Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsfoodscitech.4c00954

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

In this study, the effects were explored of digestive enzymes and pH on the bioaccessibility of polyphenols, flavonoids, and antioxidant activities in Hojicha (roasted green tea, RT) infusions during simulated in vitro digestion. Roasting modifies its polyphenolic profile and reduces bitterness, making it a popular variation of green tea. In this study, RT was used for assessing how the roasting-induced changes influenced the tea’s bioaccessibility and stability under digestive conditions. A two-step gastrointestinal digestion model was applied to mimic real digestion. Total polyphenol content (TPC), total flavonoid content (TFC), and antioxidant activity (DPPH, ABTS, FRAP, and MIC) were measured at different digestion stages. Gastric conditions led to a 2.07-fold reduction in TPC and a 4.27-fold reduction in TFC. Digestive enzymes enhanced bioactive compound stability, with TPC and TFC bioaccessibility reaching 56% and 25% in the simulated digestion with digestive enzymes (MD) group, compared to 52% and 20% in the without digestive enzymes (WOE) group. Antioxidant activities were also better preserved, with antioxidant activity retention at 31% in the MD samples versus 19% in the WOE. These findings emphasize the key role of digestive enzymes in maintaining the antioxidant potential of roasted green tea during digestion, providing insight into future research on roasting methods and tea functionality for product development.

DOI： 10.3390/foods14020311

Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The consumption of raw yam tuber through grated yam “tororo” is a major and popular diet in Japan. However, few studies have been undertaken to evaluate the digestive characteristics of raw yam tubers. This study aimed to fill this gap by investigating the changes in the protein profile, protein and starch digestibility, antioxidant capacity and microstructure of two typical yam tubers (Nagaimo N-10 and Nebaristar) in the Japanese diet, applying a simulated in vitro digestion method. Results showed that both samples contained a considerable protein content of about 11% (dry basis) and a protein digestibility of 43–49%. The electrophoretic patterns confirmed that dioscorin was the main protein of the yam tuber, and it could be digested into peptides and free amino acids with low molecular weight during in vitro digestion. The starch hydrolysis results suggested that eating raw yam tuber cannot induce a fast glycemic increase for consumers due to a low starch digestibility of 4.4–6.1%. In addition, Nebaristar showed a higher bioaccessibility in some key amino acids and total phenolic content than the Nagaimo N-10. This study provides some essential nutritional information and simulated digestion behaviours of the raw yam tubers, which could be useful for consumers and industries when buying and processing yam tubers from the perspective of changes in the nutritional profile during digestion.

DOI： 10.3390/foods11233892

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Dried green tea leaves (Sencha) were manufactured using various scale manufacturing systems, which processed batch‐wise for 15 kg (15 K), 60 kg (60 K), and 120 kg (120 K) fresh leaves. Total polyphenol content (TPC) and antioxidant activity (FRAP and DPPH) of dried tea leaves and infusions were evaluated. The values of TPC, FRAP, and DPPH of dried tea leaves processed by the larger systems (120 K and 60 K) were significantly higher than the values by the smaller system (15 K). In contrast, with the larger system scale, some of the leaves were not fully rolled and were not mechanically damaged during processing. These incomplete processing conditions led to the extraction of significantly fewer polyphenols in hot water, which might influence the health benefits of green tea infusions. This study indicated that there could be an optimal system scale that considers the balance between economic and health benefits, involving the optimization of production quality/amount.

Practical Applications

After harvest, Japanese green tea leaves are gradually dried using batch‐wise processing systems. The processing system scale is permanently fixed by the size of one batch, which is selected according to the circumstances of the production area and demand for tea production. However, tea leaf producers have experientially been aware of the quality variations in the final tea products, depending on the system scale. In this study, the impact of the scale of the manufacturing system on the functional properties of green tea was investigated. The results revealed that the hot water extract of dried tea leaves processed by a larger system scale tended to have less functional properties than those by a smaller system. This was due to the comparatively incomplete rolling conditions of tea leaves processed by larger manufacturing systems. These differences influence the preservability and extractability of the chemical components of the green tea leaves. Our findings provide beneficial information regarding processing conditions for better functional green tea infusions.

DOI： 10.1111/jfpe.14185

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jfpe.14185

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Tsinghua University Press  

DOI： 10.1016/j.fshw.2021.12.024