Frozen food risk: The unfrozen water inside
With all food, texture and taste is important; we like our vegetables crisp, our fruits juicy and sweet, and our ice cream creamy. In frozen foods, texture and taste, along with other attributes like color and nutrient levels, are impacted by the amount of water in the food and the rate at which that water was frozen. Many people are not aware that even when food is frozen it still contains some liquid water due to the sugars and minerals that lower the water’s freezing temperature. “For example, 7 to 10% of the water in frozen meats remains in a liquid state even when storage temperatures are as low as -40° Celsius,” says Dr. Dennis Heldman, Endowed Professor of Food Engineering at The Ohio State University.
Any increase in temperature will increase the amount of unfrozen water in food, a phenomenon known as micro-thawing. Conversely, any decrease in temperature will freeze some of that water, known as micro-freezing. Cycles of micro-thawing and micro-freezing will negatively impact food’s texture because refreezing at a slower rate creates larger ice crystals that damage the structure of our food, creating soggy vegetables and sandy ice cream and reduces the food’s shelf-life. This slow refreezing also degrades the food’s flavor, color, and nutrient levels.
Preventing the formation of large ice crystals from micro-thawing and micro-freezing can only be achieved through ensuring temperature stability throughout the cold chain beginning immediately after food is initially frozen. Many will agree, however, that maintaining temperature stability is often easier said than done. Temperature stability in a freezer can be affected by a variety of factors, including heat infiltration from traffic in and out of storage areas, outdoor ambient temperature, the condition of the building, and even energy prices. Cold storage facilities maintain the highest energy demand of any industrial load per cubic foot and energy costs are their second highest expense. In markets with peak-demand pricing, these peak charges can comprise up to 70 percent of a facility’s electricity bill. To help reduce these burdensome costs, operators and grocers sometimes shut off equipment during peak periods to mi nimize energy consumption. Commonly known as ‘fly-wheeling’ or ‘floating’, this practice can inadvertently cause temperature fluctuations that could induce a cycle of micro-thawing and micro-freezing.
It IS possible to balance the competing demands of better temperature stability and lower energy costs, however. Thermal energy storage (TES) for walk-in freezers and low-temperature warehouses can act as a heat sink, helping cold storage operators and grocers reduce their energy consumption without risking food quality or shelf life. Viking Cold Solutions’ TES systems use food-safe phase change material (PCM) that is frozen during hours with lower energy costs using a cold storage facility’s existing refrigeration equipment. During higher cost hours, the refrigeration equipment can be safely cycled off for extended periods of time, and the PCM maintains stable temperatures by absorbing up to 85 percent of all heat infiltration in the freezer. The PCM ensures temperature stability, food quality and shelf life, and low energy consumption.
Viking Cold Solutions’ TES systems also include an intelligent controls system and 24/7 remote monitoring, notification and reporting software. These provide cold storage operators and grocers with an intelligent, cost effective way to balance temperature stability and energy expenses plus a higher degree of visibility into their operations. With real-time data for temperatures, refrigeration equipment status, and energy consumption, operations can make better decisions, reduce energy costs, and better protect food.
Delivering high quality food is of the utmost importance to cold storage operators, grocers, and their customers, and the best way to assure frozen food quality is through stable temperatures to minimize micro-freezing and micro-thawing. Thanks to thermal energy storage, the cold chain no longer has to risk temperature stability and food quality to achieve lower energy costs and better profits