So what exactly is a non reducing sugar? Well, as we discussed previously, a non reducing sugar is a sugar that, when mixed with some type of oxidizing agent, will not react via an oxidation reduction reaction. On the other hand, if we have a reducing sugar, when a reducing sugar is in the presence of some type of oxidizing agent, it will be oxidized. It will react in an oxidation reduction reaction. Now, Maltose and lactose are examples of reducing sugars. And that's because if we examine this sugar here and this sugar here, if it opens up into its open chain form, it will have an aldehyde group.