Food Technology
Aliehsadat Rafaathaghighi; Leila Jafari; Abdolmajid Mirzaalian Dastjerdi; Farzin Abdollahi
Abstract
Introduction
Ziziphus mauritiana, also known as Ber fruit, is a tropical fruit from the Rhamnaceae family with high nutritional value and a short shelf life. Edible coatings the surface of the fruit can play a positive role in increasing its shelf life. The application of alginate (Al), a linear polysaccharide ...
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Introduction
Ziziphus mauritiana, also known as Ber fruit, is a tropical fruit from the Rhamnaceae family with high nutritional value and a short shelf life. Edible coatings the surface of the fruit can play a positive role in increasing its shelf life. The application of alginate (Al), a linear polysaccharide derived from brown seaweed (Macrocystis pyrifera), which has the advantage of moisture retention, and also Shirazi thyme (Zataria multiflora) essential oil (ZEO), which contains antioxidant and antimicrobial compounds, can improve the fruit's characteristics and preserve its quality for a longer period. In recent years, the application of ZEO together with organic coatings in order to enhance the quality characteristics of different fruits during storage has been the focus of researchers. This study aims to investigate the effect of alginate coating and ZEO on the post-harvest and physicochemical characteristics of Ber fruit during storage at 6±1 C˚ and a relative humidity of 90-95%.
Material and Methods
This study was conducted to enhance the shelf life of Ber fruits by treating them with alginate (Al) and Shirazi thyme essential oil (ZEO). Ber fruits at their mature green stage were harvested in 2022 from a commercial orchard in Minab, Hormozgan province. After harvesting, the fruits were transported to the Horticulture Laboratory University of Hormozgan, to apply the treatments. Factors include six treatments (control, Shirazi thyme essential oil 0.5%, Shirazi thyme essential oil 1%, alginate, alginate + Shirazi thyme essential oil 0.5% and alginate + Shirazi thyme essential oil 1%) and five storage periods(zero, 7, 14, 21, 28 days). The treated fruits were then stored at 6±1 C˚, and relative humidity of 90-95% for 28 days. The factorial experiment was conducted as a completely randomized design with four replications, and ten fruits were used in each replication. Fruit parameters such as fruit weight loss, respiration rate, total soluble solids (TSS), organic acid, ascorbic acid, fruit firmness, carotenoids, and chlorophyll content were evaluated. Statistical analysis of data was done using SAS software. Figures were drawn using Excel software.
Results and Discussion
Based on the results of the analysis of variance, the main effects of time and treatment were significant (P<0.01) for all characteristics. Additionally, the interaction effect of treatment and time was significant (P<0.01) for all traits except for ascorbic acid. Comparisons of means showed that all treatments, maintained fruit quality compared to the control. The Al + ZEO treatment had a significant effect on reducing respiration rate. This combined treatment reduced weight loss, decay percentage, and fruit softening while slowing down the increase in TSS. The alginate coating and Shirazi thyme essential oil delayed ripening and subsequent fruit softening by reducing ethylene activity. Furthermore, the coated fruits had higher levels of ascorbic acid compared to the untreated fruits. These coatings are impermeable to water vapor and create a saturated atmosphere, preventing fruit evaporation and wrinkling, thus delaying ripening. The use of essential oils in the form of a semi-permeable layer also reduces respiration and surface transpiration by inhibiting the movement of oxygen, carbon dioxide, and moisture, playing a positive role in preserving fruit quality.
Conclusion
The aim of this study was to investigate the effect of alginate coating and Shirazi thyme essential oil on the post-harvest and physicochemical characteristics, as well as the shelf life of Ber fruit. The results clearly indicated the enhancement of fruit quality using edible coatings compared to the control. The combination of Al + ZEO (0.5%) had significantly positive effects on preserving the postharvest quality of Ber fruit. In fact, by creating a semi-permeable coating on the surface of the fruit, thyme essential oil and alginate lead to limiting the fruit respiration and metabolism and fungi growth, thus delaying the ripening process, increasing TSS and ascorbic acid and total acidity. According to these results, to reduce post- harvest losses and increase productivity of fruit, the use of 0.5% Shirazi thyme essential oil in combination with alginate coating is recommended due to its beneficial effects on the appearance and physicochemical characteristics of Ber fruit during storage.
Acknowledgement
The authors of this article express their gratitude and appreciation for the financial support from the Hormozgan Science and Technology Park and the University of Hormozgan.
Maryam Mandegari; Abdol Majid Mirzaalian Dastjerdi; Laleh Mosharaf; Maryam Tatari
Abstract
Introduction: Pomegranate (Punica granatum L.) is an important horticultural fruit that is generally very well adapted to the Mediterranean climate. Arils are the edible part of this fruit, being rich in anthocyanins and bioactive compounds such as phenolic compounds and flavonoids which act as antioxidants ...
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Introduction: Pomegranate (Punica granatum L.) is an important horticultural fruit that is generally very well adapted to the Mediterranean climate. Arils are the edible part of this fruit, being rich in anthocyanins and bioactive compounds such as phenolic compounds and flavonoids which act as antioxidants and free radical scavengers. Susceptibility to chilling injury in pomegranate fruits is a major limiting factor in storing fruits at low temperatures. Below 5 °C, pomegranate fruits show symptoms such as surface pitting, browning, discoloration, and decay. The control of temperature is an effective tool for extending the shelf life of fresh horticultural products. Oxidative stress, as caused by an excess of reactive oxygen species (ROS), is usually associated with chilling injury in fruits. Nitric oxide (NO) is an important gas molecule, the involvement of which in many physiological processes can protect plant cells against oxidative stress by reducing the accumulation of ROS. Postharvest studies have shown that the application of NO gas can extend the storage life of a range of horticultural produce by delaying ripening or senescence. Due to the high number of pomegranate cultivars in Iran, limited amounts of information exist on how the qualitative characteristics of arils in the Malas pomegranate can be affected by nitric oxide and different temperatures during storage. The Malas cultivar comprises a large share of pomegranate exports from Iran. In this research, the positive effects of nitric oxide were examined on reducing the chilling injury and maintaining the fruit quality of pomegranate. The application of this treatment at different concentrations and different storage temperatures led to variable effects on the qualitative characteristics of arils in the Malas pomegranate. Materials and methods: Malas pomegranate fruits were harvested commercially from Isfahan Province and were transferred to the Food Industry Laboratory of Isfahan Natural Resources Research. The fresh arils were separated from fruit tissues and were immersed in solutions of nitric oxide (0, 5 and 10 μM/L) for 5 min. After draining, the arils were placed in packaging films of polyethylene and were immediately stored at 2, 4 and 8 °C for 21 days. Several parameters were measured every 7 days during the storage time. These were the weight loss, total soluble solids, titratable acidity, TSS/TA, acid ascorbic, total phenol, total anthocyanin content, antioxidant activity, MA, ion leakage, POD, PPO activity and sensory evaluation. The current study was carried out as a factorial assay and was based on a completely randomized design with three replications. Data were processed by ANOVA using the SAS software version 9.4. Significant differences were identified using Duncan’s test at 1% probability level. Results and discussion: Results showed that the total anthocyanin content, total phenol, antioxidant activity, and titratable acidity decreased during storage time. The control group and the treatment with low temperatures significantly reduced the qualitative characteristics of arils during storage. The water content of arils treated with 5 and 10 μM nitric oxide was maintained considerably for 21 days during storage. According to these results, unlike titratable acidity and ascorbic acid which decreased in both treated and untreated fruits, there was an increase in the total soluble solids and POD activity of arils during storage. However, nitric oxide reduced the rate of these changes, whether it be the decrease or increase in the measured parameters. During the experiment, the control samples showed lower values of quality regarding all parameters. The use of nitric oxide in fruits reduced lipid peroxidation and ion leakage significantly, whereas the antioxidant activity increased. The decrease in ion leakage was observed most notably in fruits that were treated with 10 μM nitric oxide. Furthermore, low temperatures managed to disrupt the metabolic balance of reactive oxygen species, leading to the accumulation and destruction of antioxidant enzymes. In the present study, exogenous treatments with nitric oxide at 5 and 10 μM significantly reduced the lipid peroxidation content and electrolyte leakage of arils being stored at cold temperatures, compared to untreated arils. Nitric oxide suppressed the activity of polyphenol oxidase (PPO) and preserved the physical appearance and the internal quality of pomegranate arils. The decrease in phenolic compounds (29.32%) and antioxidant activity (39.91%), besides the increase in lipid peroxidation (38.37%) and ion leakage (36.98%), caused deteriorations in the appearance and organoleptic properties of the control samples. To alleviate these problems, nitric oxide has beneficial effects on maintaining the anthocyanin content of pomegranate arils by partially inhibiting PPO enzyme activity during storage. It prolongs the postharvest life, helps to preserve the quality of pomegranate arils, suppresses the formation of ethylene, reduces the respiratory rate and controls weight loss, in addition to maintaining the firmness of fruits. Delaying the changes in peel color and TSS are also considered as useful effects of nitric oxide on pomegranate arils. Nitric oxide impeded the process of senescence by slowing down PPO-related activities, thereby maintaining the total phenolic content of pomegranate arils.In conclusion, the application of nitric oxide was observed to reduce ion leakage and PPO activity in pomegranate arils, while also maintaining the quality of arils. Ultimately, the use of 10 µM nitric oxide at 8 °C can be suggested as the most optimum treatment herein.
