D2.303 - The effect of extrusion on the in vivo allergenicity of pistachio and walnut in allergic children

Extrusion has been reported as a method that might reduce protein allergenicity. The aim of this study was to investigate the effect of extrusion on the in vivo allergenicity of pistachio and walnut.

Eight children (5 boys), aged 4–18 years, with confirmed IgE-mediated allergy to pistachio (n=5) or walnut (n=3) participated. Skin prick tests (SPTs) were performed using pistachio (P) and walnut (W) preparations at logarithmic dilutions (1:10, 1:100, 1:1000). Three nut concentrations [30% (H), 3% (M), 0.3% (L)] and three extrusion temperatures (40°C, 100°C, 140°C) were tested against raw nut preparations (R). Mean wheal diameters were compared using paired t-tests. Logarithmic dose–response models, multiple linear regression, and curve correlation analysis were also performed. Statistical significance was set at p<0.05.

For pistachio, the extrusion at 140°C resulted in a significant reduction in mean wheal diameter compared with the raw preparation, both in the undiluted samples [PH140: 4.6±3.44 mm (p=0.05), PM140: 4.4±1.34 mm (p=0.01), and PL140: 2.4±1.52 mm (p=0.01) vs PR: 8.2±2.95 mm] and at the 1:10 dilution [PH140: 1.4±2.19 mm (p=0.01) and PM140: 2.4±1.82 mm (p=0.01) vs PR: 5.6±1.34 mm]. The reference curve showed nearly perfect logarithmic behavior for PR [R²=0.9944, sensitivity (a) 0.999, baseline reactivity (b) 0.9]. In 30% preparations, extrusion at 140°C reduced both sensitivity and baseline reactivity (PH40: a=1.303, b=3.6, PH100: a=1.183 and b=4.04, and PH140: a=0.52 and b=1.3). While PH40 and PH100 generated steeper slopes than the reference, the PH140 curve showed a milder incline (Figure 1). Multiple linear regression analysis showed that 68.3% of the the variance in wheal size was attributable to temperature (p=0.011) and dilution (p<0.001). In the correlation analysis, the PR and PH100 curves showed perfect agreement (R=1.00), whereas correlation with PH140 was lower (R=0.85).

For walnut, results were less clear, mainly due to the inconsistent behavior of the reference curve (R²=0.871) and the small sample size.

Extrusion at 140°C appears to significantly reduce the allergenicity of pistachio and represents a promising approach for the development of safer food products. Larger studies are required, particularly for walnut, to draw reliable clinical conclusions.