| Blueberry is rich in anthocyanins,polyphenols,flavonoids,vitamins,minerals and other active components of health functions,and has a large proportion in the fresh fruit market.Blueberry fruits are mostly harvested in the rainy and high-temperature months from June to August each year.In addition,blueberry fruits are soft in texture and thin in the skin,and easily injured at the stalk during mechanical harvesting,which makes the stalk of blueberry fruit extremely susceptible to be infected by pathogenic fungi.According to statistics,the infection caused by pathogenic fungi accounts for 80% of the annual postpartum disease losses of blueberries.At present,methods such as low temperature and chemical agents are often used worldwide for postharvest preservation of blueberry fruits.However,the above methods usually have disadvantages such as short duration of action and residues on the fruit surface.Therefore,it has become a better choice to develop green,safe and long-acting preservatives.Among them,plant essential oils have become the most common biological preservatives due to their broad-spectrum antifungal properties,no residues,environmental-friendly,and low cost.Currently,many plant essential oils including clove oil,cinnamon oil and thyme essential oil et al.are used as biological preservatives.However,some influencing factors are also reflected in the actual application process,such as the high volatility,thermal instability and poor dispersion of plant essential oils.In order to solve these problems,it was prepared into nanoemulsions to improve the applicable properties of plant essential oils,and to improve their mechanical stability,thermal stability and dispersibility.Based on the above background,this paper conducts the following research and draws relevant conclusions:1.20 kinds of fresh aromatic plants were used to conduct preliminary research on the decay protection of blueberry stalks.It was found that Monarda didyma L.has an obvious protection effect,and its essential oil was extracted and analyzed.2.Three species of potential pathogens(B1,B2 and B3)were isolated from the rotten tissue of blueberry fruit pedicle.The results of morphological and molecular biological identification showed that the homology between B1 and Alternaria destruens was 99.79%.The homology between B2 and Colletotrichum fioriniae,B3 and Mucor circinelloides was 100%.It was determined to be Alternaria sp.,Colletotrichum sp.and Mucor circinelloides;Further verification confirmed that Alternaria sp.and Colletotrichum sp.were the dominant pathogens of blueberry fruit decay.3.14 kinds of plant essential oils were extracted and their in-vitro antifungal activities were explored.It was found that Monarda didyma essential oil(MEO)had extremely significant in-vitro antifungal activities(p?0.01).The fungistatic rate of fumigation reached 100% when the amount of MEO added was 4 ?L,and the contact fungistatic rate reached 100% when the concentration of MEO was 1 ?L/mL4.In order to improve the water solubility and stability of essential oil,the nanoemulsion was prepared based on MEO and characterized accordingly,and explored its in-vitro antifungal activity.It was found to have extremely significant in-vitro antifungal activity(p?0.01).When the concentration of EC was 12 ?L/mL,the fungistatic rate against Colletotrichum sp.was 100%,and when the concentration of EC was 16 ?L/mL,the fungistatic rate against Alternaria sp.was 90.32%.5.The protection effect of MNEO on postharvest blueberries was verified according to the weight loss rate,anthocyanin content,polyphenol and flavonoid content in preservation simulation.The decay rate of blueberries in the treatment group was reduced by 90% compared with the control group.The above results indicated that MNEO essential oil has obvious inhibitory effect on the decay of blueberry stalk and preservation effect on the nutritional components of the blueberry after harvesting.This research provides a theoretical basis for developing a green,safe and long-acting biological preservative. |
PDF Full Text Request