# Mixing Ratio and Packaging Amount Synergistically Improved Antioxidant Properties of Baby Lettuce (Lactuca sativa L.) and Spinach (Spinacia oleracea L.) Mixes

## TL;DR

Mixing baby lettuce and spinach in specific ratios and packaging amounts helps preserve their antioxidant qualities during storage.

## Contribution

The study reveals a synergistic effect of mixing ratios and packaging amounts on preserving antioxidants in fresh salad mixes.

## Key findings

- A 50% lettuce + 50% spinach mix with 250 g packaging preserved higher antioxidant capacity, phenolics, and vitamin C.
- Lower oxygen and higher carbon dioxide levels were observed in the optimal mix and packaging.
- Microbial growth was minimal and did not affect freshness over 9 days of storage.

## Abstract

Fresh baby leaves are commercially marketed in various mixing ratios and packaging amounts, creating very distinct microenvironmental conditions that significantly affect the postharvest quality of the fresh product. This study investigated the synergistic effect of mixing ratio (50LB, 50% lettuce + 50% spinach; 75LB, 75% lettuce + 25% spinach; 100LB, 100% lettuce) and packaging amount (125F, 125 g; 250F, 250 g) on the antioxidant qualities of baby lettuce and spinach mixes during 9 days of storage at 4 °C. The results showed that 50LB × 250F inhibited the degradation of chlorophyll and carotenoids and preserved 28% higher total antioxidant capacity (TAC), 43% higher total phenolic compounds (TPC), and 20% higher vitamin C (Vit.C) than the mean values of all samples, resulting in 0.8% lower O2 and 14.7% higher CO2 levels at the end of storage. TPC, Vit.C, and carotenoids were the main contributors to TAC, with strong correlations (p < 0.001). The total bacterial (TB) and yeast + mold (Y + M) counts were only affected by the mixing ratios, with TB increasing by only 1 Log10 cfu g−1 FW, and Y + M remaining within the same order of magnitude over time. After 9 days of storage, the leaves were still fresh and marketable. This study not only provides a practical strategy for the fresh-cut industry to enhance product quality but also underscores the significance of multifactorial synergism in salad mix packaging.