Ethylene and CO

2

production before treatments

Ethylene production of persimmon fruit is usually affected by maturity stage [22]. Ethylene production measured on Rojo Brillante persimmon fruit immediately after harvest time at 20 °C was 0.2 ± 0.1 mL kg–1 h–1 while a value of 0.09 ± 0.3 mL kg h–1 was registered after storage for 72 h at 5 °C. At those stages, fruit respiration rate was 20.0 ± 1.5 and 5.3 ± 1.8 kg h–1 CO2, respectively.

Sugar concentration and total solid soluble (TSS)

The sugar concentration is very important to determine sensory quality and taste of fresh-cut persimmon fruit during storage time [23] (Table 1).

Table 1 Sugar compositions (glucose, fructose and sucrose), in minimally processed persimmon fruit (Diospyros kaki L.), cv Rojo Brillante immediately after harvest (T0) and after 3, 6 and 9 days of storage

CTR Passive and CTR + MAP sucrose content showed a low decrease during the 9 days of storage, while in the other treatments, the mean values increase after 6 days of storage. After 9 days of storage EC + MAP reported the highest mean values. Glucose content increased in CTR PASSIVE and EC + MAP samples of 10.1% and 20.4%, respectively, while in CTR + MAP and EC PASSIVE treatments it decreased of 22.6% and 19.3% during storage. Furthermore, our results showed that EC + MAP samples slices had reached the highest mean values immediately after 3 days of storage. Glew et al. [24] showed that sucrose content remained relatively low and decreased during ripening while the glucose content reported a mean value of about 35.4 mg.100 g−1 fw. The high value of glucose in EC + MAP could be due to a lower respiration rate of persimmon slices if compared to other treatments were an higher respiration rate could cause an higher consumption of glucose as substrate [4] (Figs. 8, 9). After cutting, fructose content remained stable in CTR PASSIVE treatment while the mean values of EC PASSIVE and CTR + MAP decreased until the 9th day of storage.

A different trend occurred in fructose content of EC + MAP treatment from 6 to 9 days of storage reporting significant differences unlike other treatments. Different results were reported by Zhang et al. [25] on persimmon fruit registering an increase of fructose during 30 days while on fruit treated with 1-MCP the fructose remained stable during storage. The TSS content did not show significant differences in all treatments but at 9th day EC PASSIVE reported the lowest mean values than other treatments.

Organic acids and titratable acidity content

Ascorbic, citric, malic and succinic acid were detected in all persimmons sample slices during storage time (Table 2). In persimmon fruit, levels of ascorbic acid are considerably greater (10 times) in cultivars that are non-astringent than in cultivars that are astringent [26]. Our results on Rojo Brillante showed that ascorbic acid content decreased in all treatments from cut to the 9th day of storage. Significant differences were shown between treatments on 6th day of storage when CTR + MAP samples had lower mean values (0.1 µmol g−1 fw) than other treatments. Malic acid content decreased in all treatments until the 9th day of storage registering significant differences of about 11%.

Table 2 Organic acid (ascorbic, malic, citric and succinic acids) in minimally processed persimmon fruit (Diospyros kaki L.), cv Rojo Brillante immediately after harvest (T0) and after 3, 6 and 9 days of storage

Veberic et al., [27] showed that total organic acid content could change by different cultivars. The authors reported different a level ranging from 681 ± 26.4 mg kg−1 in cultivar ‘Jiro’ to more than twice in cultivars ‘Triumph’ and ‘Tipo’, which on average contained 1439 mg kg−1, of organic acids. Amongt the individual organic acids, the highest content of malic acid (1044 ± 43.2 mg kg−1 FW) was measured in cultivar ‘Triumph’, and the lowest (401 ± 16.7 mg kg−1 FW) in cultivar ‘Jiro’.

Citric acid content decreased in all times and treatments. CTR + MAP and CTR PASSIVE treatments showed significant differences on 9th day reporting lower values than other treatments. Similar results shown that citric acid decreases during ripeness while malic acid increases [28].

The same citric acid trend occurred on succinic acid content showing significant differences immediately after 3 days of storage. Those results showed that EC + MAP and CTR PASSIVE treatment had the highest mean values in terms of succinic acid content. In another work on persimmon fruit succinic acid increased after 2 days of storage at 13 °C and 27 °C [29]. In breba fig fruit, malic acid and citric acid were higher in Opuntia ficus-indica mucilage-coated sample than in untreated samples used as control, analyzed at commercial harvest time [30]. The addition of ascorbic and citric acids in edible coating solutions may have affected their content in persimmon slices, while titratable acidity content did not show significant differences between treatments (P ≤ 0.05).

Firmness and weight loss

Persimmon fruit suffered rapid softening, [31, 32] while the use of 1-methylcyclopropene exhibited gradual softening during storage at 20 °C [25]. In our samples, firmness showed a decrease of mean values in all sample times at 5 °C. Significant differences occurred between treatments after 3, 6 and 9 days when CTR PASSIVE and CTR + MAP showed lower mean values if compared to EC + MAP and EC PASSIVE (Fig. 1).

Fig. 1
figure 1

Development of firmness (N) of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cut of persimmon (Diospyros kaki L.), CV Rojo Brillante just after cut (0) and at 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test. Data are provided as a mean standard error (n = 3) average

The flesh deterioration appeared to be associated with the increased activity of PPO (Fig. 4). Others authors [33] have shown that an increase of PPO activity in persimmon fruit cv. Fuyu bruised. The persimmon slices treated with EC + MAP reported the best results in terms of firmness. Probably, calcium content in EC has protected and maintained fruit quality by enhancing antioxidant capacity, avoiding softening, and preventing deterioration during shelf life [13, 34]. Indeed, the addition of calcium on fresh-cut fruit stability improved the stiffness of the middle lamella and cell walls.

Persimmon slices treatments reported an increase in mean values in terms of weight loss, but CTR PASSIVE samples showed a weight loss of 3.2% and 3.0% after 6 and 9 days, respectively (Fig. 2).

In EC + MAP, EC PASSIVE and CTR + MAP there were no significant differences after 3, 6 and 9 days (Fig. 2).

Fig. 2
figure 2

Development of weight loss (%) of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cut of persimmon (Diospyros kaki L.), cv Rojo Brillante just after cut (0) and at 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test. Data were provided as a mean standard error (n = 3) average

In another study, no significant differences were found in firmness of Fuyu persimmons coated with gelatin-based frog skin oil stored for up to 9 days at 25 °C [35] while on Rojo Brillante persimmons, starch–gellan coatings formulated with and without thyme essential oil maintained higher fruit firmness than uncoated fruit for 14 days of storage at 25 °C [36].

Browning index and PPO activity

Color is an analytical parameter that has a significant impact on consumer approval, since it is the first aspect he considers [37, 38]. From the data analysis, treatments had a considerable influence on fruit quality.

The mean values of browning index in treated and untreated persimmon slices increased during storage time (Fig. 3).

Fig. 3
figure 3

Development of browning index of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cut persimmon (Diospyros kaki L.), cv Rojo Brillante just after cut (0) and after 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test

On 3rd day of storage EC + MAP and CTR PASSIVE showed significant differences if compared to other treatments. EC + MAP persimmon slices showed lower mean values than other treatments from 3 to 9 days of storage, registering significant differences between treatments only after 6 and 9 days (Fig. 3). In another work, the use of CaCl2 reduced enzymatic browning on fresh-cut persimmon, having higher hue and lower ΔE values (change color) than the control samples, but its effectiveness was lower than ascorbic and citric acid, with lower hue values [39].

The same treatment showed lower mean values than other treatments in terms of PPO activity from on 3rd to 9th day of storage at 5 °C (Fig. 4).

Fig. 4
figure 4

Development of PPO of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cuts of persimmon (Diospyros kaki L.), cv Rojo Brillante just after cut (0) and at 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test. Data are provided as a mean standard error (n = 3) average

No differences occurred on 3rd day of storage between EC + MAP and CTR + MAP treatments while, after 3 days, EC + MAP treatment showed the lowest values (Fig. 4). CTR Passive and EC passive reported an increase in PPO activity while CTR + MAP remained stable only on 3rd day of storage and then increased during storage. In another study on Fuyu persimmon bruised fruit, the increment of PPO activity seemed to be associated with flesh deterioration [33] while ascorbic and citric acid and cysteine on fresh-cut Rojo Brillante persimmon, proved to be the most effective antioxidants to control enzymatic browning [39].

Carotenoids content

Persimmons fruits are a good source of carotenoids, mostly found in skin and flesh, which are responsible for the color of the fruits and whose amount increases as the fruit ripens [40, 41]. Zhou et al. [42], showed that β-cryptoxanthin was the most abundant carotenoid among all individual components in both peel and flesh. The same authors reported that zeaxanthin was also the most abundant in all persimmons fleshes besides β-cryptoxanthin. In our work, we evaluated (alpha)-cryptoxanthin, β-cryptoxanthin, (alpha)-carotene, β-carotene and total carotenoids during storage. As reported by Niikawa et al., [43], β-cryptoxanthin accumulates immediately after skin and flesh color changes. After cutting, the mean values of (alpha)-cryptoxanthin, β-cryptoxanthin, (alpha)-carotene, β-carotene and total carotenoids showed a decrease in all time and all treatments. EC + MAP and EC PASSIVE treatments showed higher mean values in terms of (alpha)-cryptoxanthin content than CTR PASSIVE and CTR + MAP during cold storage. EC + MAP persimmon slices showed higher mean values in terms of β-cryptoxanthin content than other treatments during storage time.

The same significant differences occurred on EC PASSIVE if compared to other treatments, in terms of (alpha)-carotene and (beta)-carotene from cut to 9th day (Table 3). Significant differences occurred on total carotenoids showing the higher mean values of EC + MAP compared to other treatments while in other works carotenoids content of fresh-cut persimmons (Sanchis et al., 2015) and kiwifruit [44] were not affected by antioxidant treatment, nor by storage at 5 °C.

Table 3 Evolution of carotenoids ((alpha)-cryptoxanthin (beta)-cryptoxanthin (alpha)-carotene (beta)-carotene total carotenoids), in minimally processed persimmon fruit (Diospyros kaki L.), cv Rojo Brillante immediately after harvest (T0) and at 3, 6 and 9 days of storage

In other works, the use of low-molecular-weight chitosan (LC)–( −)-epigallocatechin-3-gallate (EGCG) delayed the degradation due to the β-carotene selective permeability of chitosan coating. The high (beta)-cryptoxanthin content in Rojo Brillante persimmons contributed largely to the provitamin A value. Considering that the recommended daily allowance (RDA) for females is 800 RE, the persimmons harvested at commercial ripe provided between 5 and 8% of the RDA in a 100 g serving. This contribution was larger than those reported in literature for other persimmon cultivars [26].

Sensory quality

After 3 days of storage, significant differences occurred in terms of flavor and overall evaluation among the treatments (Fig. 5). Furthermore, EC + MAP fruits recorded the highest value with an average score of 8; CTR + MAP and CTR PASSIVE fruit had a score of 6.

Fig. 5
figure 5

Sensory analysis of treated (EC + MAP and EC passive) and untreated (CTR Passive and CTR + MAP) fresh-cut of persimmon on 3rd day of storage at 5 °C. Legend: visual appearance (VA); compactness (C); sweetness (S); acidity (A); juiciness (J); astringent (AS); pungent (PU); fruit odor (FO); floury (FAR); off-odor (OFO); fruit flavor (FRF), alcoholic flavor (ALF), off-flavor (OFF) and overall evaluation (OVE). Data correspond to the means ± standard deviations of three replicates

On 6th day of storage, significant differences were found in terms of consistency, smell of fruit and flavor. EC-treated fruits, both MAP and PASSIVE, was in a range of 6 and 5 for what concerns the overall evaluation (OVE), CTR PASSIVE and CTR + MAP, instead, recorded a value of 3.4 and 4, respectively, for the same descriptor OVE (Fig. 6).

Fig. 6
figure 6

Sensory analysis of treated (EC + MAP and EC passive) and untreated (CTR Passive and CTR + MAP) fresh-cut of persimmon on 6th day of storage at 5 °C. Legend: visual appearance (VA); compactness (C); sweetness (S); acidity (A); juiciness (J); astringent (AS); pungent (PU); fruit odor (FO); floury (FAR); Off-odor (OFO); fruit flavor (FRF), alcoholic flavor (ALF), off-flavor (OFF) and overall evaluation (OVE). Data correspond to the means ± standard deviations of three replicates

On 9th day of storage, visual appearance, compactness, sweetness and overall evaluation recorded the highest values in EC + MAP, followed by EC PASSIVE treated sample (Fig. 7). It was possible to state that EC treatments significantly prevent the loss of firmness and the organoleptic decay of persimmon fruits. The use of edible coating on fresh-cut persimmon fruit did not affect off-flavor during cold storage time. Similar results showed on fresh-cut persimmon fruit treated with honey, prevented off-aroma development and delayed jelling. However, the softness and exuding juice of the fresh-cut persimmon cubes increased with time, with the increase in both parameters being significantly suppressed by honey solution dips [45].

Fig. 7
figure 7

Sensory analysis of treated (EC + MAP and EC passive) and untreated (CTR Passive and CTR + MAP) fresh-cut of persimmon on 9th day of storage at 5 °C. Legend: visual appearance (VA); compactness (C); sweetness (S); acidity (A); juiciness (J); astringent (AS); pungent (PU); fruit odor (FO); floury (FAR); off-odor (OFO); fruit flavor (FRF), alcoholic flavor (ALF), off-flavor (OFF) and overall evaluation (OVE). Data correspond to the means ± standard deviations of three replicates

CO

2

and O

2

inside packaging

The rate of CO2 production exhibited a typical climacteric pattern of respiration during ripening of persimmon fruit at 20 °C. As reported by Sanchìs [46], the combination of high O2 (21 kPa) and elevated CO2 (10 or 20 kPa) did not prevent enzymatic browning and softening of fresh-cut Rojo Brillante persimmons, and high CO2 concentrations induced flesh browning on tissues. To prevent browning phenomena, antibrowning agents and MAP proved to be the most effective combination to prevent enzymatic browning and maintain visual quality above the limit of marketability for 9 days at 5 °C. In our work, an increase was observed from day 3 to day 6 of storage in CTR MAP and EC MAP. The EC + MAP treatment greatly inhibited CO2 production in persimmon fruit during the first 3 days. On 6th and 9th day of storage CO2 content inside packaging increased of 30% and 43.3%, respectively. Significant differences between CTR + MAP and EC + MAP occurred only at 12th day of storage (Fig. 8). No significant differences were detected between CTR passive and EC passive treatments in all time of storage. In fresh-cut peach stored under passive atmosphere, with or without chemical treatment, the shelf life was extended by up to 7 days [47].

Fig. 8
figure 8

Development of carbon dioxide (CO2)content of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cut of persimmon (Diospyros kaki L.), cv Rojo Brillante just after cut (0) and after 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test. Data are provided as a mean S.E. (n = 3) average

With regard to oxygen (O2) content inside packaging, CTR passive and EC passive showed a sharp decrease during storage time, while other treatments reported a slightly decrease in mean values. Significant differences occurred between CTR and EC passive treatments during the storage period and no significant differences were recorded between EC MAP and CTR MAP treatments (Fig. 9). The effect of the edible coating to reduce respiration rate of persimmon slices was only observed in samples packed under active MAP. EC has proved to be a good way to decrease the respiration rate of fruits, by creating a semipermeable layer that minimizes gas exchange. Indeed, Benitez et al., [48] reported the effect of Aloe v. edible coatings on reducing of CO2 production in kiwi fresh-cut fruit. In other works, the effects of Aloe v. coating in reducing respiration rate on table grapes [37] and on cherry fruit during storage at 1 °C and at 20 °C [49] were shown.

Fig. 9
figure 9

Development of oxygen (O2) content of treated (CTR PASSIVE, EC PASSIVE, EC + MAP and CTR + MAP) fresh-cut of persimmon (Diospyros kaki L.), cv Rojo Brillante just after cut (0) and after 3, 6, 9 days of storage at 5 °C. At each sampling date, different letters indicate substantial changes between treatments. P ≤ 0.05 was used in the Tukey’s significant test. Data are provided as a mean S.E. (n = 3) average

Microbiological analysis

Rojo Brillante persimmon is considered a perishable fruit, due to its susceptibility to microbial spoilage since it exhibits a pH around 6 [22]. Therefore, a microbiological analysis is an important factor to consider for the preservation of these fruits during handling or processing. The microbial loads detected on the different fruit samples collected during the experimentation are reported in Tables 4, 5. The results of viable counts performed on A. vera coating did not evidence the presence of any of the microbial groups objects of investigation (for this reason, these results are not reported in Table 4). According to Tukey’s test, statistically significant differences among treatments appeared after 6 d of storage when CTR + MAP (Table 4) and CTR PASSIVE (Table 5) samples showed levels of TMM, TPC, yeasts and molds higher than 103 CFU/g, while these microbial groups were below the detection limit in EC + MAP (Table 4) and EC PASSIVE (Table 5) fruits at each storage time. The levels of members of Enterobacteriaceae family, that might include potential pathogenic microorganisms [50], were below the detection limit for CTR + MAP and CTR PASSIVE treatments after 3 days of storage, but they increased at around 103 Log CFU/g at 9 d. On the other hand, no colonies of these bacteria were detected in EC + MAP and EC PASSIVE. These results confirmed previous investigations [49, 51] which evaluated the effects of A. vera coating in apple slices and sweet cherry and showed a reduction of mesophilic aerobic bacteria, as well as yeast and mold counts. The absence of microorganisms in EC fruit samples confirmed the antibacterial activity of A. vera [52] even after edible coating application.

Table 4 Evolution of microbial loads of ready-to-eat persimmon fruits samples (CTR + MAP, EC + MAP) during cold storage (9 days)
Table 5 Evolution of microbial loads of ready-to-eat persimmon fruits samples (CTR PASSIVE, EC PASSIVE) during cold storage (9 days)

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