60 Days, Untreated Blueberries Scored Zero. MAP Bags Scored 53.6%.
Blueberries have a natural advantage most soft fruit doesn’t: a protective outer wax layer, the “bloom,” that helps resist water loss. It’s not enough on its own for long-term storage though — and an independent university trial puts a precise number on exactly how much that gap matters.
The Trial: A PhD Study, Not a Marketing Test
Researcher Nha Huynh, a PhD candidate at the University of Tasmania, supervised by Prof. Roger Stanley and Dr. Matthew Wilson, ran a formal comparative trial on blueberry shelf life. Seven treatments were tested — two vented liner types, a purpose-built MAP bag, an SO2-releasing pad on its own, combinations of liners with SO2, and an untreated clamshell control — all stored at 0–1°C for 60 days.
The Headline Result
At the 60-day mark, the untreated control scored 0.0% marketable weight — every single berry had degraded past saleable condition. The MAP bag alone scored 53.6% marketable weight, the best result of any treatment tested, including every combination that added an SO2 pad on top of a liner.
That gap — zero versus over half — is the trial’s clearest finding, and it isn’t subtle: shrinkage and softening were the two disorders driving rejection across every treatment, exactly the two things a correctly engineered MAP atmosphere is built to slow down.
Where SO2 Helped, and Where It Didn’t
The trial’s SO2-releasing pads did have a genuine, measurable benefit: no mouldy fruit and no off-odours were recorded in any treatment that included one. SO2’s anti-fungal effect is real and the researchers confirmed it directly.
But for overall marketable weight, adding SO2 on top of the MAP bag actually reduced the result — from 53.6% down to 44.7%. The researchers’ own conclusion was direct: MAP appeared to be the beneficial factor for long-term blueberry storage, and packaging that improves moisture retention is what actually addresses the shrinkage driving most of the rejections. Blueberry is also a climacteric fruit, continuing to ripen and soften after harvest via its own ethylene production — which is a separate mechanism from the fungal decay SO2 targets, and helps explain why atmosphere and moisture control did more heavy lifting in this trial than fungal suppression did.
What the Chemistry Confirmed
The trial also ran chemical analysis — anthocyanin content (colour), Brix (sugar), and titratable acidity — across all treatments at day 60. Colour and sugar held steady across every treatment, including the untreated control. The one place a real difference showed up: MAP treatments (with or without SO2) maintained titratable acidity significantly better than the vented liners or control. Since acidity is a major driver of how fresh berries actually taste, this is a second point in the MAP bag’s favour that goes beyond simple visual shrinkage.
What This Means for Packaging
A Lifepack® MAP bag engineered for blueberry’s respiration rate is what this independent trial’s own data points to as the primary driver of marketable shelf life at 60 days — ahead of every liner-only and liner+SO2 combination tested. Because blueberry keeps ripening via its own ethylene after harvest, adding a Fresh Up® ethylene absorber sachet targets that separate mechanism directly, complementing the atmosphere and moisture control the MAP bag already provides — addressing softening from two angles rather than one.
The Practical Takeaway
This is one of the more useful trials available for blueberry because it directly tested the “more is better” assumption — MAP plus SO2 — and found the simpler answer, MAP alone, actually performed better on the metric that matters most: how much of the fruit was still saleable at 60 days. Zero percent versus over half isn’t a marginal difference — it’s the entire commercial outcome of a shipment.
Related: Full UTAS trial report (PDF) · Blueberry MAP Bag specifications
