The objective of this work was to quantify the total phenolic content (TPC) and total antioxidant activity (TAA) of fruit from Brazilian genotypes of feijoa (Acca sellowiana). Skin and flesh tissues of the fruit were evaluated for the Alcântara, Helena, Mattos, and Nonante cultivars, and for the 2316 accession. TPC and TAA were both assessed in aqueous and hydroalcoholic extracts, and TAA was assayed by the DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)] methods. The TPC values, for aqueous extracts of the skin and flesh tissues, were 114.9 and 88.3 mg gallic acid equivalent (GAE) per 100 g fresh weight (FW), respectively. The corresponding values for TAA determined by the DPPH method, the skin and flesh tissues, given as EC₅₀ (substrate concentration which leads to 50% reduction of the DPPH), were 10.7 and 39.7 mg FW per g DPPH, respectively; and, by the ABTS method, the TAA values were 12.01 and 8.33 μmol L^-1 Trolox per g FW, respectively. The greatest values for TPC and TAA were obtained for 'Mattos' and 'Nonante', in the skin, and for 'Nonante' and accession 2316, in the flesh. Feijoa fruit has important functional value, particularly in the skin, characterized by high TPC and TAA.

The increase in solar radiation and temperature as a result of climate change and variability has increased sunburn damage to fruits, which highly affects quality and yield in tropical and subtropical fruit plants. Solar injuries increase because of conditions with low relative humidity, fruits left uncovered by foliage, and plantations at higher altitudes as a result of increased UV radiation. Three different types of sunburn on fruits are distinguished: photooxidative sunburn, sunburn browning, and necrosis on the epidermis. Fruits employ self-protection mechanisms against this stress through the production of enzymatic and non-enzymatic antioxidants. Fruit growers try to mitigate the impact of sunburning by planting species and varieties that are tolerant to this stress, pruning and training plants, leaving enough leaves above the fruit, efficient irrigation and intercropping for shading. More technical sunburn mitigation strategies include 1) improving the microclimate (shading nets, fruit bagging, evaporative cooling), 2) suppressors (kaolinite clay particle films, calcium carbonate) or 3) chemical protection (tocopherol, abscisic acid, ascorbic acid, anti-transpirants). This paper presents the state of research and its results for this abiotic stress in some tropical and subtropical fruit trees, such as avocado, banana, citrus, mango, pineapple and pitaya, along with observations for other fruit trees in tropical altitude zones. Continued research is recommended for this stress in different varieties with the use of environmentally friendly protective materials, along with studies on molecular mechanisms that direct the acclimatization of plants to a combination of these two types of stress, excessive radiation and temperature.

The objective of this work was to evaluate the effect of rosemary, cinnamon, citronella grass, and clove essential oils on the in vitro growth of Penicillium expansum, on the diameter of blue mold lesions, and on the physical and chemical attributes of 'Fuji' apples stored under refrigeration for different periods of time. The compositions of the essential oils were determined, and their effects on the growth inhibition, number, and viability of fungal spores in vitro were evaluated at 0, 100, and 1,000 μL L^-1 oil concentrations. At postharvest, evaluations were performed for fruit treated with 0, 50, 100, and 500 μL L^-1 essential oil and kept under refrigeration for 30 days, and for fruit treated with 0, 100, and 500 μL L^-1 oil and kept under refrigeration for two days. The essential oils - eucalyptol (rosemary), eugenol (cinnamon), citronellal (citronella), and eugenol (clove) - reduce the growth, number, and viability of P. expansum spores 24 hours after the induction to germination, as well as the diameter of blue mold lesions in apples, except for citronella oil at 500 μL L^-1 after 30 days of cold storage. There are no changes in the physicochemical attributes of apples, treated with different concentrations of the oils after refrigeration for five months, followed by seven days at room temperature.