2.6.1. Fruit Pigments

Chlorophyll and carotenoid contents in the pulp of guavas (three replicates) were spectrophotometrically measured using the assay of Wellburn (1994). The absorbance of the extract was determined at a spectrum of 663 nm for chlorophyll a, 646 nm for chlorophyll b and 470 for carotene using a spectrophotometer (UV1901PC spectrophotometer). Pigment contents were calculated by the next equations:

$$\text{Chlorophyll a (\(\mu\) mL}^{-1}\text{)} = 12.21 \to 663 - 2.81 \to 646\tag{4}$$

$$\text{Chlorophyll b (\(\mu\) mL}^{-1}) = 20.13 \to 646 - 5.03 \to 663\tag{5}$$

$$\text{Total chlorophyll} \left(\text{\(\mu\) mL}^{-1}\right) = \text{Chlorophyll a} + \text{chlorophyll b} \tag{6}$$

Total carotenoide (μg mL<sup>−</sup>1) = [(1000 E470) <sup>−</sup> (3.27 <sup>×</sup> Chlorophyll a + 104 <sup>×</sup> Chlorophyll b)]/198 (7)

where E = Optical density at the specified spectrum length and findings were calculated as mg/100 g of fresh weight (FW).

2.6.2. Ascorbic Acid, TSS, Titratable Acidity (TA), and TSS/TA Ratio, TPC and TAA of the Pulp

After each cold-storage period, 15 guava fruits from each treatment (3 replicates) were separated by pounding the pulp; then, the juice was drained via a muslin cloth and utilized for quantifying interior fruit quality [37], as indicated.

For ascorbic acid analysis, sections of fruit juice were utilized, the oxalic acid solution was mixed to each sample, titrated with 2,6-dichlorophenol-indophenol dye solution, calculated as a mg of ascorbic acid, and expressed as mg/100 mL of the juice.

Fruit juice TSS was quantified using a hand refractometer, 0–32 scale (ATAGO N-1E, Japan) and conveyed in Brix after making the temperature correction at 20◦.

For juice TA, an aliquot of fruit juice was taken and titrated against 0.1 N NaOH with phenolphthalein as a marker to the endpoint, and stated as (%) of citric acid.

Fruit TSS/TA ratio was expressed from the values noted for fruit juice TSS and TA revealed.

Total phenolic content (TPC) and total antioxidant activity (TAA) were quantified in the MeOH extract (80%) of dried guava pulp. TPC was assessed using the Folin–Ciocalteu reagent, as explained by Kähkönen et al. [38]. TAA was assessed based on the scavenging activity of the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and conveyed as IC50 (mg/mL), which signified the quantity of the plant sample extract essential to decrease the early concentration of DPPH radicals by 50% [39].

### 2.6.3. Total Pectin

Quantities of pectic substances in guava were calorimetrically quantified by the carbazole sulfuric acid, using the assay of Yu et al. [40]. The results were conveyed as g anhydro galacturonic acid (A. G. A) per 100 gm on a dry weight basis.

### *2.7. Shelf-Life Period*

After 24 days of cold storage at 7 ± 1 ◦C, the guava (15 fruit per replicate) were obtained and arranged at ambient conditions (22–24 ◦C and 65 ± 5% RH), till 30% of fruits became bad, or rotting happened. Then, the number of days was documented as deemed for the shelf-life period of the guava.

### *2.8. Inoculation of Fruits*

Inoculation of guava was performed by squirting fruits with spore suspension (10<sup>6</sup> spores/mL) of *R. stolonifer* as causative agents of soft rot disease, then air-dried at RT. All were treated with each dose, and the control treatment were exemplified at 3 replicates, with 15 fruits for each replicate. All fruits were kept at 20 ± 2 ◦C for 15 days and infection (%) was noted. All the above-noted parameters were quantified in 20 fruits, and the average values were selected at the early time (Table 1).

**Table 1.** Characteristics of guava fruit prior to storage.


### *2.9. Statistical Analysis*

This experiment was assembled in a wholly randomized design, with 3 replicates consisting of two factors: postharvest treatments and storage period. This experiment was analyzed as a factorial experiment. Data calculated as (%) were altered to the arcsine of the square root before statistical analysis, and non-transformed means are displayed as they were. The effects of postharvest treatments and cold-storage period on several properties were statistically analyzed by ANOVA, using the MSTAT-C statistical package. Comparisons among means were performed by Duncan's multiple range test (DMRT) at probability ≤ 0.05.
