The Sensory Quality and the Textural Properties of Functional Oolong Tea-Infused Set Type Yoghurt with Inulin

Effects of instant controlled pressure drop treatment combined with refractance window drying on infusion quality of made green tea

BACKGROUND

The study aimed to determine the effects of instant controlled decompression of steam pressure, termed as ICPD (instant controlled pressure drop) on fresh tea leaves, when combined with refractance window drying (RWD) of rolled green teas during green tea manufacturing. The ICPD steam treatment pressure (TP; 0.1-0.3 MPa), treatment time (TT; 10-20 s) and refractance window drying temperature (RWDT; 70-90 °C) were used as the processing parameters for manufacturing of green tea.

RESULT

Response surface methodology was employed to enumerate the effects of ICPD process conditions and temperature of RWD on total phenolic content (TPC), total flavonoid content (TFC) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity of the green tea infusion. An optimum condition for green tea processing was found at TP 0.2 MPa, TT 20 s with RWDT at 70 °C. In comparison to made green tea manufactured without ICPD treatment, the ICPD treated green tea showed enhanced TPC, TFC and DPPH radical scavenging activity along with better colour and sensory attributes. The microstructural study of ICPD treated green tea samples showed more deformed cell surface integrity, larger stomatal pore size and cracks at the leaf surface in comparison with non-treated green tea sample.

CONCLUSION

Present study reveals that an ICPD treatment at 0.2 MPa for 20 s can be used as an alternative to the traditional enzyme inactivation step of hot water treatment, for green tea leaves to improve the infusion quality in terms of increased levels of TPC and TFC and DPPH radical scavenging activity. © 2024 Society of Chemical Industry.

Effects of microencapsulation in dairy matrix on the quality characteristics and bioavailability of docosahexaenoic acid astaxanthin

BACKGROUND

Compared with free astaxanthin (Asta), docosahexaenoic acid astaxanthin monoester (Asta-C22:6) has higher stability and bioavailability. However, Asta-E is still unable to be used in the water system. Hence it is necessary to build a water-soluble delivery system. In this study, Asta-C22:6 microemulsion and microcapsule using whey protein isolate (WPI) and hydroxypropyl-β-cyclodextrin (HPβ-CD) as composite wall material were prepared. They were added to three dairy products (milk powder, yogurt and flavored dairy product). A dairy product rich in Asta-C22:6 with high bioavailability was designed by measuring quality characteristics, sensory evaluation and in vivo experiments.

RESULTS

Compared with spray drying, the freeze-drying microcapsule had a higher encapsulation efficiency (72.5%), water content (4%) and better solubility, and Asta-C22:6 microcapsule (1 g L^-1 ) yogurt had the best quality. The bioavailability of Asta-C22:6 microcapsule yogurt was further evaluated. After a single oral dose in mice, the bioavailability of Asta-C22:6 microcapsule in yogurt was significantly increased (C_max  = 0.31 μg mL^-1 , AUC_0-T  = 3.20 h μg mL^-1 ).

CONCLUSION

We successfully prepared Asta-C22:6 microcapsule yogurt, which improved the stability and bioavailability of Asta. The present research is meaningful for delivering unstable bioactive small molecules based on WPI and HPβ-CD. It provides an experimental basis for the application of Asta-C22:6 and the development of functional dairy products. © 2022 Society of Chemical Industry.

The Sensory Quality and the Physical Properties of Functional Green Tea-Infused Yoghurt with Inulin

The purpose of this study was to investigate the influence of the addition of inulin (3%, 6% and 9%) to green tea-infused set type yoghurt on its sensory quality and physical properties. Yogurts were made by combining green tea with milk and inulin and inoculated with freeze-dried starter cultures YO-122. Incubation was conducted at 43 °C for approximately 4.5 h until a pH value of 4.5–4.6 was achieved. For the prepared yoghurts, a panel of experts (n = 10) was selected, characterized 35 attributes and conducted a sensory quality assessment of these yoghurts using the Quantitative Descriptive Profile method. Additionally, instrumental analyses such as yield stress, adhesiveness, firmness, physical stability and color parameters were also carried out. The use of green tea infusion increased the perception of green tea flavor, bitterness, astringency, dark color of the yoghurt and the existing whey, which worsened the overall sensory quality of the yoghurt. The addition of inulin (9%) to the green tea yoghurt, increased the perception of sweet, peach flavor and aroma and improved the firmness of the yoghurt while reducing the perception of sour taste, which improved the sensory quality of the yoghurt. Both inulin and green tea affected the physical properties of the yoghurts, causing an increase in the yield stress (43%, and 20%, respectively) and deteriorated the stability of the yoghurts. Green tea affected the color of the yoghurts, causing the lightness to decrease. The L* parameter decreased from 89.80 for the control sample to 84.42 for the green tea infused yoghurt. The use of infused green tea in yoghurt production makes it necessary to use ingredients that will neutralize its adverse effects on sensory quality and physical parameters of yoghurt, and such an additive can be prebiotic fiber–inulin at a concentration of 9%.