鲜切甘薯酶促褐变调控的研究

采用不同浓度的D-异抗坏血酸钠和柠檬酸分别处理鲜切甘薯,研究其在10℃贮藏过程中的酶促褐变反应,揭示不同褐变抑制剂对鲜切甘薯酶促褐变的调控机制。结果表明,0.5%～1.5%D-异抗坏血酸钠和低浓度(0.01%～0.03%)柠檬酸均延缓了鲜切甘薯酶促褐变的发生,有效抑制了PPO和POD的活性,降低了总酚含量;但高浓度(≥0.05%)柠檬酸处理反而加速了酶促褐变反应的进行。比较两种褐变抑制剂,D-异抗坏血酸钠抑制效果更好,其最佳浓度为1.0%。     

柠檬酸处理抑制鲜切香蕉褐变的研究

研究在4℃贮藏条件下不同浓度柠檬酸处理鲜切香蕉防褐变效果的影响。结果表明,适宜浓度的柠檬酸处理能显著延缓鲜切香蕉失重率的下降,同时还抑制了鲜切香蕉多酚氧化酶(PPO)及过氧化物酶(POD)活性,降低了丙二醛(MDA)含量,有利于保持鲜切香蕉良好的外观品质和营养价值。综合各项理化指标来看,2.0%柠檬酸处理的贮藏效果最佳,1.0%柠檬酸处理次之。      

The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes

Abstract: The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh‐cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L‐values and lower a‐values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L‐values, lower a‐values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh‐cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh‐cut potatoes along with NatureSeal®'s PS‐10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh‐cut potato products.     

Acids in combination with sodium dodecyl sulfate caused quality deterioration of fresh-cut iceberg lettuce during storage in modified atmosphere package

Recent studies showed that sodium acid sulfate (SAS) and levulinic acid (LA) in combination with sodium dodecyl sulfate (SDS) was effective in inactivating human pathogens on Romaine lettuce. The present study investigated the effects of LA and SAS in combination with SDS (as compared with citric acid and chlorine) on the inactivation of E. coli O157:H7 and sensory quality of fresh-cut Iceberg lettuce in modified atmosphere packages during storage at 4 °C. Results showed that LA (0.5% to 3%) and SAS (0.25% to 0.75%) with 0.05% SDS caused detrimental effects on visual quality and texture of lettuce. LA- and SAS-treated samples were sensorially unacceptable due to development of sogginess and softening after 7 and 14 d storage. It appears that the combined treatments caused an increase in the respiration rate of fresh-cut lettuce as indicated by higher CO(2) and lower O(2) in modified atmosphere packages. On the positive side, the acid treatments inhibited cut edge browning of lettuce pieces developed during storage. LA (0.5%), SAS (0.25%), and citric acid (approximately 0.25%) in combination with SDS reduced population of E. coli OH157:H7 by 0.41, 0.87, and 0.58 log CFU/g, respectively, while chlorine achieved a reduction of 0.94 log CFU/g without damage to the lettuce. Therefore, compared to chlorine, LA and SAS in combination with SDS have limited commercial value for fresh-cut Iceberg lettuce due to quality deterioration during storage.     

柠檬酸与五种褐变抑制剂的交互作用对马铃薯护色的影响

以鲜切马铃薯为护色对象,研究柠檬酸分别与五种褐变抑制剂(亚硫酸氢钠、L-半胱氨酸、苹果酸、抗坏血酸、氯化钠)在抑制鲜切马铃薯褐变上的交互作用。采用两因子两水平析因实验设计,结果以方差分析和交互作用效应图表示。结果表明:柠檬酸与氯化钠、抗坏血酸和L-半胱氨酸之间有极显著的交互作用,且柠檬酸对氯化钠、抗坏血酸和L-半胱甘酸的护色效果有增效作用,而柠檬酸与亚硫酸氢钠和苹果酸之间没有交互作用,柠檬酸浓度的改变不影响这两种褐变抑制剂的作用效果。     

不同清洗剂对鲜切马铃薯贮藏过程品质变化的影响

通过电解水和次氯酸钠两种不同清洗剂对鲜切马铃薯进行清洗杀菌处理,探讨了其对鲜切马铃薯贮藏过程品质的影响。清洗切分后的马铃薯丝于4℃冰箱中贮藏7d,每天对其色差(L*,a*,b*值)、褐变度(BD)、失重率、多酚氧化酶(PPO)活性和整体感官质量(OVQ)进行检测与评定,每隔一天对菌落总数进行测定。研究表明:强酸电解水清洗能够较好地保持鲜切马铃薯丝的色泽(较高的L*和b*值及较低的a*值)和OVQ,减少表面微生物的数量,抑制贮藏期内褐变现象的产生及降低PPO活性;而次氯酸钠对降低贮藏期内样品失重率的效果稍优于电解水,但两者在保持鲜切马铃薯色泽品质、降低失重率、抑制表面褐变及PPO活性方面的差异性不具有显著性(p>0.05)。综合方便、安全、环保等因素,得出结论为电解水的清洗效果优于次氯酸钠,其对鲜切马铃薯丝在贮藏期内的品质有一定的保持作用。      

柠檬酸和氯化钠抑制地衣芽孢杆菌生物被膜的研究

地衣芽孢杆菌是食品中常见腐败菌。该研究发现地衣芽孢杆菌在常见培养基（如TSB、NB、LB、1/2LB）中均有较强的产生物被膜能力,地衣芽孢杆菌稀释100倍、在胰酪胨大豆肉汤（TSB）培养基中30 ℃静置培养更利于地衣芽胞杆菌在96孔板上产生物被膜。测得地衣芽孢杆菌对柠檬酸和氯化钠的最低抑菌质量浓度（MIC）分别为1.28 mg/mL和64 mg/mL。采用结晶紫染色法,研究不同质量浓度柠檬酸和氯化钠对地衣芽孢杆菌生物被膜的抑制效果。结果显示,1/2MIC的氯化钠即能显著抑制地衣芽孢杆菌生物被膜形成（P＜0.01）;而1/2MIC和1MIC的柠檬酸对地衣芽孢杆菌生物被膜形成无明显抑制效果（P＞0.05）。     

紫外线照射与柠檬酸处理对鲜切苹果的保鲜作用

目的研究柠檬酸、紫外线照射、柠檬酸和紫外线照射联合处理对鲜切苹果生理生化的影响。方法以富士苹果为实验材料,分成4组,分别是0.5%柠檬酸(CA)溶液中浸泡5 min、紫外照射(UV)5 min/面、0.5%柠檬酸溶液中浸泡5 min+紫外照射(CA+UV)5 min/面、不处理的对照组(KB)。分别于0、1、3、5、7、10、13、15 d测定鲜切苹果的色差、多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)活性。结果富士苹果经过切分后,褐变严重。PPO、POD活性升高,PAL活性变化曲折,总体呈上升趋势。柠檬酸、紫外、柠檬酸和紫外联合处理的3三种处理方式都可以抑制鲜切苹果的褐变,降低PPO、POD、PAL的活性。在4种处理方法比较中,柠檬酸和紫外联合处理的效果比较好。结论柠檬酸和紫外联合处理是鲜切苹果的理想的保鲜方法。     

柠檬酸和异抗坏血酸钠处理对冷藏鲜切菠萝质量的影响

采用响应面方法,研究柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝颜色、硬度、失重和包装内气体组成的影响。新鲜菠萝片分别用0%～1.0%的柠檬酸和异抗坏血酸钠处理3min,然后装在塑料泡沫碟中,用PVC薄膜密封,在5℃冷库中贮藏0～14d。结果表明,异抗坏血酸钠显著地减缓L、a、b、失重(p≤0.001)和硬度(p≤0.1)的变化,但对包装内O2和CO2含量没有影响。柠檬酸对L、硬度和失重有影响(p≤0.1)。所有考察的指标在贮藏过程中均显著变化(p≤0.01)。建立的回归模型可充分预测柠檬酸、异抗坏血酸钠处理和冷藏时间对鲜切菠萝质量的影响。     

Application of edible coatings in minimally processed sweet potatoes (Ipomoea batatas L.) to prevent enzymatic browning

To control browning phenomenon, an edible coating of cassava starch along with ascorbic acid (AA) (combined treatment) was applied to minimally processed sweet potatoes var cv. ‘Blanca Correntina’. The samples were stored at 4 °C for 16 days, and the activities of polyphenol oxidase, peroxidase and phenylalanine ammonia lyase were studied; also, surface colour, antioxidant capacity, ascorbic acid, chlorogenic acid content were evaluated. The combined treatment showed a beneficial impact on the quality of the product, avoiding browning when compared with untreated samples and individual treatments (coating without AA or immersion in AA solution). The improvements were evidenced by the absence of changes in hue, minor changes in a* parameter and a major inhibitory effect of AA on the activity of the three enzymes. Ascorbic acid content and antioxidant capacity increased (P < 0.05). The combined treatment not only was effective in preventing enzymatic browning but also retained freshness and improved nutritional value.     

酸性电解水对鲜切马铃薯酶促褐变抑制效果研究

研究了酸性电解水对鲜切马铃薯酶促褐变的抑制效果,并进一步探究了影响酸性电解水抑制酶促褐变效果的外因。通过比较几种方式处理的马铃薯切片在不同贮藏期的褐变度,结果表明,与无处理相比,3种指标的酸性电解水均能够显著(P<0.05)抑制鲜切马铃薯的酶促褐变,其抑制效果与草酸(20mg/L)、柠檬酸(20mg/L)相当。同时研究发现,处理时间、酸性电解水的温度、处理方式(静止浸泡、流水冲洗、振荡)对酸性电解水的褐变抑制效果均产生影响,而料液比变化对酸性电解水的褐变抑制效果影响不大。处理时间为15min,酸性电解水温度为40℃,振荡处理酸性电解水的褐变抑制效果好,且振荡速度越大,效果越好。     

Diffusion of citric and ascorbic acids in pre-peeled potatoes and their influence on microbial growth during refrigerated storage

The most common chemical preservatives used to inhibit both enzymatic browning and microbial growth in pre-peeled potatoes are sodium sulphite and bisulphite. Since 1987 the FDA has limited their use as food ingredients; consequently, during recent years the tendency to replace sulphites by GRAS chemical additives such as citric and ascorbic acids has become stronger. In the present work, surface colour variations, exudate production and microbial growth were analysed on pre-peeled potatoes treated with citric and ascorbic acids. These preservatives were applied individually and as mixtures; shelf-life was extended and microbiologically safe products were obtained. Mathematical models were solved to analyse the diffusion of these acids during immersion and storage periods in order to determine the concentration profiles within the product and to predict the surface concentration to which the microorganisms are exposed.     

Heated Ascorbic/Citric Acid Solution as Browning Inhibitor for Pre-Peeled Potatoes

Treatment of pre-peeled potatoes with heated ascorbic acid (AA)/citric acid (CA) solution to extend shelf-life was investigated. Potatoes were abrasion or high pressure steam peeled, heated for 5–20 min in 1% AA + 2% CA at 45–55°C cooled, and then dipped for 5 min in browning inhibitor (BI) solution containing 4% AA +1% CA +1% sodium acid pyrophosphate. Combined treatment inhibited potato discoloration for 14 days at 4°C compared to 3–6 days with BI treatment alone. Raw material and treatment conditions were selected to minimize graying and textural abnormalities encountered with some treatments. Treatment with heated AA/CA may be an alternative to use of sulfites to control browning in pre-peeled potatoes.     

Microbiological quality of fresh-cut sweet potatoes

Sweet potato roots were dipped in various concentrations of chlorine for 5 min at 1 or 20 °C before and after slicing, and then stored at 2 or 8 °C for 14 days to evaluate the effects of different chlorine treatments and storage temperatures on the microbiological quality of fresh‐cut sweet potato slices. The microflora of fresh‐cut sweet potato slices was dominated by mesophiles, followed by psychrotrophs and fungi initially and during storage. The 2 °C storage was necessary to keep the microbial load at a low level. No spoilage was observed in fresh‐cut sweet potatoes at both storage temperatures for 14 days. Chlorination of sweet potatoes before slicing was not effective in ensuring acceptable microbiological quality of fresh‐cut sweet potatoes. Dipping slices in 200 ppm chlorine at 1 °C reduced the population of all micro‐organisms during storage.     

Oral administration of docosahexaenoic acid attenuates colitis induced by dextran sulfate sodium in mice

Scope: Dietary supplementation of n‐3 PUFAs, containing docosahexaenoic acid (DHA), modulates the symptoms of colitis. Hence, we investigated the effects of oral administration of pure DHA and the therapeutic agent sulfasalazine (SAL) on chemically induced colitis in mice, and analyzed the expression levels of DHA‐responsive genes in colonic tissue using cDNA arrays. Methods and results: Colitis in BALB/c mice was induced by feeding 5% dextran sulfate sodium (DSS) in drinking water for 7 days. DHA (30 mg/kg/day, DHA) or SAL (100 mg/kg/day, SAL) was administered orally throughout the treatment along with DSS. The DHA‐treated group showed significant reduction of the weight loss and colon shortening compared to the DSS‐treated colitis group. In contrast, SAL treatment was effective in reducing colon shortening, stool consistency and bleeding scores. DHA and SAL treatments also significantly reduced the changes in inflammation of the colon, and reversed the increase in myeloperoxidase activity induced by DSS. Among DSS‐responsive genes, those for inflammatory cytokines (IL‐1β, CD14 antigen and tumor necrosis factor receptor superfamily, member 1b), membrane remodeling genes (matrix metalloproteinase‐3, ‐10 and ‐13) and acute phase proteins (S100 calcium‐binding protein A8), which were increased by DSS, were downregulated by DHA or SAL treatment. Conclusions: DHA was effective in alleviating DSS‐induced colitis in mice, partly by modulating the expression levels of genes involved in colitis.     

气相色谱法测定食品添加剂柠檬酸脂肪酸甘油酯中柠檬酸的改进

目的改进气相色谱法测定食品添加剂柠檬酸脂肪酸甘油酯中柠檬酸的分析方法。方法对测定食品添加剂柠檬酸GB 29951-2013《食品安全国家标准食品添加剂柠檬酸脂肪酸甘油酯》的气相色谱法中衍生剂、色谱柱以及升温程序进行优化,并对优化后的方法进行验证。结果选择N,O-双(三甲基硅烷基)-三氟乙酰胺(BSTFA)作为衍生剂,HP-5毛细管柱作为分离柱,温度程序为80℃(1 min)-20℃/min-165℃(5 min)-30℃/min-250℃(1 min),可在15 min内完成对目标物的分离,线性方程为Y=0.67193X+0.05490,r=0.9935,方法回收率为93.0%～98.7%,相对标准偏差(relative standard deviation,RSD)为0.4%,检出限为0.1%。结论该方法目标物分离效果好,回收率及灵敏度高,适用于食品添加剂柠檬酸的定量检测。     

Dual effectiveness of sodium chlorite for enzymatic browning inhibition and microbial inactivation on fresh-cut apples

The dual effectiveness of sodium chlorite for browning inhibition and microbial inactivation on fresh-cut apples was investigated and compared to other anti-browning and antimicrobial agents. Results indicate that sodium chlorite significantly (P < 0.001) inhibited the browning reaction of fresh-cut Red Delicious apples stored at 5 °C for 14 days. This treatment also significantly reduced polyphenol oxidase activities. Treatments with acidified sodium chlorite, calcium chloride, or calcium ascorbate exhibited strong inhibition on apple browning during the early storage, these treatment effects diminished after 7 days in storage. Combining calcium chloride with sodium chlorite further significantly (P < 0.001) improved the firmness of apple slices, and browning inhibition during storage. Additionally, treatments with acidified sodium chlorite, sodium chlorite, or the combination of sodium chlorite and calcium chloride significantly (P < 0.001) reduced Escherichia coli populations on fresh-cut apples by 3.0, 3.6, and 3.9 log cfu g⁻¹ over the water control. The dual effectiveness of sodium chlorite to inhibit enzymatic browning and inactivate E. coli may allow this compound to achieve a prominent role in improving the quality and safety of products in the fresh-cut apple and other food industries.     

Nisin和柠檬酸对鲜切皇冠梨储藏期间单增李斯特菌生长的影响

分别采用0.05mg/m L乳酸链球菌素(Nisin)、0.3%柠檬酸复配溶液和自来水清洗接种单增李斯特菌(LM)的鲜切皇冠梨,将清洗后的鲜切皇冠梨分别于4、12、24℃的条件下储藏,以未清洗的样品为对照,测定储藏过程中LM的生长情况。结果显示Nisin和柠檬酸清洗能显著降低(p<0.05)鲜切皇冠梨中LM的初始带菌量。在4℃储藏过程中,Nisin和柠檬酸清洗的鲜切皇冠梨中LM数量没有明显变化(p>0.05),自来水清洗和未清洗的鲜切样品中LM数量略有升高。在12℃和24℃储藏期间,三种处理方式的鲜切皇冠梨LM数量均显著上升(p<0.05)。Nisin和柠檬酸复配清洗处理结合低温储藏能有效控制鲜切皇冠梨中LM的生长。      

Phenolic acid detection thresholds in processed potatoes

Phenolic acids in potatoes vary naturally and due to handling practices, but little is known about their effects on potato flavor. Best-estimate thresholds (BET) were calculated on data obtained from a 12 member panel utilizing the ASTM Standard Practice E 679-91. Six scale steps were used at a concentration factor of 1.25. Thresholds were determined for chlorogenic and ferulic acids in water and in reconstituted dehydrated mashed potatoes with and without corn oil margarine. Total phenolic concentration of the processed potatoes was measured by HPLC. Aqueous thresholds were 82 ppm and 62 ppm for chlorogenic and ferulic acids, respectively. The chlorogenic acid threshold value was higher in potatoes with added margarine (152 ppm). Addition of margarine to potatoes did not affect the ferulic acid threshold.