pH对高能量密度全营养配方乳剂食品稳定性的影响

Effects of pH on the stability of high-energy density total nutrient formula emulsion foods

中文关键词:  pH  高能量密度  全营养配方食品  乳剂  稳定性

英文关键词:pH  high-energy density  total nutrient formula food  emulsion  stability

中文摘要:

      目的 分析不同pH高能量密度全营养配方乳剂食品的理化性质、物理稳定性与流变学特性及其在贮藏过程中的变化规律, 并探讨pH对其品质稳定性的影响。方法 鉴于肠内营养制剂接近中性更符合人体肠胃耐受性, 分别制备pH为6.90、7.00、7.10、7.20、7.30且能量密度为2.0 kcal/mL的全营养配方乳剂食品, 以离心沉淀率、粒径及其分布、Zeta电位、动力学不稳定性指数(turbiscan stability index, TSI)、流变学特性、色度、感官评分及电子舌信息为评价指标, 并结合短期贮藏测试, 研究pH对高能量密度全营养配方乳剂食品稳定性的影响。结果 在pH 6.90~7.30范围内, 乳剂的离心沉淀率、平均粒径先减小后增大, 在pH 7.10时最小, 各组乳剂粒径分布均呈单峰, 粒径范围为0.1~5.0 μm; 乳剂的Zeta电位绝对值均处于36~37 mV, 组间无显著差异(P>0.05); TSI逐渐增大, 在pH 6.90时最小; 表观黏度逐渐减小, 各组均呈剪切稀化的假塑性流体特性; 乳剂色度a*、b*逐渐增大, L*、E*逐渐减小; 感官评价和电子舌分析结果表明, pH 7.10的乳剂评分最高、味感最好。在28 d的贮藏期内, 随贮藏时间延长, 粒径分布均向大粒径方向偏移, pH 6.90和pH 7.30的乳剂在贮藏后期出现双峰; 微观形貌显示大颗粒片段逐渐增多。结论 pH对高能量密度全营养配方乳剂食品的稳定性影响显著, pH为7.10的乳剂具有较小的平均粒径、离心沉淀率和TSI, 适中的黏度, 感官评分最高, 短期贮藏期间粒径分布变化较小, 体系均匀、稳定性较好。本研究可为提升高能量密度全营养配方乳剂食品的稳定性提供参考。

英文摘要:

      Objective To investigate the effects of pH on high-energy density total nutrient formula emulsion foods stability by analyzing the physicochemical properties, physical stability, rheological characteristics and changes during storage. Methods Based on near-neutral enteral nutritional preparations could better ensure human gastrointestinal tolerance, total nutrient formula emulsion foods with energy density of 2.0 kcal/mL in pH of 6.90, 7.00, 7.10, 7.20 and 7.30 were prepared respectively. The stability of emulsions were assessed in terms of such evaluation indexes as centrifugal sedimentation rate, particle size distribution, Zeta potential, turbiscan stability index (TSI), steady-shear rheological properties, chromaticity, sensory scores and electronic tongue information. Combined with short-term storage tests, the effects of pH on the stability of high-energy density total nutrient formula emulsion was studied. Results The results showed that in the pH range of 6.90–7.30, the centrifugal sedimentation rate and average particle size of the emulsions decreased initially and then increased, reaching a minimum respectively at pH 7.10. All particle size distributions appeared as a unimodal curve accompanied by particle size ranged from 0.1 to 5.0 μm. The absolute values of Zeta potential were between 36-37 mV with no significant difference among emulsion samples (P>0.05). The TSI was minimum at pH 6.90 and gradually increased with the increase of pH. Apparent viscosity decreased with the increase of pH, showing a shear-thinning pseudoplastic flow behavior. The chromaticity results showed that both a* and b* increased gradually, while L* and E* decreased gradually. Sensory evaluation and electronic tongue analysis showed that the emulsion at pH 7.10 had the highest score and the best taste. During the 28 day storage period, with the increase of storage time, the particle size distribution peak of all emulsions moved towards the larger particle size direction and double peaks appeared in the particle size distribution of the emulsions at pH 6.90 and pH 7.30. The microscopic morphology also indicated the large particle fragments increased gradually. Conclusion The stability of high-energy density total nutrient formula emulsion foods is significantly influenced by pH, emulsion at pH of 7.10 gets a small average particle size, low centrifugal sedimentation rate and TSI, as well as moderate viscosity, highest sensory score, little change in particle size distribution during short-term storage, making it a uniform system and keeping it good stability. This study provides a reference to improve the stability of high-energy density total nutrient formula emulsion foods.