Puer Tea is a geographical indication product of Yunnan Province, and as the provincial capital, Kunming serves as the distribution center for Puer tea across China and worldwide, playing an irreplaceable role in its development. Located at a low latitude (25°N, 103°E) and high altitude (1892m), Kunming experiences a spring-like climate year-round, influenced by atmospheric circulation, geographic location, and altitude.
The seven-son Cake tea is one of the main representative shapes of Yunnan Puer tea. A single cake often represents the smallest sales unit, and the weight of a single cake (commonly known as the cake weight) should comply with the requirements of JJF1070-2005, “Rules for Metrological Inspection of Net Content of Quantitatively Packaged Commodities.”
The researchers conducted experiments in Kunming, storing 10 cakes each of raw and ripe Puer tea. They recorded the daily cake weights and temperature and humidity values over a period of 12 months.
During the 12-month storage period, the monthly average cake weights of both raw and ripe Puer teas fluctuated. From the seventh month (February 2019) to the tenth month (May 2019), there was a dry and hot climate with temperature values exceeding humidity values for four consecutive months. During this time, the monthly average cake weights of both raw and ripe teas fell below 357g. The lowest monthly average cake weights were reached in the tenth month (May 2019) for raw tea and the ninth month (April 2019) for ripe tea, while the highest monthly average cake weights occurred in the third month (October 2018) and second month (September 2018). The appearance of the lowest and highest monthly average cake weights for raw tea lagged behind that of ripe tea by one month.
Based on the results of this study, during the 12-month storage period, the monthly average cake weights of raw tea were non-compliant for four months, and those of ripe tea were non-compliant for five months. Although the product standard GB/T22111-2008 for Puer tea specifies that the net content of compressed Puer tea should be measured with a moisture content of 10%, inspections are carried out according to JJF1070-2005, using direct weighing methods. Even when spot checks are conducted at the production site, the results do not guarantee compliance with the net content throughout the entire distribution process.
Over the 12-month storage period, the fluctuation range of single cake weights for both raw and ripe teas was 13.30–22.43g, causing a variation of 3.7%–6.3%. If the volume of transactions is large and settled by weight, it could inevitably lead to disputes. Recognizing the changes in weight during the storage of Puer tea can effectively address any anomalies that arise during storage.