Nut bars: choosing, pressing, cutting

A nut bar holds together when three things are done right: nuts and piece size that suit the bar, a binder in the right amount cooked to the right point, and pressing at the right pressure followed by cutting at the right moment. Get one of the three wrong and the bar crumbles when the wrapper opens, or turns rock hard after a few weeks. At Color of Vietnam nut bars belong to the Natural & Healthy brand, with cashew as the main nut. Here is each step, and where it goes wrong.

Choosing nuts: type, size and roast

Cashew is the main nut in our bars because it is buttery, barely bitter and a Vietnamese ingredient. Peanuts are cheaper and stronger in flavour, and often sit alongside. Oats are not a nut but form the base, giving the binder something to grip. Three choices for every nut:

• Size: whole, halves or pieces. Whole kernels look good. Pieces have more surfaces in contact, so they bind better and cut cleaner.
• Roast level: roasting sets the aroma, the crunch and the remaining moisture. Under-roasted nuts make a soft bar that loses its aroma quickly. Over-roasted nuts turn bitter. Roasted nuts must cool completely before mixing, because warm nuts thin the binder.
• Moisture on arrival: damp nuts make a bar soften slowly inside the wrapper. So the COA (certificate of analysis) for every nut lot must carry a moisture line, and we read that line before the price.

The binder: what holds the bar together

The binder is the liquid part mixed with the nuts that firms up as it cools. Common ones are rice syrup, glucose syrup, honey, date paste or a nut butter. A syrup is cooked to a set temperature so that it is thick enough. Undercooked, the bar does not hold. Overcooked, the bar is hard and sticks to the teeth.

One thing that surprises newcomers: the sugar in the syrup provides both the sweetness and the hold. Reducing sweetness and keeping the shape therefore pull against each other. To make a bar less sweet and still keep it in one piece, you change the type of binder or the piece size, not just the amount of syrup.

Pressing: pressure, thickness and warmth

The warm mix of nuts and syrup is spread into a frame or onto a belt and rolled or pressed to a set thickness. The pressure decides whether the bar is dense or open, soft or firm. Even thickness gives even weight per bar, and weight is the first thing an inspector puts on the scale. Press once the mix has cooled and the syrup no longer flows into the gaps between the nuts, so the bar comes apart.

Cutting and packing

The pressed slab cools until it is firm enough, and only then is it cut. A straight blade gives a flat face. With large pieces, an ultrasonic blade (one that vibrates at high frequency) gives a cleaner face because it does not drag the nuts along. The edges of a bar are the weakest point: nuts sitting at the rim are not held by the base and fall away during cutting and again when the wrapper opens.

After cutting, each bar is weighed against the tolerance and wrapped straight away in laminated film, because a bar picks up moisture quickly. Nuts carry oil, so they fear oxygen and light. The film has to block both, and cartons of finished goods are stored cool and dry. A bar that goes rancid is rarely a recipe fault. It is usually a film fault or a warehouse fault.

An example: whole or broken cashew for a Natural & Healthy bar

Recently we compared two Natural & Healthy samples from our partner facilities, made from the same cashew lot with the same binder. Sample A used mostly whole kernels and halves. Sample B used pieces in the body and scattered a few halves across the top face.

Sample A looked beautiful from above. But the cut faces at both ends lost kernels, bar weights varied noticeably, a few bars fell outside the tolerance, and the facility had needed to raise the binder to hold the large pieces, so the bar came out sweeter than intended. Sample B cut cleanly, weighed evenly, tasted identical because it was the same lot, and still showed halves on top. At the review table the second-piece question leaned towards B because it was less sweet.

The outcome: B, and three new lines in the specification: a size range for the pieces in the body, halves on the top face only, and pieces sifted to remove nut dust, because dust makes a bar pasty. On the buying side, pieces cost less than whole kernels, but the quality specification for pieces is as full as for whole nuts: moisture, rancidity, foreign matter. Cheaper does not mean less demanding.

If you want to learn to read the cut face of a bar and tell which step went wrong, our Fresher Product R&D (FMCG) role in Hanoi is open on the Careers page. If you supply nuts, or you are a buyer who would like bar samples and the specification, get in touch through the Contact page or at support@colorvietnam.com.