*4.14. Fruit Firmness Measurement and Determination of Water-Soluble Pectin Content*

As described by Wu and Abbott [59], the fruit firmness was quantified using a Firmness tester (GY-2). Fifteen unbroken tomatoes were taken from each group. The equator of the fruit was placed under a flat probe, and the maximum value was read after pressing down. Each fruit was measured at least three times. Test parameters: Probe pressure rate 1 mm/s, Pressing distance 3 mm.

The content of pectin in tomato fruit was detected by the water-soluble pectin content kit of Suzhou Keming Biotechnology Co., Ltd. (Suzhou, China The principle of determination is to use the acid solution to extract water-soluble pectin, and to determine the content of pectin by carbazole colorimetry. Pectin is hydrolyzed to galacturonic acid, which condenses with carbazole reagent in sulfuric acid solution. The resulting material has a maximum absorption peak at 530 nm.
