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Hard candies are sugar confections comprising mainly water and sucrose. Corn syrup, colorants and flavors are also usually added to hard candy formulations. The production of hard candy requires heating of the ingredients to very high temperatures to reduce moisture content and subsequent cooling to obtain a solid matrix. Cooling of the mixtures achieves the final, well known glassy state of the products. In this glassy state, the system is kinetically stable and molecular mobility is restricted, providing longer shelf life to hard candies. There are, however, several factors affecting the final quality and consumer acceptance of hard candies. Production methods and parameters, initial formulations as well as storage conditions all play a crucial role in the physicochemical, textural and sensory properties of hard candies. Addition of colorants and flavors also plays a vital role in the final quality. Although hard candy production is a simple process with few production stages, even small changes in the method of production and process parameters may induce substantial changes in the final product characteristics. Additionally, storage conditions such as temperature and humidity can change the product properties leading to graining and stickiness which are the two major problems for hard candies during storage. Both production and storage conditions should therefore be carefully chosen and controlled for desirable hard candy properties. This review addresses the general production methods and considers process parameters and quality parameters of hard candy products. Moreover, a comprehensive review of the related hard candy literature is also presented. The majority of hard candy reviews focus on specific methods and processes, but this review will present a more general frame on the subject.

In this study, a new functional product using Mediterranean ingredients (tomato, tomato peel powder and olive powder) was formulated where two different concentrations of protein (1 and 2%) and peel (2 and 4%) were tested. Olive powder was kept at a constant concentration of 2%. Physico-chemical, Rheological, and Sensorial analysis were carried out on the formulated samples. Soluble protein content was found as the highest in the sample containing 4% peel and 2% protein and it was affected by the pH and tomato peel concentration. Rheological results reveal shear-thinning behavior, as defined by the Herschel-Bulkley model, with protein and peel concentrations having a major influence on yield stress and viscosity. A positive trend was noticed between apparent viscosity and peel concentration, meantime protein concentration affected apparent viscosity adversely. Contrary relation between consistency index (k) values and apparent viscosity illustrate the complex interaction between protein and peel, particularly at higher concentrations. Furthermore, Principal Component Analysis (PCA) was used to investigate the complicated sensory landscape of tomato products with different quantities of pea protein and tomato peel. While higher tomato peel and protein levels have no direct impact on rheological qualities, they do add to astringency and sourness, which influences overall acceptability. Remarkably, the sample with the greatest quantities of peel and protein exhibits a delicate balance, with a loss in perceived tomato taste intensity and overall acceptability offsetting an increase in astringency. In terms of overall acceptability, the most preferred beverage was selected as the sample formulated with 2% peel and 1% protein.

The TD-NMR technique mostly involves the use of T1 (spin-lattice) and T2 (spin-spin) relaxation times to explain the changes occurring in food systems. However, these relaxation times are affected by many factors and might not always be the best indicators to work with in food-related TD-NMR studies. In this study, the non-conventional TD-NMR approaches of Solid Echo (SE)/Magic Sandwich Echo (MSE) and Spin Diffusion in food systems were used for the first time. Soft confectionary gelatin gels were formulated and conventional (T1) and non-conventional (SE, MSE and Spin Diffusion) TD-NMR experiments were performed. Corn syrups with different glucose/fructose compositions were used to prepare the soft candies. Hardness, °Brix (°Bx), and water activity (aw) measurements were also conducted complementary to NMR experiments. Relaxation times changed (p < 0.05) with respect to syrup type with no obvious trend. SE/MSE experiments were performed to calculate the crystallinity of the samples. Samples prepared with fructose had the lowest crystallinity values (p < 0.05). Spin Diffusion experiments were performed by using Goldman–Shen pulse sequence and the interface thickness (d) was calculated. Interface thickness values showed a wide range of variation (p < 0.05). Results showed that non-conventional NMR approaches had high potential to be utilized in food systems for quality control purposes.