Pulsed light treatment of packaged pistachio seeds: impact on microbiological and quality parameters with storage

Pistachios (Pistacia vera L.) are susceptible to microbial contamination, causing quality and safety issues. Heat treatments of pistachio provide effective reduction on microbial load, but they also cause undesirable changes in quality properties. Thus, this study explored pulsed light (PL) application to improve pistachio seeds safety and quality. PL treatment (10-30-60 s) of packaged pistachios (varying pistachio layer thickness) reduced bacterial counts, particularly at 30–60 s in monolayer samples, but had limited effect on yeasts and molds. PL did not significantly affect moisture, chlorophylls or color parameters. Total acidity increased significantly in samples treated for 30 and 60 s, reaching values in the range of 4.69–5.67 g/kg. However, after 12 months of storage, no significant differences were observed between treated and untreated samples. PL treated samples, after 12 months of storage, showed lower peroxide values (ranging from 1.99 to 6.78 meq O2/kg) than the untreated ones (18.39 meq O2/kg), indicating a protective effect against lipid oxidation. Total phenolic content increased in stored samples of about 1.44 and 1.73 fold, in untreated and treated pistachios respectively, suggesting defense activation. PL improved microbial safety without compromising quality also after long storage, demonstrating its potential as a non-thermal pistachio processing method.