Abstract

The incorporation of red raspberries in bakery and dairy products is limited due to the fragility of the berries. This compromises the appearance of the food product due to the bleeding of juice caused by tissue rupture. In this study, we developed vacuum-impregnated dehydrofrozen red raspberries from fresh fruit. Initially, we optimized drying and freezing conditions for red raspberries that were not vacuum impregnated using air drying alone and in combination with osmotic dehydration, followed by air blasting and cryogenic freezing methods. Later, optimal conditions of partial drying and freezing were used for raspberries that were vacuum impregnated with low methoxyl pectin (LMP) at 10 g of pectin kg⁻¹ of solution and calcium chloride (CaCl₂ · 2H₂O) at 30 g of calcium kg⁻¹ of pectin. Conditions for the vacuum impregnation of raspberries were based on our previous research. The berries were partially dehydrated using hot air (65 °C) until a final water content of 0.65 g of water g⁻¹ of fruit was reached. Next, the berries were placed in glass jars, sealed, and cooled at 4 °C for 2 h. They were then frozen by air blasting and stored for 2 months at −35 °C prior to evaluation. The mechanical properties of the berries, including the maximum force (F_M) and gradient (G_C), were considered to be suitable indicators of fruit firmness. Results demonstrate that raspberries impregnated with pectin and calcium and then partially dried and frozen have higher F_M and G_C values than commercially frozen-thawed berries. These dehydrofrozen raspberries show improved structural integrity for use in bakery and dairy products.

摘要

由于浆果的脆性，红树莓在烘焙和乳制品中的加入受到限制。由于组织破裂导致汁液渗出，这会损害食品的外观。在这项研究中，我们从新鲜水果中开发了真空浸渍的脱氢冷冻红树莓。最初，我们优化了未真空浸渍的红树莓的干燥和冷冻条件，单独使用空气干燥并结合渗透脱水，然后是鼓风和低温冷冻方法。随后，采用部分干燥和冷冻的最佳条件，将低甲氧基果胶 (LMP) 以 10 g 果胶 kg ^-1溶液和氯化钙 (CaCl ₂ · 2H ₂O) 30 克钙 kg ^-1果胶。覆盆子真空浸渍的条件基于我们之前的研究。使用热空气（65°C）对浆果进行部分脱水，直到最终水含量达到 0.65 g 的水 g ^-1水果。接下来，将浆果放入玻璃罐中，密封并在 4°C 下冷却 2 小时。然后将它们通过鼓风冷冻并在评估前在 -35°C 下储存 2 个月。浆果的机械特性，包括最大力( F _M ) 和梯度 ( G _C )，被认为是水果硬度的合适指标。结果表明，用果胶和钙浸渍，然后部分干燥和冷冻的覆盆子具有更高的F _M和G _C值高于商业冻融浆果。这些脱氢冷冻覆盆子在烘焙和乳制品中显示出改进的结构完整性。