Stalls with jellies of various flavors and shapes are an inseparable element of fairs, festivities, sometimes even indulgences or other ecclesiastical celebrations. Plastic containers with colorful sweets sold by weight can also be found in amusement parks, on promenades in seaside resorts, as well as in hypermarkets and marketplaces. Although nicely displayed delicacies with their appearance and smell are a real temptation for families with children, one should be careful while tasting these sweets. Jellies stored for many hours without cover, in changing weather conditions, can impair our health, and at best turn out to be simply hard and go stale.