The effect of some enzymatic browning inhibiting compounds in maintaining the quality and increasing the shelf life of Japanese parsnip (Eriobotrya japonica) fruit.

Academic Thesis for Master's Degree

Field: Agricultural Engineering-Horticultural Sciences Major: Physiology and Breeding of Fruit Trees

Abstract

Enzymatic browning is the most important physiological abnormality that It strongly affects the post-harvest quality and shelf life of Japanese parsnip. In order to investigate the effect of distilled water and a number of enzymatic anti-browning agents including ascorbic acid (1 and 2 percent), citric acid (0.5 and 1 percent), sodium hexametaphosphate (0.5 and 1 percent) and the combined effect of these substances (in 2 concentrations), a factorial experiment with 3 factors of time (7 levels), packaging (2 levels) and chemical treatment (9 levels) for the attribute of weight loss and 2 packaging factors (2) level) and chemical treatment (10 levels) for other traits were designed based on completely randomized design in 3 replications. Treated fruits after packing in two ways (polystyrene containers or polystyrene containers covered with light polyethylene films) were kept in cold storage for 35 days and then they were placed uncovered for another 2 days at 25 degrees Celsius in order to create the same condition as the market. Some physicochemical characteristics such as weight loss, browning index, soluble solids (TSS), titratable acidity (TA), TSS/TA, vitamin C, total phenol, total flavonoid and antioxidant activity of fruits were measured. The results showed that sodium hexametaphosphate had the greatest effect in controlling the weight loss of the samples. The treatments of 2% ascorbic acid, 1% citric acid and 1% sodium hexametaphosphate had the lowest browning index. After 35 + 2 days of storage, TSS (except for 2% ascorbic acid treatment) and TA decreased in all samples and on the contrary, TSS/TA increased. It was also found that the vitamin C of the fruits decreased significantly at the end of the storage period, but the 2% ascorbic acid treatment was able to maintain it at an optimal level. In addition, the highest amounts of total phenol, total flavonoid and antioxidant activity were observed in fruits treated with 2% ascorbic acid and the combined solution with a lower concentration. In total, it was found that 2% ascorbic acid was the most effective treatment for maintaining the quality of Japanese parsnip fruits during storage.

Key words: Japanese parsnip, ascorbic acid, citric acid, enzymatic browning, sodium hexametaphosphate.

Fruits are rich sources of They are carbohydrates, vitamins, antioxidants, polyphenols, minerals and dietary fibers. Studies show that a diet rich in fruits and vegetables reduces the risk of cardiovascular disease, various cancers, skin diseases, and other chronic diseases (Bertaza et al., 2003). The high nutritional value of these products has increased their demand among consumers in recent years and has provided a platform for economic development (Faller and Fialo, 2010).

Production of fruits with good quality is possible through the adoption of management measures during the growing season, but one of the serious problems in the horticulture industry is maintaining the quality after harvesting. Metabolic reactions in products continue even after harvest, which can affect their quality indicators, including color, taste, aroma, nutritional value, and texture, and reduce their marketability. This applies more to tropical and subtropical fruits, which have a more perishable nature (Fernando et al., 2004).

Post-harvest losses can occur at any point in the production and marketing chain and are estimated between 10 and 50%, depending on the type of product and place of production (Maria, 2007). Wounds and mechanical injuries are one of the most important causes of losses in fruits, and preventing such injuries at the time of harvest or after can be effective in maintaining the quality of products (Capellini and Seponis, 1984). It is also important to know about the physiology after harvesting garden products, which consists of studying the biological processes of plant tissues after they are separated from the mother plant, along with the application of post-harvest technologies and types of physical and chemical treatment to maximize quality characteristics (Maria, 2007).. Of course, today, with the increase in consumer awareness, the lack of use of artificial chemicals in the food industry has been emphasized, so the need to investigate and identify natural and non-toxic substances effective in increasing the shelf life of products is felt more (Robert et al., 2003). including nutritional and climatic conditions during growth and development, maturity stage during harvest, genetic differences between different cultivars and so on. They are involved in physiological and biochemical changes after harvesting (Maria, 2007).

1-1- The origin and history of Japanese parsnip

The origin of Japanese parsnip is the banks of the Dado River[1] in southern China and has been cultivated in those areas since about 2000 years ago (Zhang et al., 1990; Lin et al., 2007). This plant was introduced to Japan from China in ancient times and was cultivated in Japan since 1180 AD (Ding et al., 1998). Despite the historical background of Japanese parsnip in East Asia, the familiarity of people in other parts of the world with this plant goes back to the not-so-distant past. There is not much information about the history of Japanese parsnip cultivation in Iran, but this plant was cultivated in Europe for the first time in 1784 as an ornamental plant in the botanical garden of Paris, and from there it made its way to England and Mediterranean countries, and between 1867 and 1870, it was introduced from Europe and Japan to Florida and California, America (Villanova et al., 2001; Lin et al., 1999). Although Japanese parsnip was initially considered as an ornamental plant in many countries, gradually the selection of cultivars with larger fruits led to the attention of gardeners to this plant as a tree, so that today the production of this ancient fruit is carried out on a commercial scale in more than 30 countries of the world (Badans et al., 2000).

1-2- Botanical characteristics

Japanese parsnip with scientific name Eriobotrya japonica and English name Loquat is an evergreen and semi-tropical tree and belongs to Rosaceae family and Pomoideae subfamily. The name Eriobotrya is derived from the two Greek words erion and botrys, meaning hair and cluster, which refers to the hairiness of the leaves and fruits of this plant and its flowering form. The word japonica also goes back to Japan, because the Japanese parsnip was introduced to many parts of the world from this country (Hossein et al., 2009).

This plant has full flowers and most of its cultivars are self-fertilizing, but self-incompatibility is also seen in some cultivars. Japanese primrose's white flowers bloom in the fall, the fruits develop over the winter and ripen in the spring. The color of Japanese parsnip fruits varies from pale yellow to orange. Their taste is usually sweet with a mild sourness and they are very juicy. The fruits are spherical or egg-shaped and their diameter is 2 to 5 cm and their average weight is 30 to 40 grams, which reaches 70 or even 170 grams in large varieties. There are usually 2 to 4 brown seeds in each fruit (Lin et al., 1999; Lin et al., 2007). but problems such as differentiation of traits, self-incompatibility and long youth period prevent the use of this propagation method in commercial gardens. Also, other methods such as bud grafting, air dormancy, tissue culture and micropropagation can also be used to propagate Japanese parsnip, but the best method is branch grafting on Japanese parsnip seedlings, beech trees, and some species of the genus Eriobotrya. Tongue grafting, Nimanim grafting, and chisel grafting are among the types of branch grafting that are used to propagate this plant (Lin et al., 1999). Japanese parsnip is found in areas near the sea and between 20 and 35 degrees latitude and sometimes up to 45 degrees north and south (Badens et al., 2000).