Quality changes in air blast frozen tempe during storage and thawing

Abstract

Tempe is a highly nutritious fermented soybean product with growing global demand. However, its short shelf life limits its export potential, making effective preservation crucial. Freezing using an Air Blast Freezer (ABF) and storage at -19 C is one method to extend shelf life, but its impact on quality over time is not fully understood. This study aimed to evaluate how storage duration and thawing methods affect the physical and sensory quality of ABF-frozen tempe over 12 weeks. Tempe was frozen, stored, and assessed for changes in texture, water activity, and appearance. Sensory evaluations using hedonic and Check-All-That-Apply (CATA) tests were also conducted to determine consumer perception. Results showed that tempe quality declined over time. After 12 weeks, samples had increased water activity, reduced hardness, and a yellow-brown color. Sensory tests indicated a shift toward undesirable traits, such as a bitter taste, alcoholic aroma, and crumbly texture. Thawing at room temperature (25-30oC) for 30 minutes preserved the best quality. In conclusion, ABF freezing can preserve tempe short-term, but quality deteriorates with prolonged storage. To maintain consumer acceptance, storage should be limited to less than 12 weeks, and further improvements in preservation techniques are needed.