Thẩm định phương pháp phân tích và đánh giá ảnh hưởng của nhiệt độ pha trà đến hàm lượng polyphenol tổng trong nước trà của một số sản phẩm trà Việt Nam

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Tác giả: Thị Anh Đào Lê, Công Hậu Nguyễn, Phạm Như Quỳnh Nguyễn, Thành Nho Nguyễn

Ngôn ngữ: vie

Ký hiệu phân loại: 663.94 Tea

Thông tin xuất bản: Tạp chí Khoa học - Đại học Sư phạm TP Hồ Chí Minh, 2021

Mô tả vật lý: 993-1005

Bộ sưu tập: Metadata

ID: 498012

Thêm vào giỏ

Produced from leaves of Camellia sinensis L. (Kuntz), tea is among the most common beverages worldwide. Tea plants have been grown in nearly 30 countries. In this study, the Folin-Ciocalteu method was applied to determine the total polyphenol contents (referred to milligrams gallic acid mass equivalence or GAE) in tea products (one oolong and three ancient teas, including red, green, and white) based on ISO 14502-1:2005 with some modifications, typically ultrasonic-assisted single extraction using methanol:water (7:3 v/v) as an extraction solvent at 70oC with the extraction ratio of 0.200:10.00 (g:mL). The analytical method was validated using Shimadzu 1800 UV-Vis instrument with favorable linearity of R2 >
0.995, linear range of 10-70 mg GAE L-1, acceptable repeatability, reproducibility (% RSDs were 0.79 and 1.2 for intra-day and inter-day, respectively), and high recoveries (higher than 98% for spiked samples). The total polyphenol contents (mean values, mg GAE g-1 dried weight, in brackets) performed a descending order of white (206.62) ~ green (201.33) >
red (167.42) >
oolong (139.18) teas due to the variation in the oxidation levels during the fermentation, particularly for red and oolong teas. Higher polyphenol contents released in tea infusions were observed regarding the increasing brewing temperature, except for oolong tea with its specific fluctuation, maybe due to its "wrap-curled" structure, leading to longer brewing durations for polyphenol to be extracted stably and completely. This study contributes to enriching data for Vietnamese tea products in the context of high production and export.Sản xuất từ lá của cây Camellia sinesis L. (Kuntz), trà được xem là một trong những thức uống phổ biến nhất trên thế giới và cây trà được trồng ở khoảng 30 quốc gia. Trong nghiên cứu này, phương pháp Folin-Ciocalteu được áp dụng để xác định hàm lượng polyphenol tổng (quy về milli đương lượng gam của gallic acid, GAE) trong các mẫu trà thành phẩm (ba mẫu trà cổ thụ bao gồm trà đỏ, trà xanh, trà trắng và một mẫu trà oolong) dựa trên ISO 14502-1:2005 với một số thay đổi, cụ thể là chiết một lần bằng dung môi chiết methanol:nước (7:3, v/v) có sự hỗ trợ của siêu âm ở 70 oC với tỉ lệ chiết 0.200:10.00 (g:mL). Phương pháp phân tích được thẩm định trên thiết bị UV-Vis 1800 của hãng Shimadzu với độ tuyến tính phù hợp (R2 >
0.995), khoảng tuyến tính 10-70 mg GAE L-1, độ lặp lại và độ tái lặp tốt (%RSD lần lượt là 0.79 và 1.2% cho độ lặp trong ngày và giữa các ngày) và tỉ lệ phục hồi cao (trên 98% cho các mẫu thêm chuẩn). Hàm lượng polyphenol tổng (giá trị trung bình tính bằng mg GAE g-1 khối lượng khô trong dấu ngoặc đơn) thể hiện xu hướng giảm dần giữa các mẫu trà, cụ thể trà trắng (206.62) ~ trà xanh (201.33) >
trà đỏ (167.42) >
trà oolong (139.18) do sự khác biệt về mức độ oxy hoá trong quá trình lên men, đặc biệt đối với trà đỏ và oolong. Hàm lượng polyphenol phóng thích vào nước trà thể hiện xu hướng chung tăng dần khi tăng nhiệt độ pha trà, ngoại trừ mẫu trà oolong có xu hướng riêng, có thể do cấu trúc "cuộn xoắn" của loại trà này, dẫn đến thời gian ngâm trà cần phải dài hơn để polyphenol có thể được phóng thích ổn định và hoàn toàn. Nghiên cứu này đóng góp một phần khiêm tốn để làm giàu thêm dữ liệu cho các sản phẩm trà Việt Nam trong bối cảnh lượng trà sản xuất và xuất khẩu cao.

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