUND: It is well known that duration of pre-drying storage impacts on hop quality. However, little knowledge existsregarding its actual effects on valuable hop components. To investigate these effects, fresh hop cones were stored for 5 or24 h and dried for 210 min at 65 °C thereafter. Furthermore, to understand the effect of freezing hop cones on the essentialoil content, both fresh and stored samples were frozen before and after drying. RESULTS: The results from gas chromatography analysis show an increase in linalool, -caryophyllene, humulene, geraniol con-tent and decrease in myrcene content dependent on the period of storage. Total colour difference ∆E values of 4.61 and 5.27were obtained for fresh and stored hops respectively, indicating discoloration of hops during storage. Modelling of moisturecurves revealed the Wang and Singh model to be suitable, with R2adjvalues of 0.978 and 0.989 and root-mean-square errorvalues 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 conesboth during storage and drying and will further help hop processors optimize their storage times

Effect of maturation and freezing on quality and drying kinetics of beef

The quality of dried meat products and the drying kinetics significantly depends on the status of the raw material going into the drying process. The aim of this study was the determination of the impact of meat status (fresh, mature, frozen-thawed) on the drying kinetics and the resulting quality in terms of colour changes and spectrally deductible information. Drying tests were conducted using meat from organically raised bulls. In fresh meat, freezing leads to a decrease of the drying rate, whilst for matured meat the opposite is true. Aging and freezing have little effect on the end product quality in terms of final product colour. However, water content can be detected hyperspectrally and resolved spatially for all stages of the pro-cess. With regards to water content prediction, the MCUVE-PLS method performs best for the fresh and fresh frozen-thawed version with seven wavelengths, an r2 of 0.97 and 0.88, and RMSE of 0.15 and 0.17 for the test set, respectively