Enzymatic Browning Control in Potato with Ascorbic Acid-2-Phosphates

Treated potato samples were evaluated for browning by tristimulus colorimetry and for browning inhibitor uptake by HPLC. Treatment effectiveness was greatly improved by reducing pH to 2.0 with phosphoric acid to inhibit endogenous acid phosphatase and by using combinations of ascorbic acid (AA), AA-2-phosphate and AA-2-triphosphate to provide for gradual release of AA at treated surfaces. Treatment with dips containing the AA-2-phosphates extended storage life of potato dice and pre-peeled potatoes by 5-7 days over that obtained with conventional browning inhibitor formulations but induced some leakage at cut surfaces.     

Shelf-Life Extension of Fresh Mushrooms (Agaricus bisporus) By Application of Hydrogen Peroxide and Browning Inhibitors

ABSTRACT: An experimental washing process for fresh mushrooms entailing immersion in 5% H₂O₂, followed by application of a sodium erythorbate-based browning inhibitor, was optimized, scaled up, and made continuous. The laboratory process described previously was modified by adding a pre-wash step using 0.5% to 1% H₂O₂, increasing the wash solution H₂O₂ concentration from 3% to 5%, and substituting 4% sodium erythorbate + 0.1% NaCl for the more complex browning inhibitor formulation used previously. A continuous, commercial-scale washing facility was built to test the new process. Mushrooms washed by this process were free of adhering soil, less subject to brown blotch than conventionally washed mushrooms, and at least as resistant to enzymatic browning as unwashed mushrooms during storage at 4 °C. Storage at 10 °C accelerated development of brown blotch and browning.     

香菇贮存中品质变化动力学模型及货架期的预测

研究了不同的储存温度下香菇的的品质变化。测定指标包括失重率、褐变强度、pH、色差。随着储存时间的延长,褐变强度增加,pH降低,L*和b*下降,a*上升,失重率上升。对几个指标进行回归分析,结合感官评价指标确定褐变强度、pH、L*可以作为衡量香菇在储存过程中品质变化的指标,并建立了3个指标的品质变化的1级动力学模型,与Arrhenius方程有很高的拟合度。pH的预测模型为:t=2.24×10-8e5608.16/T（其中T为温度,K）;褐变强度值预测模型:t=4.647×10-7e4749.8/T（其中T为温度,K）;L*值预测模型:t=4.392×10-7e4737.29/T（其中T为温度,K）。最后,结合3个指标模型的验证情况确定用褐变强度来作为衡量香菇货架期的指标,并预测了香菇的货架期,误差较小,可以很好的预测香菇在储存中的货架期,更好的控制香菇在贮存中的品质。      

Effect of vacuum cooling on mushroom browning

The effects of two cooling methods and two storage temperatures on mushroom quality, anatomy and weight loss were compared. Mushroom quality was assessed as a function of cap browning and hyphal structure. Storage of mushrooms at 5°C conserved quality and reduced weight loss as compared with those stored at 18°C. No differences in quality or hyphal structure were found between vacuum and conventionally cooled mushrooms when subsequently held at 5°C; when cool storage was followed by a period at 18°C, vacuum-cooled mushrooms were significantly better with regard to colour (enzymic browning) than those conventionally cooled. The rate of weight loss during storage at 5°C was greater for vacuum-cooled than conventionally cooled mushrooms.     

Structure and Composition of Mushrooms as Affected by Hydrogen Peroxide Wash

An experimental H₂O₂/browning inhibitor wash treatment and its effect on mushroom structure and composition were studied. Experimentally washed mushrooms ( Agaricus bisporus ) were compared with conventionally washed mushrooms and untreated controls. Examination by scanning electron microscopy showed damage to hyphae producing a matted appearance at the pileus surface with both experimental and conventional washed samples. Mushrooms after the experimental wash had an elevated sodium content from the sodium erythorbate browning inhibitor but contained no H₂O₂ residue. In pileus tissue, soluble phenol levels were higher and the content of free amino acids was lower in mushrooms after the experimental wash. No other notable compositional differences or adverse effects of treatment on quality were found.     

Effect of modified atmosphere packaging (MAP) with low and superatmospheric oxygen on the quality and antioxidant enzyme system of golden needle mushrooms (Flammulina velutipes) during postharvest storage

To quantify the effect of oxygen concentrations on the quality and antioxidant enzyme system of stored golden needle mushroom, modified atmosphere packaging (MAP) with low and initial superatmospheric oxygen was applied during mushroom storage, and physiological changes associated with postharvest deterioration, activities of antioxidant enzymes, and of cellulase, were monitored during subsequent storage for 0–34 days. Golden needle mushrooms stored in MAP without oxygen or 20–50% oxygen rate had a poorer sensory quality because of chilling injury and physiological injury. These injuries included increased levels of malondialdehyde and superoxide anion whereas some extent of browning was observed. The antioxidant enzyme system, including superoxide dismutase, catalase, peroxidase, and polyphenol oxidase, was activated, to scavenge the reactive oxygen species to reduce injury during the initial storage period. However, these injuries also induced senescence of the stored golden needle mushroom during later storage, followed by a decrease in activities of the antioxidant enzymatic system. The activities of the antioxidant enzymatic system of the mushroom stored in MAP with 80% oxygen rate were the most favorable to delay the senescence process in the later period of storage, and the mushrooms had the best quality until the end of storage. MAP with high oxygen concentrations (e.g., 80% oxygen rate) can induce relatively high antioxidant capacity, significantly decrease postharvest quality loss and improve shelf life of fresh mushrooms.     

Acid and EDTA blanching effects on the essential element content of mushrooms (Agaricus bisporus)

Many chemicals such as citric acid, ascorbic acid hydrogen peroxide and ethylene diamine tetraacetic acid (EDTA) have been used as browning inhibitors as well as to control spoilage during storage and canning operations. In this study, four essential mineral elements were determined in fresh and blanched mushrooms (Agaricus bisporus). The effects of citric acid and EDTA blanching on the copper, zinc, iron and manganese content of mushrooms were investigated. Statistical analysis indicated that the differences in Fe, Cu, Mn and Zn levels between fresh and blanched mushrooms were not significant for citric acid blanching. However, mushrooms blanched with EDTA solutions contained significantly lower concentrations of Fe and Cu than those found in fresh mushrooms on a dry weight basis. © 2000 Society of Chemical Industry     

Effect of gamma irradiation and sulphitation treatments on keeping quality of white button mushroom Agaricus bisporus (J. Lge)

Gamma irradiation, alone and in combination with sulphitation, was tested for preventing the browning and maintaining the quality attributes of the white button mushrooms. Mushrooms were subjected to treatment of gamma irradiation in the dose range of 0.5–2.0 kGy and to combination treatments of sulphitation at a concentration of 0.1% potassium metabisulphite (KMS) and gamma irradiation (dose range 0.5–2.0 kGy) followed by storage at 10 ± 2 °C (RH 85%). A dose of 2.0 kGy significantly reduced the weight loss, prevented browning and mould growth. Cap and veil opening of mushrooms was delayed by 9 days and shelf life was extended by 12 days at a dose level of 2.0 kGy. Sulphitation alone at a concentration of 0.1% KMS was effective in controlling browning only upto 3 days, beyond which both browning and cap opening increased significantly ( P  ≤ 0.05) and the samples were unacceptable after 6 days of storage. No synergistic effect of sulphitation and irradiation was observed with respect to the shelf-life extension of mushroom.     

Postharvest Hardness and Color Evolution of White Button Mushrooms (Agaricus bisporus)

ABSTRACT: The quality evaluation of mushrooms was studied by storing fresh white button mushrooms (Agaricus bisporus) for 6 to 8 d, at various controlled temperature conditions (3.5 to 15 °C) and measuring the instrumental textural hardness and color of the mushroom cap for different product batches. A nonlinear mixed effect Weibull model was used to describe mushroom cap texture and color kinetics during storage considering the batch variability into account. Storage temperature was found to play a significant role in controlling texture and color degradation. On lowering storage temperature (i) the extent of the final browning extent in the mushroom after storage was reduced and (ii) the rate textural hardness losses was slowed down. A linear dependence of the final browning index with temperature was found. An Arrhenius type relationship was found to exist between the temperature of storage and storage time with respect to textural hardness. The average batch energy of activation was calculated to be 207 ± 42kJ/mol in a temperature range of 3.5 to 20 °C. Practical Application: This article evaluates how temperature abuse affects mushroom texture and color, applying methods that allow for the consideration of the natural product variability that is inherent in mushrooms. Its results apply to mushroom producers, retail distribution, and supermarkets for effective storage management.     

Effects of UV‐C irradiation on the physiological and antioxidant responses of button mushrooms (Agaricus bisporus) during storage

Novel postharvest technology not only preserves the freshness of fruits and vegetables, but also triggers the biosynthesis of antioxidant compounds as a secondary response. This study examined the browning and antioxidant properties of button mushrooms (Agaricus bisporus) treated with UV‐C irradiation in combination with cold storage. Three sample preparation methods for antioxidant activity analysis, simulative gastrointestinal digestion (GAR), direct evaluation (QUENCHER) and traditional solvent extraction (TSE), were used to evaluate the samples, and followed analysing by both FRAP and ABTS assays. Broadly, the results indicated that, following an initial increase, UV‐C irradiation suppressed browning during a cold storage period of 18 days. And the total phenolic content of the treated mushrooms were higher than that of the control, while the ascorbic acid content decreased sharply during storage, and UV‐C treatment had negative effects on ascorbic acid content. Results from the QUENCHER and GAR methods showed that UV‐C treatment significantly increases the total antioxidant capacity (TAC) of mushrooms throughout the entire storage period, and have a larger magnitude than that of TSE method. In conclusion, the combination of UV‐C irradiation and cold storage showed great potential for improving mushroom quality as a new postharvest technology.     

Biochemical changes associated with mushroom browning in Agaricus bisporus (Lange) Imbach and Pleurotus florida (Block & Tsao): commercial implications

Biochemical changes associated with mushroom browning in Agaricus bisporus and Pleurotus florida were studied. With increasing storage temperature from 0 to 25 °C there was an increase in phenol oxidase activity up to 15 °C followed by a decrease at 25 °C in both mushrooms. Loss of water content in fresh mushrooms had a direct relationship with phenol oxidase activity, which could be correlated with the visual degree of mushroom browning. A bisporus displayed higher phenol oxidase activity, about two to three times that of P florida. The phenol oxidase activity in both mushroom varieties was studied on a range of phenolic compounds with diverse functional groups. A bisporus exhibited intense reactions to tyrosine and catechol, while P florida did so to guaiacol and catechol. The two mushrooms differed in the degree of their oxidation reactions relative to the functional groups. In A bisporus the skin had more phenolics than the flesh; P florida contained fewer phenolics, while the stalks of both mushrooms had low phenolics contents. FTIR spectral studies of intact mushrooms during browning showed a characteristic decrease in phenolic hydroxyls; first‐derivative spectra were used to assess relative peak intensities. Of the chemicals tested for their effect on phenol oxidase activity, 0.1 M sodium carbonate favoured the immediate development of an orange chromogen in P florida, while mild alkaline solutions favoured the enzyme activity, and acidic solutions at the 0.1 M level completely inhibited the browning reaction in both mushrooms. Copyright © 2003 Society of Chemical Industry     

Suitability of Aloe Vera and Gum Tragacanth as Edible Coatings for Extending the Shelf Life of Button Mushroom

Button mushroom have a short postharvest shelf life compared to most vegetables, due to a very high metabolic activity and high water content. This makes them prone to microbial spoilage and to exhibit enzymatic browning. In this research, the effects of aloe vera, gum tragacanth, and combination of both as edible coatings on the shelf life and postharvest losses of mushrooms were studied. Physical characteristics, general appearance (color and texture), weight loss, and carbohydrate percentage were evaluated during storage. Mushrooms were stored at 4, 10, and 15 °C for 13 days and physicochemical characteristics were analyzed after 2, 4, 6, 8, 10, and 13 days of storage. During cold storage, the uncoated mushrooms showed rapid weight loss, color changes, and accelerated softening while mushrooms treated with aloe vera gel, gum tragacanth, and the combination of both significantly delayed these phenomena. Among different coatings, the combination of aloe vera and gum tragacanth was more effective.     

A new method to apply and quantify bruising sensitivity of button mushrooms

Mushrooms are prone to develop brown discolouration due to bruising caused by mechanical damage during harvest, which leads to reduced quality of the mushrooms. In order to study the mechanism behind discolouration and to breed for bruise-related browning resistant strains, a high throughput bruise application method and reliable quantification of browning sensitivity is essential. In this study a new bruising device was developed to bruise mushrooms in a fast and reproducible way. The bruising device can apply damage to the cap tissue of button mushrooms by a slip-shear sliding process. The severity of the bruise was quantified with a computer imaging system combined with a newly developed software programme. A protocol was developed to obtain the most reliable and reproducible method to compare browning sensitivity of different Agaricus bisporus strains. For this purpose, the extent of damage applied, time between harvest and bruising, developmental stage of the mushrooms and flushes were taken into account. The new method of bruising and image based quantification was subsequently applied to a collection of wild, commercial and hybrid A. bisporus strains and a distinction could be made between bruise-related browning sensitive mushrooms and tolerant mushrooms.     

脉冲强光预处理联合控湿干燥提升香菇的贮藏品质

该研究探讨了脉冲强光（IPL）预处理联合控湿干燥对香菇储藏品质的影响。研究发现,脉冲强光预处理可以降低贮藏期间新鲜和干香菇的呼吸速率,分别为对照的76.69%和84.65%;脉冲强光预处理提高了还原糖的保留率。新鲜和干香菇在贮藏期间对照的多酚氧化酶（PPO）活性分别是IPL预处理样品的1.73倍和1.39倍,酶促褐变反应受到抑制,也因此提高了总酚的保留率。IPL可以提高鲜、干香菇在贮藏期间的品质、多糖保留率和抗氧化能力,延缓软化。IPL处理降低了新鲜香菇在贮藏期间的菌落总数（从6.43～8.02 log CFU/g减少至3.29～4.66 log CFU/g）,但是对干香菇在贮藏期间菌落总数影响较小。与热烫处理相比,脉冲强光处理提升香菇贮藏品质更佳。因此脉冲强光可以作为一种稳定的预处理手段用于香菇干燥和保鲜中。     

γ射线辐照对香菇采后贮藏过程中水分特性及理化指标的影响

以新鲜香菇‘808’为研究对象,考察1.0 kGy 60Co γ射线辐照对香菇贮藏（（4±1）℃、相对湿度（80±5）%）过程中理化指标（色度、质构、显微结构）、水分迁移规律和感官品质的影响。结果表明：在贮藏过程中,经辐照处理的香菇亮度（L*值）由90.06下降至87.77,而对照组L*值由90.54下降至80.71,表明辐照延缓了褐变,防止了鲜香菇色泽劣变;辐照组的硬度显著高于对照组,辐照处理减缓了香菇菌丝组织网络结构的降解;由低场核磁共振分析可知,在贮藏过程中,对照组香菇的水分状态极不稳定,自由水横向弛豫时间T23峰面积在贮藏初期有小幅度上升,随后急剧下降,结合水T21峰面积先升高后降低,并且在贮藏后期T21峰右移;而辐照组香菇自由水T23峰面积均匀下降,结合水T21峰面积并无大幅度变化,两组不易流动水T22峰面积均呈现先升高后降低的趋势,因此辐照处理提高了鲜香菇不同状态水分的稳定性,而且辐照处理延缓了鲜香菇感官品质的劣变进程。结论：1.0 kGy 60Co γ射线辐照处理可以较好地维持鲜香菇的理化特征,减少水分流失,延长香菇的货架期。     

化学法保鲜香菇的研究

本实验以新鲜香菇为原料,以其贮藏期间的感官评价、褐变率、失重率、呼吸强度以及VC的含量为指标,研究了焦磷酸钠、氯化钠和过氧化氢对其贮藏期间品质的影响。结果表明,各保鲜剂混合使用的效果优于单独使用,以3.0%H2O2+0.2g/LNaCl为最佳配比浓度。      

复氧环境对双孢蘑菇采后品质的影响

目的：探究厌氧处理后不同O2水平的复氧环境对双孢蘑菇采后品质的影响,为将厌氧处理技术应用于双孢蘑菇的贮藏保鲜中提供理论依据。方法：双孢蘑菇经过纯N2厌氧处理6 h后,通过微孔气调包装营造不同O2水平的复氧环境,然后分析呼吸速率、乙烯释放量、厌氧代谢产物含量、质量损失率、外观、质构特性和感官特性等指标的变化情况。结果：超低氧环境（1%～2%）显著抑制了贮藏期内蘑菇样品乙烯的释放;蘑菇在15 d时质量损失率仅为1.38%,硬度和弹性较初始值分别升高36.38%和5.02%,蘑菇在整个贮藏期均未出现明显褐变并能够维持最高的感官评分。然而高氧环境（19%～20%）加速了蘑菇采后品质劣变,第9天左右菇体表面开始出现褐色斑点和腐烂迹象,15 d时蘑菇颜色、黏性、风味、质地和腐烂的感官评分均为最低。结论：超低氧水平的复氧环境可通过抑制乙烯的生物合成更好地维持双孢蘑菇采后品质。     

Mushroom Response to Postharvest Hyperbaric Storage

Vessels suitable for storing mushrooms [Agaricus bisporus (Lange) Singe] at absolute pressures to 35 atm were constructed from 43 liter (1A) gas cylinders and plumbed for conducting static or continuous-flow experiments. Neither pressurization nor gradual depressurization over 6 hr injured mushrooms. Pressure did not affect respiration, but significantly reduced moisture loss during storage. Mushrooms depleted O₂ to very low levels and showed high tolerance to CO₂. Pressure was used to safely increase CO partial pressure (p) 35-fold. At 0.035p, CO reduced mushroom browning but not respiration. A completely autonomous storage system with CO₂ removal and automatic O₂, replenishment was developed.     

褪黑素处理对香菇采后品质及活性氧代谢的影响

实验分别设置不同浓度（0.25、0.50、0.75 mmol/L）褪黑素对香菇进行喷淋处理,通过贮藏42 d内对香菇采后硬度、褐变度、亮度及开伞度等表观品质的测定,筛选得到0.50 mmol/L褪黑素处理浓度效果最好;在该处理浓度下进一步探究了褪黑素处理对香菇采后活性氧代谢的影响,并观察了贮藏28 d时香菇细胞超微结构的变化。结果表明：0.50 mmol/L褪黑素处理可以显著降低香菇采后呼吸强度,抑制细胞内活性氧代谢产物超氧阴离子的生成速率和羟自由基生成能力;贮藏结束（42 d）时,褪黑素处理组香菇的呼吸强度、超氧阴离子自由基的生成速率、羟自由基生成能力与对照组相比分别降低44%、39.1%、24.4%,褪黑素处理还可以减少香菇细胞丙二醛和过氧化氢的积累,维持较低的羰基化蛋白水平和较完整的细胞膜结构;且褪黑素处理组香菇的总酚、抗坏血酸含量及1,1-二苯基-2-三硝基苯肼自由基清除能力均显著高于对照组;超微结构观察表明褪黑素处理组香菇细胞壁和线粒体形态维持较好。综上,褪黑素处理可以有效维持香菇采后品质,降低活性氧代谢产物生成速率,提高机体的抗氧化能力,进而减少活性氧对机体的伤害,其中,0.50 mmol/L处理组效果相对最好。     

POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED 'JONAGORED' APPLES (MALUS DOMESTICA)

The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA‐treated apple cubes.