Maaser Sheni, Chapter One, Mishnah Three
The rest of this chapter deals with using maaser sheni money to buy food in Jerusalem. There are two important rules to keep in mind here: first of all, food that one buys becomes holy and there are certain rules that apply to it. Second, one can only buy food products with maaser sheni money. If one buys non-food products with maaser sheni money, the tule is that he must go and buy in Jerusalem an equivalent value of food.
Our mishnah teaches that if there is a product that contains both food and non-food parts, it can be bought with maaser sheni money and the non-food part of it does not become holy.
1) One who bought a domesticated animal for a shelamim offering or a wild animal for non-sacrificial eating, the hide becomes hullin [non-sacred], even though the value of the hide exceeds the value of the flesh.
2) Sealed jars of wine [which were bought] in a place where they were usually sold sealed, the jars are hullin.
3) Walnuts and almonds, their shells become hullin.
4) Grape-skin wine: before it has fermented it cannot be bought with second tithe money, but after it has fermented it may be bought with second tithe money.
Section one: It was considered normal to buy sacrifices with maaser sheni money. Only domesticated animals, sheep, goats and cows, can be used for such offerings. Wild animals such as deer are kosher, but cannot be used as sacrifices. One can buy them with maaser sheni money. In these cases, since he acted in a proper manner, the hide, which obviously cannot be eaten, becomes hullin, non-sacred. This is true even if the value of the hide is greater than that of the food-part of the animal, the flesh.
Section two: The wine referred to here was sold in sealed jars, meaning that the jars were sold with the wine. This was typical of the place where he bought the wine. The jars were secondary to the wine, and therefore, the sanctity of the maaser sheni money is not transferred to the jugs. The jugs become non-sacred.
Section three: Nut shells, such as those of walnuts and almonds, remain hullin, because what he was really buying was the meat of the nuts. The shells were only secondary to the nuts themselves.
Section four: Before grape-skin wine is fermented, it is considered like water. One cannot buy water with maaser sheni money because water is not food. Once it has been fermented, one can buy it with maaser sheni money.