Hydrogen Peroxide and Calcium Chloride Added to Irrigation Water as a Strategy to Reduce Bacterial Populations and Improve Quality of Fresh Mushrooms

The quality and value of fresh mushrooms are often diminished by the presence of high bacterial populations that cause a brown, blotchy appearance. The objective of the present research was to evaluate the addition of hydrogen peroxide and/or calcium chloride to irrigation water as a means to reduce total bacterial populations on fresh mushrooms. Crops were grown using commercial mushroom growing practices except for the addition of 0.75% hydrogen peroxide and/or 0.3% calcium chloride irrigation water added to the crop starting 11 d after the casing layer was applied on top of mushroom compost. Irrigation water without the added treatments acted as the control. Mushrooms were aseptically sampled from the production beds for enumerating bacterial counts. Total aerobic bacterial populations were determined by standard microbiological plating procedures. Mushroom whiteness (L‐value) and color (delta E) after harvest and postharvest storage were measured using a Minolta chromameter. Harvested mushrooms were separated by treatment and weighed to record yield. Mushrooms irrigated with water (control) had 7.3 log colony‐forming units (CFU) of aerobic bacterial populations per gram of fresh mushroom tissue. Compared with the control, irrigation with 0.75% hydrogen peroxide and 0.3% calcium chloride reduced the bacterial populations on fresh mushrooms by 87% (6.4 log CFU/g). Irrigation with hydrogen peroxide and calcium chloride significantly enhanced mushroom whiteness after harvest as well as after 6 d of postharvest storage at 12 °C. The irrigation treatments did not have a significant effect on crop yields; hence, the addition of hydrogen peroxide and calcium chloride to irrigation water was demonstrated to have good potential as a practical strategy to reduce bacterial populations and to improve the quality of fresh mushrooms.     

Pre‐harvest application of calcium to control black heart disorder in Mauritius pineapples during low‐temperature storage

The chill‐sensitive pineapple cv. Mauritius grown in Sri Lanka was subjected to different pre‐harvest calcium treatments in order to determine an effective means of increasing calcium levels in the fruit, thereby reducing the incidence and severity of black heart disorder. Treatments of CaO and CaSO₄ (10 g and 15 g per plant) were applied to soil as side dressing 6 weeks after planting, while CaCl₂ (1.3 g and 2 g per fruit) were applied as a spray treatment to 1‐month‐old fruit (red bud stage). Fruit were harvested at the 10–20% yellow stage of maturity. Incidence of black heart disorder and observations on total acids, °Brix, ascorbic acid content and total calcium levels were recorded on waxed and unwaxed fruit before and after 17 days storage at 10 °C and 85–90% relative humidity, followed by 2 days at ambient temperature 28 ± 2 °C. Combined treatment of pre‐harvest CaCl₂ fruit spray (1.3 g per fruit) followed by post‐harvest wax treatment showed 80% good fruit with no black heart symptoms after low‐temperature storage at 10 °C for 17 days followed by 2 days at ambient temperature of 28 ± 2 °C. However, side dressings of CaO and CaSO₄ were found to be less effective in reducing the symptoms, showing less than 30% of good fruit without black heart symptoms. Both core and flesh regions of pineapples subjected to pre‐harvest fruit spray treatment showed higher total calcium levels compared to controls as well as other calcium treatments. Results obtained from the field experiment confirmed that the calcium chloride fruit spray treatment of 1.3 g per fruit in three split doses at 2‐week intervals could be used to reduce the incidence of black heart disorder in Mauritius pineapples. Copyright © 2005 Society of Chemical Industry     

Effect of some thermal and chemical pretreatments on smoked Oyster mushroom quality

The effect of different thermal and chemical pretreatments on quality and enzyme activities of smoked mushroom was investigated. Mushrooms were blanched (water and steam) and dipped in different concentrations of sulphites (SO₂), hydrogen peroxide (H₂O₂), ethylene‐di‐amine tetra‐acetic acid (EDTA) and citric acid for 10 min before smoking. Enzyme activities, colour characteristics, microbiological and sensory examinations were carried out every 2 weeks up to 8 weeks of storage in refrigerator at 4 °C. Results could be concluded that smoked mushroom pretreated with SO₂, H₂O₂ and steam blanching had the best colour values, the better score for all sensory characteristics and lower non‐enzymatic browning compared with other pretreatments. The most effective pretreatment against total aerobic bacteria and yeast & moulds were citric acid, EDTA and steam, and then smoking of mushroom can be attributed to the reduction of microbial counts. The most effective pretreatments on quality and safety of smoked mushrooms were H₂O₂ and steam. It can be concluded that thermal and chemical treatments, rather than smoking of mushroom, reduce enzyme activities and are suitable to preserve mushrooms.     

Radical‐scavenging properties of extracts from the white button mushroom,Agaricus bisporus

BACKGROUND: Agaricus bisporus is the premier cultivated edible mushroom but is usually considered to be of lesser value nutritionally and medicinally compared with other cultivated mushrooms. The objective of this study was to investigate the radical‐scavenging properties of methanolic extracts and the free radical‐processing enzyme activities of water extracts from A. bisporus fruit bodies. Analyses were performed on total fruit bodies from three strains and on separated stipe, cap and gills from one strain, all cultivated experimentally under the same conditions. RESULTS: EC₅₀ values of scavenging ability on 1,1‐diphenyl‐2‐picrylhydrazyl radicals (DPPH^?), scavenging ability on 2,2‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical cations (ABTS^?+) and reducing power of methanolic extracts from total fruit bodies ranged between 1.7 and 5.0 and were 1.1–1.9 times higher in a white hybrid than in two wild strains, cream and brown. The gills exhibited higher antioxidant activities relative to the stipe and cap. In water extracts, glutathione peroxidase activities were up to eight times higher than glutathione reductase activities and no difference was observed between strains. Catalase activity was highest in the brown wild strain. The only significant differences in free radical‐processing enzymes between the three parts of the mushroom were higher catalase activity in the gills and lower glutathione reductase activity in the stipe. CONCLUSION: The radical‐scavenging properties of the button mushroom are comparable to those of other edible mushrooms and dependent on the strain and on the section of the fruit body. Copyright © 2008 Society of Chemical Industry     

Modified Atmosphere and Modified Humidity Packaging of Fresh Mushrooms

Sorbitol and sodium chloride were used to modify the in-package relative humidity (IPRH) of fresh mushrooms (water irrigated and CaCl₂ irrigated) stored in a modified atmosphere package (MAP) at 12°C. No differences were observed for maturity index and microbial population between mushrooms stored in modified atmosphere package (MAP) with or without moisture absorbers. Lower IPRH was observed in packages containing water irrigated (normally grown) mushrooms with sodium chloride, but resulted in over-drying of mushrooms and did not improve color. Normally grown mushrooms with 10 and 15g sorbitol had the best color. IPRH of 87–90%, within 9 days storage was considered optimum. No improvements in quality were found with moisture absorbers with normally grown mushrooms. However, a small amount of sorbitol helped to avoid condensation with CaCl₂ irrigated mushrooms.     

Effect of nanocomposite-based packaging on storage stability of mushrooms (Flammulina velutipes)

In this study, a polyethylene (PE) packaging material that contained nano-Ag, nano-TiO₂, nano-SiO₂, and attapulgite was prepared and its effect on storage stability of mushrooms (Flammulina velutipes) was investigated. The results showed that the nanocomposite-based packaging material (Nano-PM) regulated oxygen and carbon dioxide level, eliminated ethylene and inhibited the growth of microbes, which is a benefit on preservation quality of mushrooms, compared to the normal PE material (Normal-PM). After 14 days of storage, mushroom weight loss, mushroom cap opening, stipe elongation and respiration of Nano-PM stored mushroom were significantly (P < 0.05) inhibited. Furthermore, treatment with the Nano-PM improved the retention of vitamin C, soluble protein, and total soluble solids contents of F. velutipes. The results therefore are promising for the preservation of F. velutipes in order to expand its shelf life and improve its preservation quality by use of this Nano-PM.Industrial relevanceFlammulina velutipes, also named as golden needle mushroom, is one of the most popular edible mushrooms worldwide. Its production and consumption ranked the fourth place among all edible mushrooms in the world. However, fresh golden needle mushrooms are highly perishable. Therefore, preserving freshness of the mushrooms is the main objective of postharvest technology. In the present study, we developed a new type of effective and economic nanoparticle packaging materials and applied it to mushroom preservation. A local company (Jiangsu Tianfeng Biological Technology Co., Ltd) producing mushrooms has started to use this nano-preservation technology during the postharvest transportation and sales. In conjunction with the results of present research, we suggests that nano-composite based packaging materials is a good way for preserving fresh mushrooms and has the potential to be commercialized.     

Quality aspects of fresh‐cut ‘long‐storage tomato’ as affected by package,calcium chloride and storage time

In this research, some quality changes during storage at 4 °C were assessed in fresh‐cut fruits of a ‘long‐storage tomato’ landrace, packaged in biocompostable materials (PLA Ingeo tray/NatureFlex? film) or in conventional plastics (PET tray + polypropylene film). The effects of dipping in CaCl₂ on the shelf‐life extension were also assessed. Plants were cultivated both off‐season (greenhouse) and in‐season (open field). CO₂ and O₂ concentration, fruit weight loss, firmness, colour, microbial load were measured at 0, 4, 7, 12 days of storage. Headspace gas changes and fruit weight loss were minimised in conventional package. BIO package prevented water condensation, led to max 5% weight loss and made fruits less susceptible to spoilage. Dipping in CaCl₂ induced better firmness, especially in biopackage. Off‐season fruits had overall lower quality than in‐season fruits; however, these may contribute to extend the production season, with interesting marketing implications for the agri‐food industry.     

Changes in respiration and soluble carbohydrates during the post-harvest storage of mushrooms (Agaricus bisporus)

The CO₂ production and soluble carbohydrate content were studied in the cultivated mushroom (Agaricus bisporus) during storage at 18 °C. The pattern of postharvest respiration was seen to be dependent on the maturity of the sporophore at harvest. A post-harvest respiratory peak was observed and this appeared to correspond with the phase of rapid gill development which occurs after harvest of immature, fruit bodies. The disappearance of significant quantities of mannitol from the sporophore during storage seemed to indicate that this was one of the main respiratory substrates during storage, although it was evident that other substrates were utilised. The results obtained are discussed in relation to the postharvest development of the sporophore and the function of its tissues.     

Gelatine–starch films: Physicochemical properties and their application in extending the post‐harvest shelf life of avocado (Persea americana)

BACKGROUND: Several storage techniques have been developed to extend the post‐harvest shelf life of horticultural products. One method involves the use of edible or biodegradable coatings. Such coatings are made of biological materials that are used to coat fresh products, providing a semi‐permeable barrier to water vapour and gases, e.g. O₂ and CO₂. The influence of starch concentration, glycerol content and pH on the carbon dioxide permeability (CO₂P) and mechanical properties of gelatine–starch edible films were evaluated. RESULTS: Results showed that increments in the starch concentration and pH resulted in higher CO₂P values. Film puncture strength increased when the starch concentration decreased and the maximum resistance value (32.6 N) was obtained at pH 6. Deformation was mainly affected by glycerol and starch content. Some films were chosen in order to evaluate their effect, as coatings, in the post‐harvest shelf life of avocados (Persea americana Mill c.v. Hass). Fruits were immersed in the coating solutions, air dried and stored at two temperatures. Changes in colour, weight loss and pulp firmness were determined in fruits stored at 6 °C. In addition, respiration rate was measured in avocados kept at 20 °C. CONCLUSION: The application of gelatine–starch coatings delayed the ripening process of avocados, as indicated by a better pulp firmness and retention of skin colour, and lower weight loss of coated fruits in comparison with control avocados. The coatings also resulted in a delayed respiratory climacteric pattern, by 3 days, for coated fruits. Copyright © 2007 Society of Chemical Industry     

Structure and composition changes in the cell wall in relation to texture of shiitake mushrooms (Lentinula edodes) stored in modified atmosphere packaging

BACKGROUND: Firmness in shiitake mushroom (Lentinula edodes) is an important textural attribute affecting consumer attitudes toward freshness and quality. In this study, the effects of modified atmosphere packaging (MAP) treatments on structure and composition changes in cell walls in relation to the texture of mushrooms were investigated. RESULTS: Shiitake mushrooms were packaged in low density polyethylene bags with no holes (M₀₎, two microholes (M₁), four macroholes (M₂), stored at 4 °C for 16 days with non‐wrapped mushrooms as control. Control mushrooms showed the highest firmness value due to significant increase of cellulose and chitin. All three MAP treatments reduced losses of protein and polysaccharides; the M₂ treatment can best preserve the original texture while mushrooms in M₀ became soft and deteriorated, possibly due to higher CO₂ accumulation, lower cellulose and chitin content. Transmission electron microscopy performed on caps at harvest and after 16 days indicated that disintegration of plasmalemma had been alleviated by M₂ treatment, leading to better preservation of the cell wall. CONCLUSION: Our results suggest that differences in firmness of shiitake mushrooms during storage may be due to differences in cellulose and chitin concentrations. M₂ treatment may be a useful way of maintaining shiitake mushrooms texture during storage at 4 °C. Copyright © 2010 Society of Chemical Industry     

Sensory and microbiological quality of shiitake mushrooms in modified‐atmosphere packages

The aim of the present work was to study the influence of modified‐atmosphere packaging on the microbiological and sensory quality of shiitake mushrooms (Lentinula edodes). Mushrooms were packaged under atmospheric air (passive modified atmosphere) and an initial gas mixture of 5% O₂ and 2.5% CO₂ (active modified atmosphere), in bags of two different films: low‐density polyethylene (PE) and polypropylene (PP). As control, mushrooms were packaged in macroperforated PP films. Bags were stored at 5 °C for 20 days. Package atmosphere composition, mushroom respiration rate, weight loss, microbiological counts and sensory quality were determined during storage. Risk assays were also performed. Under the studied conditions, shiitake mushroom deterioration was not due to microorganism growth, and therefore the shelf‐life of this product might be defined by changes in its sensory characteristics. Sensory analysis showed that mushrooms stored under modified atmosphere (active and passive) had a higher deterioration rate than those stored in PP macroperforated films, and lower sensory quality values during the entire storage time. These results suggest that mushroom deterioration was probably due to shiitake mushrooms' sensitivity to high CO₂ concentrations. Copyright © 2007 Society of Chemical Industry     

Stipe Trimming at Harvest Increases Shelf Life of Fresh Mushrooms (Agaricus bisporus)

Trimming the stipe of cultivated mushrooms, Agaricus bisporus, from 35 mm to 5 mm from the cap immediately after harvest resulted in improved shelf life as indicated by reduced browning and slower cap opening. This effect was evident after 3 days storage at 12°C, and became more pronounced after 6 days. Trimming the stipes had no significant effect on postharvest respiration rate or bacterial growth; thus, the shelf life improvement was due to other factors. Stipe trimming reduced the weight (yield) of saleable mushrooms by about 10%; thus, shelf life improvement would need to offset any economic loss to growers to make this practice commercially feasible.     

Effect of high oxygen modified atmosphere on post‐harvest physiology and sensorial qualities of mushroom

The changes in physiology and sensorial qualities of mushroom stored at 2 °C for 12 days under high oxygen (100% O₂, 80% O₂) atmosphere and air had been investigated. Respiration rate was suppressed in mushroom in 80% O₂ and 100% O₂. No significant differences were found between 80% O₂ and 100% O₂. Weight loss was not more than 1.5% in all treatments. Weight loss and firmness of mushroom held in high oxygen were significantly (P < 0.05) higher than in air. Total soluble solid (TSS) was only slightly affected by high oxygen treatment. High oxygen, especially 100% O₂ treatment was effective at reducing browning degree and electrolyte leakage of mushroom. The surface colour of mushroom changed slightly before tenth day under high oxygen treatment. From day 2 the L‐value of mushroom flesh was significantly (P < 0.05) lower under air atmosphere compared with high oxygen treated mushroom. High oxygen, especially 100% O₂ was effective at inhibiting discoloration. The PPO activity of mushroom was significantly (P < 0.05) higher in 100% O₂ compared with air treatment. The POD activity was highest in high oxygen at eighth day, then reduced. High oxygen, especially 100% O₂ was effective at maintaining the quality of mushroom.     

Fresh Mushroom Quality as Affected by Modified Atmosphere Packaging

The effect of O₂ concentration, at 2–6% CO₂ on shelf-life of fresh mushrooms in modified atmosphere packages (MAP) was studied. For conventional mushrooms optimum in-package O₂ was 6% to reduce cap development. Mushrooms irrigated with 0.3% calcium chloride during cropping had a higher rate of maturation and optimum O₂ was 2% during storage. At this low O₂ concentration, however, storage may be potentially hazardous and is not recommended. Surface moisture of mushrooms significantly increased during storage and may have obscured any beneficial effect of MAP on mushroom color. Precise control of relative humidity in the package is recommended.     

EVALUATION OF PRODUCTIVITY AND POSTHARVEST QUALITY DURING STORAGE OF FIVE AGARICUS BISPORUS STRAINS

Five Agaricus bisporus commercial strains (S100, A15, F56, F40 and F62) were evaluated as regards their colonization rates, yields, quality characters and storability. Concerning their colonization performance, the mycelial growth rates examined in “race tubes” on sterile compost, as well as earliness in fructification did not differ significantly. Significantly lower was the yield of strain S100 compared to the yield of strains F62 and F56, which presented the greatest cumulative biological efficiency values. However, mushroom number and average weight presented negative relation. For the storage and quality study, mushrooms at the “closed‐cap” stage packaged in 500‐g plastic containers were stored for 5 days at 2C and 5 days at 18C (shelf life). The respiration behavior of the five strains was similar with the mass loss not exceeding 15% during storage at 2C and 40–50% at the end of the shelf life. Also, no differences in the whiteness and texture change were detected and a correlation between the period of pileus diameter increase and the respiration rate was found. According to their color and texture quality assessment, mushrooms deriving from the first four strains may be considered well acceptable at the end of the shelf life, whereas these from strain F62 just saleable.     

Quality of enoki mushrooms as affected by packaging conditions

Fresh enoki mushrooms (100 g) were packaged under various conditions and stored at 10 °C for 14 days. Package atmosphere, weight loss, stipe elongation, surface colour and sensory quality of the mushrooms were measured during storage. Different levels of initial vacuum application did not have a significant influence on the in‐package atmosphere after 2 days. The half‐vacuum package was best in terms of quality preservation of the fresh mushrooms. A polyolefin film with respective gas permeabilities of 166 and 731 ml m⁻² h⁻¹ atm⁻¹ to O₂ and CO₂ established an equilibrated atmosphere of 1.7–2.4% O₂ and 4.1–5.6% CO₂ inside the package at 10 °C. This polyolefin film was shown to contribute to preserving the freshness of the mushrooms. Temperature fluctuations between 5 and 15 °C did not induce a harmful atmosphere inside the polyolefin package, though high temperatures accelerated the quality loss. © 2000 Society of Chemical Industry     

Determination of amatoxins in different tissues and development stages of Amanita exitialis

BACKGROUND: Mushroom poisoning is the main cause of human death by food poisoning in China. Most lethal mushrooms belong to the Amanita genus, whose amatoxins are responsible for the death of humans. Amanita exitialis is a lethal white mushroom commonly found in Guangdong Province, China. In this study the contents and distribution of the major amatoxins in different tissues and development stages of A. exitialis were systematically analysed. RESULTS: The amatoxin contents and distribution in six different mushroom tissues of A. exitialis were analysed by reverse phase high‐performance liquid chromatography. The highest concentrations of amatoxins were found in the gills and pileus, followed by the stipe and annulus, with the lowest concentrations in the volva and spores. Further analysis of mushrooms in different development stages showed that the amatoxin content was relatively high and steady during early development, reached its peak when the fruit body was in the vigorous growth stage and then decreased sharply when the mushroom entered its mature stage. Furthermore, the α‐amanitin/β‐amanitin ratio varied significantly in different tissues but remained constant within a specific tissue throughout development. CONCLUSION: The contents and distribution of amatoxins in different tissues and development stages of A. exitialis are markedly different. The distribution of α‐amanitin and β‐amanitin varies in different tissues but remains constant throughout development. Copyright © 2012 Society of Chemical Industry     

Calcium Treatments Affect Storage Quality of Shredded Carrots

Carrot shreds, sticks and slices were dipped in solutions of CaCl₂ alone, or with chlorine and stored at 0, 5 or 10°C to determine the effects of calcium (Ca) on storage quality. A 0.5% or 1% CaCl₂ treatment maintained firmness and reduced microbial growth of carrot shreds at all temperatures. These treatments also resulted in lower tissue pH than in the water-dipped controls. Treatments increased Ca content slightly in sticks and slices and substantially in shreds and had no effect on storage quality of sticks or slices.     

Physiological and biochemical changes of different fresh-cut mango cultivars stored at 5 °C

Treatments to inhibit browning, decay and to extend shelf life of ‘Keitt’, ‘Kent’ and ‘Ataulfo’ mango cultivars as a fresh‐cut produce were investigated. Combinations of calcium chloride (CaCl₂), antioxidants [ascorbic acid (AA), citric acid (CA)] and two commercial film coatings resulted in a reduction of browning and deterioration of fresh‐cut mangoes stored at 5 °C, especially for the Ataulfo cultivar. The use of CaCl₂ + AA + CA significantly reduced colour deterioration, loss of firmness and did not affect sensory characteristics of fresh‐cut mango, with a larger effect in the Ataulfo cultivar. In general, these treatments prevented loss of sugar and vitamin C of cubes during storage at 5 °C. Shelf life of this cultivar was 21 days, while that of Keitt and Kent was only 9 and 12 days, respectively. There is a correlation between carotene and vitamin C content of Ataulfo mango and its longer shelf life compared with the other cultivars.     

Consumer Acceptability of Cucumber Pickles Produced by Fermentation in Calcium Chloride Brine for Reduced Environmental Impact

Fermentation of cucumbers in calcium chloride (CaCl₂) brine has been proposed as an alternative process to reduce the environmental impact of traditional, high salt fermentations. The objective of this research was to determine whether consumer acceptability of pickle products would be impacted by fermentation and storage of cucumbers in CaCl₂ brine. Cucumbers were fermented and stored with 0.1M CaCl₂ or 1M sodium chloride (NaCl) in open‐air, 3000 gal tanks at a commercial facility and processed into hamburger dill chips containing 0.38M NaCl. Cucumbers fermented in CaCl₂ required additional desalting to reduce CaCl₂ concentrations to that of current products. Consumers (n = 101) showed no significant preference for pickles from different fermentation treatments, whether stored for 2 mo (P = 0.75) or 8 mo (P = 0.68) prior to processing. In contrast, NaCl fermented pickles were preferred over CaCl₂ fermented pickles stored for 10 mo and desalted only once (P < 0.01). A series of preference tests indicated that the taste of CaCl₂ was not the factor affecting consumer preference, and the 50% detection threshold of CaCl₂ in dill pickle chips was found to be 61.8 ± 7.6 mM, indicating that processors could potentially use CaCl₂ fermentations with a single desalting step. Consumer liking of flavor (n = 73) was not influenced by fermentation in CaCl₂ or by 23 or 35 mM CaCl₂ in finished products (P > 0.05), but variability in texture decreased consumer liking (P < 0.05). Although promising, individual fermentation variability and texture quality of CaCl₂ fermented products should be further evaluated prior to broad implementation of this process.