Calcium impregnation during isochoric cold storage to improve postharvest preservation of fresh blueberries

Authors: Bilbao-Sainz, Cristina; MILLE, ANGELE - US Department Of Agriculture (USDA); Chiou, Bor-Sen; Takeoka, Gary; RUBINSKY, BORIS - University Of California Berkeley; McHugh, Tara

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2024
Publication Date: 2/14/2024
Citation: Bilbao-Sainz, C., Mille, A., Chiou, B., Takeoka, G.R., Rubinsky, B., McHugh, T.H. 2024. Calcium impregnation during isochoric cold storage to improve postharvest preservation of fresh blueberries. Postharvest Biology and Technology. 211,112841. https://doi.org/10.1016/j.postharvbio.2024.112841.
DOI: https://doi.org/10.1016/j.postharvbio.2024.112841

Interpretive Summary: Blueberries are a very popular fruit due to their sensory properties, such as color, flavor, juiciness, and texture, as well as their content of powerful antioxidants with recognized health benefits. Blueberries are often consumed fresh. However, compared to other fruits, fresh blueberries are highly perishable. Retention of nutritional value and freshness of blueberries as well as reducing food waste are major challenges for the food industry. The main objective of this study was to assess the effectiveness of isochoric impregnation with CaCl2 on the quality of blueberries during isochoric cold storage at -2.5 °C and refrigerated storage at 5 °C. This study showed the possibility of using isochoric cold storage with calcium impregnation to develop ready-to-eat fresh blueberries with higher nutrient content and extended shelf-life. Isochoric cold storage of blueberries impregnated with 1 % calcium chloride exhibited the most favorable preservation benefits. After 4 weeks, blueberries had similar appearance to fresh blueberries. Blueberries also gained 3.4 % weight and 23 % firmness. In addition, the blueberries showed higher nutrient content than refrigerated blueberries. Isochoric cold storage for one week with 1 % calcium chloride and subsequent refrigeration at 5 °C reduced the microbial load and improved the mechanical properties of blueberries. After 4 weeks of storage, the blueberries showed no signs of wilting and had only 1 % weight loss, compared with 20 % weight loss for non-impregnated samples. Impregnated samples also had higher nutrient content than non-impregnated samples.

Technical Abstract: Isochoric cold storage can be used to extend the shelf-life of fresh produce by delaying senescence through storage at subfreezing temperatures as well as hinder microbial growth with pressure. The effect of isochoric impregnation with CaCl2 on qualitative parameters of blueberries during isochoric cold storage at -2.5 °C and refrigerated storage at 5 °C for four weeks was investigated in this study. The results showed the synergistic effect of calcium impregnation and isochoric cold storage on the quality of blueberries. Isochoric impregnated blueberries better retained their weight, had better mechanical properties and had higher nutrient contents (anthocyanins, total phenolics and antioxidant capacity) than non-impregnated blueberries refrigerated at 5 °C. The benefits of isochoric impregnation with CaCl2 were greater for samples stored under isochoric conditions than under refrigerated conditions. However, the impregnated refrigerated samples still had better quality properties than non-impregnated refrigerated samples. Furthermore, panelists found no significant differences in preference for any of the sensory attributes between fresh blueberries and impregnated blueberries. Also, isochoric cold storage inhibited the growth of mesophilic aerobic bacteria, yeasts and molds under isochoric and refrigerated storage conditions.