Influence of Conservation Methods on the sour cherry (Cerasus vulgaris Mill.) fruits quality

Abstract

Objective: Sour cherry fruits (Cerasus vulgaris Mill.) belong to the Rosaceae family and are designed as a GRAS ingredient based on the FDA data. Animal experiments and clinical practice confirm that there are many positive pharmacological effects mainly related to anthocyanins. Development of standard regulations for this kind of medicinal plant raw materials is actual to introduce sour cherry fruits into official medical practice. In our research, we investigate macroscopic and microscopic properties and determine the content of tanning substances and anthocyanins in sour cherry fruits of various kinds of conservation. Materials and methods: Modern complex of physicochemical methods was used in pharmacognostical research. Microscopic analysis was performed on a LOMO Micmed-6 microscope with 10× eyepieces, 4×, 10×, 40× and 100× objectives, photographies were taken with a Sony Xperia Z3 compact digital camera. The content of total anthocyanins in terms of cyanidin-3-О-glucoside was determined by differential UV-spectrophotometry, total tannins content – by redox titration. Results and discussion: The anomocytic stomatal complex, fruits pulp druses, anthocyanins containing in the epidermis and fruits pulp cells, and vessels are typical signs for the sour cherry fruits anatomy structure. A conservation method has not to effect on visual representation of diagnostic signs. The contents of tanning substances are little; it is from 2.73±0.08% to 4.12±0.13% in terms of tannin. Maximal anthocyanin contents (in terms of cyanidin-3-glucoside and in absolutely dried raw material) were determined in fresh-frozen sour cherry fruits (after defrosting (with juice and without kernel) is 5.40±0.15% or in terms of moisture-containing raw materials (without kernel) – 0.690±0.019%. In the defrosted fruits without juice, the content of anthocyanins is two times lower in terms of completely dried raw material (without kernel), it is 2.77±0.12% or in terms of moisture-containing raw material (without kernel), it is 0.410±0.018%. In the juice released from cherry fruits after defrosting anthocyanin content in terms of cyanidin-3-glucoside is of 0.450±0.007% (g/100ml juice), in dried sour cherry fruits (without kernel) – 4.34±0.17%, which is lower than in fresh-frozen raw materials. It can be explained by the varietal features, as well by the conservation conditions; this matter is to be further studied. Contents of tanning substances in fresh-frozen and dried sour cherry fruits when storage during 4 months is insignificantly reduced, but it is established that contents of anthocyanin in terms of cyanidin-3-glucoside reduces 1.5 times in 4 months, if the raw material is frozen, and it reduces by 10% if the raw material is dried. Conclusion: Diagnostic signs of macroscopic and microscopic structures, contents of tanning substances and anthocyanins in terms of cyanidin 3-glycoside in sour cherry fruits were studied. The content of the main groups of biologically active substances decreases equally during storage of dried and frozen cherry fruits. When defrosting, it is necessary to carefully collect the juice, as it contains the bulk of the anthocyanins. It is promising to study various options for freezing and drying of cherry fruits with kernels in order to reduce the loss of fruits juice to a minimum. In this case, it is important to ensure that the kernels are whole (not destroyed), in order to avoid the ingress of cyanogenic glycosides into the medicinal plant material. The results will be used to develop normative documentation for sour cherry fruits.