Fruit firmness is often the first of many quality major attributes judged by the consumer and is, therefore, extremely important in overall product acceptance. Guava suffers a rapid loss of firmness during senescence which contributes greatly to its short postharvest life and susceptibility to fungal contamination. Changes in flesh firmness between control and coated fruit samples during 12 days of storage at 11◦C are shown in Fig. 1A. Initial flesh firmness values were similar for control and coated samples. On the third day of storage uncoated guavas began to show a gradual loss of firmness. The firmness of coated guavas also decreased progressively, but on and after the sixth day of storage firmness values for coated samples were higher compared to the control samples, and then significant differences were noted between 0.5 and 2.0% chitosan coating treatments for the same period. With regard to coated samples, 2.0% chitosan coating was more effective in preventing decrease of fruit firmness than the other treatments at 11◦C. For example,
firmness in the fruit treated with 0.5, 1.0 and 2.0% chitosan was 6, 10 and 14% higher than that in the control after 9 days of storage,respectively.