Date of Award

Summer 8-15-2025

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

First Committee Advisor

Jennifer Perry

Second Committee Member

Robson Machado

Third Committee Member

Denise Skonberg

Abstract

Wild blueberries (Vaccinium angustifolium Ait. And V. myrtilloides Mitchx.) are a lowbush fruit crop native to North America and a cornerstone of Maine’s agricultural economy, contributing over 95% of U.S. production. Valued for their intense flavor, high anthocyanin content, and associated health benefits, they are predominantly marketed frozen, with fresh berries comprising only ~1% of sales due to their short postharvest life. Limited research exists on the shelf life of fresh wild blueberries, particularly under commercial handling and storage conditions. This study assessed the quality and shelf life of fresh wild blueberries harvested from three commercial farms in Maine, with the aim of identifying key factors influencing deterioration and providing recommendations to extend market availability.

Over the 2023 harvest season, fruit was collected from farms A, B, and C, sorted, and stored under controlled conditions. Quality assessments were conducted at multiple storage intervals (0–21 days) using physicochemical measurements such as °Brix, pH, moisture content, and weight loss, alongside microbial analyses for yeast and mold counts. Farm origin and storage duration were treated as primary variables. The impact of mechanical damage was also evaluated, with drop height during harvest and packing line processing noted as potential contributors to bruising and subsequent decay.

Results indicated that storage time and farm origin significantly influenced most quality parameters. °Brix values remained relatively stable in early storage but declined after day 15, suggesting sugar metabolism during respiration. pH increased gradually, particularly in later storage, correlating with a perceived loss of flavor intensity. Moisture content and firmness decreased steadily across all farms, with higher rates of weight loss observed in berries from farms with lower initial moisture levels. Mechanical damage was linked to accelerated softening and increased susceptibility to fungal colonization. Microbial analysis revealed that yeasts were the predominant spoilage organisms, proliferating rapidly under conditions of high moisture and mechanical injury, while mold incidence increased notably after day 12 at 4 °C storage.

Differences between farms were attributed to variations in genotype composition, field management practices, and harvest handling. Farm A berries exhibited the lowest weight loss and maintained firmness longest, while farm C berries showed the highest microbial counts by mid-storage. Across all farms, maintaining storage at 4 °C with relative humidity between 90–95% significantly slowed deterioration compared to ambient storage.

This study confirms that the perishability of fresh wild blueberries is driven by a combination of physiological and microbial factors, compounded by handling-induced damage. Effective interventions include rapid postharvest cooling, minimizing drop heights during mechanical handling, and exploring advanced packaging technologies such as Modified Atmosphere Packaging (MAP) to slow respiration and microbial growth.

By establishing baseline shelf life data and identifying critical control points in the postharvest chain, these findings address a key knowledge gap for Maine’s wild blueberry industry. Adoption of improved postharvest practices could expand the fresh market share beyond the current 1%, potentially increasing economic returns for growers and providing consumers with extended access to high-quality fresh wild blueberries.

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