Sweet Science

Throughout history, people have used honey to sweeten and add flavor. Although its sweetness is similar to that of granulated sugar, honey has a distinctive flavor that is largely determined by the flower type from which the nectar is gathered.

According to the Food and Agriculture Organization of the United Nations (FAO), current world honey production is estimated at 1.3 million tons annually.1 The majority of honey produced each year is designated as table honey and intended for direct consumption. The remainder is used as an ingredient in a wide range of products. The food industry uses honey extensively to sweeten and flavor baked goods, cereals, sauces, and beverages. It is also used as a coloring and an emollient in cosmetics such as soap, shampoos, and lotions, as well as in the pharmaceutical industry, primarily to flavor cough remedies and throat lozenges and to soothe and coat the throat.

In total, about 300,000 tons of honey is traded internationally each year. The European Union, the United States, and Japan, which all depend heavily on imported honey to meet consumer demand, together account for 70% of all imports. Given the global patterns that exist in the movement of honey between consuming and producing countries, there is a great international need for analysis to prevent honey that has been contaminated by pesticides, insecticides, or antibiotics from reaching the market.

Environmental contaminants and antibiotics are the most common residues found in honey. For instance, nectar and pollen collected from pesticide-treated flowers can result in contaminated honey. Persistent residues from the antibiotics used to control bacterial diseases in bees can also be a contaminant. Because of extensive honey exporting and importing, analyzing for these contaminants is challenging. One country may approve certain pesticides or antibiotics, while another may ban them. Approved compounds may have varying restrictions on permissible exposure levels.

The Challenge

Increasing concern over the presence of antibiotic and pesticide residues in honey and the related potential health threats to humans has led food quality control laboratories to develop fast and efficient detection methods. The complex honey matrix and the large number and variety of potential contaminants mean that analysis is extremely challenging.

Fundamentally, honey is a highly concentrated solution of two invert sugars, dextrose and levulose, in water with small amounts of numerous complex sugars. In addition to these sugars, which are responsible for the principal physical characteristics and behavior of honey, it also contains aromatic volatile oils, which give it flavor, along with minerals, various enzymes, vitamins, and pigments. These minor constituents, largely responsible for the differences among individual honey types, contribute to the complexity of the honey matrix.

The basic analytical requirements for food analysis are high-resolution, high-throughput, high-sensitivity detection and the quantitation of contaminants at or below the maximum residue limit (MRL) of the compound in a given food matrix.2 Professionals in the food safety and quality control fields recognize liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the central analytical technology. LC-MS/MS provides high-speed, high-resolution, and high-sensitivity separation and quantitation of various chemical compounds. An LC-MS/MS-based technique is also useful as a simultaneous screening method for the multiple classes of contaminants at trace levels in honey.

Honey analysis, like every food analysis, starts with sample preparation. Sample preparation is widely accepted as one of the most critical steps of the LC-MS/MS analysis. The increased demand from food analysis laboratories for higher throughput, higher accuracy, and lower matrix interference has made sample preparation the bottleneck step in the analysis.

Conventional sample preparation for LC-MS/MS analysis of honey is time and labor intensive and often involves pH modification, hydrolysis, liquid-liquid extraction (LLE), solid phase extraction (SPE), solvent evaporation, and pre-concentration steps to isolate and enrich target analytes from the honey matrix. When manually undertaken, these offline techniques are often costly and can result in low sample throughput.

One Solution

Food quality control laboratories are challenged by their need for multi-component quantitation, their desire for limited or no sample preparation, and their requirement to make quality control screening cost effective. New automated, online sample extraction techniques, such as Thermo Scientific TurboFlow technology coupled with LC-MS/MS, can reduce sample preparation and eliminate the disadvantages of conventional techniques.