Biochemical changes in pear fruits during storage at ambient conditions

‘Patharnakh’ (PN) (Pyrus pyrifolia Burm. Nakai) and ‘Punjab Beauty’ (PB) [Pyrus communis L. × Pyrus pyrifolia Burm. (Nakai)] are leading low­chill pear cultivars of subtropics of India. Diurnal temperature and relative humidity during fruit harvest period is high which considerably affect the shelf life of fruits. Fruits of ‘PN’ and ‘PB’ pear harvested at physiological maturity were stored for 12 days at ambient temperature and effects of storage temperature on physical and qualitative parameters were studied. Both cultivars showed reduction in fruit weight and firmness, reducing sugars, sucrose, starch and pectin content. However, total soluble solids and juice acid content increased during storage. Sucrose synthase activity and sucrose content showed signifi­ cant positive correlation in ‘PN’ cultivar. Activities of fruit softening enzymes such as polygalacturonase (PG) and cellulase was enhanced; whereas, pectin­ methylesterase (PME) was reduced during storage. Fruit firmness was negative­ ly correlated with PG in both the cultivars. In ‘PN’ cultivar, fruit firmness was positively correlated with cellulase and negatively with PME enzyme but reverse trend was observed in ‘PB’ cultivar. Fruit minerals content didn’t show any substantial disparities in both the cultivars during storage. ‘Patharnakh’ and ‘Punjab Beauty’ fruits maintain desirable quality parameters up to 6­9 days and 3­6 days, respectively, during storage at ambient conditions.


Introduction
Pear (Pyrus spp.) ranks second next to apple fruit crop in the world in terms of area, production and varietal wealth among temperate fruits. It belongs to the family Rosaceae and sub family Pomoideae. In India, it is cultivated in Himachal Pradesh, Uttarakhand, Punjab, Jammu & Kashmir and some parts of Assam and Nilgiris hills. In Punjab province of North West India, the area under pear cultivation is dominated by low chill culti var 'Patharnakh' that belongs to Oriental or Sand pear group (Pyrus pyrifolia Burm. Nakai) and semi soft pear cultivar 'Punjab Beauty, a hybrid between Pyrus communis L. × Pyrus pyrifolia Burm. (Nakai) (Sharma and Singh, 2011) and fruits are harvested at physiological maturity during II nd fortnight of July. Diurnal tempera ture and relative humidity during fruit harvest period is high which considerably affect the shelf life of fruits. It is documented that pear fruits have post harvest shelflife of about 10 days at ambient condi tions (2530°C) and quality related parameters are reduced rapidly during storage (Nath et al., 2011). After harvest, consumers' preference and market price depends on fruit's attractive colour, flavor, taste, aroma and firmness. The variability observed in volatile organic compounds, physicochemical and sensory parameters can be used to understand the ripening behavior of pear cultivars (Taiti et al., 2017). It is suggested that fruits should be harvested at opti mal physiological maturity and kept under optimal storage conditions to enhance the shelf life of fruits (Hafez et al., 2019). Fruit quality deteriorates after harvest due to rapid change in respiration, activity of cell wall degradation enzymes and infestation of pathogens during transportation and storage (Ge et al., 2017).
The quality related attributes constantly depend on the storage temperature which primarily affect fruit freshness and shelf life. Quantification of organic acids and soluble sugars (sucrose, glucose and fruc tose) are correlated to the production of quality fruits (Itai and Tanahashi, 2008). Sugars content in pear fruit improve during early storage period and further decline with the advancement of storage period at ambient conditions is due to fermentation into alco holic content (Kaur and Dhillon, 2015). Softening is associated with the degradation of cell wall polysac charides and biosynthesis of cellulase, polygalactur onase and pectin methyl esterase enzymes (Zhou et al., 2011). Fruit minerals content can also modify the quality attributes and storability (Saquet et al., 2019). It is well recognized fact that pome fruits are harvest ed at proper maturity stage and must be stored under explicit low temperature to extend the shelf life with out exhibiting any deterioration in fruit quality attrib utes (Itai et al., 2015;Yu et al., 2016). However, less information is available on the ripening behavior of pear fruits harvested at physiological maturity (135 DAFS) and kept in ambient conditions and subse quently, its effect on the biochemical composition during storage. Therefore, the study was performed to record the changes in physical characteristics, sug ars composition, activities of hydrolytic fruit softening enzymes and minerals profile during storage of pear fruits at ambient conditions.

Experimental procedure
Fruits of 'Patharnakh' 'PN' and 'Punjab Beauty' 'PB' cultivars ( Fig. 1)  . Fifteen fruits/replication free from any type of visual injury and bruises of each cultivar were washed with sodi um hypochlorite 4% (2.5 ml L 1 ) solution for 5 min utes (PAU, 2020). Fruits were dried in shade and packed in three ply corrugated fiberboard with 5% perforation and stored at ambient temperature (28±2 o C). Physicochemical parameters, physiological changes and enzymatic activities were estimated after the intervals of 0, 3, 6, 9 and 12 days of storage.

Physiological loss in weight (PLW)
Fruits stored at ambient temperature were weighed before storage and at a subsequent storage interval. The values were expressed as PLW (%) (Singh et al., 2021).

Fruit firmness
Fruit firmness was measured at every storage interval with penetrometer (Model No. FT327, QA Supplies LLC, USA) and values were expressed lbs (Mahajan et al., 2010).

Total soluble solids, Titratable acidity and fruit color coordinates
Titratable acidity (TA) was determined with titra tion method described by Ranganna (2007) and expressed as percent of maleic acid. Fruit color coor dinates (L*, a*, b*, C* and h*) were randomly mea sured on two opposite sites at fruit equator using Color Flex Spectrophotometer (Hunter Lab Color Flex, Hunter Associates Inc., Reston, VA, USA). These coor dinates were expressed in CIE units (Hunter, 1975).

Sugars
Fruit pulp was homogenized with 80% ethanol and refluxed twice for 20 min. The supernatants were pooled to evaporate ethanol and volume was made 10 ml with distilled water. This extract was used for the estimation of reducing sugars, fructose and sucrose by the methods already described by Kaur et al. (2018). For the estimation of fructose, 0.1% resorcinol reagent and 30% HCl were added to sugar extract and color intensity was recorded at 540 nm. Estimation of sucrose was done using the same procedure except that free fructose was destroyed by treating the sample with 6% KOH and the absorbance was measured at 490 nm. The residue left after sugar extraction was dried and treated with perchloric acid to hydrolyze starch into simpler sug ars and were estimated using the method of Dubois et al. (1956).

Sucrose metabolizing enzymes
Enzymes viz. sucrose synthase (SS), sucrose phos phate synthase (SPS) and invertases (acid and neu tral) were extracted from fruit pulp using HEPES NaOH buffer (pH 7.5) and assayed by the methods described by Asthir and Singh (1995) and Singh et al. (1978). For SS assay, 0.1 ml fructose (150 mM), 0.1 ml UDPG solution (20 mM) and 0.2 ml enzyme extract were incubated for 30 min at 37°C, followed by addition of 0.1 ml of 30% KOH and contents were boiled. Added 1 ml resorcinol reagent and 3 ml of HCl and tubes were kept for 10 min at 80°C. After cooling the tubes, the absorbance was noted at 490 nm. For SPS assay, fructose6phosphate (150 mM) was used as substrate and enzyme activity was expressed as mg sucrose formed g 1 min 1 fresh weight (fw). For acid invertase, 0.6 ml sodium acetate buffer (0.2 M, pH 4.8), 0.2 ml sucrose (50 mM) and 0.2 ml of enzyme extract were incubated for 1 h at 37 °C fol lowed by addition of 1 ml Nelson reagent C. Contents were boiled for 20 min and then 1 ml Nelson reagent D and 7 ml of distilled water was added and mixed well. Absorbance was read at 510 nm. Sodium phos phate buffer (0.2 M, pH 7.5) was used for neutral invertase assay in place of acetate buffer and rest of the procedure was same as described for acid inver tase. Invertase activity was expressed as mg glucose formed min 1 g 1 fw.

Pectin content and cell wall degrading enzymes
For pectin content, 50 g fruit pulp and 50 ml of 0.01 N HCl were boiled for 30 min and supernatant was collected. The process was repeated twice using 0.05 N and 0.3 N HCl and volume of filtrate was made to 100 ml. Two ml of diluted extract was neutralized using 1 N NaOH. To this, calcium chloride was added next day for precipitation. Precipitates were collect ed, weighed and % calcium pectate content was cal culated (Okimasu, 1956). Fruit pulp was crushed with 0.1 M sodium acetate buffer (pH 5.2) and super natant was used for the assay of cellulase and poly galacturonase enzymes. For cellulase, 1 ml of 0.1 M sodium acetate buffer (pH 5.2), 1 ml of 0.5% car boxymethyl cellulose (prepared in buffer) and 1 ml of enzyme extract were incubated for 1 h at 55 °C, one ml of dintrosalicyclic acid was added to terminate the reaction. The contents were boiled for 10 min and absorbance recorded at 560 nm. Enzyme activity of cellulase was expressed as mg glucose released min 1 g 1 fw. Pectic acid (0.5%) was used as substrate for PG assay and enzyme activity was expressed as mg galacturonic acid released min 1 g 1 fw (Malik and Singh, 1980). Fruit tissue was crushed with 0.1 M cit rate phosphate buffer (pH 5.0) and supernatant obtained was used for PME enzyme assay. For reac tion, 2 ml of 1% pectin, 2 ml of 0.1 M citrate phos phate buffer (pH 5.0) and 1 ml of enzyme extract were incubated at 35 °C. From this reaction mixture, 1 ml was pipetted out at 0 and 1 h of the incubation and titrated against 0.005 N NaOH. The PME activity was expressed as milliequivalents of methoxyl groups released min 1 by 1 ml of enzyme (Balaban et al., 1991).

Mineral's analysis
For nitrogen (N) estimation, dried powder of fruits was digested with H 2 SO 4 and content were deter mined using Kjeldahl method (Gehrke et al., 1972). Phosphorus (P) and potassium (K) in fruit samples were digested with a mixture of nitric acid and per

Fruit color
Color coordinates depicting peel color where L* expresses as lightness, a* positive value measures the red intensity and negative value as green color; b* positive value measures yellow color intensity. The value of b* coordinate was improved in both the pear cultivars during storage being highest in 'PB' and lowest in 'PN' cultivar. However, hue angle (h*) showed the reverse trend (Table 1). Significant improvement in a* values from 9 to 12 DAS in 'PN' cultivar was observed; however, other color coordi nates showed nonsignificant variations when the storage period was increased from 3 to 12 days. Initial negative a*values indicated greener colour at zero day as compared to 12 days of storage in 'PN' cultivar. chloric acid. P estimation was done by the method described by Jackson (1973) and K by flame photo metric method (AOAC, 1990). Nutrients like Ca, Mg, Cu, Zn, Fe and Mn were determined using atomic absorption spectrophotometer (Perkin Elmer Analyst 200). The instrument optimization, calibration and elemental analysis were carried out using WinLab32 software as described by Bradfield and Spencer (1965).

Statistical analysis
The experiment was conducted during the year 2020 in a complete randomized design with four replications. Two hundred and forty fruits of each cultivar for different storage intervals were stored at ambient temperature. A lot of 60 fruits for each stor age interval with 15 fruits/replication were stored in cardboard boxes. The data was analyzed by oneway analysis of variance. The differences were considered statistically significant at the level P value of < 0.05 using software CPCS1 developed by PAU, Ludhiana and WASP 2.0. Experimental data was represented as mean ± standard error. The data were subjected to Pearson's correlation analysis to assess the relation ship between attributes. Principal component analy sis (PCA) was used to examine the interrelations between different quality parameters.

Physical characteristics
Physiological loss in Weight (PLW) of 'Patharnakh' (PN) and 'Punjab Beauty' (PB) pear cultivars increased during different storage intervals and the higher rate up to 4.75 to 8.18 % was noted in 'PB' between 6 to 9 days compared to 3.21 to 4.16 % in 'PN' at ambient storage conditions ( Fig. 2A). The val ues of reduction in fruit firmness were increased with advancement of the storage period in both the culti vars. The rate of softening of 'PN' fruits was lower than that of 'PB' fruits and values were higher between 6 to 9 days in 'PN' and 36 days in 'PB' culti var (Fig. 2B). During storage, values ranged from 11.6 lbs at 0 day to 9.35 lbs at 12 days in 'PN' and 10.75 lbs at 0 day to 8.38 lbs at 12 days in 'PB'.

Total soluble solids and Titratable acidity
TSS content increased in 'PB' fruits during storage with the mean value of 14.97 o Brix and a significant rise in values was recorded from 13.39 o Brix at 3 DAS to 16.98 o Brix at 9 DAS (Fig. 2C). 'PN' cultivar showed significant variations in TSS content up to 6 days after storage and values varied from 11.05 o Brix to 11.63 o Brix. There was a significant increase in juice acid content from 3 DAS to 9 DAS and then values remained almost comparable until 12 days of storage in both the cultivars (Fig. 2D). 'PB' showed higher acidity values at all the storage intervals as compared to 'PN' cultivar.

Carbohydrate composition and Sucrose metabolizing enzymes
Reducing sugars increased up to 3 DAS in 'PN' and 6 DAS in 'PB' fruits and then declined during advanced storage period (Fig. 3A). Fructose content increased in pear fruits from harvest to 6 DAS and later showed a declining trend up to 12 DAS in both the cultivars (Fig. 3B). In 'PB' fruits, sucrose content did not show any differences until 9 days of storage and values were declined at 12 DAS (Fig. 3C). Starch    3D). Both starch and sucrose content improved up to 6 DAS and a decrease in its content was observed from 6 to 12 DAS in 'PN' fruits. Sucrose synthase (SS) enzyme showed fluctuation in values in both the cultivars with the advancement of storage period (Fig. 4A). After 12 days of storage; SS activity was about 2fold higher in 'PB' than 'PN' fruits. In 'PN' cultivar, sucrose phosphate synthase (SPS) activity increased at 3 DAS and exhibited a steady variation with less effectiveness until 6 DAS. In 'PB' cultivar, SPS activity during initial storage period decreased significantly and later showed an upsurge to 6th DAS by 1.5fold from the initial values and comparably had higher values than 'PN' cultivar. At 6 DAS, both cultivars showed a decline in SPS enzyme activity up to 9 days of storage followed by an upsurge up to 12 DAS (Fig. 4B). Acid invertase (AI) activity increased from 0 to 3 DAS in both the culti vars and subsequently declined at 6 DAS followed by a significant enhancement with progression in stor age at ambient temperature (Fig. 4C). Neutral Invertase (NI) activity increased up to 3 days of stor age followed by a declining trend after 6 days of stor age in both the cultivars. In 'PN' cultivar, NI activity increased until 9 DAS but decreased progressively afterwards. In 'PB' cultivar, NI activity decreased from 3 to 12 DAS (Fig. 4D). In both the cultivars, reducing sugars, fructose and sucrose attributes were correlated positively (data not shown). These sugars presented nonsignificant negative relationships with PLW except in reducing sugars with PLW (r= 0.483; p ≤ 0.05). In 'PN' cultivar, substantially positive correla tion between sucrose accumulation and SS activity (r= 0.46; p≤0.05) and nonsignificant correlation with SPS (r= 0.09) was observed (Table 2). In 'PB' cultivar, sucrose exhibited negative correlation with SS (r= 0.73, p≤0.01) and SPS (r= 0.54, p≤0.05). AI activity was nonsignificantly and negatively correlated with sucrose accumulation in 'PN' (r= 0.38) and 'PB' (r= 0.43) cultivar. NI activity and sucrose content were negatively correlated in both pear cultivars.

Pectin and cell wall degrading enzymes
Total pectin content was decreased significantly in both the cultivars during storage (Fig. 5A). PG activity increased significantly in both the cultivars during progression of storage period and values were 1.54 and 2.12fold higher during last storage period com  pared to harvest stage in 'PN' and 'PB', cultivars, respectively (Fig. 5B). Cellulase activity also enhanced in pear fruits during storage but showed a significant declining trend from 6 to 12 days of storage in both the cultivars under ambient conditions (Fig. 5C). PME activity was 1.18 ('PN') and 1.24fold ('PB') lower until 6 days of storage period (Fig. 5D). Thereafter, an increment in PME activity up to 12 DAS was noticed in both the cultivars.
In 'PB', fruit firmness was negatively correlated to cellulase (r= 0.632) and PG (r= 0.857) activities and values were significant at 1% level of significance. PME activity was positively correlated to firmness in these fruits (r= 0.450) at 5% level of significance dur ing storage at ambient conditions. In 'PN' fruits, PG activity showed a significant negative correlation with fruit firmness (r= 0.738, P≤0.01) and PME (r= 0.523, P≤0.05) and a positive correlation with cellu lase enzyme (r= 0.624, P≤0.01).

Minerals
Nitrogen content decreased significantly at 3 DAS by 1.6fold in both the cultivars and then increased from 6 to 12 DAS (Table 3). Phosphorus content in both the pear cultivars varied nonsignificantly during storage. Potassium content in 'PN' significantly increased between 3 to 6 days of storage period and then values remained higher until 12 DAS in both the cultivars. Magnesium content in both the cultivars showed almost similar pattern during storage inter vals and significantly lower values at 12 DAS in 'PN' and at 9 DAS in 'PB' fruits were observed. Calcium content in fruits of both the cultivars enhanced signifi cantly until 3 DAS. Iron and zinc content decreased significantly in both the cultivars from harvest to 12 days of storage periods under ambient conditions (Table 4); whereas, manganese content displayed a reverse trend in 'PB' fruits. Copper content was sub stantially lower during different storage intervals in comparison to harvest stage in both the cultivars.

Principal component analysis (PCA)
Biplot for PC1 and PC2 in pear fruits are given in figure 6. The results showed that first two compo nents explained 62.8% and 71.4% of the total vari ability in 'PN' and 'PB' cultivars, respectively. In 'PN' cultivar, PC1 includes sucrose, cellulase, starch, PG, AI and acidity attributes which explained 35.9% of total variability. PC2 comprises reducing sugars, fruc tose, firmness, pectin, and PME parameters and showed total variability of about 26.9% (Fig. 6A). In 'PB' cultivar, PC1 includes cellulase, SPS, TSS, PG and acidity characteristics that described 51.8% of total variability. PC2 comprises reducing sugars, fructose, sucrose, starch, NI, firmness, pectin and PME that described 19.6% of the total variability in physico chemical parameters in 'PB' cultivar during storage at ambient conditions (Fig. 6B).

Discussion and Conclusions
Physiological loss in weight (PLW) consists of metabolic activities, respiration and transpiration, Table 3 Macrominerals (%) content in pear fruits during storage at ambient conditions water pressure gradient between fruit tissues, envi ronment, stage of ripening as well as storage temper ature (Ma et al., 2014;Hafez et al., 2019). It acts as a detrimental factor to aggravate the fruit freshness, which might be associated with loss of moisture from the tissue (Barman et al., 2014). A nonsignificant rela tionship between SSC and weight loss in PatharNakh pear during storage was reported by Kaur et al. (2019). Fruit firmness is considered as an important index of texture and storage life of pears. Bhat et al.
(2012) reported a significant reduction in pear fruit firmness with the lowest value after 15 days of stor age. Softening of pear fruit during storage could be partly attributed to an increase in depolymerization and degradation of the cellwall polysaccharides con taining pectin, hemicellulose, and cellulose; and loss of moisture (Nath et al., 2011). Charoenchongsuk et al. (2015 observed a slight variation in Hunter values and hue angle of 'La France' pears during storage. Although L*, a*, b* and C* values showed an increas ing trend with storage but these values are not con sidered for maturity indices of pear fruits. Increment in TSS content may be due to breakdown of organic polymers into simple sugars as reported by Mahajan and Singh (2014) or dehydration of fruits and trans formation of pectic substances (Dave et al., 2017). Titratable acid content of fruit helps in keeping the fruit taste and flavor (Sajid et al., 2019). The increase in TA during storage may be due to conversion of sugars to organic acids and their utilization as a source of energy. Similar findings have been reported by Piga et al. (2003) in Cactus pear and ' Bartlett' pear (Bhat et al., 2012) during storage. The reduction in sugars is characterized by higher respiration during storage; whereas, sugars and acids are readily used as substrates for metabolic process es (Ackermann et al., 1992) or fermentation of over ripe fruits which converts sugars into alcohol (Kaur and Dhillon, 2015). The decrease in fructose content with advanced storage has also been reported by Chen et al. (2006) and Dave et al. (2017). SS, SPS and invertases enzymes substantially regulate sucrose synthesis in plants. These findings are corroborated with the observations reported by Chen et al. (2019) and they explained that activities of SS and SPS increased during initial storage period. Duan et al. (2019) reported that activities of SS cleavage and syn thesis of isozymes was increased until 7 DAS in pears and subsequently, decreased during storage period. Itai et al. (2015) opined that higher activity of acid invertase from 6 to 12 DAS considerably declines sucrose content in Japanese pears. Acid invertase has the highest level during initial storage period in pear fruits (Itai and Tanahashi, 2008). A similar trend of NI activity was observed by Ren et al. (2020). The decline in sucrose content until 12 days of ambient storage (Fig. 3D) might be due to conversion into free sugars by various enzymes including SS and inver tases (Itai and Tanahashi, 2008). These enzymes also exhibited similar trends in both the cultivars and high temperature improved their activities as shown in fruits of loquat . SPS synthesizes sucrose6phosphate molecule which results in the conversion to sucrose by sucrose6phophate phos phatase enzyme. Invertase enzymes cleave sucrose into glucose and fructose content. A positive correla tion between SS and sucrose content in 'PN' cultivar suggests that sucrose is synthesized during storage; whereas, a significant negative correlation between sucrose and SS, SPS and invertases depicts sucrose cleavage in 'PB' cultivar. Cell wall degrading enzymes play an important role in fruit ripening. PME does not have pronounced effect on deviation in the texture of ripening fruit and partial demethylation of pectin occurs before PG causes significant hydrolysis. Thus, PME may function to prepare the substrate for hydrolysis by PG (Awad and Young, 1979). PG catalysis the hydrolysis of (1→4) galacturonan linkages of demethylated pectin and releases shorter chains, thereby causing the depolymerization and dissolution of pectin (Singh and Dwivedi, 2008), cell wall dissolution, and ulti mately, fruit softening (Brummell et al., 2004). Cellulase acts on cell wall components such as cellu lose and xyloglucan of hemicelluloses (Chen et al., 2015). In the present studies, the degradation of sol uble pectin is related to the higher PG activity in the fruits during ambient storage resulting in softening of flesh. Zhou et al. (2011) also observed that a reduc tion in pectin content in pear fruits during storage might be due to higher depolymerization of cell wall polysaccharides and conversion of pectin's to non soluble form. Correlation studies revealed a negative relationship between fruit firmness, cellulase and PG enzymes in 'PN' and 'PB' cultivars. The activity of cel lulase and PG enzymes increased in both the cultivars which causes decrease in fruit firmness with PG as main enzyme contributing to the degradation of cell wall polysaccharides. This relation revealed that the cell wall polysaccharides in pear were associated with the fruit softening.
In fruits, optimal concentration of N and K allows a proper development of peel color, fruit size, firm ness, TSS, acidity, juiciness, flavor, and aroma. High N content reduces the fruit storability and K is also an important nutrient during storage of fruits to main tain K: Ca ratio (Brunetto et al., 2015). Lepaja et al. (2018) reported that 'Williams' pear fruit contains 7.83 mg kg 1 P, 152.67 mg kg 1 K, 11.33 mg kg 1 Mg, 10.60 mg kg 1 Ca, 1.11 mg kg 1 Fe, 1.17 mg kg 1 Zn and 1.14 mg kg 1 Cu during storage. The concentration of N 3.7 g kg 1 , P 1.0 g kg 1 , K 10.3 g kg 1 , Mg 0.4 g kg 1 , Fe 15 mg kg 1 , Mn 3.2 mg kg 1 , Zn 8.9 mg kg 1 and Cu 6.1 mg kg 1 was recorded in 'Rocha' pear fruit after stor age for 22 days (Saquet et al., 2019).
Principal component analysis (PCA) is a multivari ate technique to analyze the observations which are described by intercorrelated variables. The sugars are clustered together in one group indicating posi tive correlations with each other and juice acidity, SS and PG enzymes in second group had positive rela tionships but both groups had exhibited negative cor relations during storage. Similar findings have been reported in pome fruits (Billy et al., 2008;Linda Garcia et al., 2019;Li et al., 2019).
This study represents the shelflife of fruits of pear cultivars 'Patharnakh' and 'Punjab Beauty' during storage under ambient conditions. The results showed loss in weight, firmness, pectin and sugar content in fruits of both the cultivars. The activities of cellulase, PG and PME showed the positive effect on fruit softening; hence spoilage occurred during stor age of fruits. It can be summarized from the results that reduction in sugar content and fastening of activ ities of cellwall degrading enzymes between 69 days after storage in 'Patharnakh' and 36 days in 'Punjab Beauty' fruits makes them less desirable for further storage under ambient temperature conditions.