Postharvest Quality and Physicochemical Analysis of Strawberry (Fragaria ananassa L.) to Various Application of Mulching and Organic Fertilizers

Strawberry, Fragaria ananassa is known as the most well-known non-climacteric fruits that belong to the Rosaceae family. This perishable fruit has lot of nutritional and organoleptic characteristics that are commercially acceptable, so it grown to eat that as fresh, processed, beverage or preserved (Nasrin et al., 2017a). This fruit contains high content of flavonoids (dihydrochalcones (phloridzin), epicatechin, catechin, proanthocyanidin B1 and flavonols (quercetin derivatives) (Giampieri et al., 2012; Hilt et al., 2003).  Novel flavonol biosynthesized called Fisetin in the strawberry fruit plays an important major role that improved anticancer and antioxidant activity (Syed Deeba  et al., 2013). It also contains significant content of hydrolysable tannins (gallotannins and ellagitannins) with an estimated content ranges from 8-23 mg per 100 fresh weight strawberry fruit (Buendia et al., 2010). 
       
Being a non-climacteric fruit, a strawberry attains its highest quality features like firmness, glossiness, normal size, regular shape, sweet taste, full red color and aroma when fruits fully ripe when still attached to the plant, before harvest (Parvez  et al., 2018). Marketable strawberry fruits have a healthy stem and calyx, however, at this stage, they need more delicate, skillful and careful harvesting method due to very thin pericarp (Hayashi et al., 2010). Strawberries with ≥75% red color development are preferably picked to withstand rigors of transport. The firmer fruits are intended for distant or export markets. Even though fruits are already harvested, taste can no longer be improved fruits softening and color development to full red. The strawberry fruits are harvested in the cooler part of the day; generally, in morning hours, when the pulp temperature does not exceed 25^oC and fruits are not wet.
       
Poor harvesting methods and undesirable time of harvest will cause decay incidence, shriveling and bruising to the strawberry fruits, to avoid that, precooling is necessary. Too large and over mature or ripe berries fetch a low market  due to low characteristic value. Several studies on intelligent robotic and mechanical harvesting methods of strawberries were reported, which are mostly used in hydroponic systems and high-tech protected cultivation units.
       
The quality of strawberry fruit is influenced by improper cultural management. Mulching significantly influenced the quality of strawberries produced.The application of mulching is practice which helps proper development and growth of the plants by modifying the temperature of the soil, better moisture conservation and adequate nutrient availability (Shukla et al., 2021). In addition, Sharma and Sharma (2004) reported that mulching has a significant impact on the yield, quality and duration of the harvesting that improves modification in soil temperature, soil moisture conservation, control weeds and enhanced nutritional value. Moreover, organic farming not only enhances growth and yield performance but also can enhance soil biodiversity and improve food safety (Kumar et al., 2023).
       
Several research have been conducted as to the influence on the postharvest quality of perishables applied with various organic fertilizer particularly on the aspect of agricultural yield production. It is common that chemical fertilizers are generally used to significantly increase yield, but at high environmental cost and production have led to the use of organic fertilizers considered as an alternative to synthetic farm inputs. Many characteristics of several studies as to the use of organic fertilizers have been scientifically proven consisting mostly of waste. Scientific literature on increasing the yield with the used of organic fertilizers includes chicken manure and vermicompost in beans (Upenji et al., 2020), tomatoes (Sönmez  et al., 2019; Wang et al., 2017), lettuce and strawberry (Kiliç  et al., 2019; Negi et al., 2021) were reported.
       
With several past studies, this investigation was carried out with an objectives that aimed to evaluate the postharvest quality and physicochemical analysis of strawberry (Variety: Shoga) as influenced by mulching (ricehull and plastic mulch) and organic fertilizers (vermitea, vermicompost and vermicast).

Source of fruits and site of field experimental area
 
The site of harvested fruits used in the study was located at Sitio Sayaban, Barangay Ilovamis, Kidapawan City Philippines (Latitude: 6.735009; Longitude: 124.818287) from December 2015- March 2016. The area has an elevation of 756.5 meters above sea level.
 
Field experimental set-up
 
Mulching materials were applied three days before transplanting strawberry runners. A total of 10 sample plants with a plot size of 0.5 x  3 m. Mulching materials/treatment used in the experiment are as follows: without mulching (control); plastic mulch and rice hulls. Organic fertilizers applied in strawberry under various mulching materials were vermicompost and vermicast using localized placement application (100 g/ plant) and vermitea through drenching application technique at 50ml/plant. Inorganic fertilizer (10 g/plant) was also applied as commercial standard check. The application of all treatments was done every 15 days from the start up to the termination of the study (3 months duration).
 
Harvesting and selection of strawberry fruits
 
Strawberry fruits were carefully harvested based on the different treatments of the experiment (mulching materials and organic fertilizers) following the criteria for commercial stage of maturity: 2/3^rd maturity stage (fruit surface turns pink to red color at 25-28 days after anthesis).
       
Harvested fruits were collected from experimental plots applied with various treatment combinations evaluated were as follows (a. nm + control (without fertilizer application); b. nm+ vermitea; c. nm+ vermicompost; d. nm+vermicast; e. nm+ inorganic; f. rc+ control; g. rc+vermitea; h. rc+ vermicompost; i. rc+vermicast; j. rc+inorganic; k. pm+control (without fertilizer application); l. pm+ vermitea; m. pm+vermicompost; n. pm+vermicast; o. pm+ inorganic. Legend: nm (no mulching); pm (plastic mulch); rh (rice hull)
 
Laboratory experimental set-up
 
The experiment on postharvest quality evaluation was conducted at the Department of Horticulture, Physiology Laboratory with an average room temperature of 26.2^oC. A total of ten sample fruits per treatment, properly tagged and collected to ensure the uniformity of samples at harvest with an average weight ranging from 7-10 g/ fruit.
       
Postharvest quality evaluation was conducted for 10 days storage duration measuring the parameters with the following rating scale: Visual Quality Rating (VQR)- 9- excellent; field fresh; no defects; 7-good, minor defects (slight surface discoloration); 5- fair; moderate defects (moderate surface discoloration); limit of marketability; 1-poor; serious defects; limit of edibility; 0-non-edible. Firmness- 1-firm; 2- yielding; slightly soft; 3- moderately soft; 4- extremely soft; Shriveling- 0- no shriveling; 1- slight (1-25% surface shriveling); 2-moderate (26-50% surface shriveling); 3- severe (above 50% surface shriveling); A total of 10 sample fruits per treatment were used for the analysis. In terms of General Acceptability, fruits were evaluated by 30 panel members consisting of the fruit consumers (15), strawberry enthusiast (10) and trained panel experts (5) using the following rating scale: 5- like extremely, 4- like moderately, 3-like slightly, 2- neither like nor dislike, 1- dislike extremely.
       
Physicochemical analysis evaluated such as titratable acidity (%) and total soluble solid (obrix), were analyzed in Crop Science Laboratory, University of Southern Mindanao Agricultural Research and Development Center, Philippines. The stepwise procedure in analyzing the Total Soluble Solid includes preparation and extracting the juice of samples fruits using a blender, filtering and measuring the extracts using a refractometer, calibration and reading in ^oBrix. For titratable acidity (TA), juice of samples was extracted, diluted in water, pH adjustment using NaOH, titration in a standardized acid, endpoint detection using pH paper and calculation of TA as percentage of citric acid or malic acid equivalent.
 
Data analysis
 
The data collected specifically for physicochemical analysis was subjected to appropriate statistical tool analysis. The level of significance was set at 5% and significant differences were analyzed using Friedman Test. Postharvest quality parameters were evaluated using a Likert rating scale with verbal descriptions. 

Sensory evaluation: General acceptability parameter
 
The general acceptability of strawberry in response to application of mulching and organic fertilizers were shown in Table 1a and 1b. Strawberry fruits under plastic mulch condition (Table 1) significantly produced sweeter strawberry fruits with highest average rating scale of 3.85 verbally described as “like very much” with comparable description to strawberry plants planted under the rice hull mulching (3.64). Least acceptability was observed to strawberry plants with no mulching application (3.36) verbally described as “like slightly”.




       
As shown in Table 1b, application of organic fertilizers (vermitea, vermicompost ad vermicast) greatly influenced the general acceptability of harvested strawberry fruits with comparable mean ratings (3.65, 3.71 and 3.63) verbally described as “like very much” with closely related result to strawberry applied with inorganic fertilizer as standard check treatment.
       
The result implies that the eating quality of harvested strawberry fruits can be influenced by the application of appropriate mulching materials and organic fertilizer application. The findings of the study agreed with the report of Sayği 2021 that organic fertilizers can enhance the quality of the strawberry fruits produced. Reganold  et al. (2010), also stated that organic strawberry production has great impact on fruit quality rather than the conventional practice of farming that applies synthetic farm inputs. In addition, studies of Cayuela  et al. (1997); Abu-Zahra (2006); Kai and Adhikari (2021); Zhang  et al. (2020) reported that application of organic fertilizers had a significant positive effect on fruit quality by increasing the starch and soluble solids content of fruit that enhances eating quality and prolong the shelf life reducing perishability. Furthermore, Mohanapriya  et al (2024), mentioned that organic fruits and vegetables contain higher amount of vitamins such as ascorbic acid and beta carotene, total polyphenols, dry matter accumulation and fiber content including other mineral nutrients like Ca, Mg, K, Cu, Fe and Zn. In addition, Raihing and Vijayalakhmi (2022), also revealed significant results in terms of the effects of organic fertilizer (vermicompost) in enhancing the yield and quality of black gram.
       
Moreover, results of Mishra and Trirpathi (2011) and Tripathi  et al., (2015) revealed that the application of various mulching techniques can substantially influenced the ascorbic acid of harvested fruits that causes variability of the eating quality of fresh produced strawberry particularly on the application of plastic mulch.
 
Physicochemical analysis: Total soluble solids (oBrix) and titratable acidity (%)
 
In terms of the physicochemical attributes of harvested strawberry fruits. Plants under plastic mulched (8.90 ^oBrix) significantly influenced the amount of total soluble solids compared to other treatments, the results correlates to the findings of Shukla et al., (2021) revealed that maximum soluble solids content was recorded under black mulch whereas the mean minimum soluble solids content was recorded under the control. However, results showed no significant differences in terms of the titratable acidity of strawberry planted to various mulching materials as shown in Table 2a. 


       
Table 2b revealed significant differences in the total soluble solids of harvested strawberry fruits applied with different organic fertilizers. Vermitea (8.33 ^oBrix), vermi-compost (8.50 ^oBrix) and vermicast (8.42 ^oBrix) application significantly enhanced the total soluble solids which were comparable to standard check fertilizer application. The result implies that the application of organic fertilizers not only enhances fruit quality of strawberry but the amount of soluble content as well. Similar findings were observed in the study of Apriyani  et al., (2021) and Zhang et al., (2020) that application of organic fertilizers greatly influenced the amount of organic matter in the soil, improve the soil pH and enhanced the macro and micronutrients that enhanced quality of fresh produced fruits at harvest.


 
Postharvest quality assessment
 
The visual quality rating as shown in Fig 2 was evaluated from the time of harvest until its storability fruit capacity. All fruit samples have VQR 9, described as excellent or without defects and remained in excellent condition for a period of 2 days. However, gradual change and decline in visual quality rating were noted starting on the 3^rd day of storage (VQR 7). Fruits harvested in some treatment combinations reached the limit of marketability (VQR 5) at 5 days of storage and some fruits in 4 days. Longer duration of fruits based on the visual quality rating reaching the limit of marketability were among the strawberry fruits harvested from treatment combination under plastic mulch condition applied with vermicast, vermitea, vermicompost and inorganic fertilizers (standard check). Firmness of harvested strawberry fruits shown in Fig 3 remained firm from all the treatment combinations on the first 2 days but started to manifest slight softness at 3^rd day of storage. On the other hand, the shriveling index as shown in Fig 4 shows partial shriveling on the 1^st day of storage among various treatment combinations and attained moderate shriveling on the 5^th day of storage. General observation showed that the application of organic fertilizer and mulching has comparable effects on the firmness of harvested strawberry fruits with the length of storage. 






               
Moreover, longer duration attained the limit of marketability among postharvest quality parameters evaluated were observed from treatment combination applied with plastic mulch and organic fertilizers (vermitea, vermicast and vermicompost). Results of the study correlate to significant findings of Mufty and Taha (2021) that the effect of the application of organic fertilizers increased quality and yield of Albion strawberry variety; same results were also observed to studies of Balci et al., (2008) were the effects of organic fertilizers clearly enhanced fruit quality and yield of Camarose strawberry variety. The results also corroborated with the results of Rahman  et al. (2015); Singh and Ahmed (2013); and Kher et al., (2010) that minimum fruits were obtained to strawberry without mulching while increase and quality of fruits was observed to strawberry under plastic mulch. 

This study investigated the effects of various types of mulching and organic fertilizers on the postharvest quality and physicochemical analysis of strawberry. Harvested strawberry under plastic mulching applied with the application of different organic fertilizers (vermitea, vermicompost, vermicast) enhanced the postharvest quality of berries particularly on the visual quality appearance and firmness. Moreover, it also enhances the total soluble solids of the berries which significantly contributed to high general acceptability of harvested fruits. Among the various mulching materials application, harvested strawberry fruits under plastic mulch condition produced the most and good quality strawberry fruits. Furthermore, in relation to economic factors, organic fertilizers are locally available with lower production cost that offers long-term benefits in terms of soil health and improvement, increased crop resilience and improved postharvest life of strawberry fruits. Considering the results, it can be concluded and further recommended that the use of plastic mulch applied with organic fertilizers thereby improved quality and enhanced shelf life and contributed to longer perishability of strawberry fruits

The authors would like to acknowledge the University of Southern Mindanao for supporting the researchers endeavor in actively engaging in crop science related research.
 
Funding
 
Self-funded research.

Author’s contribution
 
The authors carried out experimental design and treatments, developed the conceptual framework, verified the analytical methods and performed the data gathering and monitoring of the study. The author discussed the results and contributed to the final manuscript.

No potential conflict of interest was declared by the authors.