鲜切莲藕防褐变剂配方优化及保鲜效果研究

为了得到鲜切莲藕最佳的复合防褐变剂配方,以柠檬酸、抗坏血酸、天冬氨酸质量分数为因素,褐变度为响应值,通过响应面优化鲜切莲藕复合防褐变剂配方,在此基础上将处理后的鲜切莲藕置于冰箱中冷藏,研究优化防褐变剂对鲜切莲藕品质的影响。结果表明,各因素对响应值的显著性表现为：无水柠檬酸>抗坏血酸钙>L-天门冬氨酸,最佳防褐变剂配方为：1.0%无水柠檬酸+0.1%抗坏血酸钙+0.2%L-天门冬氨酸。与对照相比,优化防褐变剂处理可显著减少维生素C的损失并延缓还原糖的生成,抑制鲜切莲藕褐变,抑制呼吸强度和乙烯生成速率,对莲藕相对电导率和丙二醛含量也具有较好的抑制效果,抑制褐变底物总酚含量的消耗和褐变相关酶活性上升。因此,优化防褐变剂(1.0%无水柠檬酸+0.1%抗坏血酸钙+0.2%L-天门冬氨酸)结合冷藏可较好地延缓褐变发生,延长贮藏时间达4 d。     

山药化学成分及皂苷类成分药理作用的研究进展

本研究以‘长山细毛山药’菜山药及‘河南温县’铁棍山药为试验材料,研究在4 ℃贮藏0、30和60 d对鲜切山药货架期酚类物质含量和褐变关键酶活性的影响。结果表明,两种鲜切山药褐变指数均随货架期的延长而增大,但随着贮藏期的延长,菜山药的褐变指数较低,而铁棍山药的褐变指数则较高。货架期第8 d时,贮藏30 d的鲜切菜山药的褐变指数仅比贮藏60 d的低4.6%,差异不显著,而同期的鲜切铁棍山药其褐变指数比贮藏60 d的低8.4%,差异显著（P<0.05）。鲜切铁棍山药随着贮藏期和货架期的延长,其货架期内呼吸速率、乙烯释放量、木质素含量、酚类物质、绿原酸、褐变关键酶活性均增加;然而,鲜切菜山药呼吸速率、木质素含量随贮藏期的延长而下降,褐变关键酶活性随贮藏期的延长而呈先升后降的趋势,酚类物质货架后期有所上升,其他指标与铁棍山药的变化规律比较一致。进一步相关性分析表明,随着贮藏时间的延长,铁棍山药中酚类物质和酶活性变化较大,且与褐变指数呈正相关,而菜山药随着贮藏时间的变化,褐变指数只与酶活性之间成正相关性。总之,菜山药更适于鲜切加工,贮藏60 d其鲜切产品货架期可达8 d,而铁棍山药贮藏60 d鲜切产品货架期只有4 d。     

复合护色剂对杏片干制中护色效果的研究

以新疆主栽品种赛买提杏为主要原料,开展不同褐变抑制剂对鲜切杏片在太阳能干制(solar-drying,简称SD)过程中护色效果的研究。实验结果表明,柠檬酸在初始浓度范围0.1%～0.2%、抗坏血酸浓度在>0.02%、氯化钠在初始浓度范围0.1%～0.2%、亚硫酸钠浓度在>0.02%时,对鲜切杏片的褐变均有抑制作用。采用L9(34)正交实验,利用各种护色剂的协同作用,最终得到最佳的复合护色液:0.1%柠檬酸+0.03%抗坏血酸+0.1%氯化钠+0.04%亚硫酸钠。经复合护色液处理后的鲜切杏片在干制后色差值为:L*=22.92,a*=9.26,b*=19.4,均比对照高,能较好地维持其原有色泽。     

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.     

Control of Listeria monocytogenes in Vacuum-Packaged Pre-Peeled Potatoes

Growth of Listeria monocytogenes on the surface of fresh peeled potatoes, treated with sulfite or a commercial browning inhibitor (CBI), packaged under vacuum and stored at 4,15 and 28°C was determined. At 4°C, L. monocytogenes did not grow in all treated potatoes even after 21 days. At 15°C, L. monocytogenes grew to 7 log₁₀ CFU/g within 12 days in the potatoes treated with sulfite or CBI. At 28°C, L. monocytogenes population was greater than 3 log₁₀ CFU/g by 24 h in all samples regardless of treatment. Sulfites or a CBI appeared to provide a measure of safety in pre-peeled potatoes packaged under vacuum when kept at proper refrigeration temperatures.     

包装、臭氧和保鲜剂处理对‘大红袍’鲜花椒呼吸强度与贮藏效果的影响

为筛选延长鲜花椒贮藏寿命的适宜包装以及臭氧与保鲜剂的适宜浓度,以‘大红袍’鲜花椒为材料,采用聚乙烯PE20(厚20 μm)、PE30(30 μm)和PE50(50 μm)包装袋以及臭氧(O₃,5、15、30 mg/L)、二氧化氯(ClO₂,15、40、80 mg/kg)和双乙酸钠(C₄H₇NaO₄,100、200、400 mg/kg)处理后于(0±0.5) ℃贮藏,测定其冷藏期间的感官品质、褐变率和呼吸强度的变化。结果表明:PE20包装对抑制鲜花椒的褐变和保持感官品质具有较好效果;15 mg/L O₃、40 mg/kg ClO₂和100 mg/kg C₄H₇NaO₄的处理效果较好,尤以40 mg/kg ClO₂处理可显著抑制鲜花椒的呼吸强度和褐变率,保鲜效果最佳,冷藏42 d时褐变率为42%。综上,聚乙烯PE20包装袋及40 mg/kg ClO₂对鲜花椒的保鲜效果最好。     

Control of Enzymatic Browning in Pre-peeled Potatoes by Surface Digestion

Feasibility of lye digestion to remove surface tissues from peeled potatoes prior to treatment with browning inhibitors to extend shelf-life was investigated. Russet and round-white potatoes were digested in 14–20% NaOH at 35–55°C for 1–13 min. After removal of digested tissue, tubers were treated with ascorbic acid-based browning inhibitor. Browning was measured by tristimulus calorimetry. Digestion extended shelf-life of high pressure steam- and abrasion-peeled potatoes to 13–15 days at 4°C, compared to 3–11 days for undigested controls. Digestion resulted in weight losses of 12–26%, depending on treatment conditions. Lye digestion in conjunction with conventional browning inhibitors represents a viable alternative to sulfiting pre-peeled potatoes.     

不同品种马铃薯泥加工过程中褐变抑制研究

通过对比7个马铃薯品种的多酚氧化酶活性,选择青薯9号、宣薯2号、红宝石和黑美人4个马铃薯品种作为护色试验品种,在马铃薯泥加工过程中测定多酚氧化酶活性抑制率。无硫护色工艺响应面优化试验得到最佳护色工艺为:柠檬酸0.66%,氯化钙0.73%,V_C0.06%,护色时间15 min,此时酶活抑制率平均值达98.7%;彩色马铃薯护色工艺试验得到最佳护色工艺为:氯化钙0.7%,V_C0.05%,护色时间15 min,此时酶活抑制率可达89%以上。两种护色剂配方能有效抑制普通和彩色马铃薯泥加工过程中的褐变现象。     

Slicing increases antioxidant capacity of fresh‐cut lotus root (Nelumbo nucifera G.) slices by accumulating total phenols

Slicing is an abiotic stress during fresh‐cut lotus root slices (FLS) preparation. To evaluate the potential ability of slicing to induce antioxidant capacity (AC) in FLS, fresh lotus roots were sliced into 0.4 cm thick slices and stored at 7 °C for 7 days using intact root segments as control. Results showed slicing induced 68.3% higher phenylalanine ammonia‐lyase (PAL) activity and parallel 130.5% more total phenol (TP) accumulation after 7 days storage compared to control. AC values in FLS assayed by FRAP and ABTS^●+ were 41.5% and 93.8% more than those in control samples at the end of storage, respectively. Such increases in AC values were mainly attributed to TP accumulation as a positive correlation existed between AC and TP. However, slicing significantly accelerated FLS browning by increasing the polyphenol oxidase (PPO) activity during storage. Nevertheless, FLS was still marketable with the maximum browning index of 1.9 after 7 days storage.     

荔枝果实褐变的研究与调控

就 pH、温度、湿度和多酚氧化酶等对荔枝色泽稳定性的影响进行了研究 ,发现高 pH值、高温、低湿以及多酚氧化酶活性对荔枝颜色的保持十分不利 ;本实验研制的 pH在 3 5以下 ,含有抗菌剂、酶抑制剂的涂膜保鲜剂可显著延长荔枝在常温下的货架寿命     

热处理对鲜切马铃薯褐变及挥发性物质的影响

褐变是影响鲜切马铃薯贮藏品质的重要因素之一。该研究探讨45、50℃热处理1～4 min对鲜切马铃薯褐变和挥发性风味物质的影响,以期为鲜切马铃薯品质保持提供调控技术和理论依据。45、50℃热处理4 min鲜切马铃薯在室温下2 h就观察到轻微的褐变,L*值下降10.51%、14.96%;a*值上升2.74、3.84,而45、50℃热处理1～3 min组鲜切马铃薯6 h内均未观察到褐变现象。与对照组相比,45℃热处理1～3 min组鲜切马铃薯硬度无显著变化,而其余热处理组硬度显著降低;两种温度1～3 min热处理组鲜切马铃薯苯丙氨酸解氨酶（PAL）、过氧化物酶（POD）酶活性和总酚含量分别降低了27.81%～33.68%、18.33%～50.37%、6.22%～28.92%。45℃热处理1～3min和50℃热处理1～2min热处理组较好的维持鲜切马铃薯原有的挥发性风味物质。总的来说,45、50℃热处理1～3 min可有效的抑制鲜切马铃薯褐变;其中,45℃热处理3 min抑制马铃薯褐变的同时较好维持了硬度、色泽、抗坏血酸含量和挥发性风味物质。