Assessing the impact of isochoric freezing as a preservation method on the quality attributes of orange juice

Authors: Atci, Sumeyye; MCGRAW, VALERIE - US Department Of Agriculture (USDA); Takeoka, Gary; Wu, Vivian; McHugh, Tara; RUBINSKY, BORIS - University Of California Berkeley; Bilbao-Sainz, Cristina

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2024
Publication Date: 6/13/2024
Citation: Atci, S., Mcgraw, V.S., Takeoka, G.R., Wu, V.C., Mchugh, T.H., Rubinsky, B., Bilbao-Sainz, C. 2024. Assessing the impact of isochoric freezing as a preservation method on the quality attributes of orange juice. Journal of Food Science. 89(6):3167-3182. https://doi.org/10.1111/1750-3841.17071.
DOI: https://doi.org/10.1111/1750-3841.17071

Interpretive Summary: Orange juice (OJ) is one of the most popular fruit juices and is highly consumed worldwide. Recent trends indicate consumer preference for fresh squeezed OJ due to its superior taste, aroma, and nutritional qualities. Although fresh squeezed has a relatively short shelf life compared to thermally treated OJ, it avoids irreversible losses of nutritional quality and sensory attributes that are a consequence of heat treatment. In this study, the effect of isochoric freezing (IF) as an alternative to heat treatment or conventional freezing on microbial load and quality attributes were investigated. Microbial count immediately following all treatments were below the detection limit, with microbial count increasing only for untreated control after one week of storage at 4 °C. However, IF treatments caused less color difference and less pulp sedimentation compared to heat treatment. Furthermore, an increase in vitamin C content was observed following IF treatments. The findings demonstrate that IF treatment retains color and nutritional value and reduces precipitation in OJ, indicating that IF treatment has the potential to improve OJ quality.

Technical Abstract: Isochoric (constant volume) freezing is a novel food preservation technology that has demonstrated the ability to preserve food products at subfreezing temperatures in an unfrozen state, thereby avoiding the detrimental effects of ice formation. It minimizes the quality loss of fresh fruits and juices, increases their nutrient content, and reduces microbial counts. In this study, orange juice (OJ) samples were subjected to conventional isobaric (constant atmospheric pressure) freezing (CF) and isochoric freezing (IF) for 7 days and then stored at 4 °C for an additional 7 days. We evaluated the microbiological and physicochemical quality of CF and IF OJ before and after storage, comparing them with fresh OJ, fresh OJ stored for seven days at 4 °C, heat-treated OJ, and heat-treated OJ stored for seven days at 4 ºC. The IF was performed at three different conditions: -5 °C/73 MPa, -10 °C/93 MPa, and -15 °C/143 MPa. The results indicate that the total aerobic count of OJ remained below the detection limit after heat treatment, 7 days of CF and 7 days of IF. Yeast and mold counts increased in fresh and CF OJ after 7 days of storage at 4 °C, while IF OJ remained below the detection limit. IF OJ exhibited similar color and viscosity values to fresh OJ. Furthermore, heat treatment inactivated 42% of pectin methylesterase (PME), whereas 7-day long IF at -5 °C/73 MPa and -15 °C/143 MPa increased PME activity by 150% and 130%, respectively. The increased PME activity in IF samples might result in less intense cloudiness. Additionally, IF OJ showed reduced pulp sedimentation, which can be advantageous, as sedimentation in juices has been a recognized technological issue in the juice industry. Ascorbic acid (AA) levels were significantly higher in IF (-10 °C/93 MPa and -15 °C/143 MPa) OJ (p < 0.05). Although some degradation of AA was observed after storage, IF (-15 °C/143 MPa) OJ retained the highest values.