Autor:Equipo de I + D, saborizante de Cuiguai

Publicado por:Guangdong Unique Flavor Co., Ltd.

Last Updated: Jul 06, 2026

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Tropical Hops Beer

Introduction: The Tropical Frontier in Craft Beer Brewing

The craft beer industry has experienced one of the most dramatic flavor revolutions in modern food science. Between 2015 and 2025, thenumber of craft breweries in the United States alone grew from approximately 4,200 to over 9,500, according to theBrewers Association— and the flavor complexity of their products grew commensurately. At the center of this revolution is the intersection oftropical fruit aromatics and modern hop variety science: a discipline that requires deep understanding of terpene chemistry, ester biology, fermentation biochemistry, and food-grade flavor ingredient science.

Today’s most celebrated craft beer styles — Hazy IPAs (also known as New England IPAs), Milkshake IPAs, Tropical Stouts, and Catharina Sours — are defined by theirexplosion of tropical fruit character: ripe mango, passionfruit, guava, pineapple, lychee, and papaya aromas that transform the beer glass into something closer to a blender full of fresh tropical fruit. Yet achieving these flavors requires far more than simply adding fruit to the fermentation tank.

This comprehensive technical guide examines the science behind tropical fruit-hop pairings: the molecular chemistry that makes certain hop varieties inherently “tropical,” the biology of fermentation and how yeast transforms both fruit and hop compounds, the practical techniques for achieving authentic tropical character at different brewing scales, and the role of food-grade flavor concentrates in delivering consistent, stable tropical profiles in commercial craft beer production.

Whether you are a craft brewer, a beverage product developer, or a food flavor formulation professional, understanding the chemistry and practice of tropical fruit-hop pairing is essential for navigating the most commercially dynamic flavor frontier in the global beverage industry.

1. The Molecular Architecture: Why Hops Are Inherently “Tropical”

The starting point for understanding tropical fruit-hop pairing is recognizing that certain hop varieties arenot merely complementary to tropical fruits— they are molecularly related. The same classes of terpene and thiol compounds that define the aroma of mango, passion fruit, and guava are also found, in varying concentrations, in the essential oils and biotransformation products of specific hop varieties.

1.1 Hop Essential Oils: The Primary Terpene Toolkit

Hop cones (Humulus lupulus) containessential oil glandsthat produce a complex mixture of volatile compounds. The essential oil fraction of hops typically constitutes0.5–3% of the dried hop weightand is responsible for the vast majority of the hop’s aromatic contribution to beer. According to research published inPubMed Central (PMC ID: PMC9407075), the major terpene alcohols — linalool, geraniol, and β-citronellol — are the primary drivers of hoppy aroma in finished beer, with their coexistence demonstrating a meaningful additive effect on overall aroma intensity.

Key tropical-associated terpenes in hops include:

1.2 Polyfunctional Thiols: The Secret Engine of Tropical Intensity

Beyond terpenes, a second class of compounds has transformed the scientific understanding of tropical hop flavor:polyfunctional thiols— sulfur-containing volatile molecules that are present at extremely low concentrations but possess extraordinarily powerful aroma activity. The three most important thiols for tropical beer flavor are:

• 3-Mercaptohexan-1-ol (3MH): passion fruit, grapefruit, guava character; detection threshold as low as 0.06 μg/L in beer
• 3-Mercaptohexyl acetate (3MHA): passion fruit, blackcurrant, tropical flower notes; detection threshold approximately 0.004 μg/L
• 4-Mercapto-4-methylpentan-2-one (4MMP): blackcurrant, guava, cat-urine (at very low doses, highly pleasant and tropical)

These thiols exist in hops primarily ascysteine-conjugated precursors— molecules bound to the amino acid cysteine in a non-volatile, aroma-inactive form. During fermentation, specific yeast strains expressing the enzymeIrc7p (β-lyase)cleave these precursor bonds, releasing the free, aroma-active thiols into the beer. Research from theLallemand Brewing Technical Centerhas established that thiol release efficiency varies dramatically between yeast strains — from near zero to over 40% conversion of available precursors — makingyeast selectionas important as hop selection in achieving tropical character.

1.3 The Tropical Hop Varieties: A Technical Profile

Not all hop varieties carry meaningful tropical character. The following varieties have been most consistently associated with tropical fruit flavor profiles in peer-reviewed brewing literature and industry sensory research:

• Citra (US): intense tropical citrus; dominant linalool and myrcene content; paired notes of lime, passion fruit, mango. One of the highest-demand hops globally for tropical beer applications.
• Mosaic (US): complex tropical-earthy profile combining blueberry, mango, herbal, and citrus notes; high myrcene and moderate geraniol. The most versatile single-hop for tropical character.
• Galaxy (Australia): clean, intense tropical stone fruit; dominant in passion fruit and peach notes with significant thiol precursor content. A cornerstone of Australian New World hop breeding.
• Simcoe (US): passion fruit and earthy pine duality; excellent complexity when combined with pure tropical varieties; moderate thiol precursor content.
• Riwaka (New Zealand): distinctive grapefruit-passion fruit character with exceptional linalool content; premium pricing reflects its uniquely clean tropical profile.
• Azacca (US): mango and tropical citrus dominant; named after the Haitian god of agriculture. Particularly effective in dry-hop applications.

Hop Terpene Diagram

2. The Fermentation Dimension: How Yeast Transforms Tropical Character

Understanding hop chemistry is only half the picture. In the fermentation vessel,yeast activity dramatically transforms both hop compounds and any fruit additions, producing new flavor-active molecules and amplifying or muting the natural tropical character of the raw ingredients. This “biotransformation” dimension is one of the most exciting frontiers in craft beer science.

2.1 Yeast Biotransformation of Hop Terpenes

When hops are added to actively fermenting beer (a technique called “biotransformation dry hopping”), yeast cells take up and enzymatically modify hop terpenes through several pathways:

• Geraniol reduction to citronellol: yeast reductases convert the rose-like geraniol into the sweeter, more tropical beta-citronellol, shifting the aroma profile from floral toward citrus-tropical.
• Ester formation from terpene alcohols: yeast acyltransferases esterify terpene alcohols with acetyl-CoA, creating new fruity ester compounds (e.g., geranyl acetate provides a tropical-floral ester note).
• Thiol liberation: as discussed in Section 1.2, yeast IRC7 activity cleaves cysteine-conjugated thiol precursors to release free passion fruit and guava thiols.

Eltiming of dry hop additionduring active fermentation — specifically, the addition point between 25% and 75% apparent attenuation — has been shown in multiple brewery trials tomaximize biotransformation yieldby maintaining the highest yeast cell viability and enzymatic activity. The practical result is that beers dry-hopped during active fermentation often exhibitsignificantly more intense and complex tropical characterthan beers hopped post-fermentation, even when using identical hop quantities.

2.2 Yeast Ester Production and Tropical Fruit Synergy

Yeast naturally producesfruity estersas byproducts of fermentation. The most important for tropical beer profiles areacetato de isoamilo(banana, pear) andethyl hexanoate(apple, anise, tropical fruit). Crucially, these yeast-derived esters can interact synergistically with both hop terpenes and fruit additions — creating combined aromas that aregreater than the sum of their parts

Yeast strains used for Hazy IPAs are specifically selected forhigh ester productionat typical ale fermentation temperatures (18–22°C). TheLondon Ale III (Wyeast 1318 / Lallemand Verdant IPA)strain is particularly prized for its ability to produce lush tropical esters while also being highly expressive of hop biotransformation. Its combination of high isoamyl acetate production and excellent Irc7p activity makes it a cornerstone of the tropical craft beer style.

2.3 Fruit Addition Timing and Fermentation Interaction

When tropical fruits are added to the fermentation vessel (as fresh fruit, puree, or extract), they interact with the ongoing yeast activity in ways that are both useful and potentially problematic:

• Sugar from fruit extends fermentation: tropical fruits add fermentable sugars (primarily glucose and fructose) that extend fermentation activity, potentially altering the attenuation profile and final gravity.
• Malic acid in some fruits (passion fruit, pineapple) can alter beer pH, requiring water chemistry adjustments.
• Enzymatic browning of certain fruits (mango especially) can introduce oxidative off-flavors if not managed through ascorbic acid addition or nitrogen purging of the fruit.
• Wild yeast or bacteria on raw fruit surfaces can introduce unwanted fermentation activity; fruit purees from licensed suppliers with confirmed microbial specs are strongly preferred over fresh fruit additions.

For these reasons, many commercial craft brewers prefer to addfood-grade fruit flavor concentrates or certified pureesat post-fermentation stages (conditioning or packaging) rather than during active fermentation. This approach providesgreater flavor predictability, microbiological control, and batch-to-batch consistency— critical requirements for commercial-scale production.

3. Five Classic Tropical Fruit-Hop Pairing Frameworks

With the underlying chemistry established, we can now examinefive proven pairing frameworksthat deliver reliable tropical flavor outcomes across different beer styles.

3.1 Mango × Citra + Mosaic: The “Tropical IPA Foundation”

This is the most commercially proven tropical pairing in modern craft brewing. Mango and the Citra-Mosaic hop combination share an exceptionally strong molecular affinity: both carry high concentrations ofmyrcene, linalool, and ethyl butyrate, creating a multi-layered tropical fruit character that isgreater in both intensity and complexitythan either component alone.

Por qué funciona:Citra’s sharp, citrus-forward tropical character combines with Mosaic’s deeper, blueberry-mango complexity to create a full “tropical spectrum” that mirrors the flavor architecture of ripe Alphonso mango: bright citrus top note, ripe sweet mid-note, and subtle earthy undertone.

Brewing guidelines:

• Hop rate: 15–25 g/L Citra + 10–20 g/L Mosaic (combined dry hop for NEIPA)
• Mango addition: 100–200 g/L of pasteurized mango puree (e.g., Alphonso variety) at secondary fermentation/conditioning
• Alternatively: 0.5–1.5 g/L of food-grade mango flavor concentrate at packaging for consistent dosage control
• Recommended yeast: London Ale III / Verdant IPA for maximum ester expression
• Style target: Hazy/NEIPA, 6.0–7.5% ABV, SRM 4–6, IBU 35–55 (perceived)

3.2 Passion Fruit × Galaxy + Riwaka: The “Southern Hemisphere Intensity”

Galaxy (Australia) and Riwaka (New Zealand) are among the highest thiol-precursor-content hops commercially available. Paired with passion fruit — itself one of the most thiol-rich tropical fruits — this combination createsextraordinary passion fruit intensitythat can survive even the most aggressive dry beer palates.

Por qué funciona:Passion fruit’s signature aroma is defined primarily by 3MH and 3MHA thiols — the exact same compounds released by Galaxy and Riwaka hops through yeast biotransformation. The two thiol sources operateadditively, and because they derive from different molecular precursors, they do not compete for the same yeast enzymatic pathways. The result is a compounding effect on thiol intensity that produces genuinely transformative passion fruit character.

Key formulation note:Because Galaxy carries moderate resinous earthiness alongside its tropical character,Riwaka is used to clean and brighten the profile, suppressing the earthy undertone and pushing the combined aroma toward pure tropical fruit. The balance point is typically65% Galaxy : 35% Riwakaby hop weight.

3.3 Pineapple × Citra + Azacca: The “Bright Tropical Acidic”

Pineapple’s flavor chemistry is dominated byethyl butanoate (ethyl butyrate)for the classic “pineapple candy” note,allyl hexanoatefor tropical complexity, andácido málicoproviding the characteristic sharp acidity that “cuts” through sweetness. Citra and Azacca both carry significant ethyl butyrate-mirroring esters, making this an exceptionally natural pairing.

The acidity dimension of this pairing is particularly valuable for brewing. Pineapple’s malic acid content (typically 3–8 g/kg in ripe fruit) canlower fermenter pH by 0.1–0.3 unitswhen used at 100 g/L addition rates, which has an important secondary effect: lower pH suppresses perceived bitterness from hop iso-alpha acids, making the beer taste“softer” and more fruit-forwardthan the measured IBU suggests. This is a key reason why tropical fruit additions can make high-IBU beers more approachable.

3.4 Guava × Mosaic + Simcoe: The “Complex Earthy Tropical”

Guava is one of the most complex tropical fruits from a flavor chemistry perspective, combiningsweet tropical esters (ethyl hexanoate), earthy/funky notes (β-ionone), and floral terpenes (geraniol, linalool). Mosaic + Simcoe is the perfect companion: Mosaic’s complex fruity-earthy profile mirrors guava’s dual character, while Simcoe’s distinct passion fruit + pine duality adds depth without competing with the guava’s unique character.

This pairing works particularly well forSour IPAs and Catharina Sour style beers, where theinteraction between Lactobacillus-derived lactic acid and the earthy-tropical guava profilecreates a genuinely complex flavor experience. Research published inFood Chemistry (Elsevier, 2025)on the Catharina Sour style — recognized as the first Brazilian craft beer category — demonstrated that tropical fruit additions significantly modulate the perceived sourness of lactic acid, allowing brewer to push acidity levels that would otherwise be too harsh without fruit character.

3.5 Lychee × Riwaka + Citra: The “Delicate Floral Tropical”

Lychee is the most delicate of the tropical fruit pairings — its flavor is characterized bygeraniol, rose oxide, and cis-rose oxide, giving it a distinctive floral-tropical character that is unlike any other tropical fruit. Riwaka, with its exceptionally high linalool content and clean citrus-passion fruit profile, provides the perfect botanical companion —floral enough to resonate with lychee’s rose character, citrusy enough to provide brightness.

For this pairing,hop rate restraint is essential: lychee’s delicate floral esters are easily overwhelmed by aggressive hop bitterness or excessive resinous character. The recommendation is to use this pairing at lower overall hop rates (8–15 g/L combined), focus on cold-side hop additions only, and treat the lychee flavor as theprimary sensory driverwith hops providing only supportive complexity.

Dry-Hop Fruit Process

4. Practical Brewing Techniques: From Homebrew to Commercial Scale

Understanding the theoretical framework of tropical fruit-hop pairings is necessary but not sufficient. The following section addresses thepractical executionof these pairings across different brewing scales, with specific attention to the challenges of consistency, microbiological control, and flavor stability.

4.1 Dry Hopping Protocols for Tropical Character

Dry hopping — the addition of hops after primary fermentation without boiling — is the primary technique for expressing tropical hop character in beer. Because the hops are not subjected to heat, volatile aromatic compounds arepreserved rather than volatilized, producing the “raw” tropical fruit character that defines NEIPA and other hop-forward styles.

Key parameters for tropical dry hopping:

• Addition temperature: 18–22°C (during active fermentation for biotransformation) or 0–4°C (post-fermentation cold-side for terpene preservation)
• Contact time: 48–72 hours for biotransformation dry hops; 24–48 hours for cold-side dry hops
• Hop form: T90 pellets (most common; good surface area contact); cryo hops (concentrated lupulin fraction; 2× effective rate of T90 for tropical character)
• Oxygen management: critical — ensure zero oxygen pickup during and after dry hop addition; use CO2 or N2 purge. Oxygen at dry hop causes rapid terpene oxidation and destroys tropical character.
• Multiple additions: a “double dry hop” protocol (one addition during active fermentation for biotransformation, one post-fermentation for terpene freshness) typically delivers superior complexity vs. single additions

4.2 Tropical Fruit Addition Methods: A Comparative Analysis

For commercial craft breweries aiming to deliver consistent tropical character across high-volume production,food-grade flavor concentrates and natural flavor extractsoffer the most reliable performance. OurFruit Flavor product range at CUIGUAI Flavoringincludes tropical fruit concentrates specifically formulated for beverage applications: mango, passion fruit, pineapple, guava, and lychee profiles with documented stability in alcoholic beverage matrices, full GC-MS characterization, and regulatory compliance documentation.

4.3 Water Chemistry Optimization for Tropical Fruit Beer

Water chemistry is an often-underappreciated factor in tropical fruit beer quality. Thesulfate-to-chloride ratioin brewing water has a profound effect on how tropical hop and fruit character is perceived:

• High sulfate (>100 ppm SO₄): emphasizes hop bitterness and dryness; can make tropical fruit character feel “sharp” and “cutting” rather than juicy
• High chloride (>100 ppm Cl⁻): promotes malt sweetness and “fullness”; supports the perception of tropical fruit juiciness and body. Target: 1.5:1 to 2:1 chloride:sulfate ratio for tropical NEIPA
• Calcium (50–100 ppm): supports yeast health and flocculation; impacts overall mouthfeel
• Bicarbonate (<50 ppm): low bicarbonate allows hop acids to express more cleanly without alkaline interference

The ideal water profile for tropical IPA brewing is sometimes described as“London soft water” style: moderate hardness, high chloride relative to sulfate, and low bicarbonate. This profile maximizes the perception of tropical fruit character while maintaining thesoft, hazy bodythat is the hallmark of the NEIPA style.

5. Flavor Stability and Quality Control in Tropical Fruit Beers

One of the most challenging aspects of tropical fruit-hop craft beers is theirnotoriously poor shelf stability compared to conventional beer styles. The same terpene compounds that deliver vibrant tropical character on Day 1 are oftensignificantly degraded by Day 30, a phenomenon that has frustrated both brewers and consumers. Understanding and managing this instability is critical for commercial success.

5.1 The Three Primary Degradation Pathways

Terpene Oxidation:As detailed in research on hop compound volatility, monoterpenes like myrcene, limonene, and geraniol are highly susceptible to oxidative degradation. In a finished beer matrix containing dissolved oxygen — even at ppb (parts per billion) levels — these compounds rapidly oxidize to form off-flavor products including alpha-terpineol (soapy/medicinal), carvone (caraway), and carveol (herbal/harsh).Total oxygen management— including water DO, fermentation DO, dry hop oxygen pickup, and packaging DO — must target <50 ppb total package oxygen for tropical beers.

Thiol Oxidation:Free thiols (3MH, 3MHA) are even more oxygen-sensitive than terpenes. They oxidize irreversibly to disulfide compounds that haveno aroma activity— the tropical character disappears entirely. Thiol loss is the primary driver of the “faded” tropical character that develops in NEIPA within 2–4 weeks of packaging. This is why fresh NEIPA tastes dramatically different from a month-old can of the same beer.

Ester Hydrolysis:Fruity esters (ethyl hexanoate, isoamyl acetate) gradually hydrolyze in the aqueous, slightly acidic beer environment, breaking into their constituent alcohols and acids. This process is accelerated by temperature — every 10°C increase in storage temperature approximately doubles the rate of hydrolysis.Cold chain storage(1–4°C throughout the supply chain) is therefore not merely a preference for tropical beer — it is achemical necessityfor maintaining flavor integrity.

5.2 The Role of Flavor Concentrates in Stability Enhancement

An often-overlooked advantage of using food-grade tropical fruit flavor concentrates in commercial craft beer is their ability tocontribute stability to the finished flavor profile. Well-formulated flavor concentrates contain several features that raw fruit purees lack:

• Pre-selected stable ester and lactone fractions that are more resistant to hydrolysis than native fresh fruit esters
• Absence of enzymatic browning substrates (phenolic acids, polyphenol oxidase) that contribute to flavor degradation and color development
• Defined and consistent ester-to-acid ratios that maintain flavor profile integrity over the full shelf life
• Optional antioxidant inclusion (ascorbic acid, tocopherol) for additional protection of vulnerable terpene fractions

For brewers seeking to understand the broader principles of flavor stability in alcoholic beverage bases — including the physics of ester and terpene behavior under varying alcohol concentrations — our technical article onformulating high-ABV hard seltzers and overcoming flavor fadingprovides directly applicable insights into the thermodynamic and chemical mechanisms that also govern tropical beer flavor shelf life.

6. The Flavor Concentrate Advantage: CUIGUAI’s Approach to Craft Beer Flavor Solutions

EnSaborizante de cuiguai(Guangdong Unique Flavor Co., Ltd.), our beverage flavor R&D team has developed a dedicated range ofnatural tropical fruit flavor concentrates for craft beer and fermented beverage applications. Our approach is grounded in four core principles that distinguish professional flavor manufacturing from commodity ingredient supply:

6.1 GC-MS Verified Authenticity

Every CUIGUAI tropical fruit flavor concentrate for beverage applications is developed throughGC-MS (Gas Chromatography-Mass Spectrometry) fingerprinting of the target fruit varietyat optimal ripeness. This analytical process identifies the top 20–30 aroma-active compounds byOdor Activity Value (OAV)— a measure of each compound’s sensory impact relative to its detection threshold — allowing our flavor chemists to reconstruct the authentic tropical fruit profile from the compounds that actually matter sensorially, rather than from all compounds present in bulk quantity.

For mango, this means capturing the specific ester profile of the target variety (Alphonso vs. Ataulfo vs. Kent mangoes have significantly different aroma fingerprints). For passion fruit, it means balancing the thiol-like character (3MH-adjacent compounds) with the fruity esters (ethyl hexanoate, allyl hexanoate) in the correct ratio. OurFruit Flavor product categoryprovides a range of tropical profiles engineered with this analytical rigor.

6.2 Beverage Matrix Compatibility Testing

A flavor that performs beautifully in water may perform entirely differently in a5–7% ABV beer matrix with pH 4.0–4.4 and significant dissolved CO₂. All CUIGUAI tropical fruit concentrates intended for beer applications undergo matrix compatibility testing in representative base beers — including NEIPA-style beers with varying dry hop rates — to verify that the flavor interaction is additive and synergistic rather than competitive or suppressive.

6.3 Clean Label and Regulatory Documentation

Craft beer brands care deeply about their label integrity. Our flavor concentrates are available in“Natural Flavor”declaration formats under US FDA 21 CFR 101.22 regulations and EU Regulation (EC) 1334/2008 flavoring standards, ensuring that their use on the beer label can be declared as “Natural Tropical Fruit Flavor” without artificial additive declarations. We provide full ingredient disclosure, FEMA GRAS code listings, and allergen statements with every product.

7. Conclusion: The Science of Tropical Expression in Beer

The pairing of tropical fruits with hops in craft beer brewing is one of the most scientifically rich and commercially rewarding endeavors in the modern food and beverage industry. It demands simultaneous mastery ofhop terpene chemistry, yeast biotransformation biology, fermentation biochemistry, fruit flavor stability science, and packaging technology— a genuinely interdisciplinary challenge that rewards both intellectual curiosity and practical brewing skill.

The core insights of this guide can be distilled into five actionable principles:

• Select hops based on terpene and thiol precursor chemistry, not just sensory description — Galaxy and Riwaka for thiol-driven passion fruit; Citra and Mosaic for terpene-driven mango; Azacca and Citra for ester-driven pineapple.
• Choose yeast for its biotransformation capabilities — high Irc7p expression for maximum thiol release; high ester production for tropical complexity amplification.
• Time fruit additions strategically — biotransformation dry hops during active fermentation for compound transformation; flavor additions post-fermentation for stability and precision control.
• Obsess over oxygen management — every ppb of dissolved oxygen is an enemy of tropical flavor stability.
• Consider food-grade flavor concentrates for commercial-scale consistency — they deliver superior batch reproducibility, microbiological safety, and flavor stability compared to raw fruit purees, with no compromise on sensory authenticity when sourced from a rigorous manufacturing partner.

The tropical craft beer revolution shows no signs of slowing. As hop breeding programs around the world continue to develop new varieties with ever-higher thiol precursor content and novel terpene profiles, and as food flavor science delivers increasingly authentic tropical fruit concentrates, the expressive range offruit-forward craft beer will continue to expand. The brewers — and ingredient suppliers — who understand the chemistry will define the category’s next decade.

Tropical Beer Flavor Concentrates

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Elevate Your Craft Beer Flavor with CUIGUAI Flavoring

Whether you are developing a new tropical IPA, scaling up a mango sour, or seeking a reliable OEM food-grade flavor concentrate supplier for craft beer applications — our R&D team is ready to collaborate. We offer GC-MS-verified tropical fruit flavor samples, custom formulation consultations, and full regulatory documentation for global craft beverage markets.

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Referencias y citas de autoridad

[1] Brewers Association. “Number of Craft Breweries Operating in the US, 2015–2025.” Available at:brewersassociation.org.

[2] PubMed Central (PMC). “Effect of Czech Hop Varieties on Aroma of Dry-Hopped Lager Beer — Monoterpene Alcohols and Dry-Hop Aroma.” PMC ID: PMC9407075. Molecules, MDPI, August 2022. Available at: pmc.ncbi.nlm.nih.gov/articles/PMC9407075/

[3] Lallemand Brewing. “Terpenes and Biotransformation Resources.” Biotransformation Research Center. Available at:lallemandbrewing.com.

[4] Food Chemistry (Elsevier). “Catharina Sour: Innovation in the first Brazilian beer style, notable for incorporating tropical fruits.” Food Chemistry Advances, 2025. doi: 10.1016/j.fochad.2025.100900.

[5] FEMA — Flavor and Extract Manufacturers Association. “GRAS Program and Flavor Ingredient Safety.” Available at:femaflavor.org.