DRIVING along Route 53, you're not likely to find Brookside cottage without help from a native Mainer. "Take the first dirt road on your left. Drive a little, and you'll see it on your left," one road worker directs.Sure enough, there it is, graced with a beautiful English garden in front and vegetable garden off to the side. Behind the cottage is a brook that is unusually quiet from the dry weather. But the real draw of Brookside cottage isn't the landscape, it's what's cooking inside: wild blueberry jam. Angela and Ray Towle own Brookside Cottage, the home, and also the business of the same name. They specialize in homemade preserves. In the true spirit of cottage industry, the couple's business is one of possibly hundreds in this large state that offer homemade foodstuffs. But the Towles don't serve just their local community during Maine's precious blueberry season. They fill mail-orders for their jams, jellies, and syrup and ship anywhere in the United States most of the year. They also wholesale to shops. While Angela takes care of the cooking end, Ray helps with the labeling and shipping. As for the preserves, well, "They're wonderful," says Jonathan Perkins of the Belfast Co-Op, in Belfast, Maine, which sells Brookside Cottage items. "It's nice to have something locally made; a lot of people look for that." To realize the treasure Angela Towle bottles, one must be privy to Maine blueberries. They are wild, low-bush berries that are harvested by "raking." Angela, who grew up on Long Island, N.Y., says she remembers going blueberry picking in Maine for the first time and saying "Where are they? I don't see them," and a friend telling her "You're stepping on them!" The cultivated high-bush blueberries, such as those grown in New Jersey, are plumper, filled with water. "They don't have the flavor that wild blueberries have," says Mrs. Towle. "Wild blueberries have a much stronger piquant and are smaller than the cultivated," explains Joan Smith, food editor of the Bangor Daily News in Bangor, Maine. "They are considered 'gourmet' and they're only grown here." Towle buys her blueberries flash-frozen from an oufit in Blue Hill, Maine. That way she can make her blueberry jam and syrup all year. Making jam isn't as difficult as some think, says Towle during an interview in her living room on a warm September day. It's not difficult unless you make as much as she does - 5,000 jars a year. "I do it all myself," she says. "Making 5,000 jars on your own is not that easy." In late spring and summer, she says she puts in up to 10 hours a day. "That's a lot for someone who's supposed to be retired," she says with a laugh. At her busiest time, she makes 200 to 300 jars a week. Her husband, Ray, of course helps out. He's director of shipping and sometimes part-time pot-washer. "I rest on my laurels in the wintertime," Angela says. She takes February and March off. Towle started making jam when her three children were growing up. "I used to take my children to pick our own berries," she remembers. In addition to the delicious blueberry jam and syrup (a special recipe she will not divulge), Angela makes several other jams: blackberry, peach, strawberry, strawberry and rhubarb, raspberry, raspberry and rhubarb, and cranberry. She also makes apple butter, orange marmalade, and a green pepper jelly ("great over hors d'oeuvres"). She offers honey-sweetened products, too ($3.25 per half-pint vs. $2.95 for sugar-sweetened). "I use the Maine wild raspberry blossom honey, which is very mild and lets the flavors of the berries dominate," she says. The jars are topped with gingham and tied with a bow of yarn. Unlike commercial manufacturers, Towle makes preserves in small batches. "I do it just as you would make it for your family," she says. One batch yields about seven jars, she says. "That's why you taste the flavor of the berries - they're not cooking for so long." To be fair, the work is labor intensive, says Towle, but "I get a lot of satisfaction. I receive letters from people all over telling me how much they like it." Today, Towle's kitchen is spotless. But one can imagine the sound of a rolling boil, the smell of sweet syrup, and the sight of fresh fruit, sugar, lemon juice, honey, glass jars about. Her kitchen is inspected and licensed annually by the Maine Department of Agriculture. O she and her husband still like jam? "Oh yes, we like jam," says Towle. One of their favorite ways to eat blueberry jam is on whole-grain bread with low-fat cream cheese - or on blueberry muffins. As for making your own jam, Angela Towle a few tips: * Follow directions carefully. * If you don't boil enough, the jam won't gel properly. * Too little sugar won't allow it to gel properly either. * Don't change the ingredients. * It's very important to do the hot water bath - it kills bacteria (see recipe). * Don't overcook. "Ten minutes is tops," she says.