Maintaining the quality of sugarcane juice with blanching and ascorbic acid

The physicochemical changes in fresh sugarcane juice stored at 10 °C were studied by determining juice yield, color, reducing sugar, titratable acidity, viscosity, pH, polyphenol oxidase (PPO), sucrose neutral invertase (SNI) and total microbial count. Results showed that blanching of stems before squeezing effectively prevented degreening and/or browning, and reduced activities of PPO and SNI in fresh sugarcane juice. Added ascorbic acid delayed the increase of reducing sugar, titratable acidity, viscosity and total microbial count, and also prevented degreening and/or browning with reduced PPO and SNI activities in fresh sugarcane juice during storage. Addition of 0.1% ascorbic acid seemed to be more effective than blanching of sugarcane stems, and was able to maintain the quality of fresh sugarcane juice for up to 5 days at 10 °C. Deterioration of fresh sugarcane juice was demonstrated as a rapid increase of titratable acidity and viscosity with a obvious browning.     

甘蔗压榨提汁过程褐变抑制研究？

制糖脱色成本占糖浆精制成本的1/3,而酶促褐变是蔗汁颜色加深的一个主要原因。本文探讨了制糖压榨过程中褐变对蔗汁颜色变化的影响,进一步研究了亚硫酸盐对蔗汁酶促褐变的抑制。结果表明：褐变对蔗汁色值贡献率大于50%,前10 min褐变速度最快;蔗梢蔗汁相对于成熟蔗茎蔗汁酶促褐变程度高;压榨后立即预灰能减少酶促褐变色素生成;多酚氧化酶活性在蔗汁预灰pH大于9.5时为0,在pH6.0~6.5最高;3 mmol/L NaHSO3的添加量能完全抑制蔗汁酶促反应发生。研究可为甘蔗制糖工艺的改进提供依据。     

裂褶菌多糖抑制枇杷果汁褐变的工艺优化

以“宁海白”枇杷为实验对象,研究不同质量分数裂褶菌多糖粗提物、4 种常用褐变抑制剂（草酸、柠檬酸、VC、L-半胱氨酸）对抑制枇杷果汁褐变的影响。结果发现,5 种褐变抑制剂的作用效果强烈顺序为：L-半胱氨酸＞草酸＞VC＞柠檬酸＞裂褶菌多糖,其中裂褶菌多糖质量分数在0.8%时,褐变抑制率达到80%以上。基于果汁风味考虑,选择裂褶菌多糖、VC、L-半胱氨酸一起作为抑制剂组合,并通过响应面优化试验得出最佳组合为：裂褶菌多糖质量分数1%、VC质量分数0.025%、L-半胱氨酸质量分数0.004%。经回归分析和验证实验,得到的果汁褐变抑制率为98.04%,与理论模型预测值99.22%接近,响应模型可靠。优化处理后的果汁可溶性固形物、VC和总酚含量都得以提高。可见,裂褶菌多糖可以与其他抑制剂复合使用,运用于枇杷果汁褐变防控。     

雪梨多酚氧化酶酶学特性及其果汁褐变控制技术研究

雪梨在加工过程中极易发生酶褐变,为抑制雪梨汁的酶褐变,试验以雪梨为原料制备多酚氧化酶(Polyphenol oxidase,PPO)粗酶提取液,加入邻苯二酚为底物,采用分光光度法对其PPO的酶学特性及不同护色剂对PPO活性的影响进行了研究;并选择L-半胱氨酸、D-异抗坏血酸钠、抗坏血酸3种添加剂对雪梨汁进行护色,通过响应面优化试验确定雪梨汁最优护色组合。结果表明:雪梨PPO的最适pH为4.5,最适温度为30 ℃;雪梨PPO具有一定的热稳定性,随着温度的提高,抑制PPO活性所需要的时间逐渐减少;雪梨PPO催化底物邻苯二酚的酶促反应动力学与米氏方程高度符合,最大反应速率Vmax=217.39 U/min,米氏常数Km=0.152 mol/L。雪梨汁加工的最优护色剂组合为:6.56 mmol/L的L-半胱氨酸、4.58 mmol/L的D-异抗坏血酸钠和6.18 mmol/L的抗坏血酸,在此条件下对雪梨汁褐变的抑制率可达90.82%。     

Effect of basil leaves and wheat bran water extracts on enzymatic browning of shredded storage iceberg lettuce

The impact of functional solutions (water infusions of radish sprouts, wheat bran (WBE), basil leaves (BLE) and lentil protein hydrolysate) on enzymatic browning of shredded iceberg lettuce was studied. BLE and WBE, limiting enzymatic browning in the highest degree, were tested during cold storage. The best inhibitors of PPO activity in lettuce stored for 8 days were 10% WBE (a decrease by 97%). POD activity was substantially decreased by ascorbic acid (by 75%) and 1% BLE (by 83%). POD and PPO inhibition was reflected in a decrease in enzymatic browning, that is 91% and 88% reduction was found in 8-day stored lettuce treated with 1% BLE and 1% WBE, respectively. In the case of POD, mixed inhibition was recorded for BLE and WBE, while these solutions acted as competitive inhibitors of PPO activity. The enzymatic browning of shredded iceberg lettuce during cold storage may be effectively suppressed by natural extracts.     

Process development for stabilization of sugarcane juice using response surface methodology

Sugarcane juice is a very popular drink in India and other Asian countries, where sugarcane is an important crop. Since sugarcane juice spoils very quickly and there is a lack of research in this area, no commercialized sugarcane juices are available in India. Here, stabilized sugarcane juice was developed using response surface methodology. Total soluble solids, reducing sugar, total sugar, polyphenol oxidase activity, ascorbic acid, pH, optical density, transmittance, titrable acidity, microbiological properties, and sensory scores of the stabilized juice were evaluated using a Box–Behnken design. The composition was optimized and the sugarcane drink was further processed using blending and hot filling techniques. The processed juice was hot-filled into glass bottles under aseptic conditions. The predicted shelf life of the processed sugarcane juice was 3 months at 18 °C and 6 months at 10 °C.     

混浊苹果汁加工过程中的的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用.半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂.在所测试条件下,抗褐变的能力(褐变抑制率)为0.1%的抗坏血酸＞0.1%的偏重亚硫酸钠＞0.1%的曲酸＞0.1%的氯化钙＞0.005%半胱氨酸＞0.1%氯化钠.它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸.柠檬酸在所测试条件下没有抗褐变效果.0.044%NaCl+0.0125%Vc的组合较经济且可使果汁40min不变色.果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变.     

混浊苹果汁加工过程中的酶促褐变及其防止的研究

将几种可用于食品的防褐变剂在苹果破碎时加入,考察了它们对苹果浆和苹果鲜榨汁的防褐变效果及它们之间的协同作用。半胱氨酸、抗坏血酸、曲酸、氯化钠和氯化钙都是较好的防褐变剂。在所测试条件下,抗褐变的能力(褐变抑制率)为:0.1％的抗坏血酸>0.1％的偏重亚硫酸钠>0.1％的曲酸>0.1％的氯化钙>0.005％半胱氨酸>0.1％氯化钠。它们抗褐变能力都表现为浓度依赖型,特别是抗坏血酸。柠檬酸在所测试条件下没有抗褐变效果。0.044％NaCl 0.0125％Vc的组合较经济且可使果汁40min不变色。果浆脱气可减缓其褐变;减小果汁及果浆与空气的接触面也可防止褐变。     

双孢蘑菇酶促褐变特性及褐变的控制

为有效控制双孢蘑菇褐变,研究pH值、温度、底物浓度以及抑制剂对双孢蘑菇的多酚氧化酶(polyphenol oxidase,PPO)活性的影响。结果表明：以邻苯二酚为底物,双孢蘑菇PPO最适反应pH6.8,最适反应温度20℃,最适反应底物浓度为0.06mol/L,米氏常数Km为0.1072mol/L。采用计算机图像处理技术对双孢蘑菇褐变程度进行定量检测,得出对双孢蘑菇贮藏保鲜效果较好的褐变抑制剂及其最佳配比为0.30mmol/L半胱氨酸、0.06％抗坏血酸、0.05%乙酸。     

化学抑制剂对果蔬食品多酚氧化酶性质影响的研究进展

多酚氧化酶(polyphenol oxidase,PPO)引起的酶促褐变会导致果蔬食品色泽劣变,营养成分降低,甚至使其丧失商品价值。化学抑制剂对PPO具有较好的抑制效果,并且使用方便,在果蔬食品中广泛使用,因此对它的研究具有理论和实际意义。该文论述了羧酸、抗坏血酸及其衍生物、含硫氨基酸、酚酸及其他抑制剂对PPO的抑制作用和机理,并分析了它们在食品工业应用中的优缺点。同时,从分子水平上探讨了化学抑制剂处理后PPO构象变化,以及抑制剂与PPO的相互作用方式,得出了化学抑制剂可通过强酸作用、螯合作用、还原作用和强结合作用来导致PPO构象变化而抑制酶活,为深入研究抑制剂对PPO的抑制机理提供了理论参考。     

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.     

不同添加剂对香蕉褐变的抑制作用研究

选取柠檬酸、抗坏血酸、氯化钠、茶多酚、L-半胱氨酸、草酸作为香蕉褐变的抑制剂,研究其对香蕉经过切片打浆过程中酶促褐变的抑制作用.结合色差测定的定量分析,结果表明L-半胱氨酸是最有效的褐变抑制剂,而且与抗坏血酸具有协同作用.通过正交实验,得出最佳抑制剂复配处理为0.2%L-半胱氨酸和0.3%抗坏血酸复配,处理30min.结合最佳抑制剂处理,在微波功率495W处理30s可得到满意的护色效果.     

Mechanism for the inhibition of apple juice enzymatic browning by Palo Fierro (desert ironweed) honey extract and other natural compounds

Inhibition of Red Delicious apple juice browning and apple polyphenoloxidase (PPO) activity by four natural anti-browning agents [palo fierro honey extract (PFH), caffeic acid phenethyl ester (CAPE), l-cysteine (Cys), and 4-hexylresorcinol (4HR)] has been studied. Browning of apple juice was markedly reduced by 4HR, Cys, and PFH, however, little effect was observed with CAPE. PFH, CAPE, and 4HR showed high inhibition of apple juice PPO. When the inhibition mechanism of these compounds over partially purified apple PPO was studied using chlorogenic acid as substrate, PFH acted as a noncompetitive inhibitor of apple PPO, with K_i = αK = 0.8 g/L, and IC₅₀ ranging 1.1-1.7 g/L. Cys showed an inhibitory pattern which could not be fitted to any type of reversible inhibition (IC₅₀ 0.02-0.03 g/L), while CAPE showed low inhibitory activity, which could be due to co-precipitation processes. PFH could be considered as an effective natural compound to reduce apple juice browning.     

雪莲果防褐变技术的研究

从雪莲果块茎中提取多酚氧化酶(Polyphenol Oxidase,PPO),采用分光光度法对其最大吸收波长最适反应温度进行研究,还研究了VC、氯化钠、柠檬酸、柠檬汁、橘子汁对雪莲果PPO活性的影响。结果表明:雪莲果多酚氧化酶最大吸收波长为400nm,最佳反应温度为30℃。氯化钠、抗坏血酸、柠檬酸、柠檬汁、橘子汁都有抑制褐变的效果。组合抑制剂抑制褐变效果比单一抑制剂好且最佳组合抑制剂为1.5%氯化钠+0.5%抗坏血酸+1.5%柠檬酸+10%柠檬汁。     

雪莲果发酵酒的防褐变技术研究

在不影响雪莲果果酒发酵过程和品质的前提下,通过添加抗坏血酸、柠檬酸、蜂蜜、菠萝汁等抗褐变剂来解决雪莲果果酒生产中的褐变问题,得到营养成分损失少、风味佳、色泽鲜亮的雪莲果果酒。结果表明,抑制雪莲果褐变程度的先后顺序为柠檬酸>抗坏血酸>菠萝汁雪莲混合比,蜂蜜在雪莲果酒陈酿期会产生深色物质,不适宜作为雪莲果果酒的抗褐变剂。影响感官的顺序分别为菠萝汁雪莲混合比>抗坏血酸>柠檬酸,最后得出抑制雪莲果酒褐变的最佳组合为抗坏血酸的添加量1.00%,柠檬酸的添加量0.75%,菠萝雪莲混合比为1:4。     

Non-enzymatic browning in clarified cashew apple juice during thermal treatment: Kinetics and process control

The effect of thermal treatment on clarified cashew apple juice was studied at temperatures from 88 to 121 °C. Changes in colour measured with colorimetric parameters (reflectance spectra, colour difference and CIELAB), and the variation in ascorbic acid, 5-hydroxymethylfurfural (5-HMF) and sugar content were used to evaluate non-enzymatic browning. Kinetic models were applied to the changes in reflectance spectra, ascorbic acid and 5-HMF. The effect of temperature on kinetic constants was described by an Arrhenius type equation. The sugar content remained constant during thermal treatment and did not affect non-enzymatic browning, which was mainly affected by degradation of ascorbic acid. The kinetic models were used to optimise and control the thermal treatment for clarified cashew apple juice.     

INHIBITION OF SURFACE BROWNING, CUT AVOCADO

Browning prevention of avocado halves using polyphenol oxidase (PPO) inhibitors along with sulfites was investigated. Browning inhibitiors were selected on the basis of the inhibition of a crude extract of avocado PPO. The most effective inhibitors were ascorbic acid and sodium sulfite, these compounds plus citric acid were mixed to get an inhibitory solution. In vivo experiments were performed on avocado halves by measuring Hunter color values after 15 days' storage to test the potential of solutions to prevent browning. Results showed that immersion in solutions along with refrigerated storage was needed to get an inhibitory effect. Color preservation was not due to oxygen exclusion nor to low pH and sulfite was unnecessary. The best treatment was the storage of avocado halves in a 1% ascorbic acid/1 % citric acid solution at pH 5 and 7C.     

砍后露天堆放对原料蔗工艺性状和鲜重影响的研究

本研究通过测定不同堆放期3个栽培品种的原料蔗主要工艺性状和鲜重的变化情况,探讨品种间砍后露天堆放原料蔗工艺品质方面的差异,筛选出符合榨季生产需要的栽培品种.结果表明:露天堆放3天,甘蔗蔗糖分和蔗汁重力纯度的变化不大,而蔗汁还原糖分、甘蔗纤维分和鲜重的变化较大;随着堆放时间的增长,甘蔗蔗糖分和蔗汁重力纯度的降幅也在增加,而蔗汁还原糖分和甘蔗纤维分的增幅不断加大,鲜重的损失也在增大,显示原料蔗工艺品质变劣加剧.结果还表明,F90-7909是个工艺性状相对较稳定的栽培品种.     

Purification and characterisation of polyphenol oxidase (PPO) from eggplant (Solanum melongena)

Eggplant (Solanum melongena) is a very rich source of polyphenol oxidase (PPO), which negatively affects its quality upon cutting and postharvest processing due to enzymatic browning. PPO inhibitors, from natural or synthetic sources, are used to tackle this problem. One isoform of PPO was 259-fold purified using standard chromatographic procedures. The PPO was found to be a 112 kDa homodimer. The enzyme showed very low K_m (0.34 mM) and high catalytic efficiency (3.3 × 10⁶) with 4-methyl catechol. The substrate specificity was in the order: 4-methyl catechol > tert-butylcatechol > dihydrocaffeic acid > pyrocatechol. Cysteine hydrochloride, potassium metabilsulphite, ascorbic acid, erythorbic acid, resorcylic acid and kojic acid showed competitive inhibition, whereas, citric acid and sodium azide showed mixed inhibition of PPO activity. Cysteine hydrochloride was found to be an excellent inhibitor with the low inhibitor constant of 1.8 μM.     

带壳百香果与甘蔗汁混酿复合果酒工艺研究

将带壳百香果和甘蔗汁作为原料酿造复合果酒,并研究其发酵工艺。 运用单因素试验和正交试验对发酵破壳时间、原料配比、原料初始含糖量、主发酵温度及主发酵时间进行优化。 结果表明,百香果甘蔗复合果酒的最优工艺条件为：百香果发酵破壳时 间5d,百香果与甘蔗汁配比1∶3（g∶mL）,调节原料初始含糖量至32.5%,于发酵温度24℃条件下发酵9d。 在此最佳工艺条件下,百香果甘蔗复合果酒感官评分达到79分,酒精度达到14.1%vol,色泽呈玫瑰红色,澄清透亮,具有典型的百香果浓郁香气和甘蔗汁的清 香风味。