Band 14, Heft 3 -

The structural characteristics of lotus ( Nelumbo nucifera Gaertn.) seeds preserved by microwave vacuum drying (MVD) were investigated under various drying parameters, including microwave power density and vacuum degree. Dried lotus seeds were examined for microstructure by field emission scanning electron microscopy. Fractal dimension of the microscopic images was calculated by the box counting method. The apparent physical changes of the seeds, namely shrinkage ratio, rehydration rate, and hardness index, were determined to correlate well with their microstructural changes computed by the normalized changes of the fractal dimension (ΔFD/FD 0 ). The samples at −90 kPa, 15 W/g exhibited a lower shrinkage ratio (46.2 %), higher rehydration rate (187.5 %) and lower hardness (3692.4 N). Although the physical and microstructural changes of the samples prepared by different drying methods (MVD, microwave drying, and hot air drying) varied, the changes of the ΔFD/FD 0 of the dried samples exhibited the same trends.

Apple jam is one of the favorite foods consumed worldwide. This study investigated the effect of storage time and sugar concentration on water dynamics in Fuji and Yinduqing , using low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques. The samples were taken for jam preparation with various concentrations of sugar solution (0, 25, 50 and 75- o Brix) and stored at a room temperature of 20 °C for 16 days. The LF-NMR relaxation time T 2 distribution displayed bound, intermediate and free water, respectively. The lowest T 2 range reflected lowest sugar hydrogen mobility depending on total soluble solids (TSS) and water content. A significant correlation ( r > 0.9) existed between LF-NMR analysis and physicochemical parameters (water content, color, pH and TSS). MRI displayed uniform water distributions in samples with low sugar concentration. Fluorescence microscopy was used to evaluate sugar crystals and microstructural changes during processing. The study demonstrated the viability of LF-NMR method in determining water dynamics in the apple jams upon processing and storage that may be implemented for quality analysis in other jam products.

Since materials are the substantial foundation for 3D printing, the lack of theoretical research on 3D printing food materials restricts the development of 3D printing in food field. Based on the principle of 3D starch gelatinization printing, this study revealed the effects of pea protein on the printability of potato starch-based 3D printing materials in granular structure, crystalline structure, chemical structure, textural properties, and thermal properties, through scanning electron microscope, X-ray diffraction, Fourier-transformed infrared, differential scanning calorimetry, and textural method, and developed new food materials for 3D printing. The study indicated the structural properties and physicochemical properties changed regularly with the increase in the content of pea protein, when the content of pea protein was 1%, the printing quality was best. The study provides a new theory for the application of 3D printing in food production and technical support for actual production.

The structural and functional properties of slowly digestible starch (SDS) modified using pullulanase and prepared from chestnut starch were studied. The modified chestnut starches had 41.9 % SDS, which was higher than native chestnut starches (6.51 %) and cooked chestnut starches (18.6 %). The hydrolysis rate of the modified starches was 74.1 %. Scanning electron microscopy showed that the modified starch granules had a large surface area with signs of cracks and dents, and the cross-sections showed hollow internal structures. X-ray diffraction indicated that the crystallisation of the starch changed from the Cb-type to the V-type, although it retained a few C-type characteristics. Compared with native chestnut starch, the modified starches have a higher gelatinisation temperature using differential scanning calorimetry; and the texture profile analysis hardness, chewiness, cohesiveness, and gumminess of modified starch gels decreased significantly, while adhesiveness increased. When debranched using pullulanase there was a decreased solubility, swelling power, and freeze-thaw stability of the modified starches. These findings suggest that pullulanase modification changed the in vitro digestibility and crystalline structure of the modified starches.

Edible bird’s nest (EBN) has a high nutritional and medicinal value. In this study, physicochemical and processing properties of EBN proteins were investigated for better application of EBN. EBN proteins were extracted by combination of several methods. Electrophoresis showed that EBN contained proteins with molecular weight of 128, 106, 80, 55, 43, and 34 kDa. The denaturation temperature of EBN proteins was 62.5°C and heating promoted hydrophobicity as well as dramatically affecting the gel microstructure of EBN proteins. EBN proteins also showed excellent emulsifying activity and stability while their foaming properties were not good enough.

Carrot peel generated from the juice factories is considered as waste and it can be potential for further recovery of carotenoids. Drying treatment is essential to minimise degradation of carotenoids and ease transportation as well as storage of the peel for further processing. This study aimed to determine the impact of different drying conditions on its physicochemical and antioxidant properties to propose the most suitable conditions for drying carrot peel for further recovery of carotenoids. Drying conditions were found to significantly affect retention of total carotenoids, β-carotene, lutein and lycopene as well as antioxidant capacity in carrot peel. Optimal conditions for hot-air drying were at 40 °C for 3.5 h; vacuum drying were at 60 °C, −60 kPa for 4 h; dehumidification drying was at 50 °C for 2.5 h with relative humidity (RH) of 16–21 %; and microwave drying was at 600 W for 7 min. In comparison with freeze drying (control) and other three different drying methods at each optimal conditions, dehumidification drying at 50 °C with RH of 16–21 % was the most effective method as it retained high levels of total carotenoids (2.75 mg/g DW), β-carotene (1.57 mg/g DW), lutein (0.17 mg/g DW) and lycopene (0.78 mg/g DW). Dried carrot peel also had potent antioxidant properties (ABTS: 4.71 and CUPRAC: 19 mM TE/g DW). Therefore, these conditions are recommended for drying carrot peel for further recovery of carotenoids.

In this study, the quality of matured coconut water was improved through fermentation with Saccharomyces cerevisiae D254. During fermentation, the kinetic models of yeast growth, alcohol production, and sugar consumption were established based on logistic and Leudeking–Piret equations. Fructose, glucose, sucrose, total phenolic content, and antioxidant capacity (FRAP and ABTS values) were measured consecutively during fermentation. Results showed that R 2 for the three models of yeast growth, alcohol production, and sugar consumption were 0.9772, 0.9983, and 0.9887, respectively. Total phenolic and antioxidant assays showed a similar evolution during fermentation, with a rapid increase in exponential phase and an unchanged trend in stationary phase. Moreover, total phenolic and the two antioxidant capacity methods were highly positively correlated. Pyruvic, lactic, citric, and succinic acids were the main organic acids in coconut water after fermentation.

The effect of hot air convective drying (HACD), microwave-vacuum drying (MWVD) and combined drying (HACD + MWVD) on the drying kinetics, bioactive compounds and color of blueberry pomace was evaluated. Drying time of blueberry pomace ranged from 0.6 to 6.7 h and moisture diffusion coefficients ranged from 7.94 × 10 –8 to 1.83 × 10 –7 m 2 /s. Drying caused degradation of total polyphenolics (TP) (39–76%), monomeric anthocyanins (21–77%) and antioxidant capacity values (24–76%). Drying time was shortened even by 91%, when MWVD was used instead of HACD. MWVD of blueberry pomace resulted in the smallest, while HACD at 60°C in the greatest loss of bioactive compounds and antioxidant capacity. HACD at 60°C + MWVD allowed to obtain a product with a higher content of TP, monomeric anthocyanins and a stronger antioxidant capacity than HACD at 90°C + MWVD. Combination of HACD at 60°C with MWVD allowed for the shortening of HACD time by 75% as well as for hapering the chemical changes as compared to HACD at 60°C. Even when the combination of HACD at 90°C with MWVD shortened the drying time by 68%, it did not improve the retention of TP, monomeric anthocyanins and antioxidant capacity when compared to HACD at 90°C.

The aim of this study was to select among lactic acid bacteria (LAB) and yeast a potential β-galactosidase producer, based on bioprocess parameters. From the selected microorganism,  different organic cheaper nitrogen sources (single and combined) with low cost for β-galactosidase production were evaluated. Lactobacillus reuteri B-14171 showed the highest enzymatic activity (1,286 U L −1 ), high productivity (28.78 U L h −1 ) and yield factor (82.32 U g −1 ), evidencing its potential for β-galactosidase production. All organic nitrogen sources tested were viable for the enzymatic production using L. reuteri B-14171. The MMRS casein (3.0 g L −1 ) + inactive beer yeast (3.0 g L −1 ) as nitrogen source increased the enzymatic activity (1269 U L −1 ) with 1.83 times lower production costs of culture medium when compared to MMRS-yeast extract B. The MMRS casein + inactive beer yeast has proved to be an innovative and cheaper nitrogen source for β-galactosidase production by L. reuteri B-14171.

We aimed to develop a process for making salted duck eggs using recycled mustard pickle brine. Saturated brine was generated from mustard pickle salt (experimental) or solar salt (control). Mustard pickled egg (MPE) weight slightly decreased and salted egg (SE) weight slightly increased following pickling. For MPE and SE egg yolk (MPEY/SEY), yolk index, NaCl content, total solids, and hardness significantly increased ( p < 0.05) during the pickling period, with significantly greater increases ( p < 0.05) in yolk index and NaCl content at 28 days for MPEY vs. SEY. MPE and SE egg white (MPEW/SEW) parameters, including albumen index, moisture, pH value, G′, G” and η, decreased significantly ( p < 0.05), whereas NaCl content, total solids, and tan δ increased significantly ( p < 0.05). Our results showed that mustard pickle brine could be applied in making salted duck eggs, thereby decreasing the disposal of excess brine from food production.