043: What Is the Just Noticeable Difference for Overrun in Ice Cream?

Introduction

Overrun (OR) measures the amount of air incorporated into ice cream during freezing. The level of OR in ice cream influences both physical and sensory properties. The JND of a product is the smallest change in a specific attribute that consumers can systematically detect. While JND has been used in other foods, this technique has not been applied to assess OR in frozen desserts. Here, we determine the JND of OR in ice cream, ranging from ~23% to 105% OR. Also, we assessed numerous physical properties in an attempt to correlate JND with physical changes.

Methods

Ice cream mix, with ~15% fat and ~42% solids, was frozen in a continuous freezer at set target OR, packaged in 4-ounce containers, and hardened at -25°C. Prior to testing, samples were tempered at -18°C for three days. Physical properties assessed included hardness, drip-through rate, fat particle size, and turbidity. JND was assessed using a two-alternative forced choice test (2-AFC), which included 291 participants. Specifically, participants were given a pair of samples (test and reference) and asked to identify which was more airy/fluffy. JNDs and Weber Ratios (WR) were calculated using group data. All data were collected in Compusense20; 90-second breaks were enforced between pairs.

Results

Drip-through rate and hardness decreased with increasing overrun, while fat particle size (d43) increased due to the formation of larger fat particles at higher overruns (65%-105%). Based on physical data, samples were categorized into groups of low OR (23% to 55%) and high OR (65% to 105%). Sensory testing analysis revealed the just noticeable difference (JND) in overrun increased with OR in reference samples as expected; a mean Weber Ratio of 0.35 (±0.07) was observed, meaning ice cream with an OR of ~42% could move up or down ~11% of OR before consumers notice. Additional experiments are planned to assess the impact of emulsifiers and other compositional variables on the JND of ice cream.

Significance

The findings demonstrated the successful application of the JND concept to ice cream in the OR. In addition, there appears to be a clear distinction in the physical attributes of “low” and “high” overrun samples.

Authors: Nhu Pham, Robert F. Roberts, John E. Hayes, Gregory R. Ziegler