Titrimetric analysis of jams, fruit and vege- table juices and their concentrates

Significance of the Topic

The accurate quantification of acidity, mineral content and preservatives in jams, fruit and vegetable juices is critical for food safety, sensory quality and regulatory compliance. Titrimetric methods offer cost effective, reproducible protocols widely adopted in food laboratories for routine quality control and product development.

Objectives and Study Overview

This application bulletin presents step by step potentiometric titration procedures for key parameters in jams, fruit and vegetable juices and their concentrates. The methods cover pH measurement, total titratable acidity, ash alkalinity, formol number, total sulfurous acid, chloride, sulfate, calcium and magnesium determinations.

Methodology and Used Instrumentation

The titration workflows employ Metrohm Titrino or Titrando systems with Dosino or Dosimat dosing modules and magnetic stirring. A combined pH glass electrode with integrated temperature sensor, platinum electrodes, silver Titrode and ion selective electrodes for calcium are used alongside a double junction Ag/AgCl reference. Sample preparation includes dilution and heating for acidity assays or incineration in a muffle furnace for mineral and sulfite analysis. Titrations are performed in SET or MET modes with defined end points at specific pH values or current signals.

Main Results and Discussion

• pH Value: Measured directly in undiluted juices or diluted jams with 0.1 unit precision.
• Total Titratable Acidity: Expressed as meq per 100 g or per liter, determined by titration to pH 8.5.
• Ash Alkalinity: Ash residues titrated to pH 4.5 after incineration, reported in meq/L.
• Formol Number: Base consumption per 100 mL juice indicating amino acid content.
• Total Sulfurous Acid: Sulfite quantified by iodometric titration, results in mg SO2 per 100 g or per liter.
• Chloride: Titrated with silver nitrate, reported in mg Cl– per liter.
• Sulfate: Determined gravimetrically after ashing and titration with EDTA, expressed as g K2SO4 per liter.
• Calcium and Magnesium: Ash dissolution followed by complexometric EDTA titration with ion selective detection, values in mg per liter or per 100 g.
Each method yields precise end point detection and clear calculation schemes using conversion factors for standardized units.

Benefits and Practical Applications

These titrimetric protocols enable fast, reliable monitoring of acidity, preservative levels and mineral profiles in fruit products. They support product development, quality assurance, nutritional labeling, and compliance with national and international food standards.

Future Trends and Possibilities

Advances in automation, inline sensor integration and flow injection analysis can further streamline titrimetric assays. Development of new selective electrodes and microfluidic titration systems may enhance throughput and reduce reagent consumption. Coupling with digital data management will bolster traceability and real time quality control.

Conclusion

The outlined potentiometric titration methods provide a comprehensive toolkit for quantifying acidity, inorganic constituents and preservatives in jams and juices. Their robustness, adaptability and adherence to standard protocols make them indispensable in modern food analysis laboratories.