Analysis of quality indicators in crunchy vegetable snacks

Abstract

Due to the present style of life, consumers are very interested in new and healthy products which provide, not only nutritive value, but also bioactivity and surprising sensorial properties. In this context, dehydrated vegetables are one of the foods that occupy a preponderant place. Although dehydration is one of the oldest preservation methods in food technology, during the last years it has suffered a huge evolution with the aim of solving the problems of conventional convective drying. As it is known, the high temperature of the drying process is an important cause for loss of quality, and by lowering this parameter, the operating time and the associated cost can become unacceptable. As an alternative, freeze-drying can better preserve the quality of foods; however, this technique is reserved for high added value products due to the expensive cost of water sublimation under vacuum. Nowadays, among the different commercial products that can be purchased by the consumers, the crunchy vegetable snacks can be highlighted. These attractive vegetables, presumably obtained by texturization by expanded micro-perforation, are offered in metal cans under modified atmosphere as healthy, tasty, surprising, environmentally friendly and with a wide range of applications, not only as snacks, but also as ingredients in several foodstuffs.

However, to the best of our knowledge, no investigations have been published on the analysis of quality indicators in this type of products and on the evolution of the main chemical changes that can take place during their storage. In this work, the determination by GC-FID of carbohydrates and by RP-HPLC of vitamin C and furosine (indicator of lysine loss due to the Maillard reaction evolution) has been carried out in crunchy pepper, tomato and onion commercial samples. For this purpose, three different cans from the same batch of each vegetable were purchased and immediately analysed after their acquisition and during their storage at ambient temperature (21-30ºC) and relative moisture conditions within the range 14-45% throughout their shelf-life. Once the cans were opened, a parallel storage, at ambient temperature and at 40°C, was carried out with the aim of simulating domestic conditions used by consumers and extreme conditions of storage. The dry matter was high (84.8-90.4%), in agreement with the low values of water activity (0.25-0.27). As expected, the main carbohydrates in onion were sucrose (144 mg/g DM) and fructooligosaccharides (348 mg/g DM), while in tomato and pepper were fructose (155 and 286 mg/g DM, respectively) and

glucose (97 and 190 mg/g DM). However, the most relevant result was the finding of sedoheptulose for the first time in tomato (3.7 mg/g DM) and pepper (2.4 mg/g DM).This higher-carbon monosaccharide can be used as starting material for the chemical synthesis of biologically active compounds. Furosine was determined in pepper for the first time, in a higher amount (185.3 mg/100 g DM) than in tomato (96.5 mg/100 g DM) and onion (69.7 mg/100 g DM). Similar values had previously been reported for onion and tomato. An increase in furosine amount was observed during storage, particularly high under the most severe conditions. The highest vitamin C content was found in pepper (647 mg/100 g DM) and, according to the lower content of this vitamin in raw tomato, only 20 mg/100 g DM was quantified in the crunchy sample. No presence of vitamin C was detected in onion, since this compound has been reported as especially labile in this vegetable [4]. In pepper samples, the retention values of vitamin C at ambient temperature and 40ºC were 34 and 5%, respectively, after 90 days of storage when the modified atmosphere was removed. According to the quality parameters studied in the present work, it is possible to conclude that crunchy vegetable snacks obtained by this process are safe and keep their quality and bioactivity if the samples are stored under the conditions rec.