Improving the nutritional value and extending shelf life of red guava by adding calcium chloride

Nutrient Uptake of Two Semidomesticated Jaltomata Schltdl. Species for Their Cultivation

The nutrient uptake of a species under cultivated conditions is important for program fertilization. The Jaltomata genus has two semidomesticated species, J. procumbens and J. tlaxcala, used as food and considered with potential for their study in controlled environments. The objective of this research was to determine nutrient uptake curves of these species in a greenhouse and using hydroponics. The research was carried out at the Colegio de Postgraduados, Campus Montecillo, Texcoco, State of Mexico, from August to November 2020. The treatments included the following: two species and three electrical conductivity levels: 1, 2, and 3 dS m-1. Nutrients in leaf and total dry matter (TDM) were determined. Variability between species and phenological stages on the nutrient concentration and accumulation of TDM was observed. For macronutrients, J. procumbens concentrated in descending order more P from the vegetative stage (4.21-2.43 g kg-1 dry matter), and Mg until fructification (4.92-3.26 g kg-1 dry matter), for K it was higher at vegetative (52.29 g kg-1 dry matter) and harvesting stages (26.05 g kg-1 dry matter), and N (23.92 g kg-1 dry matter) at flowering; J. tlaxcala concentrated more Ca from fructification (10.10-13.85 g kg-1 dry matter). For micronutrients, J. tlaxcala concentrated more Fe from the vegetative stage (157.7-207.5 mg kg-1 dry matter), B and Zn at 23.3-38.4 and 26.04-28.45 mg kg-1 dry matter, respectively, from flowering, and Mn (108.4-232.28 mg kg-1 dry matter) from fructification. The main structures of TDM accumulation by vegetative stage in J. procumbens were the leaf and root (vegetative and flowering), root and stem (fructification), and reproductive structures and root (harvesting); in J. tlaxcala, the main structures were the leaf and root (vegetative), root and leaf (flowering and fructification), and root and reproductive structures (harvesting). Due to this variability, specific fertilization programs are required for each species.

Ascorbic acid on the induction of salt stress tolerance in guava in the seedling formation phase

Guava is a fruit crop widely exploited in the Northeast region of Brazil. However, its exploitation is limited by water scarcity and, in many cases, producers are forced to use water with high levels of salts in irrigation. Thus, it is necessary to develop techniques to induce plant tolerance to salt stress, and the foliar application of a non-enzymatic compound such as ascorbic acid is a promising alternative to mitigate the deleterious effects on plants. The objective was to evaluate the effects of foliar application of ascorbic acid on guava plants, irrigated with saline waters in the seedling formation phase in a semi-arid region. The experiment was carried out in a greenhouse adopting a randomized block design, in a 5 × 4 factorial scheme, with five levels of electrical conductivity of water - ECw (0.3, 1.3, 2.3, 3.3 and 4.3 dS m-1) and four concentrations of ascorbic acid - AsA (0, 200, 400 and 600 mg L-1) with four replicates. Water salinity from 0.57 dS m-1 compromised the gas exchange and biosynthesis of photosynthetic pigments, besides inhibiting the growth and quality of guava seedlings cv. Paluma. The concentration of 375 mg L-1 AsA increases the production of photosynthetic pigments under low salinity conditions (0.3 dS m-1) and increases the number of leaves and dry matter of seedlings up to 1.55 dS m-1. Foliar application of up to 450 mg L-1 attenuated the deleterious effects of salt stress on gas exchange and growth of guava seedlings. Guava cv. Paluma seedlings present higher quality when produced with an ECw of 0.55 dS m-1 and under a concentration of 75 mg L-1 of AsA at 150 days after sowing.

Postharvest Immersion in Slightly Acidic Electrolyzed Water Improves Guava Storability by Regulating Phenylpropane Metabolism

Postharvest guava fruit are at high risk of decay and spoilage, which extremely restrains the further advancement of guava industry in China. Currently, slightly acidic electrolyzed water (SAEW) has been shown to be potent in maintaining the storability of fruits and vegetables. Accordingly, this work was designed to figure out the effectiveness of SAEW on storability maintenance in postharvest guavas via regulating the phenylpropane metabolism. On the harvest day, fresh guavas were immersed in distilled water or SAEW (available chlorine concentration: 30 mg L-1) for 10 min, followed by storage for 15 d (25 °C, 80% RH). Results showed that, in comparation with the control guavas, SAEW-treated guavas exhibited lower levels of fruit disease index, malondialdehyde, and cell membrane permeability, while showing higher levels of fruit firmness and commercially acceptable fruit rate, as evidenced by enhanced contents of titratable acid, total soluble solids, vitamin C, total soluble sugar, and reducing sugar. Moreover, SAEW treatment improved the activities of disease-resistance enzymes and the contents of sinapic acid, p-coumaric acid, ferulic acid, caffeic acid, and lignin. The above data revealed that SAEW treatment-enhanced storability of guavas was attributed to the increased disease-resistance enzyme activities and disease-resistance substance contents, which improved the fruit disease resistance and slowed down the disease occurrence.

Recent advancements in polysaccharides, proteins and lipids based edible coatings to enhance guava fruit shelf-life: A review

Fresh fruits are highly needed for the health benefits of human beings because of the presence of high content of natural nutrition in the form of vitamins, minerals, antioxidants, and other phenolic compounds. However, some nutritional fruits such as guava are climacteric in nature with very less post-harvest shelf-life because of the ripening in a very short period and possibility of microbial infections. Thus security of natural nutrients is a serious concern in order to properly utilize guava without generating a huge amount of waste. Among reported various methods for the enhancement of fruits shelf-life, the application of edible coatings with antimicrobial activities on the outer surface of fruits have attracted significant attention because of their eco-friendly nature, easy applicability, high efficacy, and good durability. In recent years, researchers are paying more and more attention in the development of antimicrobial edible coatings to enhance the post-harvest shelf-life of guava using polysaccharides, protein and lipids. In this review, basic approaches and recent advancements in development of antimicrobial and edible coatings on guava fruit by the application of polysaccharides and protein and lipids along with the combination of nanomaterials are summarized. In addition, improvements in basic properties of edible coatings to significantly control the permeation of gases (O2/CO2) by the optimization of coating components as well as delay in ripening process are reviewed and discussed.

Understanding CaCl2 induces surface gelatinization to promote cold plasma modified maize starch: Structure-effect relations

To investigate the influence of surface gelatinization on cold plasma (CP) modification of starch, this study used CaCl2 to modify maize starch by surface gelatinization, further combined with CP treatment and characterized its multi-scale structure and physicochemical properties. The results revealed that starch surface gelatinization causes roughness and fragmentation on the granule surface, and CP undergoes etching effects. The synergistic modification promotes starch degradation, as evidenced by molecular weight decrease and short-chain ratio increase. Although the growth rings, FT-IR patterns, and crystal types of starch remained unchanged, the synergistic modification induced a reduction in the short-range orderliness and crystallinity of starch, thus causing a decrease in the pasting properties and contributing to its solubility. Notably, the CP treatment improved the RDS and SDS contents of the gelatinized starch due to more active sites on the granule surface after gelatinization, and this finding may provide insight into the deep processing of starch.

Physicochemical Aspects, Bioactive Compounds, Phenolic Profile and In Vitro Antioxidant Activity of Tropical Red Fruits and Their Blend

The combination of fruit pulps from different species, in addition to multiplying the offer of flavors, aromas and textures, favors the nutritional spectrum and the diversity of bioactive principles. The objective was to evaluate and compare the physicochemical characteristics, bioactive compounds, profile of phenolic compounds and in vitro antioxidant activity of pulps of three species of tropical red fruits (acerola, guava and pitanga) and of the blend produced from the combination. The pulps showed significant values of bioactive compounds, with emphasis on acerola, which had the highest levels in all parameters, except for lycopene, with the highest content in pitanga pulp. Nineteen phenolic compounds were identified, being phenolic acids, flavanols, anthocyanin and stilbene; of these, eighteen were quantified in acerola, nine in guava, twelve in pitanga and fourteen in the blend. The blend combined positive characteristics conferred by the individual pulps, with low pH favorable for conservation, high levels of total soluble solids and sugars, greater diversity of phenolic compounds and antioxidant activity close to that of acerola pulp. Pearson's correlation between antioxidant activity and ascorbic acid content, total phenolic compounds, flavonoids, anthocyanins and carotenoids for the samples were positive, indicating their use as a source of bioactive compounds.

Tropical Red Fruit Blends: The Effect of Combination of Additives on Foaming, Drying and Thermodynamic Properties

Blends combine advantageous characteristics of each species, resulting in products with different flavors and nutritional substances. Moreover, transforming them into powder provides numerous advantages. This work evaluated the properties of three blended foam formulations made from the pulps of tropical red fruits (acerola, guava and pitanga) to determine the foam layer drying kinetics and thermodynamic properties. The foam formulations were prepared by mixing the three pulps in equal proportions (1:1:1), all added with 6% albumin and 1% stabilizing agent. The foams were analyzed for density, volumetric expansion, stability and porosity in six mixing times. Subsequently, they were subjected to drying in an oven with forced air circulation at 4 temperatures, with a layer 0.5 cm thick. Seven mathematical models were fitted to the drying kinetics experimental data to determine the effective diffusivity and thermodynamic properties of the samples. The best mixing times were 5 min for the E2 sample and 30 min for the others. Formulation E2 presented the best results in the foam physical properties, and E3 presented the shortest drying times. All models tested were satisfactorily adjusted, but Page’s model was the most adequate to describe the process. Sample E3 showed the highest diffusivity and sample E2 the lowest activation energy. The drying temperature increase caused reductions in enthalpy and entropy, as well as an increase in Gibbs free energy, indicating an endergonic process. The combination of additives incorporated into the blend influences the drying process: formulation E2 shows greater efficiency in removing water, and formulation E1 presents the highest energy demand.

Application of ultrasonic incorporated with calcium gluconate maintains physicochemical quality of pink guavas during short-term storage at room temperature

The effectiveness of simultaneous calcium gluconate (0.5% w/v) (Ca-G) and ultrasonication (Ca-G + US) on physicochemical quality of pink guavas under room temperature (27 ± 1 °C) was monitored. The fruits were sonicated for 2, 4, 6 and 8 min and the untreated fruits were defined as control. Peel discoloration and black spot disease were evidently controlled by Ca-G + US for 4 min. The treatment delayed the loss of acidity and total chlorophylls content and the increase in total carotenoids content. The fruit softening and cell membrane permeability and peroxidation were retarded by Ca-G + US for 4 min. Ca-G + US for 4 min enhanced ascorbic acid content and maintained total phenols content and antioxidant activity. In conclusion, the application of Ca-G + US for 4 min is feasible approach maintaining physicochemical quality such as peel color, texture and nutritional value of pink guavas during the short-term storage.

Effects of the Use of Different Temperature and Calcium Chloride Treatments during Storage on the Quality of Fresh-Cut “Xuebai” Cauliflowers

This study revealed the effect of the use of different temperature and calcium chloride (CaCl₂) treatments on the storage quality of fresh-cut “Xuebai” cauliflowers. Fresh-cut “Xuebai” cauliflowers were soaked with 2% CaCl₂ solution at different temperatures. The change in the firmness, color, and ascorbic acid (ASA), total glucosinolates (TGLS), polygalacturonase (PG), and lipoxygenase (LOX) content of fresh-cut “Xuebai” cauliflowers during the cold storage period was assessed. In addition, the sensory quality was also evaluated. The results show that the combined treatments with CaCl₂ at different temperatures could effectively maintain the storage quality of fresh-cut “Xuebai” cauliflowers. Then, a method based on factor analysis with comprehensive quality evaluation was proposed. A factor analysis with a principal component analysis (PCA) was conducted on nine indicators of cauliflowers. Two principal components were extracted with a cumulative contribution rate of 97.513%. The results demonstrated that the treatment with the best fresh-keeping effect of cauliflowers in storage was the combination treatment at 40 °C with 2% CaCl₂ solution, while the optimal storage period was 15 days.