Making $21,000 ARR Writing About Food Safety
How this food industry professional built a profitable newsletter from just 4,000 subscribers.
What is the business and who’s behind it?
When Karen Constable launched The Rotten Apple, she had one mission: cut through the noise of the food industry and give busy professionals exactly what they needed—no fluff, no ads, and definitely no filler.
Just three years later, that bold idea turned into a paid newsletter with over $21,000 in annual revenue, a Substack Bestseller badge, and a fiercely loyal readership. All from a list of just 4,000 subscribers.
With decades of experience in food safety, quality assurance, and product development across multiple sectors, she’s a seasoned food industry expert who knows her stuff. But what makes her stand out isn’t just her knowledge—it’s how she shares it.
The Rotten Apple, hosted on Substack, is Karen’s weekly roundup of curated food and agriculture news. She scours hundreds of articles, reports, forums, and social media posts each week to deliver short, sharp, insight-packed emails that are as useful as they are digestible.
Her style? No fluff. No filler. No promotions. Just what matters—straight from a pro who’s been on the frontlines of food integrity for decades.
How was the business started?
Back in 2021, Karen was looking for a new kind of income—something scalable that didn’t require trading time for money.
Consulting, while rewarding, always tied her income to her hours. A newsletter, on the other hand, could scale infinitely without increasing her workload.
“I absolutely love the scalability of it,” she shares in this interview. “When I get more subscribers, I get more money but don’t need to do more work.”
Armed with her industry expertise, Karen launched The Rotten Apple on Substack. In the beginning, she had no audience. No email list. No fanfare.
Just a clear promise: expert-curated food safety news, every week, with zero ads.
The early months were slow—800 subscribers after six months. But rather than panic or pivot, she stayed consistent. She published regularly, kept her promises, and built trust, brick by brick.
That patience paid off.
What are some of the marketing strategies used?
Karen’s playbook wasn’t complicated—it was smart.
She doubled down on what worked and ruthlessly cut what didn’t.
Early on, she experimented with multiple platforms. But after six months, she ditched the channels that weren’t converting.
The winners? LinkedIn and her SEO-optimized website.
On her website, a pop-up invites visitors to subscribe, with a simple, benefit-driven call to action.
On LinkedIn, she shares her expertise, builds relationships, and invites people to check out her newsletter. “LinkedIn groups are great too,” she says.
And she never stopped publishing high-quality content.
“Consistent publishing. Quality content. Keeping promises. That’s been the strategy since day one,” Karen says.
She also emphasizes the importance of pacing. “Burnout is a huge risk when you’re a solo creator. I tell new Substackers to go at a speed that feels manageable. Add new growth tactics only when you’re ready.”
How does the business make money?
The Rotten Apple is a pure-play paid newsletter.
Karen introduced paid subscriptions six months in—at 800 subscribers.
Now, with 3,000 subscribers and over 200 paying members, she’s hitting a 6% conversion rate, which is higher than most newsletters on Substack.
Subscribers pay $10/month for access to exclusive content like:
Food fraud incident reports
Industry indexes and templates
Monthly supplements and deep dives
Recordings of training events
An archive of past issues in e-book format
But interestingly, she notes that many subscribers pay not just for the content—but out of appreciation. “Some people really need those resources. But others pay mainly to support me. And that’s incredibly meaningful.”
She also keeps The Rotten Apple 100% ad-free by design. It’s a key differentiator. “My competitors are packed with ads. I wanted my readers to know that everything I share is for their benefit—not a sponsor’s. That authenticity builds trust.”
Where can we go to learn more?
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