IFF generated USD5.1 billion in sales for the full year 2020, about a 1% increase on a currency-neutral basis from last year when excluding the 53rd week of 2019.
We achieved an adjusted operating margin, excluding amortization, of 18.1%, driven by our synergy efforts with Frutarom and pursuing additional productivity initiatives across the business.
We finished the year with an adjusted earnings per share, excluding amortization, of $5.70.
Reflecting on 2020, we were off to a very strong start, growing 6% in Q1 2020, until the pandemic had a profound impact on society and, ultimately, our business.
Our growth rates continued to improve in the fourth quarter, up 2% excluding the 53rd week, versus the 1% year-on-year growth seen in the third quarter.
As we have noted before, roughly 15% of our business was negatively impacted by COVID-19 and decreased by 16% in 2020, excluding the impact of the 53rd week.
This was roughly 85% of our pre-pandemic sales and these grew approximately 4% for the full year, excluding the impact of the 53rd week.
As we begin 2021, I'm very pleased to say we, on a combined company basis, had a strong performance in January, with approximately 3% currency-neutral growth against a strong year-ago comparison.
In the fourth quarter, IFF generated $1.3 billion in sales, down 2% year-over-year on a currency-neutral basis.
When excluding the roughly $50 million impact of 2019's 53rd week, our comparable currency-neutral growth was plus 2%, and as I'll explain on the next slide, up approximately 4%, counting foreign exchange-related price changes as our peers in many CPGs disclosed.
In the fourth quarter, our adjusted operating profit, excluding amortization, decreased by 10% on a currency-neutral basis, or by 9% including a one percentage point benefit of FX, with solid operating performance -- operational performance offset by a challenging year-ago comparable and COVID costs.
We delivered adjusted earnings per share, excluding amortization, of $1.32, mostly as a result of lower operating profit in the quarter.
This was down 11% on a currency-neutral basis, or 10% including the one percentage point benefit of FX.
To be clear, if we simply looked at our revenue in the current period by local currency and applied the average FX rates from the prior period to the current period, our currency-neutral growth of 2% in the fourth quarter would have been up approximately 4%, and our full year currency-neutral growth of 1% would go to approximately 3%, all excluding the impact of the 53rd week.
At the segment level, Scent would have grown 10% in Q4 2020 and 7% in the full financial year, while Taste would have been up 1% in both Q4 and the full year 2020.
A close look at our operating profit bridge shows that we were able to drive operational improvements, about 8%, largely attained through Frutarom synergy realization, productivity initiatives and reformulation activities, mostly in Scent; higher volumes ex the 53rd week and disciplined cost management.
Unfortunately, these combined items represent an 18 percentage point year-over-year headwind and were the primary driver of our 10% currency-neutral decline in operating profit.
Sales totaling $504 million were up 3%, or 7% when excluding the 53rd week comparison.
Also, the new color is, where we recently gained access in Consumer Fragrance, core to our 2021 strategy, grew more than 60% in the fourth quarter and represented more than 1/3 of our Consumer Fragrance growth.
So overall, the Scent division achieved a 15.9% profit margin on the $504 million of sales in the quarter.
Taste sales totaling $766 million declined 5%, or 1% when excluding the 53rd week comparison.
Food Service was down roughly 17% on a similar basis.
The Taste division achieved approximately 11.8% profit margin, with $90 million in segment profit.
These numbers also include approximately $42 million in amortization of intangible assets.
If you exclude that amortization, our Q4 margin would be 17.2%.
As you will see, operating cash flow for the full year was up from $699 million in 2019 to $714 million this year, an increase of 2%.
We also reduced our capex to 3.8% of sales versus 4.6% of sales in the prior year period as we prioritized spending more than ever to manage and preserve cash through the pandemic.
All this led to a significant 13% increase in free cash flow compared to 2020's $522 million.
Assumed in our full year guidance is a euro to U.S. dollar exchange rate of $1.18, which represents approximately 25% of our combined sales.
We expect approximately $50 million of merger-related cost synergies with DuPont N&B, mostly back-end loaded this year, with $45 million coming from cost synergies and an additional $5 million from the EBITDA contribution of revenue synergies.
We expect total annual depreciation and amortization to be $1.165 billion, which includes amortization of approximately $715 million.
Annual interest expense is expected to be around $315 million.
Lastly, we expect diluted shares outstanding for the pro forma company, for earnings per share calculation purposes, to be approximately 255 million shares, and that's including the approximately 141 million shares from the transaction.
In line with the projections included in our December 22 S-4 filing, plus the synergy realization plan communicated January 11, we expect to generate approximately $11.5 billion in sales at an approximately 23.2% adjusted EBITDA margin.
Please note that this is a 12-month combined company pro forma estimate and includes approximately $507 million of N&B sales that occurred in January 2021.
On a pro forma basis, sales are expected to grow nearly 4% and EBITDA margin to expand by approximately 100 basis points.
As we face a strong first quarter comparison from both IFF at 6% and N&B at 3%, we will also continue -- we also continue to manage through pandemic-related headwinds.
Building on what Andreas said earlier, I'm pleased to say that we had solid pro forma results in January, with approximately 3% currency-neutral growth on our new disclosure basis.
In January 2021, N&B finished with approximately $507 million in sales.
While this has no impact on our full year expected sales, please remember that we moved away from our previous 4, 4, five reporting cycle to calendar month reporting from January.
We've shifted from our previous financial reporting calendar of 4, 4, five weeks to the more commonly used calendar month end to eliminate comparable issues related to the 53rd week.
Our R&D investment will be 1.5 times greater than our nearest peer.
We will have #1 or #2 positions in core categories in nutrition, cultures, enzymes, probiotics, soy proteins, flavors and fragrances.
This is coupled with the broadest and most diverse customer base in our industry, more than 45,000 in total, and about 48% of our annual sales from small medium and private label customers.
We expect that execution on our plan will unlock about $50 million in EBITDA contribution in 2021.
And we -- and as we mentioned on January 11th, there are 85 separate initiatives behind the $300 million cost savings that are in our plan on the cost side and another several initiatives on the revenue side.
From a revenue perspective, we expect currency-neutral organic sales growth of approximately 4% to 5% over the next few years, led by our unrivaled product and solutions portfolio, which is set to benefit from our industry-leading R&D programs.
We also expect to see meaningful operating margin improvements for IFF, including an estimated adjusted EBITDA margin of approximately 26% in 2023, up around 400 basis points from our 2020 pro forma.
The new IFF will continue to generate strong free cash flows, and we expect a significant increase to approximately $2 billion in 2023.
We are targeting almost 3 times net debt-to-EBITDA ratio, 24 to 36 months post close and reaffirm our commitment to maintaining our investment-grade rating.

Summary:
In line with the projections included in our December 22 S-4 filing, plus the synergy realization plan communicated January 11, we expect to generate approximately $11.5 billion in sales at an approximately 23.2% adjusted EBITDA margin.