Quince jam quality: microbiological, physicochemical and sensory evaluation

Abstract

The present work aimed to study the quality of 18 brands of quince jam commercially available in the Portuguese market. Microbiological analyses included enumeration of yeasts and molds. Sugar content was determined by refractometry (°Brix), while the quantification of the preservatives benzoic and sorbic acids as well as other organic acids (citric, malic, lactic, quinic, succinic) was carried out by HPLC/UV. For sensory analysis, a panel of 10 assessors with slight training was used following the quantitative descriptive analysis methodology. Microbiological analyses revealed that four quince jam samples presented a total number of yeasts and molds higher than 10 3 cfu/g, which is above the expected levels for this parameter. With respect to sugar content, four samples presented °Brix lower than 63%, while most of the samples (eleven) contained between 63% and 70% of sucrose. Only three samples presented °Brix higher than 70%. A large variability among the commercial brands of quince jam was noticed for benzoic, sorbic, citric, malic, quinic and succinic acids contents. Benzoic acid content exceeded the legal limits of 500 mg/kg in five samples. The sum of benzoic and sorbic acids was above the limits allowed by legislation (1000 mg/kg) in two samples. Categorical principal components analysis using number of molds, number of yeasts, benzoic, sorbic, succinic, malic, citric, quinic acids as variables was performed to determine similarities/differences between quince jam samples. Results from sensory analysis revealed mainly a group of samples with typical soft odour and taste, attributes correlated with low granulous texture and shiny surfaces, in contrast to another group of samples with intense odour, but less typical, more acid and puree, sandy type of texture. Other samples were situated between this two extremes. Apart from the few points raised above, mainly in what concerns preservative levels, in general terms one can say that the products investigated are in good agreement with the major national specifications, though some action should be undertaken to assure that better practices will help lowering the number of easily avoidable non-conformities.