In recent years, it has become a research hotspot to replace chemical synthetic substances with natural plant extracts as preservatives for fruits and vegetables. The main means of controlling post-harvest diseases of fruits and vegetables is refrigerated and preservatives. However, the use of chemical preservatives to preserve fruits and vegetables is harmful to both fruits and vegetables. China's research on natural preservatives started late, but it has also achieved good results.
1. Inhibition of natural plant extracts on fruit and vegetable rot fungi
There are many kinds of natural plants used for preserving fruits and vegetables. There are more than 5,000 kinds of Chinese herbal medicines, including some spices and flavonoid-rich plants.
Song Weiguo et al studied the effect of garlic extract on inhibition of Botrytis cinerea, and found that garlic extract can inhibit the spore germination and mycelial growth of Botrytis cinerea. The inhibition rate of spore germination was 100% at a dilution concentration of 10.0 μL/mL.
Jiang Jizhi et al. used four kinds of allium water extracts and eight common Chinese herbal decoctions to inhibit the two main pathogenic fungi of strawberry root rot. The experimental results showed that garlic, leek water extract and clove and rhubarb water decoction At higher concentrations, the antagonistic activity of Rhizoctonia solani and G. anthracis has a strong inhibitory effect. When the concentration is low, there is no obvious effect or slight promotion of the growth of pathogens; G. anthracis has a strong inhibitory effect, and has no significant effect on Rhizoctonia solani.
Wu Xin'an et al. used 95% ethanol extracts of 7 kinds of Chinese herbal medicines such as peppermint, Cnidium, gentian, Polygonum cuspidatum, Andrographis paniculata, Radix Paeoniae Alba, and Betel nut, to carry out antibacterial activity tests on apple anthracnose, P. sphaeroides and T. solanacearum. The results showed that Cnidium monnieri and C. sinensis had better antibacterial activity against Fusarium oxysporum and Apple anthracnose.
Second, the inhibitory effect of different extraction methods on fruit and vegetable rot fungi
The active ingredients in natural plants are extracted by different methods, and the bacteriostatic effects are different.
Guan Wenqiang et al. used clove as raw material to study the inhibitory effect of clove oil obtained by supercritical CO2 extraction, steam distillation and direct heating water distillation on the main pathogens of fruits and vegetables after harvest. The results showed that the clove oil had good antibacterial effect on grape, winter jujube, peach and garlic stalk. Among the three different extraction methods, steam distillation essential oil has the best antibacterial effect, followed by supercritical CO2 extraction, and the effect of direct heating water distillation is poor.
Wu Guangxu et al. performed liquid fraction extraction on the methanol extract of the rhizome of the open arrow, and measured the in vitro and in vivo antibacterial activity of the extract against the Phytophthora capsici by the growth rate method and the fruit inoculation pathogen method, and treated the litchi with the extract. Carry out storage experiments. The results showed that the infection rate of litchi fruit was significantly reduced, and the extract had the effect of preventing the occurrence of litchi disease and delaying the deterioration of quality.
Luo Min et al. used the gray mold as the test bacteria to study the effect of ultrasonic extraction of the frequency, time and dosage of the active ingredients of traditional Chinese medicine on the antibacterial effect. Experiments show that this method has high extraction rate, high reliability, easy operation and short extraction time. The bamboo vinegar is compounded with clove, bitter bean, galangal, berberine, etc., and the active ingredient is extracted by ultrasonic wave. Bamboo vinegar has strong antibacterial activity, and the synergistic effect is obvious, and it is not necessary to separate after extraction.
Third, plant extracts for the preservation of fruits and vegetables
Liu Xiaorong mashed garlic, ginger and orange peel into a paste. The supernatant was centrifuged, and the extract was compounded into a preservative for grape, green pepper and tomato preservation. The shape, weight loss rate, pH value, soluble solids and vitamin C content of the preserved fruits and vegetables did not change much, which prolonged the storage period and did not affect the original flavor.
Duan Hanying et al. studied the use of rhubarb, honeysuckle, and galangal fresh-keeping cucumber, and immersed the cucumber in the Chinese herbal medicine filtrate, and then dried it. The results showed that the sensory quality, vitamin C retention rate, water retention and the like were better than cucumber without preservative.
Ma Liyi used licorice, bamboo leaf extract and mixed film solution to make fresh coating film to preserve fresh and crispy plum. After 25 days of storage, the water loss rate was only 12.5%, and the good fruit rate was as high as 70.25%. The food value has been lost after 6 days of storage.
The plant extract has good bactericidal effect, no harm to the human body and the environment, increases the safety of eating fruits and vegetables, and has good effects for preservation of fruits and vegetables. In the long run, the research direction of fruit and vegetable preservatives should be developed in a natural, safe and effective direction. The replacement of chemical synthetic preservatives by natural plant extracts for the storage and preservation of fruits and vegetables has broad prospects for development.
