Shelf-life enhancement and microbial load reduction of fresh-cut apple using ascorbic acid and carboxymethyl cellulose coating combined with ultrasound treatment.

The shelf-life of fresh-cut apples is limited because of their high water loss, deterioration rate, and surface browning. In this research, the effects of ultrasonic, ultrasonic + carboxymethyl cellulose (CMC) 1% coatings, ultrasonic + ascorbic acid (AA) 2%, and combination of ultrasonic + AA 2% and CMC 1% on fresh-cut apples were studied. Physicochemical, antioxidant properties, and microbial stability of ready to eat treated fresh-cut apple was investigated during storage at 4 °C for 12 days. Results showed that the treated fresh-cut had less changes of L*, flesh firmness, soluble solid content, and titratable acidity than that of untreated. Vitamin C, total phenol, total flavonoid, antioxidant capacity, and superoxide dismutase activity were greater in treated fresh-cut apple than that of untreated ones. Ultrasonic application mostly declined polyphenol oxidase and peroxidase activity changes. The combined treatment of ultrasonic + AA 2% + CMC 1% had the greatest impact on reducing microbial load among the treatments. These results revealed that the simultaneous application of ultrasonic and AA followed by CMC coating might have the potential to be used in minimally processed industry.

Exogenous melatonin delays strawberry fruit ripening by suppressing endogenous ABA signaling.

Ripening as a physico-chemical change is part of a continuous developmental process and hormones play a major role in this processes. The present study was carried out to investigate the effect of external melatonin (0 and 10 µM) injection at the light green stage on the ripening of strawberry fruit. The fruit was sampled for morphological, biochemical, and gene expression analysis during (0, 5, 10, and 15 days after treatment). The results showed a lower accumulation of anthocyanin content was observed in fruits treated with 10 µM. The injection of 10 µM melatonin caused a lower total soluble solid content and fruit color, and higher titratable acidity and softening. The total phenol content was higher in fruit treated with 10 µM melatonin, accompanied by increased PAL enzyme activity and gene expression, increased DPPH scavenging capacity, and higher content of quercetin, gallic, caffeic, and chlorogenic acids. The delay in fruit ripening was associated with suppression of H2O2 level and endogenous ABA accumulation caused by lower expression of NCEDs genes. In general, it is concluded that activating the melatonin ROS scavenging cascade might be responsible for the delayed ripening and development of strawberry fruit. Therefore, our study demonstrates that the exogenous application of 10 µM melatonin can slow the ripening of strawberry fruit.

Microbial antagonists to biologically control postharvest decay and preserve fruit quality.

Postharvest waste due to decay of fruits and vegetables negatively affects food security, while at the same time control of decay and therefore waste can be limited because of consumer concerns about use of synthetic chemicals. Use of antagonistic microorganisms is an eco-friendly technique that represents a promising alternative approach to the use of chemical methods. Understanding the interactions between antagonists and the fruit microbiome will enable the discovery of new methods to reduce postharvest waste. This article reviews different microbial agents, fungi, bacteria and yeasts that could control decay. Recent developments in the use of microorganisms for preserving postharvest fruit quality, formulation of effective antagonists, and the commercialization steps are also discussed. Antagonists control decay through either direct or indirect mechanisms while preserving the appearance, flavor, texture and nutritional value of horticultural products. Microorganisms do not fully control pathogens, and therefore they are usually used with other treatments or have their biocontrol ability modified through genetic manipulations. Despite of these limitations, commercialization of biocontrol products based on antagonists with required stability and biocontrol potential is occurring. Biocontrol of postharvest decay and waste agent is promising technology for fruit and vegetable industries. Further study is necessary to better understand mechanisms and increasing efficiency of this method.

Efficiency of nanoemulsion of essential oils to control Botrytis cinerea on strawberry surface and prolong fruit shelf life.

Strawberry fruit is highly susceptible to decay by fungi. The objective of this study was to determine if essential oils (EOs) or nano-emulsions (Nano-EM) of EOs from Thymus vulgaris (Th), Matricaria chamomilla (Mc), Pistacia atlantica (Pa), or Mentha longifolia (Me) could inhibit growth of strawberry spoilage fungi Botrytis cinerea and their effect, if any, on strawberry quality parameters. An In vitro study showed that Th and Me EOs had the same minimal inhibitory concentrations (MIC) of 0.021 % while the MICs for Mc and Pa EOs were 0.9 % and 1.5 %, respectively. Th and Me EOs were used for subsequent experiments. In the second experiment, the application of Th and Me EOs and their nano-EM at 0.021, 0.1, 0.5 and 1 % were studied to control B. cinerea growth on the fruit surface. Nano-EM of EOs had higher antifungal activity in the control of B. cinerea than EOs on fruit surface. Generally, antifungal activity was increased at higher concentrations of Nano-EM, but in the case of EOs, their antifungal activity was not increased by increasing concentration. Nano-EM of EOs with 0.5 % was selected for further study. Finally, the quality changes and postharvest losses of fruit treated with Nano-EM of EOs of Th and Me at 4 °C were studied. The results of third experiment showed that Nano-EM of both EOs reduced microbial load, decay index, weight loss and induced greater firmness, vitamin C, total flavonoid and antioxidant activity in strawberry during storage. NanoEM-ThEO 0.5 % was more effective than NanoEM-MeEO 0.5 % to retain strawberry firmness, vitamin C and total flavonoid.

Antifungal effects of volatile compounds produced by Tetrapisispora sp. strain 111A-NL1 as a new biocontrol agent on the strawberry grey mold disease.

An antagonistic yeast strain was isolated from the strawberry fruit cv. Paros, and its antifungal properties against Botrytis cinerea causal agent of strawberry grey mold disease were evaluated under in vitro and in vivo experiments. The isolate was tentatively identified as Tetrapisispora sp. strain 111A-NL1 based on phenotypic characteristics and sequence analysis of D1/D2 domains of the 26S rRNA gene. Volatile organic compounds (VOCs) produced by the 111A-NL1 strain inhibited the mycelial growth of fungal pathogen (75.19%) and conidial germination (63.34%); however, inhibition percentage of mycelial growth of pathogen by dual culture test was less (19.49%). Also, the strain produced pectinase, siderophore, chitinase, IAA, as well as gibberellin, and could solubilize phosphate. Additionally, the disease severity of strawberry grey mold was decreased by employing living cells and volatile metabolites methods by 47.61% and 74.05%, respectively, in comparison with untreated control seven days after inoculation. Therefore, its mode of action might consist of antibiosis and VOCs production by yeast strain 111A-NL1 against B. cinerea. The VOCs released by strain 111A-NL1 were analyzed, and thirty-three chemical compounds were determined by gas chromatography-mass spectroscopy (GC-MS). Out of them, Decane (12.79%), Squalene (9.60%), Undecane (7.98%), Benzene, 1,2,3-trimethyl- (7.67%), Nonane, 2,6-dimethyl- (5.69%), Benzene, 1-ethyl-3-methyl- (5.55%), Mesitylene (4.17%), and Phenylethyl Alcohol (3.33%) were the major components. In addition, the selected strain reduced natural decay incidence and weight loss of fruit, and preserved quality parameters of strawberry fruit including firmness, soluble solids content, and titratable acidity. This research averred, for the first time, that the creation of VOCs by Tetrapisispora sp. strain 111A-NL1 could play an essential role as a biofumigant in the antifungal activity against strawberry grey mold.

Inhibition of browning via aqueous gel solution of Aloe vera: a new method for preserving fresh fruits as a case study on fresh kernels of Persian walnut.

Aloe Vera (AV) gel is commonly used as a natural, inexpensive, edible coating that can improve the quality and shelf life of fruits. The objective of this study was to evaluate how two methods of applying AV, i.e. as an edible coating (dry environment) and as a gel solution (aqueous environment: a new method), prevent browning and maintain quality characteristics of fresh kernels of Persian walnut for 60 days during cold storage. Distilled water was used as a control group for both environments. In general, AV caused a reduction in the peroxide value (POV) of kernels, while preserving Total Phenolic Compound and Total Antioxidant Activity (TAA). The AV treatment slowed down the process of color change and maintained sensory properties during storage, compared to the control groups of both methods. The AV gel solution performed better than the AV edible coating in terms of POV, color (L* and h°) and microbial growth. In contrast, the AV edible coating was more effective in preserving TPC and TAA. Also, TAA was found to have a significant, positive correlation with L* and, simultaneously, a negative correlation with POV. As far as we know, this is the first instance that the AV gel was used as a formulated solution and as an edible coating on fresh fruits. This innovative method can be used in commercial practice, while being ecofriendly and non-chemical as a treatment for the maintenance of postharvest quality in fruits.

Improving quality and quantity attributes of grape juice concentrate (molasses) using ohmic heating.

The effect of ohmic heating method (OHM) on quality and quantity attributes of black grape molasses was investigated and compared with the conventional heating method (CHM). Results showed that the samples prepared by OHM had the highest antioxidant activity than CHM. Increasing of voltage gradient had a positive effect on the saving of antioxidant activity. Changes in pH for OHM were lower than CHM. Heating methods had no significant effect on phenol content. Antioxidant capacity and phenol content of treated samples were lower than the fresh sample at the same water content. The titratable acidity of treated samples using CHM was higher than the OHM. The OHM saved about 2.4-7.2-fold of processing time and 6.3-fold of energy consumption than the CHM. Heat generation and electrical conductivity depended on sample moisture content. OHM provides minimal damage to the sensory characteristics. As a final result, the OHM significantly improved the quality and saved the quantity parameters of the grape molasses processing than the CHM.

Preharvest methyl jasmonate's impact on postharvest chilling sensitivity, antioxidant activity, and pomegranate fruit quality.

The fruit of pomegranate is bioactive compound source but is sensitive to low storage temperature. Methyl jasmonate (MeJA) spray on pomegranate trees was used in an attempt to evaluate its possible effect on fruit bioactive constituent changes and chilling injury (CI) incidence. Pomegranates trees were treated 15 days before harvest with distilled water or 1 and 2 mM MeJA, and then harvested fruit was stored at 4°C about 80 days. It was found that preharvest MeJA treatments improved arils color at harvest and reduced the postharvest CI index. Electrolyte leakage increased over storage, however, it was significantly higher in control rather than those treated. In addition, MeJA treatments significantly increased flavonoids, total antioxidant activity (TAA), total phenolics (TP), and total anthocyanins in comparison with untreated control. PRACTICAL APPLICATIONS: The demand for pomegranate fruit is rising because of its special taste and unique bioactive constituents. Therefore, find out methods to store it and deliver in expanded time has commercial value. The common method to extend food life is low temperature but pomegranate shows chilling evidence when stored at low temperature. Several methods have been used to alleviate chilling. In current study, methyl jasmonate was sprayed on tree and its possible effect on fruit that stored at low temperature was assessed. The results revealed that MeJA might have potential preharvest application to reduce chilling, retain the quality and nutrition value in pomegranate arils by affecting the antioxidant systems.

Quality preservation of orange concentrate by using hybrid ohmic - Vacuum heating.

The effect of ohmic-vacuum heating conditions (OHVC) was evaluated on quality parameters during concentration process of orange juice and compared with ohmic heating process under atmospheric conditions (OHAC) and conventional vacuum heating (CVH). The decline of vitamin C in OHVC treatments (10-29.2%) was lower than the OHAC (18.0-38.8%) and CVH (47.4%). Changes of pH for OHVC were lower than OHAC and CVH. The difference in total phenol content of fresh and concentrated juice was 8.0-21.3% for OHVC and 18.5-42.8% for OHAC and 49.6% for CHV. Antioxidant capacity of treatments was lower than the fresh sample at same water content. Increasing of voltage gradient had a positive effect on the saving of vitamin C and total phenol and processing time. Finally, it can be resulted that the combine of vacuum treatment with ohmic heating (as hybrid ohmic-vacuum heating) could maintain food quality parameters.

Nano-ZnO/carboxymethyl cellulose-based active coating impact on ready-to-use pomegranate during cold storage.

Minimally processed pomegranate rapidly loses its overall quality because of high water loss and microbial contamination. Nano-ZnO in combination with carboxymethyl cellulose (CMC) coating was used on pomegranate arils. Arils were dipped for 4min in distilled water (control), 0.1 or 0.2% (w/v) nano-ZnO suspension and then ZnO treated arils were coated with 0.5% (w/v) CMC and stored for 12days at 4°C. Coatings decreased total yeast+mold during 12days of storage while total mesophilic bacteria was decreased during 6days of storage. Coatings decreased weight loss and also the greatest juice percent was in coated arils. Soluble solids content decreased during storage with no significant difference between treatments. CMC+0.2% nano-ZnO suppressed total phenol changes. Total anthocyanin, vitamin C, and antioxidant capacity were higher in coated arils. These findings suggest that nano-ZnO+CMC coating has the potential to extend minimally processed pomegranate storage life.

Antioxidant Bioactive Compounds Changes in Fruit of Quince Genotypes Over Cold Storage.

Quince fruit has many benefits to human health and is excellent source of bioactive compounds. The fruit of 15 quince genotypes stored at 2 °C for 5 mo to study fruit quality changes during cold storage. Fruit were sampled monthly and stored at 20 °C for 24 h. Fruit ascorbic acid (AA), total phenol (TP), and total flavonoid (TF) concentrations, total antioxidant activity (TAA), flesh browning (FB) incidence, polyphenol oxidase (PPO), peroxidase (POX), and superoxide dismutase (SOD) activities were measured during storage. A high variation in bioactive compounds was observed across genotypes. The range of 26.8 to 44.4 mg/100 g FW for AA, 86.7% to 98.2% for TAA, 157.7 to 380.7 mg GAE 100(-1) g FW for TP, and 5.3 to 10.7 mg/100 g FW for TF were observed across genotypes at harvest time. The overall AA, TAA, TP, TF, and SOD decreased while PPO and POX increased during storage. FB was first observed after 4 mo and increased thereafter while the FB index was different across genotypes. Higher bioactive content may prevent or reduce FB index so that a negative correlation was found between FB and AA, TAA, TP, TF, and SOD.

Internal browning disorder of eight pear cultivars affected by bioactive constituents and enzyme activity.

Internal browning (IB) is a disorder in pears that is frequently observed in some cultivars. The present research was carried out to study biochemical changes and IB disorder of pear fruit during storage and ripening. Eight pear cultivars harvested and stored at 1°C up to 90 days. IB incidence, some bioactive compounds, polyphenol oxidase (PPO), peroxidase (POX), and superoxide dismutase (SOD) enzymes activities were measured during storage. IB increased during storage time but the susceptibility of cultivars was different. The ascorbic acid (AA), antioxidant capacity (AC) and SOD activity decreased while POX activity increased during storage but the rate of changes were different in studied cultivars. Total phenol (TP) and total flavonoid (TF) average content varied among pear cultivars and the highest TP and TF were observed in 'Bakhi' cultivars during storage. Fruit IB had positive correlation with the PPO activity, but negative correlation with TP, AC and AA.

Postharvest polyamine application alleviates chilling injury and affects apricot storage ability.

Fruit of two apricot cultivars 'Bagheri' and 'Asgarabadi' were treated with putrescine (Put) or spermidine (Spd) at 1 mM and then were stored at 1 °C for 21 days. Fruit were sampled weekly and stored 2 days at 20 °C for shelf-life study. The treatments reduced ethylene production and maintained the firmness and color of the fruit. Peroxidase (POX), catalase (CAT), superoxide dismutase (SOD), and polyphenol oxidase (PPO) activities and total phenol (TP) concentrations were measured during storage. Both cultivars showed chilling injury (CI) incidence, and the severity in control fruit was higher than either Put or Spd treatments. CI incidence in Spd-treated fruit was lower than that of Put-treated fruit. Polyamine (PA) treatment generally increased antioxidant enzyme activity of fruit during storage. PA treatments may help maintain the quality of apricot fruit during storage by inhibiting ripening and decreasing CI incidence.