How it looks on a store shelf shapes the form of most food packaging. How it plays in a school child's lunchbox may be more important in the burgeoning healthy snacks market.

A false start with a pull-tab package underscored that point for Cirio Del Monte Ltd., the UK marketer of Del Monte Fruitini snack packs. Preschoolers through third graders were the healthy snack's target, and the ring was a bad fit with their under-developed digits. The product recently was relaunched in a plastic cup with updated graphics.

San Francisco-based Del Monte Foods went through a similar learning curve with Fruit & Gel, another healthy snack that began life in a metal package before segueing to clear plastic. The line features diced peaches and Mandarin oranges in a "lunchbox friendly" format.

Adding a sugary glaze to walnuts doesn't do much for nutritional value; on the other hand, the process doesn't compromise omega-3 content, and walnuts' low levels of saturated fat and cholesterol appeal to mothers. Diamond of California is counting on that perception in launching half-ounce snack sizes of Diamond Glazed Nuts, a line that racked up $5 million in sales in its first year of national distribution. The metalized film and easy-open lunchbox treats are standard fare, according to Diamond of California and the reclosable strip on larger packages was dropped. Nonetheless, the company gets good marks from retailers who say that the purple bags are eye-catching. The walnut cooperative is counting on that plus a kid-friendly package to help it grab a share of the lunchbox snack segment.