Orange peel (Citrus sinensis)

Orange peel comprises the flavedo (colored outer layer rich in essential oils) and the albedo (white inner layer rich in fiber and pectin). In food supply chains it appears as fresh or dried zest, candied peel (sometimes chocolate-coated), pastry pastes, and expressed essential oils/oleoresins from the flavedo.

Commercial forms
Fresh or grated zest; dried and milled peel; candied peel strips or cubes (in syrup or glazed); pastry pastes; sweet orange essential oil for flavoring.

Caloric value (100 g)
Fresh peel: about 90–110 kcal/100 g (typical ≈ 97 kcal/100 g; moisture dependent).
Dried peel: about 250–320 kcal/100 g (concentration of solids).
Candied peel: about 300–380 kcal/100 g (depends on syrup °Brix and any glazing).

Average composition (indicative)
Water (fresh): ~70–75 g.
Total carbohydrates: ~20–28 g (fresh; added sugars dominate in candied products).
Dietary fiber: ~10–12 g (pectin and insoluble fiber; higher in the albedo).
Protein: ~1–2 g.
Fat: ~0.2–0.5 g (mostly from flavedo).
Micronutrients: vitamin C, folates; minerals (K, Ca).
Phytochemicals: flavanones (hesperidin, narirutin), polymethoxyflavones (tangeretin, nobiletin), carotenoids; essential oil dominated by d-limonene with myrcene, linalool, and aliphatic aldehydes (e.g., decanal).

Sensory and technological properties
Flavedo delivers a bright, floral–citrus aroma; albedo contributes body and mild bitterness. Essential oil rich in monoterpenes is volatile and light/oxygen sensitive; drying and storage should limit loss. In candied peel, osmotic sugar infusion lowers aw and stabilizes the product; pre-blanching moderates bitterness and astringency.

Processing and controls
Zest production: Remove only the flavedo to avoid excess albedo bitterness.
Drying: Use gentle convective air or freeze-drying to reach low moisture while preserving color and aroma.
Candying: Apply stepwise osmotic cycles to target °Brix (typically medium–high), then glaze/dry as needed.
Essential oil: Obtain by cold pressing or distillation, then filter and standardize for food use.
Hygiene and safety: Operate under GMP and HACCP (cleaning, foreign-body prevention, temperature/time control).

Food applications
Bakery and pastry (panettone/colomba, cakes, biscuits), gelato and semifreddi, jams and marmalades, cereals and bars, savory sauces and light marinades, salads, and infusions/teas. Candied peel serves as inclusions or décor; fresh zest elevates emulsions and dressings.

Nutrition and health
Orange peel supplies fiber and polyphenols; flavanones and pectin contribute prebiotic and viscosifying functionality. Candied versions carry significant added sugar and should be portioned sensibly. Compared with grapefruit, sweet orange peel generally contains fewer furanocoumarins; drug–food interaction potential is considered lower, though individual sensitivity varies.

Quality and specification themes
Appearance: vivid color, uniform cut, no browning.
Aroma: fresh and clean, free from oxidized/terpenic “tired” notes.
Moisture/aw: low for dried and candied forms to ensure stability and anticaking.
°Brix: compliant with candying specification (texture and sweetness).
Contaminants: post-harvest residues on whole fruit and heavy metals within legal limits.
Microbiology: counts appropriate to category; manage osmophilic yeasts in candied products.

Storage and shelf life
Fresh zest: Refrigerate in airtight containers and use promptly to preserve aroma.
Dried peel: Store cool and dry, protected from light/oxygen; control ambient RH to prevent caking and volatile loss.
Candied peel: Hold at 10–18 °C in barrier packaging; avoid condensation that promotes sugar bloom.

Allergens and safety
Sulfites may be present in candied peel as preservatives (label when above thresholds). Manage potential residues from post-harvest fruit treatments via sourcing and washing. Essential oil can cause dermal sensitization in predisposed individuals; culinary use levels are typically low.

Troubleshooting
Excess bitterness: Too much albedo or insufficient blanching → increase blanch/rinse cycles.
Sticky or “wet” candied cubes: Final °Brix too low or drying incomplete → extend osmotic steps and optimize drying.
Sugar bloom or surface crystals: Moisture diffusion/thermal swings → improve packaging barrier and control RH and cooling.
Aroma loss in dried peel: Exposure to light/air/heat → upgrade barrier packaging and apply FIFO rotation.

Sustainability and supply chain
Orange peel valorizes a by-product of juice processing. Peels can be routed to pectin and essential-oil extraction, reducing waste and BOD/COD in effluents. Traceable sourcing and compliant post-harvest practices improve safety and environmental profile.

Conclusion
Orange peel combines intense citrus aroma, useful technological functions (pectin/fiber, color), and wide culinary versatility. Careful control of bitterness, moisture, aw, and packaging maximizes sensory quality, stability, and safety across applications.

Mini-glossary
aw — Water activity: Fraction of “free” water available for reactions and microbial growth; lower aw improves stability.
RH — Relative humidity: Percentage of water vapor in air; high RH promotes caking, condensation, and sugar bloom.
°Brix — Degrees Brix: Percentage by mass of soluble solids (sucrose equivalents) in a syrup; proxy for sweetness/consistency.
GMP — Good Manufacturing Practice: Procedures and controls ensuring hygiene, consistency, traceability, and quality.
HACCP — Hazard Analysis and Critical Control Points: Preventive food-safety system identifying hazards and defining CCPs, limits, monitoring, corrective actions, and verification.
CCPs — Critical control points: Steps where control prevents, eliminates, or reduces a food-safety hazard to acceptable levels.
FIFO — First in, first out: Inventory rotation principle—use the oldest lots first to preserve quality and aroma.
BOD/COD — Biochemical oxygen demand / Chemical oxygen demand: Indicators of organic load in effluents; higher values signal greater pollution potential.

Health

A normal intake of sugar in the body is important for human health, particularly for the brain (1).

Excessive or reiterated sugar or refined sugars consumption is primarily associated with the risk of:

• type 2 diabetes mellitus, 
• weight gain with consequent risk of obesity, 
• increase in cholesterol LDL 
• hepatic steatosis
• caries
• hypertension.

To counteract this trend, sugar levels in the blood must be lowered.

Flavonoids are phenolic compounds found in fruits and vegetables and have properties that prevent diabetes and its complications. This could improve blood sugar levels (2).

A reduction in the consumption of sugar-based sweetened beverages is recommended. The consumption of this type of beverage in early childhood is associated with increased risks of adiposity and risk of overweight/obesity (3).

Sugar studies

References_______________________________________________________________________

(1) Mergenthaler P, Lindauer U, Dienel GA, Meisel A. Sugar for the brain: the role of glucose in physiological and pathological brain function. Trends Neurosci. 2013 Oct;36(10):587-97. doi: 10.1016/j.tins.2013.07.001. Epub 2013 Aug 20. PMID: 23968694; PMCID: PMC3900881.

(2)   Al-Ishaq RK, Abotaleb M, Kubatka P, Kajo K, Büsselberg D. Flavonoids and Their Anti-Diabetic Effects: Cellular Mechanisms and Effects to Improve Blood Sugar Levels. Biomolecules. 2019 Sep 1;9(9). pii: E430. doi: 10.3390/biom9090430.

Abstract. Diabetes mellitus (DM) is a prevailing global health metabolic disorder, with an alarming incidence rate and a huge burden on health care providers. DM is characterized by the elevation of blood glucose due either to a defect in insulin synthesis, secretion, binding to receptor, or an increase of insulin resistance. The internal and external factors such as obesity, urbanizations, and genetic mutations could increase the risk of developing DM. Flavonoids are phenolic compounds existing as secondary metabolites in fruits and vegetables as well as fungi. Their structure consists of 15 carbon skeletons and two aromatic rings (A and B) connected by three carbon chains. Flavonoids are furtherly classified into 6 subclasses: flavonols, flavones, flavanones, isoflavones, flavanols, and anthocyanidins. Naturally occurring flavonoids possess anti-diabetic effects. As in vitro and animal model's studies demonstrate, they have the ability to prevent diabetes and its complications. The aim of this review is to summarize the current knowledge addressing the antidiabetic effects of dietary flavonoids and their underlying molecular mechanisms on selected pathways: Glucose transporter, hepatic enzymes, tyrosine kinase inhibitor, AMPK, PPAR, and NF-κB. Flavonoids improve the pathogenesis of diabetes and its complications through the regulation of glucose metabolism, hepatic enzymes activities, and a lipid profile. Most studies illustrate a positive role of specific dietary flavonoids on diabetes, but the mechanisms of action and the side effects need more clarification. Overall, more research is needed to provide a better understanding of the mechanisms of diabetes treatment using flavonoids.

(3)   Quah PL, Kleijweg J, Chang YY, Toh JY, Lim HX, Sugianto R, Aris IM, Yuan WL, Tint MT, Bernard JY, Natarajan P, Müller-Riemenschneider F, Godfrey KM, Gluckman PD, Chong YS, Shek LP, Tan KH, Eriksson JG, Yap F, Lee YS, Chong MFF. Br Association of sugar-sweetened beverage intake at 18 months and 5 years of age with adiposity outcomes at 6 years of age: the Singapore GUSTO mother–offspring cohort Nutr. 2019 Sep 3:1-25. doi: 10.1017/S0007114519002253

Abstract. Consumption of sugar-sweetened beverages (SSB) by infants and young children are less explored in Asian populations. The Growing Up in Singapore Towards healthy Outcomes cohort study examined associations between SSB intake at 18 months and 5 years of age, with adiposity measures at 6 years of age. We studied Singaporean infants/children with SSB intake assessed by FFQ at 18 months of age (n 555) and 5 years of age (n 767). The median for SSB intakes is 28 (interquartile range 5·5–98) ml at 18 months of age and 111 (interquartile range 57–198) ml at 5 years of age. Association between SSB intake (100 ml/d increments and tertile categories) and adiposity measures (BMI standard deviation scores (sd units), sum of skinfolds (SSF)) and overweight/obesity status were examined using multivariable linear and Poisson regression models, respectively. After adjusting for confounders and additionally for energy intake, SSB intake at age 18 months were not significantly associated with later adiposity measures and overweight/obesity outcomes. In contrast, at age 5 years, SSB intake when modelled as 100 ml/d increments were associated with higher BMI by 0·09 (95 % CI 0·02, 0·16) sd units, higher SSF thickness by 0·68 (95 % CI 0·06, 1·44) mm and increased risk of overweight/obesity by 1·2 (95 % CI 1·07, 1·23) times at age 6 years. Trends were consistent with SSB intake modelled as categorical tertiles. In summary, SSB intake in young childhood is associated with higher risks of adiposity and overweight/obesity. Public health policies working to reduce SSB consumption need to focus on prevention programmes targeted at young children.