Peyronel Fernanda, Campos Rodrigo, Marangoni Alejandro G
Department of Food Science, University of Guelph, Guelph, ON, Canada.
Mars Chocolate North America, Hackettston, NJ, USA.
Food Res Int. 2016 Oct;88(Pt A):52-60. doi: 10.1016/j.foodres.2016.04.001. Epub 2016 Apr 16.
Oil loss is a common problem in high oil volume fraction fat-structured foods, where trans fatty acids are absent and saturated fatty acids minimized. Usually a stabilizer "fat", rich in behenic and stearic acids is added to these products. This stabilizer significantly reduces oil migration and loss; however, the mechanism by which it exerts its effect is not known. Here we study the structure and oil loss characteristics of blends of palm mid fraction (PMF) and palm olein (PO) mixed with a commercial stabilizer of fully hydrogenated cottonseed and rapeseed oils added at 1.25, 3.5, and 7% (w/w) levels. The addition of as little as 1.25% stabilizer reduced oil migration from 13% to ~2% for the 80:20 PMF/PO blend and from 29% to ~3.5% for 20:80 PMF/PO blend after 14days of storage at 20°C, as judged from a filter paper assay. Polarized light microscopy results demonstrated that addition of stabilizer decreased fat crystal size and lead to the formation of a denser network with smaller pores. The rate of crystallization, determined by monitoring increases in solid fat content as function of time by pulsed NMR, increased upon addition of the stabilizer as indicated by decreases in the half-time of crystallization. Addition of stabilizer lead to an increase in the mechanical strength of the material, as indicated by increases in breaking force. Differential scanning calorimetry showed the formation of a new fraction, intermediate between the high melting fractions in both PMF and PO and the stabilizer upon incorporation of the stabilizer in the blends. We hypothesize that the stabilizer helps the formation of this new fraction which has a higher nucleation rate and thus forms a denser network of small crystals with an improved ability to bind and retain oil.
在不含反式脂肪酸且饱和脂肪酸含量降至最低的高油体积分数脂肪结构食品中，油脂损失是一个常见问题。通常会向这些产品中添加一种富含山嵛酸和硬脂酸的稳定剂“脂肪”。这种稳定剂能显著减少油脂迁移和损失；然而，其发挥作用的机制尚不清楚。在此，我们研究了棕榈中间 fraction（PMF）和棕榈油精（PO）的混合物与添加了1.25%、3.5%和7%（w/w）水平的全氢化棉籽油和菜籽油商业稳定剂的结构及油脂损失特性。通过滤纸试验判断，在20°C储存14天后，对于80:20的PMF/PO混合物，添加低至1.25%的稳定剂可使油脂迁移率从13%降至约2%，对于20:80的PMF/PO混合物，可从29%降至约3.5%。偏光显微镜结果表明，添加稳定剂会减小脂肪晶体尺寸，并导致形成孔隙更小的更致密网络。通过脉冲核磁共振监测固体脂肪含量随时间的增加来确定结晶速率，结果表明添加稳定剂后结晶速率增加，表现为结晶半衰期缩短。添加稳定剂导致材料的机械强度增加，表现为断裂力增加。差示扫描量热法显示，在混合物中加入稳定剂后形成了一个新的组分，介于PMF和PO中的高熔点组分与稳定剂之间。我们推测，稳定剂有助于形成这种具有更高成核速率的新组分，从而形成一个更致密的小晶体网络，具有更好的结合和保留油脂的能力。
