Effect of modified atmosphere packaging on quality and shelf life of 'Robusta' banana (Musa sp.) stored at low temperature

Methodological pipeline for monitoring post-harvest quality of leafy vegetables

Plants are primary source of nutrients for humans. However, the nutritional value of vegetables tends to decrease once organ and tissue sinks are detached from the plant. Minimal processing of leafy vegetables involves cutting and washing before packaging and storage. These processing procedures result in stressful conditions and post-harvest disorders senescence-related can also occur. The aim of this work is to define a methodological pipeline to evaluate the "quality" changes of fresh cut leafy vegetables over their shelf-life. At this purpose, intra-species variability has been investigated considering two varieties of Lactuca sativa (var. longifolia and capitata), showing different susceptibility to browning. Since browning mainly depends on phenol oxidation, redox parameters as well as the activity of the enzymes involved in phenol biosynthesis and oxidation have been monitored over storage time. At the same time, the metabolic changes of the lettuce leaves have been estimated as response patterns to chemical sensors. The obtained sensor outputs were predictive of browning-related biological features in a cultivar-dependent manner. The integration of the results obtained by this multivariate methodological approach allowed the identification of the most appropriate quality markers in lettuce leaves from different varieties. This methodological pipeline is proposed for the identification and subsequent monitoring of post-harvest quality of leafy vegetables.

Nanotechnology-enhanced edible coating application on climacteric fruits

Climacteric fruits continue to ripen after harvest and produce ethylene, coupled with an increase in respiration rate, which contributes to more rapid perishability. Inhibition of ethylene biosynthesis has been shown to be an efficient way to delay the onset of ripening and lengthen shelf life. The use of edible materials as coatings presents an efficient approach in preserving the quality of fruits. Edible coatings have many benefits, such as affordability, ease of application, and use of natural ingredients. Nanotechnology provides interesting approaches to the management of fruit shelf life after harvest. Nanotechnology has the capacity of producing new materials by minimizing the size of components to a nanometric level. These kinds of nanomaterials possess distinct and improved properties for delaying fruit ripening and decay. The main goal of adding nanoparticles to edible coatings is to enhance the biopolymer's mechanical and water vapor barrier properties. Nanoparticles also contain biopolymer-like features and are thought to have superior antibacterial, antifungal, and antiviral properties than edible coatings. This review is aimed at summarizing recent findings on the application of edible coatings in the form of nanoparticles, and their effect on quality parameters and shelf life extension of climacteric fruits. Peer-reviewed articles were obtained by using Scopus and science direct. The current materials widely used for coating climacteric fruits are zinc, silver and chitosan nanoparticles. Zinc nanoparticles have been shown to be more effective in delaying ripening significantly by reducing weight and moisture loss and ensuring retention of fruit firmness. Further research is needed to understand their effect on other physicochemical properties of fruits.

Combined effects of tangerine oil vapour mixed with banana flavour to enhance the quality and flavour of 'Hom Thong' bananas and evaluating consumer acceptance and responses using electroencephalography (EEG)

The objectives of this study were to investigate the effect of tangerine oil (TO) at 25, 50 and 75 µL mixed with banana flavour (BF) at 25, 50 and 75 µL to protect the quality and enhance the flavour of bananas. Then, 25 µL TO + BF 50 µL were selected for studying the quality of bananas stored at 13 °C ±   2 °C for 7 days, and was used to test consumer brain responses using an electroencephalography (EEG). Results showed that mould grew and decomposition occurred in 10 and 50% of the 25 µL TO + 50 µL BF mixture and control, respectively, after 7 days. Furthermore, this ratio increased ripening by having higher L*, b*, firmness and total soluble solid than the control (p < 0.05), whereas titratable acidity and pH were maintained (p > 0.05). The EEG demonstrated that consumption of TO-treated banana could increase brain alertness using stimulating the beta wave activity on banana stimulations for human brain. Limonene, one of the main components of TO, was found in the flesh of treated banana after storage for 4 weeks and possibly interacted with other components to improve antifungal activity and brain response.

Potentials of Medicinal Plant Extracts as an Alternative to Synthetic Chemicals in Postharvest Protection and Preservation of Horticultural Crops: A Review

Horticultural crops undergo various physiological and biochemical changes that lead to undesirable physiological disorders, decay and subsequent economic losses during storage. Quality degradation of horticultural crops is mainly caused by postharvest pathogens such as Botrytis cinerea and Penicillium spp., etc. The application of synthetic fungicides remains the most effective method to control postharvest pathogens. However, their use is becoming increasingly restricted internationally due to health concerns and consumers’ requests for safe and natural alternatives. This has led researchers to investigate natural flora as one of the alternatives to be used in crop protection and preservation. Various medicinal plant parts have different phytochemicals and antioxidants that can be used in crop protection and preservation. Extracts from plants such as Ruta chalepensis, Eucalyptus globulus, etc., have proven to be effective in controlling postharvest pathogens of horticultural crops and increased their shelf life when used as a substitute for synthetic chemicals. Furthermore, extracts from neem and other medicinal plants contain a predominant and insecticidal active ingredient. The application of medicinal plant extracts could be a useful alternative to synthetic chemicals in the postharvest protection and preservation of horticultural crops. This review paper details the application of medicinal plant extracts for postharvest protection and preservation of horticultural crops.

The Involvement of the Banana F-Box Protein MaEBF1 in Regulating Chilling-Inhibited Starch Degradation through Interaction with a MaNAC67-Like Protein

Low-temperature storage is a common strategy for preserving and transporting vegetables and fruits. However, many fruits are hypersensitive to chilling injury, including bananas. In the present study, storage conditions of 11 °C delayed the ripening of Fenjiao (Musa ABB Pisang Awak) banana, and the pulp could be softened after ethephon treatment. Storage conditions of 7 °C prevented fruit from fully softening, and fruit contained a significantly higher starch content and lower soluble sugar content. MaEBF1, a critical gene component in the ethylene signaling pathway, was repressed during ripening after fruit had been stored for 12 days at 7 °C. The expression of a series of starch degradation-related genes and a MaNAC67-like gene were also severely repressed. Both MaEBF1 and MaNAC67-like genes were ethylene-inducible and localized in the nucleus. MaNAC67-like protein was able to physically bind to the promoter of genes associated with starch degradation, including MaBAM6, MaSEX4, and MaMEX1. Yeast two-hybrid, GST-pull down, and BiFC assays showed that MaEBF1 interacted with the MaNAC67-like protein, and their interaction further activated the promoters of MaBAM6 and MaSEX4. The current study indicates that MaNAC67-like is a direct regulator of starch degradation and potential for involvement in regulating chilling-inhibited starch degradation by interacting with the ethylene signaling components in banana fruit. The present work paves the way for further functional analysis of MaEBF1 and MaNAC67-like in banana, which will be useful for understanding the regulation of banana starch metabolism and fruit ripening.

Selection of the best active modified atmosphere packaging with ethylene and moisture scavengers to maintain quality of guava during low-temperature storage

In modified atmosphere packaging of guava, moisture scavenger (MS) sachet containing 30-50 g of coarse silica gel and ethylene scavenger (ES) sachet containing 0-4 g of potassium permanganate was added as per central composite rotatable design. The headspace O₂ and CO₂ of the packages were studied at 4, 8 and 12 °C for 30 days and thereafter the guava were left for two days to ripen at 30 °C. After that the chilling injuries, percentage acceptable guava, peel color and pulp texture was analyzed. After two days ripening at 30 °C the samples with 3 g ES and 46 g MS registered higher L^∗, lower a^∗ value & firmness (16.65 N), lowest chilling injury score. About 95% of guava was found acceptable in this treatment with 1.89-2.79% reducing sugar, 0.95-1.1% titrable acidity, 59% and 46.61% retention of total phenols and ascorbic acid respectively, resulting 32 days shelf-life of guava.

Characterization, yield optimization, scale up and biopreservative potential of fermencin SA715, a novel bacteriocin from Lactobacillus fermentum GA715 of goat milk origin

BACKGROUND

Emergence of antibiotic resistance and growing consumer trend towards foods containing biopreservatives stimulated the search for alternative antimicrobials. This research is aimed at characterizing, investigating the mechanism of action, scale up optimization and evaluating the biopreservative potential of a bacteriocin from Lactobacillus fermentum.

RESULTS

Fermencin SA715 is a novel, broad-spectrum, non-pore-forming and cell wall-associated bacteriocin isolated from L. fermentum GA715 of goat milk origin. A combination of hydrophobic interaction chromatography, solid-phase extraction and reversed-phase HPLC was necessary for purification of the bacteriocin to homogeneity. It has a molecular weight of 1792.537 Da as revealed by MALDI-TOF mass spectrometry. Fermencin SA715 is potent at micromolar concentration, possesses high thermal and pH stability and inactivated by proteolytic enzymes thereby revealing its proteinaceous nature. Biomass accumulation and production of fermencin SA715 was optimum in a newly synthesized growth medium. Fermencin SA715 did not occur in the absence of manganese(II) sulphate. Tween 80, ascorbic acid, sodium citrate and magnesium sulphate enhanced the production of fermencin SA715. Sucrose is the preferred carbon source for growth and bacteriocin production. Sodium chloride concentration higher than 1% suppressed growth and production of fermencin SA715. Optimum bacteriocin production occurred at 37 °C and pH 6-7. Scale up of fermencin SA715 production involved batch fermentation in a bioreactor at a constant pH of 6.5 which resulted in enhanced production. Fermencin SA715 doubled the shelf life and improved the microbiological safety of fresh banana. Bacteriocin application followed by refrigeration tripled the shell life of banana.

CONCLUSIONS

This study reveals the huge potential of fermencin SA715 as a future biopreservative for bananas and reveals other interesting characteristics which can be exploited in the preservation of other foods. Furthermore insights on the factors influencing the production of fermencin SA715 have been revealed and optimized condition for its production has been established facilitating future commercial production.

Pentocin MQ1: A Novel, Broad-Spectrum, Pore-Forming Bacteriocin From Lactobacillus pentosus CS2 With Quorum Sensing Regulatory Mechanism and Biopreservative Potential

Micrococcus luteus, Listeria monocytogenes, and Bacillus cereus are major food-borne pathogenic and spoilage bacteria. Emergence of antibiotic resistance and consumer demand for foods containing less of chemical preservatives led to a search for natural antimicrobials. A study aimed at characterizing, investigating the mechanism of action and regulation of biosynthesis and evaluating the biopreservative potential of pentocin from Lactobacillus pentosus CS2 was conducted. Pentocin MQ1 is a novel bacteriocin isolated from L. pentosus CS2 of coconut shake origin. The purification strategy involved adsorption-desorption of bacteriocin followed by RP-HPLC. It has a molecular weight of 2110.672 Da as determined by MALDI-TOF mass spectrometry and a molar extinction value of 298.82 M⁻¹ cm⁻¹. Pentocin MQ1 is not plasmid-borne and its biosynthesis is regulated by a quorum sensing mechanism. It has a broad spectrum of antibacterial activity, exhibited high chemical, thermal and pH stability but proved sensitive to proteolytic enzymes. It is potent against M. luteus, B. cereus, and L. monocytogenes at micromolar concentrations. It is quick-acting and exhibited a bactericidal mode of action against its targets. Target killing was mediated by pore formation. We report for the first time membrane permeabilization as a mechanism of action of the pentocin from the study against Gram-positive bacteria. Pentocin MQ1 is a cell wall-associated bacteriocin. Application of pentocin MQ1 improved the microbiological quality and extended the shelf life of fresh banana. This is the first report on the biopreservation of banana using bacteriocin. These findings place pentocin MQ1 as a potential biopreservative for further evaluation in food and medical applications.

Changes in main nutrients and medicinal composition of Chinese yam (Dioscorea opposita) tubers during storage

The changes in the main nutrient and medicinal components during the storage of the Chinese yam (Dioscorea opposita) tubers were studied. The harvested tubers were stored under ambient conditions (10 °C to 18 °C, 60 % to 80 % Relative Humidity) and cold temperature and packaged conditions (4 °C, 60 % to 65 % Relative Humidity) for 45 day. The allantoin, starch, total alcohol-soluble sugar, reducing sugar, protein, and moisture contents of the samples were evaluated. Their amylase activities were also investigated. Results of ambient conditions indicated that, during storage, moisture decreased by 67.96 % to 56.51 %, and total sugars, reducing sugars, and protein increased by 6.49 % to 9.81 %, 1.7 % to 2.27 %, and 13.02 % to 14.55 %, respectively. Starch and enzyme activities increased during the early days of storage and progressively decreased, and the content of allantoin changed in volatility. The changes were more significant at cold temperatures and packaged conditions than at ambient conditions. This result suggests that after-ripening occurred in the early stages of Chinese yam tubers, which positively affected the nutritional potential of the tubers by a marked increase in nutrients. Low-temperature sweetening greatly affects the nutritional potential of tubers by a series of complicated interactions between starch and sugars at 4 °C.

Tomato quality in controlled atmosphere storage, modified atmosphere packaging and cold storage

Effects of controlled atmosphere storage (CAS) and modified atmosphere packaging (MAP) in comparison with conventional cold storage on qualitative properties of green-mature harvested tomato were evaluated. Qualitative properties included firmness, redness value (a*), hue angle, Total Soluble Solids (TSS) content, Titratable Acidity (TA) and TSS/TA. Under CAS and MAP conditions, gas composition was 5 kPa O2 and 3 kPa CO2. Results showed that the ability of CAS and MAP to retard the ripening process was more than cold storage. With regard to maintaining texture and colour, CAS treatment was the best and MAP was better than cold storage. Although amongst storage treatments, the maximum value of TSS was observed in cold storage, its decreasing trend in CAS was slower than that in cold storage. Additionally, MAP and especially CAS slowed down the diminishing trend of TA in tomatoes.

Prediction of textural attributes using color values of banana (Musa sapientum) during ripening

Banana is an important sub-tropical fruit in international trade. It undergoes significant textural and color transformations during ripening process, which in turn influence the eating quality of the fruit. In present study, color ('L', 'a' and 'b' value) and textural attributes of bananas (peel, fruit and pulp firmness; pulp toughness; stickiness) were studied simultaneously using Hunter Color Lab and Texture Analyser, respectively, during ripening period of 10 days at ambient atmosphere. There was significant effect of ripening period on all the considered textural characteristics and color properties of bananas except color value 'b'. In general, textural descriptors (peel, fruit and pulp firmness; and pulp toughness) decreased during ripening except stickiness, while color values viz 'a' and 'b' increased with ripening barring 'L' value. Among various textural attributes, peel toughness and pulp firmness showed highest correlation (r) with 'a' value of banana peel. In order to predict textural properties using color values of banana, five types of equations (linear/polynomial/exponential/logarithmic/power) were fitted. Among them, polynomial equation was found to be the best fit (highest coefficient of determination, R(2)) for prediction of texture using color properties for bananas. The pulp firmness, peel toughness and pulp toughness showed R(2) above 0.84 with indicating its potentiality of the fitted equations for prediction of textural profile of bananas non-destructively using 'a' value.

Marketability of ready-to-eat cactus pear as affected by temperature and modified atmosphere

In order to increase the diffusion of cactus pear fruits, in this study, the proper maturity index for peeling and processing them as ready-to-eat product was evaluated and characterized. Thereafter, the effects of different storage temperatures and modified atmosphere conditions on the marketability of ready-to-eat cactus pear were studied. The storage of ready-to-eat fruits at 4 °C in both passive (air) and semi-active (10 kPa O2 and 10 kPa CO2) modified atmosphere improved the marketability by 30%, whereas the storage at 8 °C caused a dangerous reduction in O2 partial pressure inside modified atmosphere packages, due to fruits' increased metabolic activity. A very low level of initial microbial growth was detected, while a severe increase in mesophilic and psychrophilic bacteria was shown in control samples at both temperatures during storage; an inhibitory effect of modified atmosphere on microbial growth was also observed. In conclusion, modified atmosphere improved only the marketability of fruits stored at 4 °C; whereas the storage at 8 °C resulted in deleterious effects on the ready-to-eat fruits, whether stored in air or in modified atmosphere.