FDSC 241 Lecture #5 Study Guide

Refrigeration Basics

• Refrigerators for food storage operate at temperatures between 40-45°F, suitable for both home and commercial use.
• Pure water freezes at 32°F, providing a standard reference for temperature.
• Most foods typically freeze around 28°F.

Freezing and Storage

• Optimal frozen storage temperature is 0°F to ensure food safety and quality.
• Freezing is recognized as the gentlest preservation method, maintaining food texture and nutrients.
• Spoilage and pathogenic bacteria can slowly proliferate in refrigeration conditions, emphasizing the importance of correct temperature control.

Refrigeration Requirements

• Controlled low temperature is crucial for effective refrigeration.
• Proper air circulation is necessary to avoid hot spots and ensure even cooling.
• Humidity control is fundamental; excessive humidity leads to condensation, potentially resulting in mold growth.
• Insufficient humidity can cause food items to dry out, compromising freshness.

Key Terms and Measurements

• Specific heat is defined as the mass required to raise the temperature of a substance by 1 degree Celsius, with water having a specific heat of 4.186.
• Respiration rates in food decrease as temperature drops, which can prolong freshness.
• Low temperatures inhibit enzyme activity, which helps to slow spoilage and maintain quality.

Cost and Storage Insights

• Choosing lower storage temperatures can increase operational costs.
• The coldest area in a household refrigerator is typically the bottom drawer, which is ideal for storing perishable items.
• Refrigeration allows for year-round availability of specific foods and stabilizes prices throughout the year.

Humidity and Food Storage

• Air is essential for moving moisture away from food, contributing to better preservation.
• Optimum relative humidity refers to established values for specific foods based on their moisture content.
• Leafy vegetables require a relative humidity of 95%, while nuts require around 70%.
• Common dry goods like powdered milk, sugar, and spices typically need around 60% RH for optimal preservation.