Controlling soft rot of green pepper by bacteriocin paracin wx3 and its effect on storage quality of green pepper

A bacteriocin paracin wx3 was investigated as a candidate of natural preservative to control green pepper soft rot. Firstly, paracin wx3 was heterologously expressed in Pichia pastoris X33 with an improved yield of 0.537 g/L. Its size and amino acid sequence were confirmed by Tricine-SDS-PAGE and LC-MS/MS. Then, result of antibacterial activity showed that its MIC value against Pectobacterium carotovorum was 16 μg/mL. In vitro, paracin wx3 completely killed the pathogen at high concentrations ≥8 × MIC. In vivo, disease incidence of green pepper soft rot was decreased from 90% (control) to <2% (8 × MIC). Subsequently, results of action mode showed that paracin wx3 inhibited the growth of pathogen by pore-formation on cell membrane. Last, paracin wx3 treatment reduced losses of weight, firmness, total soluble solid, Vc of green pepper during storage. It also inhibited the production of soft rot volatile p-xylene, 1-butanol, 2-methyl-2-propanol, 3-hydroxybutan-2-one-D, 2-pentyl furan, butanal, etc.

Influence of green pepper extract on the physicochemical, antioxidant, and sensory properties of stirred yogurt

The green pepper has garnered interest in different societies as a functional food and food additive. Numerous studies have indicated that the phytochemicals found in pepper possess antioxidant, anti-cancer, anti-inflammatory, anti-obesity, and anti-arteriosclerotic properties. In this study, green pepper extract was used in yogurt to increase the acceptability of consumption and improve its health properties. For this purpose, green pepper extract was added in concentrations 100, 200, and 300 ppm in the preparation of yogurt. And pH, acidity, total content of phenolic compounds, DPPH inhibition percentage, viscosity, syneresis, and sensory properties were evaluated in 1, 7, 14, and 21 days after production. The results showed that by increasing the amount of extract, the percentage of antioxidant activity and phenolic compounds increased significantly. The effect of storage time on these indicators was also significant (p < 0.05). in such a way that over time, there was a decrease in antioxidant activity. But, there was a slight increase in antioxidant activity on the 14th day of storage. Also, the effect of treatment type on some physicochemical characteristics of yogurt containing green pepper extract including pH, acidity, viscosity, and syneresis was significant (p < 0.05). During storage, acidity, syneresis, and viscosity increased and pH decreased significantly in all yogurt samples. Regarding the tested sensory attributes, the 200 ppm sample received the highest score among the evaluators, and in terms of overall acceptance, the samples containing the extract were more favorable than the control sample.

Preparation of polylactic acid/TiO2/GO nano-fibrous films and their preservation effect on green peppers

Polylactic acid (PLA)/nano-TiO₂(TiO₂ NPs)/Graphene oxide (GO) nano-fibrous films were prepared by ultrasonic assisted electrostatic spinning technology, and the effects of TiO₂ NPs:GO mass ratio and ultrasonic power on film morphology and mechanical, thermal, barrier and antibacterial properties were investigated. The addition of TiO₂ NPs and GO can significantly increase the tensile strength and elongation at the break of PLA nano-fibrous films, and improve the water barrier properties of the nano-fibrous films. The antibacterial experiment showed that the inhibition rates of the nano-fibrous films against Escherichia coli and Staphylococcus aureus after 24 h exposure to UV irradiation reached 94.4 ± 1.8% and 92.6 ± 1.7% At the same time, the fresh-keeping packaging experiment of green peppers at room temperature, through the determination of hardness, soluble solids, chlorophyll content to determine the degree of decay of green pepper, it showed that PLA/TiO₂ NPs/GO nano-fibrous films can better maintain the sensory quality of green peppers, delay the rate of spoilage of green peppers, and prolong the preservation period of green peppers.

Unravelling the reactivity of bifenazate in water and on vegetables: Kinetics and byproducts

In this study, we aimed to better understand the transformation mechanisms of bifenazate, a biphenyl hydrazine derivative insecticide poorly studied up to now. For this, we compared its reactivity in the dark and under simulated solar light irradiation in different media (water, non-aqueous polar solvent, surface of apolar wax films, skin of vegetable). In air-saturated pH = 5.7 water, bifenazate underwent both autoxidation in the dark (t_1/2 = 34 h) and photolysis (t_1/2 = 17 h). In an aprotic polar solvent such as acetonitrile, bifenazate was stable in the dark but was quickly photodegraded in the presence of oxygen (t_1/2 = 2 h). The phototransformation of bifenazate was due to the oxidation of excited states by oxygen and to the cleavage of the NN bond, while the autoxidation in water started by the initial oxidation of the molecule by oxygen and involved the superoxide anion as chain carrier. On paraffinic wax film, photodegradation (t_1/2 = 365 h) and dark autoxidation (t_1/2 = 1600 h) were very slow. On green pepper skin, bifenazate disappeared both in the dark (t_1/2 = 34 h) and through photolysis (t_1/2 = 23 h) at rates close to those measured in water. This shows that on green pepper skin, bifenazate is affected by water contained in the vegetable and possibly released by transpiration. Bifenazate diazene was the major degradation product in all studied conditions. Minor byproducts were detected too. They depended on the experimental conditions showing that degradation pathways are governed by the nature and properties of the medium. In particular, on green pepper one found byproducts generated in acetonitrile and on wax by photolysis and in water by autoxidation. This finding highlights the need for a better model than wax to mimic photolysis on plant surfaces.

The effect of high power airborne ultrasound and microwaves on convective drying effectiveness and quality of green pepper

The effectiveness of hybrid drying based on convective drying with application of ultrasound and microwave enhancement is the main subject of the studies. The drying kinetics, energy consumption as well as the quality aspect of green pepper is analysed. It was shown that hybrid drying methods shorten significantly the drying time, reduce the energy consumption and affect positively the quality factors. Each of the analysed aspects depend on combination of the convective-ultrasound-microwave drying programs. Besides, based on the drying model elaborated earlier by one of the authors, the effects of ultrasound on convective drying assessed by such phenomena as "heating effect", "vibration effect" and "synergistic effect" are presented.

Isolation and characterization of plant and human pathogenic bacteria from green pepper (Capsicum annum L.) in Riyadh, Saudi Arabia

Forty-three bacterial isolates in five genera were recovered from naturally infected green pepper fruits (38 samples) showing dark brown, irregular-shaped splotches. The pathogenicity test was performed on healthy green pepper fruits and red colonies were from inoculated fruits showing the same symptoms and the infected area developed into soft rot. Their identification was based on phenotypic characters and sequence of the gene fragment coding 16S rRNA. Of 43 isolates, 10 showing splotches on green pepper fruits belonged to genus Serratia on the basis of phenotypic characters. One representative isolate of the genus Serratia has been identified by partial 16S rRNA gene sequencing and phylogenetic analysis as belonging to the Serratia rubidaea and has the potential to cause spot on green pepper. Eleven phytopathogenic bacterial isolates were also obtained at the same time but did not induce any splotch symptoms on artificially infected green pepper. Five out of 11 bacterial isolates were identified as Ralstonia on the basis of biochemical tests. Partial sequencing of 16S ribosomal gene of representative isolate revealed that the isolate is Ralstonia solanacearum. The six remaining isolates were related to Xanthomonas vesicatoria on the basis of biochemical tests. Twenty-two of opportunistic human pathogens were isolated at the same time and related to Proteus and Klebsiella. Opportunistic human pathogens did not produce any symptoms on artificially infected green pepper. One representative isolate for each genus was identified as Klebsiella oxytoca and Proteus mirabilis based on their partial 16S rRNA gene sequences. The virulence of the S. rubidaea, the causal agent of green pepper fruits splotches was attributed to the production and secretion of a large variety of enzymes capable of degrading the complex polysaccharides of the plant cell wall and membrane constituents.

Postharvest quality and shelf life of some hot pepper varieties

Five hot pepper varieties were grown at Haramaya University Research Farm, Dire Dawa, Ethiopia. The experiment was undertaken using completely randomized block design (RCBD) with three replications. Green peppers were stored under ambient and evaporatively cooled conditions. Significant (P ≤ 0.05) differences were observed among cultivars and storage conditions in changes in quality of pepper. Storage at ambient conditions resulted in high weight loss and rapid deterioration in chemical composition. The highest and lowest moisture contents were recorded in Melka Eshet and PBC 600, respectively. Evaporative cooler reduced weight loss and maintained higher levels of pH, ascorbic acid and marketability. The highest weight loss was recorded in Melka Dima stored at ambient condition. The lowest weight loss and highest ascorbic acid content was obtained in Mareko Fana stored in evaporative cooler. After 16 days of storage, all pepper fruits stored at ambient condition were unmarketable while those stored in evaporative cooler were kept up to 28 days. The highest pungency level was observed in ambient storage environment than in evaporative cooler. Evaporative cooling was shown to improve shelf life by four-fold compared to the ambient condition. The shelf life of pepper was improved in all varieties tested while the quality characteristics were maintained better in Mareko Fana than in the other varieties when harvested at mature-green stage and stored under evaporatively cooled storage.