Volume 21, Issue 1

Rapid and effective preparation of hydrogels with excellent properties by cyclic freezing–thawing has remained an enormous challenge as hydrogels prepared using traditional freeze–thaw methods demonstrate poor, unstable and unalterable mechanical properties. In this study, an innovative method was introduced to develop a nanocellulose hydrogel with excellent properties via cyclic freezing–thawing and ionic cross-linking, and various methods were used to characterise the structure and properties of the hydrogel. The results showed that hydrogen and ester bonds existed in the soy hull nanocellulose–sodium alginate–calcium chloride (SHNC/SA/Ca 2+ ) hydrogel and that the internal structure of the hydrogel changed from a lamellar to three-dimensional network structure owing to low temperature, increasing the cross-linking density of SHNC and SA and enhancing the mechanical strength of the hydrogel. Meanwhile, the SHNC/SA/Ca 2+ -4 hydrogel demonstrated excellent elongation (804 %), viscoelasticity (storage modulus = 89.6 kPa), mechanical strength (tensile strength = 0.59 MPa, compressive strength = 1.52 MPa), ionic conductivity (3.84 S/m), transparency (54 %), anti-ultraviolet properties and fatigue resistance. The simple preparation process, excellent performance and three-dimensional porous network structure of the nanocellulose hydrogel offer broad application prospects in many fields.

Copper (Cu(II)) gets ionised easily, leaches into food, and becomes environmentally toxic. Hence, Cu(II) tolerant bacterial strains with high biosorption potential were screened from fruit, dairy and flour mill waste by in vitro antimicrobial susceptibility testing methods. Based on high tolerance capabilities (>250 mM Cu(II) ions), two strains, Klebsiella pneumonia (V1) and Cronobacter sakazakii (V2), were identified through genetic characterisation. The Cu(II) biosorption mechanism (V1, V2, V1 + V2) was further evaluated through the viable/dead cell method. The maximum biosorption of Cu(II) (91.3 %) was achieved in optimised conditions (pH 5–6, 30 °C and 30 min contact time) through V1 + V2 and well-fitting with Freundlich ( R 2  = 0.9764) and Langmuir ( R 2 = 0.9834) isotherm plots. Further, the exopolysaccharides from food waste were produced through a fed-batch fermentation process, where the V2 strain produced a maximum of 224.52 mg/L. The bacterial biosorbents reported in this study could benefit industrial applications.

In this study, five types of white cheese, with one serving as the control sample, were produced. While the control cheese was produced without adding any spices, the others were processed by adding capia pepper at concentrations of 0.1 %, 0.2 %, 0.3 %, and 0.4 % (w/w) relative to the milk used. Then, all cheeses were vacuum-packed and ripened at 6 ± 2 °C for a period of 3 months. Analyses, including measurements of dry matter, fat, pH, titratable acidity, salt, total protein, ripening rate, nonprotein nitrogen rate (NPN), amino nitrogen rate, electrophoretic casein fractions, color properties, and sensory evaluations, were conducted on cheese samples taken at the 3rd, 30th, 60th, and 90th days of ripening. Additionally, it was observed that cheeses with 0.4 % capia pepper added were more favored than the other cheeses. Due to the sensory evaluation made by the panellist, ripened cheeses were more highly appreciated than fresh cheese, but the sheep milk flavor was not consistently cited as the reason for preference. The extra aromatic taste from sheep milk was detected by the panelists and not perceived as irritating. The use of capia pepper in white cheese changed the color and sensory properties, but it was not statistically significant.

The impacts of hydration (45 % of water as intermediate level, 80 % for excess water) and botanical origin of starch (wheat WS, tapioca TS) on swelling, leaching and crystallinity loss were studied. A novelty was the wide temperature range (30–90 °C including the reversible domain) and the use of imaging techniques (laser scattering, optical microscopy) for swelling, in addition to the conventional technique (weighting after centrifugation). Swelling before the gelatinization onset was better revealed by using imaging techniques, while swelling in excess water at high temperature (>60–75 °C) differed between the conventional and laser scanning techniques, suggesting overestimation of the former. Gelatinization of high water-demanding starch under intermediate to low hydrations has been poorly documented and little anticipated in breadmaking for which the selected intermediate hydration applies. The study showed that TS at 45 % hydration gelatinized to a lesser extent than WS, with lower increase in granule size (<60 °C) and more heterogeneous granule integrity (>60 °C).

This study aimed to investigate the effects of home vacuum packaging on the total antioxidant capacity (TAC) and total phenolic content (TPC) levels of seven types of berries (raspberry, hawthorn, goldenberry, blackberry, strawberry, redcurrant, and blueberry) under different storage conditions. The berries were either vacuum+ or vacuum− and stored in a household refrigerator at +4 °C or frozen at −18 °C. Samples stored at +4 °C were analyzed on days 0, 7, and 30, while frozen samples were analyzed on days 0, 30, and 90. The results showed that TAC levels of fruit samples decreased by 18.88 % after 30 days at +4 °C in the vacuum− samples, while the vacuum+ samples showed only a 9.64 % reduction. Similarly, after 90 days of freezing, TAC levels decreased by 19.35 % in vacuum− samples, compared to an 11.56 % reduction in vacuum+ samples. Moreover, TPC levels of fruit samples decreased by 81.81 % after 30 days at +4 °C in the vacuum− samples, while the vacuum+ samples showed a 72.99 % reduction. After 90 days of freezing, TPC levels decreased by 75.99 % in vacuum− samples, while the vacuum+ samples showed only a 48.30 % reduction. Although TAC and TPC levels decreased over time at both +4 °C and −18 °C, the vacuum+ samples generally retained higher levels of TAC and TPC compared to the vacuum− samples, suggesting that vacuum packaging can slow down enzymatic and oxidative reactions. These findings indicate that home vacuum packaging could be a useful method for preserving the nutritional quality of berries and potentially reducing food waste.

The present study focused on the influence of different solution-based osmo-sonic pre-treatments on the drying, rehydration, and quality attributes of ginger cubes. Osmo-sonic pre-treated drying followed the empirical page model, and rehydration was better explained by the exponential model. All the pre-treatments increased the effective moisture diffusivity and mass transfer coefficient, which increased the drying rate from 22.34 to 79.78 %. Pre-treatment led to an increase in appearance by an increase in L* and a* and a decrease in b*. The FTIR spectra showed the absence of a new functional group, but a change was observed in the characteristics band upon pre-treatment. The comparison of different pre-treatment showed that the CA + US pre-treatment had a better drying profile, whereas DW + US had a better antioxidant profile with the highest TPC (22.31 mg GAE/g), TFC (58.37 mg QE/g), DPPH inhibition (89.01 %), and ABTS assay (13.27 mg TE/g).