Effect of Storage Temperatures on Physico-Chemicals, Phytochemicals and Antioxidant Properties of Watermelon Juice (Citrullus lanatus)

Watermelon (Citrullus lanatus) consists of high moisture content and is favoured for its juice products. The popular fruit has a tempting taste, sweet aroma and attractive flesh colour. It is enriched with phytochemicals and antioxidant properties that are beneficial to human health. Due to convenience, the majority of individuals are likely to consume watermelon juice. However, little is known about the fruit juice storage and temperatures that may affect its beneficial properties. This study investigated the effect of storage temperature at room temperature, refrigerator cold, refrigerator freeze and freeze-dried, and analyzed the juice physico-chemicals (weight loss, pH, ash, moisture, total soluble solid, browning and turbidity), phytochemicals (total phenolic, total flavonoid, lycopene and β-carotene) and antioxidant scavenging activities during 9 days of storage. The results showed that watermelon juice was affected by storage temperatures and conditions with significant changes in physico-chemical appearance and decrease in total phytochemical content, thus consequently affecting their antioxidant activities during 9 days of storage. Although fresh watermelon juice can be consumed for its high nutritional values, freeze-drying is the preferable technique to retain its benefits and to delay juice degradation.

Nutritional Changes and Early Warning of Moldy Rice under Different Relative Humidity and Storage Temperature

Processed unhusked rice is prone to mildew during storage. In this study, the storage conditions were simulated at temperatures of 20, 30, and 35 °C and a relative humidity of 40%, 60% and 80%, respectively. The water, fatty acid, and total starch content and the peak viscosity, mold colony number, protein secondary structure, and spatial structure of rice were monitored in order to propose the critical point of mildew during storage. In the process of rice from lively to moldy, the water content, fatty acid contents and the peak viscosity were increased. The total starch content decreased and then showed a slow increasing trend, while the microstructure of the powder particles changed from smooth and complete to loosen and hollow. With the increase in storage time, the vibration of the amide Ⅰ band of the rice samples decreased slightly, indicating that the total contents of β-fold, β-turn, α-helix, and random curl of the rice protein also changed. PCA (Principal Component Analysis) analysis showed that rice mildew index was closely related to temperature and humidity during storage. In our investigation, the best and most suitable temperature and relative humidity for rice storge is 20 °C and 40%, respectively. These results suggested that temperature and environmental humidity are vital factors affecting the physicochemical properties and nutrient changes, which provides a theoretical basis for the early warning of rice mildew during storage.

Effect of mechanical damage on the quality characteristics of banana fruits during short-term storage

Fresh fruits like bananas are very susceptible to mechanical damage during postharvest handling which can result in a substantial decline in quality. The study aims to evaluate the effect of bruise damage and storage temperatures on the quality of banana fruits after 48 h storage. Each ‘Grand Naine’ banana fruit was impacted once by using a drop impact test using three different heights (10, 30, and 50 cm) and storage temperatures (13 and 22 °C) after 48 h of storage. Different quality analyses were measured like bruise measurements (impact energy, bruise area, bruise volume, and bruise susceptibility), weight loss, total soluble solids (TSS), color (L*, a*, b*, hue°, chroma, yellowness index, yellowness value) headspace gases (respiration and ethylene production rate). The results showed that bruise measurements (bruise area, bruise volume, and bruise susceptibility) were highly affected by drop height. The quality parameters like weight, color, total soluble solids and headspace gases were affected by drop height and storage condition. Weight loss, total soluble solids, respiration rate, and ethylene production rate increased as drop height and storage temperature rise. Storage at ambient conditions (22 °C) accelerated bruising occurrence in banana fruits. Fewer changes were observed after 48 h of storage. The least value of yellowness index was observed on the non-bruised banana fruits (84.03) under 13 °C storage conditions. The findings of the study can provide baseline data to understand the mechanical damage mechanism on fruit quality, hoping to create awareness and educate farming communities and consumers. Storage temperature management is another approach that needs to be followed to reduce the occurrence of mechanical damage in fresh produce.

Evaluation of microbiological risks in cream as a raw material for buttermaking

The article presents the research results of studying the influence of various groups of microorganisms — coliform bacteria, lactic acid microorganisms, yeast, and spore bacteria — on the quality and storage capacity of cream used as a raw material for buttermaking. The objects of study were the following: cream as a raw material before and after pasteurization, as well as pasteurized cream seeded with testing cultures of various types of spoilage microorganisms. The samples were stored at temperature conditions of 30 ± 1 °C, 10 ± 1 °C, and 4 ± 2 °C. To evaluate the quality and storage capacity of cream used as a raw material, its microbiological and physicochemical indicators were determined by standardized methods: bacterial number, titratable acidity, indicators of oxidative spoilage of the fat phase. Organoleptic characteristics were evaluated in terms of taste, consistency and appearance. Research results have shown that the greatest microbiological risks during storage of cream used as a raw material are associated with lactococci, coliform bacteria and yeast. Microbiological risks caused by seeding of cream with thermophilic streptococcus, spore bacteria of the genus Bacillus and spore anaerobic microorganisms of the genus Clostridium are less significant, which is associated with the lack of development and metabolism of these groups of microorganisms at storage temperatures of 10 ± 1 °C and 4 ± 2 °C. At the same time, the reason for the rejection of cream contaminated with these testing cultures, at a storage temperature of 4 ± 2 °C, is primarily a decrease in organoleptic indicators, and at a temperature of 10 ± 1 °C — an excess in bacterial number.

Hydrochemical Characteristics of Earthquake-Related Thermal Springs along the Weixi–Qiaohou Fault, Southeast Tibet Plateau

The Weixi–Qiaohou Fault (WQF) is considered an important zone of the western boundary of the Sichuan–Yunnan block, and its seismicity has attracted much attention after a series of moderate–strong earthquakes, especially the Yangbi Ms6.4 earthquake that occurred on 21 May 2021. In the present research, we investigate major and trace elements, as well as hydrogen and oxygen isotopes, of 10 hot springs sites located along the WQF, which are recharged by infiltrated precipitation from 1.9 to 3.1 km. The hydrochemical types of most analyzed geothermal waters are HCO3SO4-Na, SO4Cl-NaCa, and SO4-Ca, proving that they are composed of immature water and thus are characterized by weak water–rock reactions. The heat storage temperature range was from 44.1 °C to 101.1 °C; the circulation depth was estimated to range between 1.4 and 4.3 km. The results of annual data analysis showed that Na+, Cl−, and SO42− in hot springs decreased by 11.20% to 23.80% north of the Yangbi Ms5.1 earthquake, which occurred on 27 March 2017, but increased by 5.0% to 28.45% to the south; this might be correlated with the difference in seismicity within the fault zone. The results of continuous measurements of NJ (H1) and EYXX (H2) showed irregular variation anomalies 20 days before the Yangbi Ms6.4 earthquake. In addition, Cl− concentration is more sensitive to near-field seismicity with respect to Na+ and SO42−. We finally obtained a conceptual model on the origin of groundwater and the hydrogeochemical cycling process in the WQF. The results suggest that anomalies in the water chemistry of hot spring water can be used as a valid indicator of earthquake precursors.

Evaluation of postharvest storability of Ponkan mandarins stored at different temperatures

ABSTRACT The effects of storage temperature on postharvest storability, quality attributes and antioxidant enzyme activities of harvested Ponkan mandarins were investigated. Fresh fruits were randomly divided into four groups and stored at different temperatures [5 ± 1 °C (S5), 10 ± 1 °C (S10), 15 ± 1 °C (S15), and 20 ± 1 °C (S20 or control)] for 120 days. The results indicated that, compared with the control fruit, low-temperature storage at 10 °C significantly delayed the increase in fruit decay rate, weight loss, citrus colour index, respiration intensity, relative electrical conductivity, the accumulation of hydrogen peroxide and malondialdehyde, retarded the decline in L* value, retained high contents of total soluble solid, titratable acid, vitamin C, total phenol and total flavonoid, as well as higher activities of antioxidant enzymes – superoxide dismutase, catalase, peroxidase and ascorbic peroxidase. The principal component analysis results showed that low-temperature storage significantly maintained the postharvest quality of Ponkan mandarins, with fruit stored at 10 °C having no significant difference from the fruit stored at 5 °C, but markedly higher than those fruit stored at 15 °C. The comprehensive result of single-factor analysis and PCA showed that 10 °C could be used as the optimum storage temperature for improving the postharvest storability of Ponkan mandarins.