Effects of lard on the formation of volatiles from the Maillard reaction of cysteine with xylose

BACKGROUND: The presence of lipid oxidation products in the Maillard reaction pathway is of particular interest today. The objective of this study was to investigate the effect of lard and its oxidation products on the formation of volatiles from cysteine and xylose model systems. RESULTS: Headspace volatiles generated in reaction mixtures were examined by solid‐phase microextraction in combination with gas chromatography‐mass spectrometry. The addition of lipid had a suppressing effect on most of the sulfur‐containing compounds derived from the reaction between cysteine and xylose, especially for 2‐methyl‐3‐furanthiol, 2‐furanmethanethiol, 2‐methylthiophene, and 3‐methylthiophene. One of the intermediates—furfural—was also formed in much lower concentration when lard was present. In addition, cysteine and xylose modified lipid oxidation pathways, so that lipid‐derived alcohols, alkylfurans and aliphatic acids were formed rather than aldehydes. Compared with the lard heated alone, most aldehydes were formed at lower levels in the lard‐containing reaction mixtures, and several aldehydes including hexanal, heptanal, (2E)‐heptenal and (2E,4E)‐heptadienal were absent. CONCLUSION: The addition of lipid was inhibitory to the formation of most sulfur‐containing compounds in the Maillard reaction. Furthermore, Maillard reaction products influenced the formation of products from lipid oxidation. Copyright © 2011 Society of Chemical Industry     

壳聚糖涂膜对鲜切马铃薯褐变程度的影响

研究了不同壳聚糖涂膜液对鲜切马铃薯色泽、褐变强度和多酚氧化酶活力的影响。结果表明:对于鲜切马铃薯的褐变程度,以复合涂膜液Ⅰ(1%壳聚糖+0.5%抗坏血酸)或以复合涂膜液Ⅱ(1%壳聚糖+0.5%抗坏血酸+0.15%氯化钙+0.8%乙二胺四乙酸二钠)抑制效果显著,且以后者更佳。     

紫薯浊汁饮料的研究

对紫薯浊汁饮料的加工技术进行了研究。通过正交试验,确定了紫薯桨防褐变、饮料稳定性等工艺条件。     

Effect of rice bran protein extract on enzymatic browning inhibition in potato puree

Effect of rice bran protein extract (RBPE) on enzymatic browning inhibition in potato puree was studied by colour measurement and polyphenol oxidase (PPO) inhibition. RBPE inhibited browning in potato puree and showed a higher per cent potato PPO inhibition at pH 4.0 and 5.0 than those at pH 3.0, 6.0 and 7.0 (P ≤ 0.05). RBPE heated to 40 and 60 °C had browning inhibition in potato puree and per cent potato PPO inhibition at a similar extent to unheated RBPE (P > 0.05). Browning inhibition and per cent potato PPO inhibition of RBPE were decreased when it was heated to 80 °C (P ≤ 0.05). RBPE inhibited browning in potato puree higher than 5, 10 and 20 mm ascorbic acid and 5 and 10 mm citric acid (P ≤ 0.05). Regarding the kinetics study, RBPE exhibited a mixed‐type inhibition for potato PPO. Therefore, RBPE has a potential to be used as a natural antibrowning agent in the potato industry.     

Effect of heat treatment on quality, thermal and pasting properties of sweet potato starch during yearlong storage

BACKGROUND: Proper postharvest handling and storage of sweet potato is an important link in the chain from producer to consumer or manufacturing industry. Heat treatments have been used as a non‐chemical means to modify the postharvest quality and reduce pathogen levels and disease development of a wide variety of horticultural products. The objective of this study was to investigate the effects of hot water treatment (HWT) on the quality, gelatinisation enthalpy and pasting properties of sweet potato starch during long‐term storage. The weight loss, sprouting, spoilage and sugar content of sweet potato were also determined. RESULTS: HWT significantly inhibited the sprouting and decay of sweet potato during the storage period. There were no significant differences (P < 0.05) in the pasting properties and onset (T_O), peak (T_P) and endset (T_E) temperatures of gelatinisation of sweet potato starch among all treatments, especially between heat‐treated and non‐heat‐treated samples. HWT also had no significant impact on the quality of the internal components of the roots. Less than 4% of the yearlong‐stored roots were discarded owing to spoilage. HWT supplied a lethal dose of heat to surface pathogens and black spot without damaging the nutritional and processing qualities of sweet potato. CONCLUSION: HWT was an effective method to reduce root sprouting and deterioration without significant impact on the quality of the internal components of sweet potato. This novel technique will open a new avenue to extend the storage life of sweet potato with good quality and minimal waste. Copyright © 2011 Society of Chemical Industry     

外源乙烯和1-MCP预处理对鲜切马铃薯褐变的影响

为评价乙烯对鲜切马铃薯褐变的影响,分别采用外源乙烯、1-MCP和乙烯+1-MCP处理鲜切马铃薯,观察色差值（L*,a*和b*）、褐变度、酚类物质含量以及相关酶活性的变化。结果表明,外源乙烯提高了马铃薯的呼吸强度,增加了褐变度,提高多酚氧化酶（PPO）,过氧化物酶（POD）的活性,而1-MCP则起到了抑制作用;外源乙烯和1-MCP均能抑制马铃薯苯丙氨酸解氨酶（PAL）的活性,与对照（118.13 U）相比,经外源乙烯和1-MCP处理的马铃薯PAL活性分别为102.71 U和82.08 U,降低了13.1%和30.5%;外源乙烯预处理促进了鲜切马铃薯的褐变,1-MCP的施用可以抑制或减缓乙烯的负面作用。      

Effects of ultrasound-assisted enzymatic hydrolysis and monosaccharides on structural,antioxidant and flavour characteristics of Maillard reaction products from sweet potato protein hydrolysates

Effects of ultrasound (US)-assisted enzymatic hydrolysis and different monosaccharides (arabinose; xylose, XY; galactose and glucose) on peptide structure, antioxidant activities and flavour characteristics of Maillard reaction products (MRP) from sweet potato protein hydrolysates were investigated. US markedly enhanced the MR progress, and USXY showed the lowest pH value of 5.04, the highest browning intensity and fluorescence intensity (P < 0.05). FTIR results revealed significant peptide structure changes in USXY, USAR and USGA compared to other samples. USXY exhibited the highest Oxygen radical absorbance capacity (ORAC) value of 109.15 µg TE/mL, followed by USGA and USAR (94.07 and 93.41 µg TE/mL), respectively (P < 0.05). USXY and USAR showed different aroma features as compared to other MRP (P < 0.05). In addition, US enhanced umami, sweetness and sourness attributes and reduced bitterness of all MRP. USXY exhibited the highest umami intensity score (7.4), followed by USGA (7.3) and USAR (7.2), respectively. Partial least square regression analysis showed that the stronger umami taste was strongly correlated to aldehydes, thiophenes, MW 1000–3000 and 500–1000 Da peptides. Thus, US-assisted enzymatic hydrolysis and MR with xylose (XY) could be a promising way to produce natural flavouring with improved antioxidant activity.     

交联淀粉对甘薯浊汁饮料稳定性的影响

将不同浓度交联剂(6%,8%,10%,12%,14%)制备得到的交联马铃薯淀粉(Cross-linked potato starch,CLPS)应用于甘薯浊汁饮料中,测定浊汁饮料的浑浊度、流变特性、稳定性、Zeta电位和离心沉淀率。结果显示,随着交联程度的增加,浊汁饮料的浑浊度上升,但30d内浑浊度的变化程度降低,饮料体系的假塑性、黏度、黏弹性、凝胶强度与Zeta电位绝对值随着交联程度的增加而增加,在交联剂浓度为12%时取得最大值;交联淀粉能够抑制浊汁饮料底部出现沉淀,但对浊汁饮料顶部析水的控制有限,稳定性动力学指数与离心沉淀率随着交联程度的提高而下降,表明交联淀粉能够提高甘薯浊汁饮料体系的稳定性。综合结果表明,交联淀粉使甘薯浊汁饮料的稳定性有一定程度的提高,12%CLPS可作为稳定剂应用于淀粉质浊汁饮料中。     

鲜切马铃薯褐变程度数学模型研究

利用测色色差仪,研究鲜切马铃薯经保鲜处理后在不同贮藏温度下贮藏过程中色差值的变化及其与褐变程度的关系,建立褐变程度数学模型。研究结果表明:贮藏温度愈高、贮藏时间愈长,褐变愈严重,总色差值ΔE愈大,且ΔE3.5可作为评断鲜切马铃薯是否具有商品性的界限值。实验中所建立的二元二次方程Y=-0.00095A2-0.26B2+0.0145AB+0.059A+1.572B-0.563,经验证实验表明可用于预测不同贮藏温度、不同贮藏时间内鲜切马铃薯的褐变程度,从而为鲜切马铃薯的快速分级,提供一个方便有效的方法。      

柑橘皮精油对鲜切马铃薯褐变及冷却猪肉保鲜的影响

以柑橘皮为原料,采用水蒸气蒸馏法制备柑橘皮精油。通过对鲜切马铃薯PPO和POD活性两个指标的测定研究柑橘皮精油对马铃薯褐变的影响。结果表明,与抑制剂柠檬酸、CaCl2和Na2SO3相比,浓度为1.2%精油的抑制褐变效果较好。通过对猪肉进行H2S实验、挥发性盐基氮和菌落总数等指标的测定研究橘皮精油对冷却猪肉保鲜的影响,得出精油浓度为2.4%时,可在保存期内保持肉样的一级新鲜度,且精油与其他保鲜剂混合使用时,对肉样保鲜效果具有协同增效的作用。     

甘薯浓缩汁中淀粉的酶转化工艺研究

该研究立足国内丰富甘薯资源,解决甘薯浓缩汁中因淀粉引起沉淀问题,同时将甘薯淀粉转化为葡萄糖。以新型耐高温α–淀粉酶为液化酶和高转化率糖化酶糖化,研究影响甘薯淀粉液化、糖化因素,优化甘薯淀粉液化、糖化工艺参数。     

马铃薯多酚氧化酶酶学特性及热稳定性模型的研究

目的:研究马铃薯中多酚氧化酶（polyphenol oxidase,PPO）的部分酶学性质及热稳定性并拟合数学模型预测酶活变化过程。方法:采用紫外可见分光光度计测定马铃薯多酚氧化酶活力,利用Matlab软件拟合二元多项式热稳定性数学模型,SPSS软件对多项式模型回归分析。结果:马铃薯多酚氧化酶的最适pH为5.5,最适反应温度为40℃,最适底物浓度为8.33mmol/L,加工温度、时间与酶活残存率的函数关系为:Z=24.5439+6.1163X+3.4064Y-0.0269X2-0.2361XY-0.0351Y2-0.0002836X3+0.001326X2Y+0.0012XY2,其中R2=0.981,F=100.695,p<0.001。结论:二元三次多项式模型能够较准确的反映并预测马铃薯多酚氧化酶在热加工过程中酶活的变化趋势。      

甘薯浓缩汁生产过程中澄清工艺的研究

为了解决甘薯浓缩汁生产过程中絮状物和沉淀,通过对果胶酶的响应曲面法的实验设计,得出果胶酶的最佳工艺条件。再通过添加硅藻土、纤维素酶、明胶、硅藻土和超滤等方法,除去引起浑浊的成分,以透光率为衡量指标,进而得到最佳澄清条件。     

马铃薯泥挥发性风味物质研究

采用顶空固相微萃取法(HS-SPME)制备样品,利用气相色谱质谱联用法(GC-MS)分离并鉴定新鲜的及在4℃下冷藏1d的马铃薯泥的挥发性风味物质。由检测结果可知,新鲜样主要风味组分有47种,而冷藏样主要风味组分有37种。新鲜样中最丰富的是醛类化合物,出峰面积相对比例76.94%,其次是呋喃类8.08%,醇类6.85%。冷藏样中出峰面积相对比例较高的是醛、酯、醇类化合物,分别为93.27%、3.45%和1.03%。新鲜样和冷藏样中醛类含量均最高,是由蒸煮阶段不饱和脂肪酸在脂肪氧合酶催化下生成的。     

酵母抽提物-猪肉酶解物-HVP之Maillard反应产生肉香味化合物的研究

分别对猪肉酶解物－酵母抽提物－HVP、猪肉酶解物－HVP两种Maillard反应模型系统所产生的挥发性香气化合物进行了分离、提取及鉴定，从两种系统中都鉴定出了2－甲基－3－呋喃硫醇、2－乙酰基呋喃、2－甲基－四氢噻吩酮、苯乙醛、3－甲基－2－噻吩醛、3－乙基－2噻吩醛、二（2－甲基－3－呋喃基）二硫醚、二（2－甲基－4，5－二氢－3－呋喃基）二硫醚、十六醛、十八醛等，猪肉酶解物－HVP模拟系统比猪肉酶解物－酵母抽提物－HVP要高许多倍。     

Comparison of the volatile components of two cultivars of potato cooked by boiling,conventional baking and microwave baking

Tubers of two cultivars (Estima and Maris Piper) of potato were cooked by three different procedures, ie boiling, conventional baking and microwave baking. Peeled and sliced tubers were boiled, while intact potatoes were baked in their skins. Flavour components from the boiled slices and the flesh of the baked tubers were isolated by headspace adsorption onto Tenax and analysed by gas chromatography–mass spectrometry (GC–MS). For all cooking procedures, Estima gave stronger isolates than Maris Piper. The two main sources of flavour compounds (regardless of cooking procedure) were lipid degradation and the Maillard reaction and/or sugar degradation. The ratio (yield derived from lipid)/(yield derived from Maillard reaction and/or sugar) decreased from 8.5–9.1 (boiling) to 2.7–3.4 (microwave baking) and to 0.4–1.1 (conventional baking). Quantitative and qualitative differences among the cooking procedures are explained in terms of the variations in heat and mass transfer processes that occurred. Each cooking procedure resulted in a unique profile of flavour compounds. © 2002 Society of Chemical Industry     

马铃薯贮藏期间褐变强度与多酚氧化酶活性变化的研究

测定了十个马铃薯品种在六个月窖藏期间褐变强度和多酚氧化酶活性的变化。结果表明:马铃薯的褐变强度和多酚氧化酶活性在品种间的差异达极显著水平,除渭薯8号外,其它品种在贮藏期间的变化也达到极显著水平。在贮藏期间,不同品种的褐变强度和多酚氧化酶活性的变化趋势不同,但同一品种褐变强度与多酚氧化酶活性之间存在中度的正相关,相关系数r为0.736。      

不同品种甘薯汁抗氧化活性的研究

研究了9个品种甘薯汁的酚类物质及其抗氧化活性,旨在为甘薯汁的开发利用提供参考依据。分别采用Folin-酚法、亚硝酸钠法、pH示差法测定了甘薯汁的总酚、总黄酮、总花色苷含量。结果表明,甘薯汁中含有丰富的酚类物质,不同品种甘薯汁的总酚、总黄酮和总花色苷含量存在差异。通过4个体外抗氧化体系（FRAP法、DPPH自由基法、ABTS+自由基法、OH自由基法）评价了甘薯汁的抗氧化能力。结果显示,不同品种甘薯汁所呈现的抗氧化能力不同,酚类物质含量较高的甘薯汁其抗氧化能力较强。从抗氧化能力方面考虑,杭引薯1号、杭引薯3号、浙紫薯1、13号这4个抗氧化能力较强的品种较适合用于果汁加工以及功能性饮品的开发。      

酸处理对烤马铃薯条品质的影响

为了改善烤马铃薯条品质,选用不同质量分数的柠檬酸、苹果酸、醋酸溶液预处理马铃薯条,通过测定烤后马铃薯条的质构、水分分布等品质指标以探究酸处理对烤马铃薯条的作用规律。结果表明,酸浸泡处理减缓了烤制对马铃薯细胞的破坏,烤马铃薯条的孔隙减少,硬度升高。质量分数越高,烤马铃薯条失重率越大（P<0.05）,水分流失越严重,2%醋酸处理5 h失重率高达（57.83±1.49）%;随浸泡时间的延长,烤马铃薯条硬度和剪切力均增加（P<0.05）,浸泡5 h时微观结构最为致密;柠檬酸和苹果酸浸泡有助于烤马铃薯条产生花香味和蘑菇味。