摘要
为优化果酱浓缩工艺,分别采用真空浓缩和常压熬煮制备柑橘酱,研究不同浓缩处理果酱的理化指标、色泽、微生物、流变特性及质构特性变化情况。结果显示:与未处理组相比,浓缩处理可显著提高果酱样品的可溶性固形物、总酸、总糖、总酚、总黄酮、总类胡萝卜素及果胶含量。其中,真空浓缩样品的总酚、总黄酮及总类胡萝卜素含量最高,分别为42.93、63.32、36.33 μg/g,且褐变程度较轻,亮度值(
果酱是一种半固体食品,由果肉、蔗糖、柠檬酸和果胶煮沸而成,广泛用于早餐、乳制品、烘焙产品及糖果产品
浓缩工序是果酱加工中关键环节,可有效降低水分活度,提高产品浓度,延长产品货架期。传统的果酱加工多采用常压夹层锅浓缩,其作用温度过高,易造成果酱产品出现色泽不均匀、热敏性营养成分和风味损失严重等品质问题。真空浓缩是近几年广泛应用于果蔬加工的浓缩工艺,具有处理温度低、能有效保留产品的营养成分和风味等优点。研究表明,真空浓缩和常压熬煮对不同果蔬制品的影响不同。陈自
新鲜脐橙:湖北省秭归县屈姑食品有限公司提供。
3M Petrifilm 6406菌落总数测试片、3M Petrifilm 6414大肠菌群测试片、3M Petrifilm 6417霉菌测试片:3M中国有限公司;正己烷、无水乙醇、丙酮、甲醇、氢氧化钠、亚硝酸钠、九水合硝酸铝、无水碳酸钠、福林-酚均为分析纯,国药集团化学试剂有限公司;芦丁标准品、没食子酸标准品均为分析纯,上海源叶生物科技有限公司。
H-400韩派打浆机,中山市韩派电器有限公司;JM系列胶体磨,温州市鹿城精益胶体磨机械厂;C22-IJ59苏泊尔电磁炉,浙江苏泊尔股份有限公司;R-1001VN旋转蒸发仪,郑州长城科工贸有限公司;SHZ-Ⅲ循环水真空泵,上海亚荣生化仪器厂;DR101数显糖度计,北京金科利达仪器;UV-1800紫外-可见分光光度计,日本岛津公司;AR 2000ex流变仪,美国TA公司;台式色差仪,美国HunterLab公司;TA-XT Plus质构仪,英国Stable Micro System公司;SPX-150BⅢ生化培养箱,天津市泰斯特仪器有限公司。
原料挑选→清洗→预处理→打浆→磨浆→调配→浓缩→分装。
操作要点:(1)脐橙果浆:挑选新鲜成熟的脐橙,用自来水洗净沥干,去皮、去籽、去囊衣后,再加1/3鲜果质量的水打浆2 min,再用胶体磨粉碎5 min,得到新鲜脐橙果浆。(2)调配:按果浆和白砂糖质量比为100∶6.3进行调配,以备后续浓缩处理。(3)浓缩:将脐橙果浆分为3组:第一组为未浓缩新鲜果浆;第二组用旋转蒸发仪(真空度90 kPa、温度65 ℃)浓缩果浆至可溶性固形物含量为42%左右;第三组用电磁炉(功率2 000 W)浓缩果浆至可溶性固形物含量为42%左右,以满足低糖类果酱含糖量的要求(25%~50%
可溶性固形物测定:采用数显糖度计测定;pH值测定:采用pH计测定;总糖含量测定:采用直接滴定法,参照GB 5009.8-2016《食品中果糖、葡萄糖、蔗糖、麦芽糖、乳糖的测定》和GB 5009.7-2016《食品中还原糖的测定》;可滴定酸含量测定:采用酸碱中和滴定,以柠檬酸当量
参考Knockaert
参考迟恩忠
参考程怡然
1)柑橘酱的黏度曲线。采用剪切模式,剪切速率范围为0.1~100
2)柑橘酱的触变性。测试条件:剪切速率先从0.1
3)柑橘酱的黏弹性。应变扫描:在1 Hz频率下对样品进行应变扫描,变化范围为0.01%~10%,以确定线性黏弹区。预试验已确定应变振幅为0.2%。频率扫描:采用振荡模式,振荡频率范围为0.01~100 rad/s,记录储能模量(G')和损耗模量(G")随角频率的变化。
参考蒋利
由
处理方式 Treating method | 可溶性固形物/% TSS | pH | 总酸/% Total acid | 总糖/% Total sugar | 总酚/(μg/g) Total polyphenols | 总黄酮/(μg/g) Total flavonoids | 总类胡萝卜素/(μg/g) Total carotenoids | 果胶/ (mg/g) Pectin |
---|---|---|---|---|---|---|---|---|
未处理 Untreated | 7.67±0.15b | 4.20±0.02a | 0.24±0.11b | 1.81±0.06b | 19.56±1.73c | 30.01±1.22c | 12.53±0.85c | 15.23±0.32c |
常压熬煮 Atmospheric boiling | 42.47±1.12a | 4.09±0.07b | 0.70±0.11a | 13.45±0.43a | 35.48±0.43b | 46.44±5.41b | 29.96±0.33b | 25.43±1.22a |
真空浓缩 Vacuum concentration | 41.63±1.26a | 4.02±0.01b | 0.55±0.11ab | 13.37±0.12a | 42.93±1.37a | 63.32±4.14a | 36.33±3.37a | 21.57±0.61b |
注: 同列不同字母表示差异显著(P<0.05)。下同。Note:Different letters at the same column indicate significant differences (P<0.05). The same as below.
由

图1 真空浓缩和常压熬煮对柑橘酱褐变度的影响
Fig. 1 Effect of vacuum concentration and atmospheric boiling on browning degree of citrus jam
由
处理方式 Treating method | ΔE | |||
---|---|---|---|---|
未处理 Untreated | 48.97±0.47b | 1.04±0.08c | 20.03±0.50c | 0 |
常压熬煮Atmospheric boiling | 47.49±0.45c | 7.31±0.20a | 30.30±0.75a | 12.13±0.73a |
真空浓缩Vacuum concentration | 50.11±0.32a | 5.81±0.15b | 28.94±0.48b | 10.18±0.49b |

图2 柑橘酱的外观形态
Fig. 2 Appearance of citrus jam
A:未处理;B:常压熬煮;C:真空浓缩。A: Untreated; B: Atmospheric boiling; C: Vacuum concentration.
由
处理方式 Treating method | 菌落总数 Total plate count | 霉菌 Total mold count | 大肠菌群 Total coliform group |
---|---|---|---|
未处理 Untreated | 5.80±0.20a | 4.31±0.04a | ND |
常压熬煮 Atmosphericboiling | 4.87±0.29b | 2.81±0.21b | ND |
真空浓缩 Vacuum concentration | 5.01±0.04b | 3.20±0.09b | ND |
注: ND表示未检出。Note: “ND” means the parameters could not be detected.
由

图3 真空浓缩和常压熬煮对柑橘酱表观黏度的影响
Fig.3 Effect of vacuum concentration and atmospheric boiling on viscosity of citrus jam
由

图4 真空浓缩和常压熬煮对柑橘酱触变性的影响
Fig. 4 Effect of vacuum concentration and atmospheric boiling on thixotropic diagram of citrus jam
从

图5 真空浓缩和常压熬煮柑橘酱的频率扫描曲线
Fig. 5 Frequency sweep curves of vacuum concentration and atmospheric boiling citrus jam
由
处理方式 Treating method | 硬度/g Hardness | 黏性/(g·s) Adhesiveness | 内聚性/g Cohesiveness | 胶着度/g Gumminess | 咀嚼度/g Chewiness |
---|---|---|---|---|---|
未处理 Untreated | 81.04±7.30c | -28.26±19.62a | 0.64±0.08a | 51.52±1.96b | 42.05±8.12b |
常压熬煮 Atmospheric boiling | 150.43±19.06a | -82.41±9.25b | 0.65±0.04a | 98.68±16.91a | 94.19±17.00a |
真空浓缩 Vacuum concentration | 111.63±16.58b | -41.42±4.56a | 0.58±0.02a | 65.09±9.68b | 59.94±9.68b |
浓缩工艺是果酱生产过程中不可或缺的环节,决定了果酱的凝胶性能及质地的稳定性。本研究结果表明,柑橘原浆中水溶性果胶含量高,达15.23 mg/g,果胶在熬制过程中通过氢键和甲基间的疏水力交联蔗糖分子形成凝胶,使果浆逐渐转变成黏稠的酱状产品。然而果酱的浓缩过程常伴随着褐变反应,包括酶促褐变和非酶促褐变,直接影响产品的色泽和品
柑橘酱是由不溶性固形物和可溶性固形物组成。不溶性固形物包括植物组织颗粒、细胞壁及不溶性大分子聚合物等,其在浓缩过程中呈现热熔状态,内部颗粒结构产生相互作用,对柑橘酱的流变特性具有重要影响。静态剪切试验结果表明,在0.1~100
触变性可表征样品经搅拌或涂抹后的流体稳定性,触变性越低,流体重建凝胶结构的速度越快,体系稳定性越高。在整个剪切速率范围内(0.1~100
弹性模量(G')和损耗模量(G")的大小可用于评判果酱产品的总体强度,可有效反映其内部结构及加工性能。动态流变试验结果表明,在一定频率范围内(0.1~100 rad/s),所有果酱样品的G'和G"随着角频率的增大而稳定上升,且G'>G",表现为弱凝胶特征,与郑炯
质构特性是评价果酱类产品口感的重要指标,能准确反映产品的组织状态,包括硬度、黏性、内聚性、胶着度、咀嚼度等一系列物理性质。一般来说,硬度、黏性、胶着度、咀嚼度可用于预测食品的感官品质。质构试验结果表明,与常压熬煮相比,真空浓缩果酱的硬度、黏性及咀嚼度较小,分别为111.63 g、-41.42 g·s、59.94 g,说明真空浓缩果酱易在口腔中扩散,流动性较好。该结果与流变曲线、触变性的测定结果相互印证,并且与郑亚军
综上所述,真空浓缩技术具有替代传统熬煮浓缩的潜力,能极大程度地保持柑橘酱的营养成分和色泽,使果酱产品具有良好的流变特性及质地。为保证柑橘酱产品安全,进一步提高产品的品质,未来有必要探究杀菌方式对柑橘酱凝胶结构的影响,或结合原子力显微镜研究果酱凝胶的形成过程及凝胶形成机制。
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