Effects of Calcium Chloride-based Prefreezing Treatments on the Quality Factors of Strawberry Jams

ABSTRACT: Vitamin C contents of pretreated strawberries did not change during 2 mo of freezing, but after jam cooking and storage, the vitamin C contents of all the studied jams decreased dramatically. Jams made from strawberries treated with CaCl₂ and PME in a vacuum had the highest firmness compared to the reference or other pretreated jam strawberries (p < 0.05). According to sensory evaluation of the jams, different prefreezing treatments were shown to have a significant influence on the sensory attributes evaluated (p < 0.001), the only exception being the redness of color after 4 mo storage.     

CaCl2溶液对柿子汁涩味的影响

本文以柿子为实验原料,采用CaCl2溶液对柿子汁进行脱涩,对CaCl2溶液浓度、脱涩温度、脱涩时间、及脱涩pH值进行探讨.通过正交试验得出,用1.6% CaCl2溶液控制在pH 4.5和40 ℃的条件下脱涩20 h,脱涩率达到88.57%.     

Ultrastructural and Changes in Pectin Composition of Sweet Cherry from the Application of Prefreezing Treatments

ABSTRACT: Thermal and calcium pretreatments applied to preserve the sweet cherry texture by the freezing/thawing process produced biochemical changes in the pectic substances and ultrastructural alterations to the cells and tissues, which were visible under scanning electron microscopy. Partial dehydration of the epidermic tissue caused by calcium (100 m M CaCl₂) and thermal (50 °C/10 min) pretreatment attenuated the surface damage produced by freezing. However, pretreatment at 70 °C/2 min caused partial destruction of the epidermic tissue and plasmolysis of the parenchymatic cells. After freezing, the cell walls in the parenchymatic tissue of the fruits pretreated with 100 m M CaCl₂ exhibited swelling as a result of gelling of the cell-wall pectic material. Thermal pretreatments increased the ethylenediaminetetraacetic acid (EDTA)-soluble pectin fraction and reduced the degree of pectin esterification. Thermal treatments at 70 °C, without immersion in calcium, reduced the water- and pectinase-soluble pectin fractions, whereas immersion in calcium prevented depolymerization of these fractions. Immersion in 100 m M CaCl₂ increased the water-soluble pectin fraction.     

Influence of Blanching-osmotic Dehydration Treatments on Volatile Fraction of Strawberries

ABSTRACT: The effects of steam (S) and microwave (MW) blanching and osmotic treatments, applied either singularly or combined, on the volatile fraction of strawberry have been evaluated. Osmotic dehydration was carried out at atmospheric conditions (OD) and by applying a vacuum pulse at the beginning of the process (PVOD). Volatiles were obtained by a simultaneous distillation-extraction procedure and identified/quantified by gas chromatography-mass spectrometry. Esters and 2,5-dimethyl-4-hydroxy-3(2H)-furanone were the major compounds. Differences in volatile concentration promoted by blanching and/or osmotic processes were evaluated. Osmotic treatments promote formation of esters and furanones, differently for either OD or PVOD treatments, but this effect was greatly inhibited when osmosis was preceded by blanching. The kind of blanching (MW or S) also affected the sample final volatile profile.     

采后氯化钙处理对红树莓保鲜的影响

以红树莓为试材,研究了1%、2%和4%的氯化钙(CaCl₂)处理对采后低温(0℃)贮藏下红树莓果实品质影响。结果表明:1%和2% CaCl₂处理均可降低果实在贮藏期间的呼吸强度,减缓果实硬度、可滴定酸(titritable acidity,TA)含量、可溶性固形物(total soluble solids,TSS)含量、维生素C(vitamin C,V_C)含量、总酚含量的下降与丙二醛(malondialdehyde,MDA)含量的上升,抑制果实多酚氧化酶(polyphenol oxidase,PPO)的活性,同时提高过氧化物酶(peroxidase,POD)活性及过氧化氢酶(catalase,CAT)活性,而4% CaCl₂处理则有相反结果。因此,适宜浓度的CaCl₂处理可以有效维持采后红树莓果实的贮藏品质,以2% CaCl₂处理效果最佳。     

Effects of Vacuum Impregnation with Calcium Lactate and Pectin Methylesterase on Quality Attributes and Chelate-Soluble Pectin Morphology of Fresh-Cut Papayas

Vacuum impregnation was used to improve the quality attributes of fresh-cut papayas. Vacuum pressure of 5 kPa was applied for 5 min, then calcium lactate (1%, w/w) and pectin methylesterase (PME) (15 U/ml), alone and in combinations (calcium lactate plus PME), were vacuum impregnated into fresh-cut papaya cubes. Papaya cubes were stored at 4 °C, and the quality of fresh-cut papaya was studied at intervals for 8 days. The hardness and chewiness levels of fresh-cut papayas that were treated with calcium lactate and PME were 8.02 and 7.83 times of untreated fresh-cut papayas at day 8, respectively. After vacuum impregnation, colour of fresh-cut papayas changed significantly (P < 0.05) and an overall weight loss was observed as well. Chelate-soluble pectin (CSP) was extracted and its content correlated well with texture properties of fresh-cut papayas. Qualitative and quantitative analyses of CSP were conducted using atomic force microscopy. The proportion of chain widths greater than 45 nm had increased 35.0% in fresh-cut papayas vacuum impregnated with calcium lactate and PME at the end of storage. The results indicate that a combination of calcium ions and PME was able to maximally preserve the quality attributes of fresh-cut papayas and extend the shelf life.     

三种黑莓果酱的研制与感官评价

以黑莓果实为主要原料,通过对组织形态和涂抹性进行考察,确定了黑莓低糖果酱的最佳果胶用量为0.35%。并通过喜好度测试和描述型测试,分别对三种不同配方的黑莓高糖、低糖和保健果酱的整体风味和色泽、组织形态、口感等风味参数进行了评价,结果显示,通过不同配方制成的三种黑莓果酱是可行的,其中黑莓低糖果酱的风味评分和接受度均为最高。     

超高压与重组果胶甲酯酶抑制剂联合应用对鲜榨橙汁果胶甲酯酶活性及品质的影响

为了探究超高压与重组果胶甲酯酶抑制剂(recombinant pectin methylesterase inhibitor,rPMEI)联合处理对鲜榨橙汁中果胶甲酯酶(pectin methylesterase,PME)活性及品质的影响,研究了超高压(400、500和600 MPa,5 min,20 ℃)与重组果胶甲酯酶抑制剂对橙汁微生物、PME酶活、色泽和V_C含量的影响。结果表明:超高压处理条件为500 MPa/5 min,rPMEI添加浓度为0.06 mg/mL时,橙汁中的菌落总数、霉菌与酵母菌数均能达到农业行业标准《NY/T 434-2016绿色食品、果蔬汁饮料》所规定的要求,同时PME被完全钝化;橙汁色泽变化显著小于热处理组(ΔE^*=1.22<2.26);V_C保留率为85.1%,显著高于热处理组(保留率=8.33%)。     

CaCl2处理对草莓采后品质及灰霉病害的影响

选用CaCl2溶液处理新鲜草莓,研究其对草莓采后品质的影响及对贮期灰霉病的抑制作用.研究结果表明CaCl2处理具有较好地保持采后草莓品质的能力,尤其是经10％浓度CaCl2处理的草莓果实在贮藏期间品质最好.CaCl2处理还可以抑制灰葡萄孢的菌丝生长与孢子萌发,并显著地降低草莓果实贮藏期间灰霉病的发病率,且该抑菌效果与CaCl2使用浓度呈正相关.此外,CaCl2处理会影响草莓果实抗病相关物质的含量.经10％、5％浓度CaC12处理的草莓果实在贮藏早期(1d)其木质素含量和苯丙氨酸解氨酶(PAL)活性均显著地高于对照;而在贮藏中后期(6～12d和9～12d),其过氧化氢酶(CAT)及过氧化物酶(POD)活性也均显著地高于对照.由此可见,CaCl2处理可以诱导采后草莓抗病性相关物质的积累并进而提高草莓果实对于灰霉病的防御能力.     

Edible Active Coatings Based on Pectin,Pullulan, and Chitosan Increase Quality and Shelf Life of Strawberries (Fragaria ananassa)

Edible active coatings (EACs) based on pectin, pullulan, and chitosan incorporated with sodium benzoate and potassium sorbate were employed to improve the quality and shelf life of strawberries. Fruits were washed, disinfected, coated by dipping, packed, and stored at 4 °C for 15 d. Application of EACs reduced (P < 0.05) weight loss and fruit softening and delayed alteration of color (redness) and total soluble solids content. In contrast, pH and titratable acidity were not affected (P > 0.05) throughout storage, and ascorbic acid content was maintained in pectin‐EAC coated strawberries. Microbiological analyses showed that application of EACs reduced (P < 0.05) microbial growth (total aerobic counts, molds, and yeasts) on strawberries. Chitosan‐EAC coated strawberries presented the best results in microbial growth assays. Sensory quality (color, flavor, texture, and acceptance) improved and decay rate decreased (P < 0.05) in pectin‐EAC, pullulan‐EAC, and chitosan‐EAC coated strawberries. In conclusion, EACs based on polysaccharides improved the physicochemical, microbiological, and sensory characteristics, increasing the shelf life of strawberries from 6 (control) to 15 d (coated fruits).     

Kinetics of Tomato Pectin Methylesterase Inactivation by Temperature and High Pressure

ABSTRACT: In this study we investigated the inactivation of endogenous pectin methylesterase (PME) in tomato juice during combined high-hydrostatic pressure (ambient to 800 MPa) and moderate temperature (60 to 75 °C) treatments under isobaric and isothermal processing conditions. PME inactivation rates increased with increasing processing temperature, with the highest rate obtained during processing at 75 °C and ambient pressure. Inactivation rates were dramatically reduced as soon as processing pressure was raised. High inactivation rates were again attained when processing pressure exceeded a value of about 700 MPa. Such a behavior was described by considering two parallel mechanisms of inactivation, each one following first order kinetics with its own kinetic parameters.     

不同小分子糖渗透草莓的传质动力学及对真空冷冻干燥草莓品质的影响

为系统地了解不同小分子糖特别是低聚糖和糖醇对草莓的渗透行为以及不同小分子糖对真空冷冻干燥草莓品质的影响,本研究利用两种数学模型对10 种常见小分子糖（白利度为40 °Brix）的渗透动力学进行拟合,并进一步对渗糖处理后真空冷冻干燥草莓的理化特性进行表征。结果表明,Weibull模型更适用于描述渗糖处理后草莓的可溶性固形物增量（solid gain,SG）,而Peleg模型可以更好地描述草莓的水分去除量（water loss,WL）。经不同糖渗透处理结束后,草莓的SG差异较大,山梨糖醇可以使草莓的SG达到6.84 g/100 g,是低聚异麦芽糖的6.16 倍。此外,渗糖处理的草莓硬度得到普遍提高（94.58%～223.23%）;葡萄糖、果糖、山梨糖醇渗透处理组的脆度分别降低了16.70%、20.74%、41.45%,低聚果糖渗透处理后的草莓质构特性与蔗糖最为接近。综合考虑渗透效率、感官营养品质和生产成本,低聚果糖是蔗糖在果蔬渗透处理方面的一种潜在替代品。     

Mild-Heat and High-Pressure Inactivation of Carrot Pectin Methylesterase: A Kinetic Study

ABSTRACT: Pectin methylesterase (PME) was extracted from carrots and purified by affinity chromatography. The thermal high-pressure inactivation of the PME was investigated in a model system. Under these conditions, the (thermo) stable fraction is not inactivated and the isobaric-isothermal inactivation followed a fractional-conversion model. At lower pressures (< 300 MPa) and higher temperatures (> 50°C), an antagonistic effect of pressure and heat was observed. A 2nd- and 3rd-degree polynomial model (derived from available thermodynamic model) was successfully used to describe the heat pressure dependence of the inactivation rate constants. From the purified carrot PME sample, the thermostable PME fraction was isolated. The thermal inactivation of this fraction followed first-order kinetics.     

Physicochemical,sensorial and rheological characterisation of whole-fat or low-fat milk jams as influenced by calcium chloride,sodium bicarbonate and sucrose content

Rheological properties of sixteen milk jam treatments produced from commercial full-fat (3 g/100 g) and skimmed (0.15 g/100 g) cow milk by the addition of sucrose, sodium bicarbonate and CaCl₂ were examined. pH, titratable acidity, total solids and ash contents in the milk jam samples ranged from 6.2 to 6.8, 1.3 to 3.3 g/100 g, 56.7 to 70.5 g/100 g and 1.7 to 3 g/100 g, respectively, with a significant variability (P < 0.05). The flow behaviour and consistency indices ranged from 0.7 to 0.9 and 2.7 to 208 Pa.sn, respectively. Rheological measurements showed that the maximal G' × 10² value showed considerable variation (5–932 Pa). As sucrose content increased, pH and total solid content increased, whereas ash content and the L value decreased. Also, a negative correlation between pH and L* (lightness) was found (P < 0.05). Dynamic rheology showed that the jam from skimmed milk with full sucrose and without sodium bicarbonate exhibited more solid-like behaviour than the ones prepared with full sucrose and with sodium bicarbonate. In conclusion, the increase in milk fat caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of quality milk jam.     

壳聚糖复合膜的制备及其在草莓保鲜中的应用

制备壳聚糖复合膜,并对壳聚糖复合膜最佳成膜条件进行研究。然后将制的壳聚糖复合膜用于草莓保鲜。结果表明,壳聚糖复合膜最佳成膜条件为,壳聚糖的浓度应该为1.0%～1.5%,添加2%葡萄糖。使用涂膜低温保鲜后,6 d时草莓的失水率为6.42%、VC减少25.8 mg/kg、总酸减少0.74 mg/kg,草莓的总体感官评价较好。     

光量子对草莓保鲜效果及草莓内部结构的影响

为探索光量子在低温条件下对草莓的保鲜效果,以"红天日本99"草莓为材料,分别置于普通保鲜箱和光量子场保鲜箱中,研究光量子辐照对草莓在0℃和-3℃、14 d贮藏期间果实主要品质指标和内部结构变化的影响。结果表明:0℃、-3℃条件下,光量子辐照均降低了草莓果实失重率、腐烂指数,延缓了果实可滴定酸、可溶性糖、可溶性固形物和Vc质量分数的下降,其中-3℃光量子处理组可保持草莓果实内部结构的完整性,且保鲜效果明显好于0℃光量子处理组。无光量子时,0℃条件的保鲜效果好于-3℃条件。上述结果表明:光量子辐照在草莓果实保鲜中具潜在的应用前景。     

果蔬加工中果胶甲基酯酶活性抑制的研究进展

果胶甲基酯酶（pectin methylesterase,PME）是一种广泛存在于高等植物、真菌和细菌的果胶降解酶,其残余活性会导致果蔬汁和鲜切果蔬等产品产生分层沉淀、析水结块、质构软化等品质劣变。因此,在果蔬加工过程中实现对PME活性的有效抑制是加工的重要目的。目前生产中对于PME活性的抑制主要以热加工方式为主,但这会对热敏性果蔬产品品质造成不可逆转的不良影响。随着人们生活水平和健康意识的提高,为了满足人们对更高品质产品的追求,一些新型热加工和非热加工技术以及PME抑制剂逐渐被研究并应用于PME活性的抑制。本文综述当前热、非热加工方式和抑制剂对于PME的抑制效果及其机理,并列举不同加工方式联合处理或加工手段与抑制剂联合处理在PME抑制方面的应用情况,以期为未来更高品质果蔬产品的加工提供理论指导。     

Study of the Influence of Osmotic Dehydration and Freezing on the Volatile Profile of Strawberries

ABSTRACT: The effect of osmotic process conditions on the volatile fraction of strawberries was studied, as well as the effect of freezing and frozen storage. Osmotic treatments were carried out on strawberries in sucrose solutions up to 20 °Brix, at atmospheric pressure (OD), and by applying a vacuum pulse (PVOD). Volatile compounds of fresh, dehydrated, and frozen-stored (at –18 °C for 1 mo) samples were obtained by simultaneous distillation-extraction. Osmotic treatments caused an increase in ester concentration and, in some cases, in furaneol less marked in PVOD. Freezing implied losses in all components, although in pre-dehydrated samples the concentration of some esters (and furaneol) remained greater than in the fresh samples.     

果胶甲酯酶抑制剂的异源表达及其在果酒降甲醇中的应用

该文从猕猴桃中克隆出果胶甲酯酶抑制剂（Pectin Methylesterase Inhibitor,PMEI）基因,经EcoRⅠ/XbaI双酶切后连接到表达载体pPICzαA上,电转化到毕赤酵母GS115筛选出阳性菌株GS115/pPICzαA-PMEI,并将重组酵母表达的PMEI浓缩纯化后应用于果酒发酵。研究结果表明：重组毕赤酵母表达菌株GS115/pPICzαA-PMEI成功构建,PMEI的发酵表达量为35.38 mg/L。将PMEI应用到果酒发酵中,桔子酒甲醇降低47.54%,含量由189.75 mg/L降低到99.55 mg/L;苹果酒甲醇降低21.52%,含量由118.15 mg/L降低到91.20 mg/L;葡萄酒甲醇变化不显著,含量均低于20.00 mg/L,表明PMEI对果胶丰富且内源性果胶酶强的桔子具有明显的降甲醇效果。桔子酒发酵工艺优化的PMEI最低抑制质量浓度8.84 mg/L,最适温度18 ℃,此时桔子酒中的甲醇降低66.40%到89.10 mg/L。这为低甲醇果酒的发酵提供了新的技术路线。